MCP9805 Memory Module Digital Temperature Sensor Features Description • Meets JEDEC Standard JC42.4 for Mobile Platform Memory Module Thermal Sensor • Temperature-to-Digital Converter • Accuracy with 0.25 °C/LSb Resolution: - ±1°C (max.) from +75°C to +95°C - ±2°C (max.) from +40°C to +125°C - ±3°C (max.) from -20°C to +125°C • Programmable Temperature Monitor Boundary • Critical Temperature Output • Operating Voltage Range: 3.0V to 3.6V • 2-wire Interface: SMBus/Standard mode I2C™ Compatible • Operating Current: 200 µA (typ.) • Shutdown Current: 0.1 µA (typ.) • Available Packages: 2x3 DFN-8, TSSOP-8 Microchip Technology Inc.’s MCP9805 digital temperature sensor converts temperatures between -40°C and +125°C to a digital word. This sensor is designed to meet the JEDEC standard JC42.4 for Mobile Platform Memory Module Thermal Sensor. This device provides an accuracy of ±1°C (max.) from a temperature range of +75°C to +95°C (active range) and ±2°C (max.) from +40°C to +125°C (monitor range) as defined in the JEDEC standard. Typical Applications • • • • Dual In-line Memory Module (DIMM) Personal Computers (PCs) and Servers Hard Disk Drives and Other PC Peripherals General Purpose Temperature Sensor The MCP9805 comes with user-programmable registers that provide flexibility for DIMM temperature-sensing applications. The registers allow user-selectable settings such as Shutdown or Low-Power modes and the specification of temperature event and critical output boundaries. When the temperature changes beyond the specified boundary limits, the MCP9805 outputs an Event signal. The user has the option of setting the Event output signal polarity as either an active-low or active-high comparator output for thermostat operation, or as a temperature event interrupt output for microprocessor-based systems. The Event output can also be configured as a critical temperature output. This sensor has a 2-wire industry-standard SMBus and Standard mode I2C compatible (100 kHz bus clock) serial interface protocol, allowing up to eight sensors to be controlled in a single serial bus. These features make the MCP9805 ideal for sophisticated multi-zone temperature-monitoring applications. Typical Application Memory Module Memory SPD* Temperature Sensor EEPROM MCP9805 Package Types MCP9805 8-Pin DFN (2x3) A1 2 8 VDD 7 Event A2 3 6 SCLK A0 1 R GND 4 5 SDA 8-Pin TSSOP R 3.3 VDD_SPD SDA SCLK Event A0 1 8 VDD A1 2 7 Event A2 3 6 SCLK GND 4 5 SDA * Serial Presence Detect © 2005 Microchip Technology Inc. DS21977B-page 1 MCP9805 1.0 ELECTRICAL CHARACTERISTICS Absolute Maximum Ratings † VDD ....................................................................... 6.0V †Notice: Stresses above those listed under “Maximum ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. Voltage at all Input/Output pins .... GND – 0.3V to 5.5V Storage temperature ..........................-65°C to +150°C Ambient temp. with power applied .....-40°C to +125°C Junction Temperature (TJ)................................ +150°C ESD protection on all pins (HBM:MM)....... (4 kV:200V) Latch-Up Current at each pin ........................ ±200 mA DC CHARACTERISTICS Electrical Specifications: Unless otherwise indicated, VDD = 3.0V to 3.6V, GND = Ground and TA = -20°C to +125°C. Parameters Sym Min Typ Max Unit Conditions VDD 3.0 — 3.6 V Operating Current IDD — 200 500 µA Continuous Operation Shutdown Current ISHDN — 0.1 2 µA Shutdown Mode VDD Falling Edge Power Supply Operating Voltage Range Power-On Reset Threshold (POR) VPOR — 2.2 — V PSRDC — ±0.3 — °C PSRAC — ±0.5 — °C VDD = 3.3V + 150 mVpp (0 to 1 MHz), TA = +25°C +75°C to +95°C TACY -1.0 ±0.5 +1.0 °C Active Temp. Range +40°C to +125°C TACY -2.0 ±1.0 +2.0 °C Monitor Temp. Range -20°C to +125°C TACY -3.0 ±2.0 +3.0 °C TA = -40°C TACY — ±2 — °C tCONV — 65 125 ms 17 samples/sec. (typ.) High-Level Current (leakage) IOH — — 1 µA VOH = 3.6V Low-Level Voltage VOL — — 0.4 V IOL= 3 mA tRES — 0.7 — s tRES — 1.5 — s Time to 63% of +22°C (Air) to +125°C (Oil Bath) Power Supply Rejection Temperature Sensor Accuracy Accuracy with 0.25 °C/LSb Resolution: Internal ΔΣ ADC Conversion Time (10-bits + Sign): 0.25 °C/LSb Event Output (Open-Drain) Thermal Response Response Time (Note): DFN TSSOP Note: Thermal response with 1x1 inch dual-sided copper clad. DS21977B-page 2 © 2005 Microchip Technology Inc. MCP9805 DIGITAL INPUT/OUTPUT PIN CHARACTERISTICS Electrical Specifications: Unless otherwise indicated, VDD = 3.0V to 3.6V, GND = Ground and TA = -20°C to +125°C. Parameters Sym Min Typ Max Units VIH 2.1 Low-Level Voltage VIL — Input Current IIN Low-Level Voltage Conditions — — V — 0.8 V — — ±5 µA VOL — — 0.4 V IOL= 3 mA High-Level Current (leakage) IOH — — 1 µA VOH = 3.6V Low-Level Current IOL 6 — — mA VOL = 0.6V CIN — 5 — pF VHYST — 0.5 — V Serial Input/Output (SCLK, SDA, A0, A1, A2) Input High-Level Voltage Output (SDA) Capacitance SDA and SCLK Inputs Hysteresis Graphical Symbol Description SDA OUTPUT SDA & SCLK INPUTS Voltage Voltage VDD VDD VIH VIL VOL time time Current Current IOL IOH IIN time time © 2005 Microchip Technology Inc. DS21977B-page 3 MCP9805 SERIAL INTERFACE TIMING CHARACTERISTICS Electrical Specifications: Unless otherwise indicated, VDD = 3.0V to 3.6V, GND = Ground, TA = -20°C to +125°C, CL = 80 pF and all limits measured to 50% point. Parameters Sym 2-Wire SMBus/Standard Mode Min Typ Max Units Conditions I2 C™ Compatible Interface (Note) fSC 10 — 100 kHz Low Clock tLOW 4.7 — — µs High Clock tHIGH 4.0 — — µs Rise Time tR — — 1000 ns (VIL MAX - 0.15V) to (VIH MIN + 0.15V) Fall Time tF — — 300 ns (VIH MIN + 0.15V) to (VIL MAX - 0.15V) tSU-DATA 250 — — ns Data Hold After SCLK Low tHD-DATA 300 — — ns Start Condition Setup Time tSU-START 4.7 — — µs Start Condition Hold Time tHD-START 4.0 — — µs Stop Condition Setup Time tSU-STOP 4.0 — — µs Bus Free tB-FREE 4.7 — — µs Time Out tOUT 25 40 50 ms Serial Port Clock Frequency Data Setup Before SCLK High Note: The serial interface specification min./max. limits are specified by characterization (not production tested). Timing Diagram tH-START tSU-START tHIGH tB-FREE tSU-STOP tLOW SCLK SDA tOUT tR, tF tH-DATA tSU-DATA START Condition Data Transmission STOP Condition TEMPERATURE CHARACTERISTICS Electrical Specifications: Unless otherwise indicated, VDD = 3.0V to 3.6V, GND = Ground. Parameters Sym Min Typ Max Units Conditions Temperature Ranges Specified Temperature Range TA -20 — +125 °C Operating Temperature Range TA -40 — +125 °C Storage Temperature Range TA -65 — +150 °C Thermal Resistance, 8L-DFN θJA — 41 — °C/W Thermal Resistance, 8L-TSSOP θJA — 123.7 — °C/W Note 1 Thermal Package Resistances Note 1: Operation in this range must not cause TJ to exceed Maximum Junction Temperature (+150°C). DS21977B-page 4 © 2005 Microchip Technology Inc. MCP9805 2.0 TYPICAL PERFORMANCE CURVES Note: The graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. The performance characteristics listed herein are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified operating range (e.g., outside specified power supply range) and therefore outside the warranted range. Note: Unless otherwise noted: VDD = 3.0V to 3.6V, GND = Ground, Cde_cap = 0.1 µF 500 VDD= 3.3V to 3.6V 400 1.0 Spec. Limits 0.0 -1.0 350 300 250 200 -2.0 150 -3.0 100 -40 -20 0 20 FIGURE 2-1: Accuracy. 40 60 TA (°C) 80 100 120 Average Temperature -40 50% 0 20 40 60 TA (°C) 80 100 120 Supply Current vs. Ambient 2.00 VDD = 3.3V to 3.6V TA = +95°C VDD = 3.3V 120 samples 1.50 ISHDN (µA) 60% -20 FIGURE 2-4: Temperature. 70% Occurrences VDD = 3.3V to 3.6V 450 2.0 IDD (µA) Temperature Accuracy (°C) 3.0 40% 30% 20% 1.00 0.50 10% 0.00 1.00 0.75 0.50 0.25 0.00 -0.25 -0.50 -0.75 -1.00 0% -40 -20 0 20 Temperature Accuracy (°C) 70% 30% 2 1.5 20% 1 10% 0.5 Temperature Accuracy (°C) FIGURE 2-3: Temperature Accuracy Histogram, TA = +75°C. © 2005 Microchip Technology Inc. 1.00 0.75 0.50 0.25 0.00 -0.25 -0.50 0% -0.75 120 2.5 40% -1.00 100 3 TA = +75°C VDD = 3.3V 120 samples VPOR (V) Occurrences 50% 80 FIGURE 2-5: Shutdown Current vs. Ambient Temperature. FIGURE 2-2: Temperature Accuracy Histogram, TA = +95°C. 60% 40 60 TA (°C ) 0 -40 -20 0 20 40 60 TA (°C) 80 100 120 FIGURE 2-6: Power-on Reset Threshold Voltage vs. Ambient Temperature. DS21977B-page 5 MCP9805 Note: Unless otherwise noted: VDD = 3.0V to 3.6V, GND = Ground, Cde_cap = 0.1 µF. 48 VOL = 0.6V IOL = 3mA 42 0.3 SDA I OL (mA) Event & SDA V OL (V) 0.4 SDA, VDD = 3.0V VDD = 3.3V VDD = 3.6V 0.2 0.1 Event, VDD = 3.0V to 3.6V 30 VDD = 3.6V 24 18 6 -40 -20 0 20 40 60 TA (°C) 80 100 120 FIGURE 2-7: Event and SDA VOL vs. Ambient Temperature. -40 -20 0 FIGURE 2-10: Temperature. 20 40 60 TA (°C) 80 100 120 SDA IOL vs. Ambient 3.0 Temperature Accuracy (°C) 125 VDD = 3.0V to 3.6V 110 tCONV (ms) VDD = 3.3V VDD = 3.0V 12 0 95 80 65 50 35 -40 -20 0 20 40 60 TA (°C) 80 100 2.0 VDD = 3.0V VDD = 3.6V 1.0 PSRDC = 0.3°C/V 0.0 -1.0 -2.0 -3.0 -40 120 -20 0 FIGURE 2-11: VDD. FIGURE 2-8: Conversion Rate vs. Ambient Temperature. 20 40 60 TA (°C) 80 100 120 Temperature Accuracy vs. 120% 1.0 PSRAC, VDD = 3.3V + 150mVPP (AC) TA = 25°C +25°C 0.5 0.0 -0.5 No decoupling capacitor -1.0 100 100 1,000 1k 1k 10,000 10k 10k 100,000 100k 100k 1,000,000 1M 1M Thermal Response (%) Normalized Temp. Error (°C) 36 100% 80% 60% TSSOP-8 DFN-8 40% 20% 22°C (Air) to +125°C (Oil bath) 0% -2 0 Frequency (Hz) FIGURE 2-9: Frequency. DS21977B-page 6 Power Supply Rejection vs. FIGURE 2-12: Response. 2 4 6 8 Time (s) 10 12 14 16 Package Thermal © 2005 Microchip Technology Inc. MCP9805 3.0 PIN DESCRIPTION The descriptions of the pins are listed in Table 3-1. TABLE 3-1: PIN FUNCTION TABLES DFN/TSSOP Symbol 1 A0 Slave Address 2 A1 Slave Address 3 A2 Slave Address 4 GND 3.1 Pin Function Ground 5 SDA Serial Data Line 6 SCLK Serial Clock Line 7 Event 8 VDD Temperature Event Output Power Slave Address Pins (A0, A1, A2 ) 3.4 A0, A1 and A2 are device slave address input pins. The address pins correspond to the Least Significant bits (LSbs) of the address byte (see Section 5.1.4 “Address Byte”). The Most Significant bits A6, A5, A4, A3 are factory set. This is shown in Table 3-2. TABLE 3-2: Device MCP9805 Note: 3.2 MCP9805 ADDRESS BYTE Address Code Slave Address A6 A5 A4 A3 A2 A1 A0 X X X 0 0 1 1 User-selectable address is shown by X. The SCLK is a clock input pin. All communication and timing is relative to the signal on this pin. The clock is generated by the host or master controller on the bus. (See Section 5.0 “Serial Communication”). 3.5 Open-Drain Temperature Event Output pin (Event) The MCP9805 Event pin is an open-drain output. The device outputs a signal when the ambient temperature goes beyond the user-programmed temperature limit. (see Section 4.2.3 “Event Output Configuration”). Ground Pin (GND) The GND pin is the system ground pin. 3.3 Open-Drain Serial Clock Line (SCLK) Open-Drain Serial Data Line (SDA) SDA is a bidirectional input/output pin, used to serially transmit data to/from the host controller. This pin requires a pull-up resistor. (See Section 5.0 “Serial Communication”). © 2005 Microchip Technology Inc. 3.6 Power Pin (VDD) VDD is the power pin. The operating voltage range, as specified in the DC electrical specification table, is applied on this pin. DS21977B-page 7 MCP9805 4.0 SMBus/Standard mode I2C compatible serial interface protocol. Figure 4-1 shows a block diagram of the register structure. FUNCTIONAL DESCRIPTION The MCP9805 temperature sensors consist of a band gap temperature sensor, a Delta-Sigma Analog-to-Digital Converter (ΔΣ ADC) and user-programmable registers using a 2-wire Event Output Hysteresis Continuous Conversion or Shutdown Critical Boundary Trip Lock Event Boundary Window Lock bit Clear Event Output Interrupt Event Output Status Enable/Disable Event Output Critical Event Output only Event Output Polarity, Active-High/Low Band Gap Temperature Sensor Event Output Comparator/Interrupt Configuration Register ΔΣ ADC Temperature Register (TA) Temperature Upper-Boundary (TUPPER) Temperature Lower-Boundary (TLOWER) Critical Temperature Limit (TCRIT) Manufacturer Identification Register Device Identification and Revision Register Device Capability Register Measurement Resolution Measurement Range Measurement Accuracy Temperature Event Output SMBus/Standard I2C™ Interface Register Pointer A0 FIGURE 4-1: DS21977B-page 8 A1 A2 Event VDD GND SDA SCLK Register Structure Block Diagram. © 2005 Microchip Technology Inc. MCP9805 4.1 Registers The MCP9805 has several registers that are user-accessible. These registers include the Capability register, Configuration register, Event Temperature Upper-Boundary and Lower-Boundary Trip registers, Critical Temperature Trip register, Temperature register, Manufacturer Identification register and Device Identification register. The Temperature register is read-only, used to access the ambient temperature data. The data is loaded in parallel to this register after tCONV. The Event Temperature Upper-Boundary and Lower-Boundary Trip registers are read/writes. If the ambient temperature drifts beyond the user-specified limits, the MCP9805 outputs a signal using the Event pin (refer to Section 4.2.3 “Event Output Configuration”). In addition, the Critical Temperature Trip register is used to provide an additional critical temperature limit. REGISTER 4-1: The Capability register is used to provide bits describing the MCP9805’s capability in measurement resolution, measurement range and device accuracy. The device Configuration register provides access to configure the MCP9805’s various features. These registers are described in further detail in the following sections. The registers are accessed by sending a Register Pointer to the MCP9805 using the serial interface. This is an 8-bit write-only pointer. However, the three Least Significant bits (3-LSbs) are used as pointers and all unused bits (bits 7-3) need to be cleared or set to ‘0’. Register 4-1 describes the pointer or the address of each register. REGISTER ADDRESS POINTER (WRITE-ONLY) W-0 W-0 W-0 W-0 W-0 W-0 W-0 W-0 0 0 0 0 0 P2 P1 P0 bit 7 bit 7-3 bit 0 Writable Bits: Write ‘0’ Bits 7-3 must always be cleared or written to ‘0’. This device has additional registers that are reserved for test and calibration. If these registers are accessed, the device may not perform according to the specification. bit 2-0 Pointer Bits: 000 = Capability register 001 = Configuration register (CONFIG) 010 = Event Temperature Upper-Boundary Trip register (TUPPER) 011 = Event Temperature Lower-Boundary Trip register (TLOWER) 100 = Critical Temperature Trip register (TCRIT) 101 = Temperature register (TA) 110 = Manufacturer ID register 111 = Device ID/Revision register Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ - n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared © 2005 Microchip Technology Inc. x = Bit is unknown DS21977B-page 9 MCP9805 4.1.1 CAPABILITY REGISTER This is a read-only register used to identify the temperature sensor capability. In this case, the MCP9805 is capable of providing temperature at 0.25°C resolution, measuring temperature below and above 0°C, providing ±1°C and ±2°C accuracy over the active and monitor temperature ranges (respectively) and providing user-programmable temperature event boundary trip limits. Register 4-2 describes the Capability register. These functions are described in further detail in the following sections. REGISTER 4-2: Upper-Half: U-0 — bit 15 CAPABILITY REGISTER (READ-ONLY) U-0 — U-0 — Lower-Half: U-0 U-0 — U-0 — U-0 — U-0 → ADDRESS ‘0000 0000’b U-0 — U-0 — R-0 R-1 Resolution U-0 — bit 8 R-1 Meas. Range R-1 Accuracy bit 7 bit 15-5 bit 4-3 bit 2 bit 1 bit 0 R-1 Temp. Event bit 0 Unimplemented: Read as ‘0’ RESOLUTION bits: 00 = 0.5 °C/LSb 01 = 0.25 °C/LSb (default resolution) 10 = 0.125 °C/LSb 11 = 0.0625 °C/LSb TEMPERATURE MEASUREMENT RANGE (Meas. Range) bit: 0 = TA = 0x0000 (Hexadecimal) for temperature below 0°C 1 = The part can measure temperature below 0°C ACCURACY bit: 0 = Accuracy → ±2°C from +75°C to +95°C (Active Range) and ±3°C from +40°C to +125°C (Monitor Range) 1 = Accuracy → ±1°C from +75°C to +95°C (Active Range) and ±2°C from +40°C to +125°C (Monitor Range) BASIC CAPABILITY (Temp. Event) bit: 0 = No defined function (This bit will never be cleared or set to ‘0’). 1 = The part has temperature boundary trip limits (TUPPER/TLOWER/TCRIT registers) and a temperautre event output (JC 42.4 required feature). Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ - n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared DS21977B-page 10 x = Bit is unknown © 2005 Microchip Technology Inc. MCP9805 4.1.2 SENSOR CONFIGURATION REGISTER (CONFIG) The temperature hysteresis bits 10 and 9 can be used to prevent output chatter when the ambient temperature gradually changes beyond the user-specified temperature boundary (see Section 4.2.2 “Temperature Hysteresis (THYST)”. The Continuous Conversion or Shutdown mode is selected using bit 8. In Shutdown mode, the band gap temperature sensor circuit stops converting temperature and the Ambient Temperature register (TA) holds the previous successfully converted temperature data (see Section 4.2.1 “Shutdown Mode”). Bits 7 and 6 are used to lock the user-specified boundaries TUPPER, TLOWER and TCRIT to prevent an accidental rewrite. Bits 5 thru 0 are used to configure the temperature Event output pin. All functions are described in Register 4-3 (see Section 4.2.3 “Event Output Configuration”). The MCP9805 has a 16-bit Configuration register (CONFIG) that allows the user to set various functions for a robust temperature monitoring system. Bits 10 thru 0 are used to select Event output boundary hysteresis, device Shutdown or Low-Power mode, temperature boundary and critical temperature lock, temperature Event output enable/disable. In addition, the user can select the Event output condition (output set for TUPPER and TLOWER temperature boundary or TCRIT only), read Event output status and set Event output polarity and mode (Comparator Output or Interrupt Output mode). CONFIGURATION REGISTER (CONFIG) → ADDRESS ‘0000 0001’b REGISTER 4-3: Upper-Half: U-0 — bit 15 U-0 — U-0 — U-0 — Lower-Half: R/W-0 R/W-0 Crit. Lock Win. Lock R/W-0 Int. Clear U-0 — R/W-0 R/W-0 THYST R-0 R/W-0 Event Stat. Event Cnt. R/W-0 SHDN bit 8 R/W-0 Event Sel. R/W-0 Event Pol. bit 7 R/W-0 Event Mod. bit 0 bit 15-11 Unimplemented: Read as ‘0’ bit 10-9 Limit Hysteresis (THYST) bits: 00 = 0°C (power-up default) 01 = 1.5°C 10 = 3.0°C 11 = 6.0°C (Refer to Section 4.2.3 “Event Output Configuration”) bit 8 Shutdown Mode (SHDN) bit: 0 = Continuous Conversion (power-up default) 1 = Shutdown (Low-Power mode) In shutdown, all power-consuming activities are disabled, though all registers can be written to or read. This bit cannot be set ‘1’ when either of the lock bits is set (bit 6 and bit 7). However, it can be cleared ‘0’ for Continuous Conversion while locked. (Refer to Section 4.2.1 “Shutdown Mode”) bit 7 TCRIT Lock Bit (Crit. Lock) bit: 0 = Unlocked. TCRIT register can be written. (power-up default) 1 = Locked. TCRIT register cannot be written to. When enabled, this bit remains set ‘1’ or locked until cleared by internal reset (Section 4.3 “Summary of Power-up Default”). This bit does not require a double-write. . Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ - n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared © 2005 Microchip Technology Inc. x = Bit is unknown DS21977B-page 11 MCP9805 CONFIGURATION REGISTER (CONFIG) → ADDRESS ‘0000 0001’b (CONTINUED) REGISTER 4-3: Upper-Half: U-0 — bit 15 U-0 — U-0 — U-0 — Lower-Half: R/W-0 R/W-0 Crit. Lock Win. Lock R/W-0 Int. Clear U-0 — R/W-0 R/W-0 THYST R-0 R/W-0 Event Stat. Event Cnt. R/W-0 SHDN bit 8 R/W-0 Event Sel. R/W-0 Event Pol. bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 R/W-0 Event Mod. bit 0 TUPPER and TLOWER Boundary Window Lock (Win. Lock) bit: 0 = Unlocked. TUPPER and TLOWER registers can be written. (power-up default) 1 = Locked. TUPPER and TLOWER registers cannot be written. When enabled, this bit remains set ‘1’ or locked until cleared by internal reset (Section 4.3 “Summary of Power-up Default”). This bit does not require a double-write. Interrupt Clear (Int. Clear) bit: 0 = No effect. (power-up default) 1 = Clear interrupt output. When read this bit returns ‘0’. Event Output Status (Event Stat.) bit: 0 = Event output is not asserted by the device. (power-up default) 1 = Event output is asserted as a comparator/interrupt or critical temperature output. Event Output Control (Event Cnt.) bit: 0 = Disabled. (power-up default) 1 = Enabled. This bit can not be altered when either of the lock bits is set (bit 6 and bit 7). Event Output Select (Event Sel.) bit: 0 = Event output for TUPPER, TLOWER and TCRIT. (power-up default) 1 = TA ≥ TCRIT only. (TUPPER and TLOWER temperature boundaries are disabled.) When the Alarm Window Lock bit is set ‘1’ (bit 6), this bit cannot be altered until unlocked. Event Output Polarity (Event Pol.) bit: 0 = Active-low. (power-up default) 1 = Active-high. This bit cannot be altered when either of the lock bits is set (bit 6 and bit 7). Event Output Mode (Event Mod.) bit: 0 = Comparator output. (power-up default) 1 = Interrupt output. This bit cannot be altered when either of the lock bits is set (bit 6 and bit 7). . Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ - n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared DS21977B-page 12 x = Bit is unknown © 2005 Microchip Technology Inc. MCP9805 4.1.3 TEMPERATURE EVENT UPPER/LOWER/CRITICAL BOUNDARY TRIP REGISTERS (TUPPER/TLOWER/TCRIT) The MCP9805 has a 16-bit read/write Event output Temperature Upper-Boundary Trip register (TUPPER), a 16-bit Lower-Boundary Trip register (TLOWER) and a 16-bit Critical Boundary Trip register (TCRIT) that contains 11-bit data in two’s compliment format (0.25 °C/LSb). This data represents the maximum and minimum temperature boundary or temperature window that can be used to monitor ambient temperature. If this feature is enabled (Section 4.1.2 “Sensor Configuration Register (CONFIG)”) and the ambient temperature exceeds the specified boundary or window, the MCP9805 asserts an Event output. (Refer to Section 4.2.3 “Event Output Configuration”). REGISTER 4-4: Upper-Half: U-0 — bit 15 UPPER/LOWER/CRITICAL TEMPERATURE BOUNDARY TRIP REGISTERS (TUPPER/TLOWER/TCRIT) → ADDRESS ‘0000 0010’b/‘0000 0011’b/‘0000 0100’b U-0 — U-0 — R/W-0 SIGN bit 11-2 bit 1-0 R/W-0 R/W-0 R/W-0 26 °C/LSb 25 °C/LSb 24 °C/LSb bit 8 Lower-Half: R/W-0 R/W-0 23 °C/LSb 22 °C/LSb bit 7 bit 15-13 bit 12 R/W-0 27 °C/LSb R/W-0 21 °C/LSb R/W-0 20 °C/LSb R/W-0 R/W-0 2-1 °C/LSb 2-2 °C/LSb U-0 — U-0 — bit 0 Unimplemented: Read as ‘0’ SIGN bit: 0 = TA ≥ 0°C 1 = TA < 0°C TUPPER/TLOWER/TCRIT bits: Temperature boundary trip data in two’s compliment format. Unimplemented: Read as ‘0’ Note: This table reflects the three 16-bit registers TUPPER, TLOWER and TCRIT located at address ‘0000 0010’b, ‘0000 0011’b and ‘0000 0100’b, respectively (see Register 4-1). Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = bit is set ‘0’ = bit is cleared © 2005 Microchip Technology Inc. x = bit is unknown DS21977B-page 13 MCP9805 4.1.4 AMBIENT TEMPERATURE REGISTER (TA) EQUATION 4-1: The MCP9805 uses a band gap temperature sensor circuit to output analog voltage proportional to absolute temperature. An internal ΔΣ ADC is used to convert the analog voltage to a digital word. The converter resolution is set to 0.25 °C/LSb + sign (11-bit data). The digital word is loaded to a 16-bit read-only Ambient Temperature register (TA) that contains 11-bit temperature data in two’s complement format. DECIMAL CODE TO TEMPERATURE CONVERSION T A = Code × 2 –2 Where: TA = Ambient Temperature (°C) Code = MCP9805 output magnitude in decimal The TA register bits (bits 12 thru 0) are double-buffered. Therefore, the user can access the register while, in the background, the MCP9805 performs an analog-to-digital conversion of the band gap temperature sensor. The temperature data from the ΔΣ ADC is loaded in parallel to TA at tCONV refresh rate. In addition, the TA register uses three bits (bits 15, 14 and 13) to reflect the Event pin state. This allows the user to identify the cause of the Event output trigger (see Section 4.2.3 “Event Output Configuration”); bit 15 is set to ‘1’ if TA is greater than or equal to TCRIT, bit 14 is set to ‘1’ if TA is greater than TUPPER and bit 13 is set to ‘1’ if TA is less than TLOWER. The TA magnitude in decimal to ambient temperature conversion is shown in Equation 4-1: The TA register bit assignment and boundary conditions are described in Register 4-5. AMBIENT TEMPERATURE REGISTER (TA) → ADDRESS ‘0000 0101’b REGISTER 4-5: Upper-Half: R-0 TA Vs. TCRIT bit 15 R-0 R-0 TA Vs. TUPPER TA Vs. TLOWER R-0 SIGN R-0 R-0 R-0 R-0 27 °C/LSb 26 °C/LSb 25 °C/LSb 24 °C/LSb bit 8 Lower-Half: R-0 R-0 23 °C/LSb 22 °C/LSb bit 7 R-0 21 °C/LSb R-0 20 °C/LSb R-0 R-0 2-1 °C/LSb 2-2 °C/LSb U-0 —(2) U-0 — bit 0 TA vs. TCRIT(1) bit: 0 = TA < TCRIT 1 = TA ≥ TCRIT bit 14 TA vs. TUPPER(1) bit: 0 = TA ≤ TUPPER 1 = TA > TUPPER bit 13 TA vs. TLOWER(1) bit: 0 = TA ≥ TLOWER 1 = TA < TLOWER bit 12 SIGN bit: 0 = TA ≥ 0°C 1 = TA < 0°C Note 1: Not affected by the status of the Event output configuration (bits 5 to 0 of CONFIG) and THYST = 0°C, Register 4-3. bit 15 2: Bit 1 may remain set ‘1’ for some devices indicating 2-3 °C/LSb or 0.125°C temperature resolution, depending on the state of the device calibration code. Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = bit is set ‘0’ = bit is cleared DS21977B-page 14 x = bit is unknown © 2005 Microchip Technology Inc. MCP9805 AMBIENT TEMPERATURE REGISTER (TA) → ADDRESS ‘0000 0101’b (CONTINUED) REGISTER 4-5: Upper-Half: R-0 TA Vs. TCRIT bit 15 R-0 R-0 TA Vs. TUPPER TA Vs. TLOWER Lower-Half: R-0 R-0 3 2 2 °C/LSb 2 °C/LSb bit 7 R-0 2 °C/LSb 1 R-0 SIGN R-0 R-0 R-0 R-0 27 °C/LSb 26 °C/LSb 25 °C/LSb 24 °C/LSb bit 8 R-0 2 °C/LSb 0 R-0 R-0 -2 2 °C/LSb 2 °C/LSb -1 U-0 —(2) U-0 — bit 0 bit 11-2 Ambient Temperature (TA) bits: 10-bit Ambient Temperature data in two’s compliment format. bit 1, 0 Unimplemented: Read as ‘0’ (Note 2) Note 1: Not affected by the status of the Event output configuration (bits 5 to 0 of CONFIG) and THYST = 0°C, Register 4-3. 2: Bit 1 may remain set ‘1’ for some devices indicating 2-3 °C/LSb or 0.125°C temperature resolution, depending on the state of the device calibration code. Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = bit is set ‘0’ = bit is cleared © 2005 Microchip Technology Inc. x = bit is unknown DS21977B-page 15 MCP9805 4.1.5 MANUFACTURER ID REGISTER This register is used to identify the device manufacturer in order to perform manufacturer-specific operations. The manufacturer ID for the MCP9805 is 0x0054 (hexadecimal). MANUFACTURER ID REGISTER (READ-ONLY) → ADDRESS ‘0000 0110’b REGISTER 4-1: Upper-Half: R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0 Manufacturer ID bit 15 bit 8 Lower-Half: R-0 R-1 R-0 R-1 R-0 R-1 R-0 R-0 Manufacturer ID bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ - n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared 4.1.6 DEVICE ID AND REVISION REGISTER x = Bit is unknown The revision begins with 0x00 (hex) for the first release, with the number being incremented as revised versions are released. The upper byte of this register is used to specify the device identification and the lower byte is used to specify device revision. The device ID for the MCP9805 is 0x00 (hex). DEVICE ID AND DEVICE REVISION (READ-ONLY) → ADDRESS ‘0000 0111’b REGISTER 4-2: Upper-Half: R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0 Device ID bit 15 bit 8 Lower-Half: R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0 Device Revision bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ - n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared DS21977B-page 16 x = Bit is unknown © 2005 Microchip Technology Inc. MCP9805 4.2 4.2.1 Sensor Feature Description SHUTDOWN MODE Shutdown mode disables all power-consuming activities (including temperature sampling operations) while leaving the serial interface active. This mode is selected by setting bit 8 of CONFIG to ‘1’. In this mode, the device consumes ISHDN. It remains in this mode until bit 8 is cleared ‘0’ to enable Continuous Conversion mode, or until power is recycled. The Shutdown bit (bit 8) cannot be set to ‘1’ while bits 6 and 7 of CONFIG (Lock bits) are set to ‘1’. However, it can be cleared ‘0’ or returned to Continuous Conversion while locked. In Shutdown mode, all registers can be read or written. However, the serial bus activity increases the shutdown current. In addition, if the device is shutdown while the Event pin is asserted as active-low or deasserted active-low (see Section 220.127.116.11 “Comparator Mode” and Section 18.104.22.168 “Interrupt Mode”), the device will retain the active-low state. This increases the shutdown current due to the additional Event output pull-down current. 4.2.2 TEMPERATURE HYSTERESIS (THYST) A hysteresis of 0°C, 1.5°C, 3°C or 6°C can be selected for the TUPPER, TLOWER and TCRIT temperate boundaries using bits 10 and 9 of CONFIG. The hysteresis applies for decreasing temperature only (hot to cold), or as temperature drifts below the specified limit. The TUPPER, TLOWER and TCRIT boundary conditions are described graphically in Figure 4-2. 4.2.3 EVENT OUTPUT CONFIGURATION The Event output can be enabled using bit 3 of CONFIG (Event output control bit) and can be configured as either a comparator output or as Interrupt Output mode using bit 0 of CONFIG (Event mode). The polarity can also be specified as an active-high or active-low using bit 1 of CONFIG (Event polarity). The Event output can also be used as a critical temperature output using bit 2 of CONFIG (critical output only). When this feature is selected, the Event output becomes a comparator output. In this mode, the interrupt output configuration (bit 0 of CONFIG) is ignored. 22.214.171.124 Comparator Mode Comparator mode is selected using bit 0 of CONFIG. In this mode, the Event output is asserted as active-high or active-low using bit 1 of CONFIG. Figure 4-2 shows the conditions that toggle the Event output. If the device enters Shutdown mode with asserted Event output, the output remains asserted during Shutdown. The device must be operating in Continuous Conversion mode for tCONV; the TA vs. TUPPER, TLOWER and TCRIT boundary conditions need to be satisfied in order for the Event output to deassert. Comparator mode is useful for thermostat-type applications, such as turning on a cooling fan or triggering a system shutdown when the temperature exceeds a safe operating range. 126.96.36.199 Interrupt Mode Interrupt mode is selected using bit 0 of CONFIG. In this mode, the Event output is asserted as active-high or active-low using bit 1 of CONFIG. The output is deasserted by setting ‘1’ to bit 5 of CONFIG (interrupt clear). Shutting down the device will not reset or deassert the Event output. However, clearing the interrupt using bit 5 of CONFIG while in Shutdown mode will deassert the Event output. This mode is ignored when the Event output is used as critical temperature output only (bit 2 of CONFIG). Interrupt mode applies to interrupt-driven, microcontroller-based systems. The microcontroller receiving the interrupt will have to acknowledge the interrupt by setting ‘1’ to bit 5 of CONFIG. When the ambient temperature increases above the critical temperature limit, the Event output is forced to a comparator output (regardless of bit 0 of CONFIG). When the temperature drifts below the critical temperature limit, the Event output automatically returns to the state specified by bit 0 of CONFIG. The status of the Event output can be read using bit 4 of CONFIG (Event status). Bit 7 and 6 of the CONFIG register can be used to lock the TUPPER, TLOWER and TCRIT registers. The bits prevent false triggers at the Event output due to an accidental rewrite to these registers. © 2005 Microchip Technology Inc. DS21977B-page 17 MCP9805 TCRIT - THYST TCRIT TUPPER - THYST TUPPER - THYST TUPPER TA TLOWER -THYST TLOWER TLOWER -THYST (Active-Low) Event Output Comparator Interrupt S/W Int. Clear Critical Note: 1 Event Output Boundary Conditions Note 1 2 3 4 5 6 * 1 3 2 4 3 5 * 6 4 TA bits Event Output Comparator Interrupt 2 Critical 15 14 13 H L H 0 0 0 TA ≥ TLOWER L L H 0 0 1 TA < TLOWER - THYST TA > TUPPER L L H 0 1 0 H L H 0 0 0 TA ≤ TUPPER - THYST TA ≥ TCRIT L L L 1 0 0 TA < TCRIT - THYST L H H 0 1 0 When TA ≥ TCRIT and TA < TCRIT - THYST, the Event output is in Comparator mode and bit 0 of CONFIG (Interrupt mode) is ignored. FIGURE 4-2: DS21977B-page 18 Event Output Boundary Conditions. © 2005 Microchip Technology Inc. MCP9805 4.3 Summary of Power-up Default The MCP9805 has an internal Power-on Reset (POR) circuit. If the power supply voltage VDD drifts below the VPOR threshold, the device resets the registers to the power-up default settings. Table 4-6 shows the power-up default summary. TABLE 4-6: POWER-UP DEFAULTS Registers Address (Hex) Register Label Default Register Data (Hex) 0x00 Capability 0x000F 0x01 CONFIG 0x0000 0x02 0x03 0x04 0x05 0x06 0x07 TUPPER TLOWER TCRIT TA Manufacturer ID Device ID/Device Revision 0x0000 0x0000 0x0000 0x0000 0x0054 0x0000 © 2005 Microchip Technology Inc. Power-up Default Register Description 0.25 °C/LSb Measures Temperature Below 0°C ±1°C Accuracy Over Active Range Basic Capability (Event output) Comparator Mode Active-Low Output Event and Critical output Output Enabled Event Not Asserted Interrupt Cleared Event Limits Unlocked Critical Limit Unlocked Continuous Conversion 0°C Hysteresis 0°C 0°C 0°C 0°C 0x0054 (hex) 0x0000 (hex) DS21977B-page 19 MCP9805 5.0 SERIAL COMMUNICATION 5.1.1 5.1 2-Wire SMBus/Standard Mode I2C™ Protocol-Compatible Interface Data transfers are initiated by a Start condition (START), followed by a 7-bit device address and a read/write bit. An Acknowledge (ACK) from the slave confirms the reception of each byte. Each access must be terminated by a Stop condition (STOP). The MCP9805 serial clock input (SCLK) and the bidirectional serial data line (SDA) form a 2-Wire bidirectional SMBus/Standard mode I2C compatible communication port (refer to the Digital Input/Output Pin Characteristics Table and Serial Interface Timing Characteristics Table). The following bus protocol has been defined: TABLE 5-1: MCP9805 SERIAL BUS PROTOCOL DESCRIPTIONS Term Master Slave Description The device that controls the serial bus, typically a microcontroller. The device addressed by the master, such as the MCP9805. Transmitter Device sending data to the bus. Receiver Device receiving data from the bus. START A unique signal from master to initiate serial interface with a slave. STOP A unique signal from the master to terminate serial interface from a slave. Read/Write A read or write to the MCP9805 registers. ACK A receiver Acknowledges (ACK) the reception of each byte by polling the bus. NAK A receiver Not-Acknowledges (NAK) or releases the bus to show End-of-Data (EOD). Busy Communication is not possible because the bus is in use. Not Busy The bus is in the idle state, both SDA and SCLK remain high. Data Valid SDA must remain stable before SCLK becomes high in order for a data bit to be considered valid. During normal data transfers, SDA only changes state while SCLK is low. DS21977B-page 20 DATA TRANSFER Repeated communication is initiated after tB-FREE. This device does not support sequential register read/write. Each register needs to be addressed using the Register Pointer. This device supports the receive protocol. The register can be specified using the pointer for the initial read (see Figure 5-4). Each repeated read or receive can then be followed with a Start condition, followed by an address byte. The MCP9805 retains the previously selected register. Therefore, it expects a read from the previously-specified register (repeated pointer specification is not necessary). 5.1.2 MASTER/SLAVE The bus is controlled by a master device (typically a microcontroller) that controls the bus access and generates the Start and Stop conditions. The MCP9805 is a slave device and does not control other devices in the bus. Both master and slave devices can operate as either transmitter or receiver. However, the master device determines which mode is activated. 5.1.3 START/STOP CONDITION A high-to-low transition of the SDA line (while SCLK is high) is the Start condition. All data transfers must be preceded by a Start condition from the master. If a Start condition is generated during data transfer, the MCP9805 resets and accepts the new Start condition. A low-to-high transition of the SDA line (while SCLK is high) signifies a Stop condition. If a Stop condition is introduced during data transmission, the MCP9805 releases the bus. All data transfers are ended by a Stop condition from the master. However, for continuous data reception from the previously-specified pointer (Register 4-1), a Start condition can be introduced at the end of data reception. The MCP9805 retains the previously-set pointer. Therefore, there is no need to repeat the pointer specification (see Register 5-4). 5.1.4 ADDRESS BYTE Following the Start condition, the host must transmit an 8-bit address byte to the MCP9805. The address for the MCP9805 is ‘0011,A2,A1,A0’ in binary, where the A2, A1 and A0 bits are set externally by connecting the corresponding pins to VDD ‘1’ or GND ‘0’. The 7-bit address transmitted in the serial bit stream must match the selected address for the MCP9805 to respond with an ACK. Bit 8 in the address byte is a read/write bit. Setting this bit to ‘1’ commands a read operation, while ‘0’ commands a write operation (see Figure 5-1). © 2005 Microchip Technology Inc. MCP9805 5.1.6 ACKNOWLEDGE (ACK) Address Byte SCLK 1 2 3 4 5 6 7 SDA 0 0 1 1 A2 A1 A0 8 9 A C K Start Address Code Slave Address R/W MCP9805 Response FIGURE 5-1: 5.1.5 Device Addressing. DATA VALID After the Start condition, each bit of data in transmission needs to be settled for a time specified by tSU-DATA before SCLK toggles from low-to-high (see Serial Interface Timing Characteristics). © 2005 Microchip Technology Inc. Each receiving device, when addressed, is obliged to generate an ACK bit after the reception of each byte. The master device must generate an extra clock pulse for ACK to be recognized. The acknowledging device pulls down the SDA line for tSU-DATA before the low-to-high transition of SCLK from the master. SDA also needs to remain pulled down for tH-DATA after a high-to-low transition of SCLK. During read, the master must signal an End-of-Data (EOD) to the slave by not generating an ACK bit (NAK) once the last bit has been clocked out of the slave. In this case, the slave will leave the data line released to enable the master to generate the Stop condition. 5.1.7 TIME OUT If the SCLK stays high or low for a time specified by tOUT, the MCP9805 releases the bus and resets the serial interface. The master will have to restart the communication cycle with a Start condition. This dictates the minimum clock speed. DS21977B-page 21 MCP9805 5.2 Timing Diagram Read 1-byte Data 1 2 3 4 5 6 7 8 0 0 1 1 A 2 A 1 A 0 W C K 1 2 3 4 5 6 7 8 0 0 0 0 0 P 2 P 1 P 0 SCLK SDA S A Address Byte A C K Pointer MCP9805 MCP9805 1 2 3 4 5 6 7 8 0 0 1 1 A 2 A 1 A 0 R C 1 2 3 4 5 6 7 8 D 7 D 6 D 5 D 4 D 3 D 2 D 1 D 0 SCLK SDA S A K Address Byte N A K P Data Master MCP9805 Read 2-byte Data 1 2 3 4 5 6 7 8 0 0 1 1 A 2 A 1 A 0 W C K 1 2 3 4 5 6 7 8 0 0 0 0 0 P 2 P 1 P 0 SCLK SDA S A Address Byte A C K Pointer MCP9805 MCP9805 1 2 3 4 5 6 7 0 0 1 1 A 2 A 1 A 0 8 1 2 3 4 5 6 7 8 D D D D D D K 15 14 13 12 11 10 9 D 8 1 2 3 4 5 6 7 8 D 7 D 6 D 5 D 4 D 3 D 2 D 1 D 0 SCLK SDA S A R C D A C K MSb Data Address Byte MCP9805 N A K P LSb Data Master Master S = START Condition P = STOP Condition FIGURE 5-2: DS21977B-page 22 Read 1-byte and 2-byte data from a Register. © 2005 Microchip Technology Inc. MCP9805 Write 1-byte Data 1 2 3 4 5 6 7 8 0 0 1 1 A 2 A 1 A 0 W C 1 2 3 4 5 6 7 8 0 0 0 0 0 P 2 P 1 P 0 1 2 3 4 5 6 7 8 D 7 D 6 D 5 D 4 D 3 D 2 D 1 D 0 SCLK SDA S A K Address Byte A C K Pointer A C K P Data MCP9805 MCP9805 MCP9805 Write 2-byte Data 1 2 3 4 5 6 7 8 0 0 1 1 A 2 A 1 A 0 W C 1 2 3 4 5 6 7 8 0 0 0 0 0 P 2 P 1 P 0 SCLK SDA S A K Address Byte Pointer MCP9805 MCP9805 1 A C K 2 3 4 5 6 7 8 D D D D D D D 15 14 13 12 11 10 9 D 8 1 A C K 2 3 4 5 6 7 8 D D 7 6 D 5 D 4 D 3 D 2 D 1 D 0 MSb Data A C K P LSb Data MCP9805 MCP9805 S = START Condition P = STOP Condition FIGURE 5-3: Write 1-byte and 2-byte data from a Register. © 2005 Microchip Technology Inc. DS21977B-page 23 MCP9805 Register Pointer Setting for Continuous Reception(Note) 1 2 3 4 5 6 7 8 0 0 1 1 A 2 A 1 A 0 W C K 1 2 3 4 5 6 7 8 0 0 0 0 0 P 2 P 1 P 0 SCLK SDA S A Address Byte A C K Pointer MCP9805 MCP9805 Receive 1-byte Data 1 2 3 4 5 6 7 8 0 0 1 1 A 2 A 1 A 0 R C 1 2 3 4 5 6 7 8 D 7 D 6 D 5 D 4 D 3 D 2 D 1 D 0 SCLK SDA S A K Address Byte N A K Data Master MCP9805 Receive Another 1-byte Data 1 2 3 4 5 6 7 8 0 0 1 1 A 2 A 1 A 0 R C 1 2 3 4 5 6 7 8 D 7 D 6 D 5 D 4 D 3 D 2 D 1 D 0 SCLK SDA S A K Address Byte Data MCP9805 Note: N A K Master User can continue to receive 1-byte or 2-byte data (depending on the specific register) indefinitely from a previously-set Register Pointer. This device does not support sequential read/write. S = START Condition P = STOP Condition FIGURE 5-4: DS21977B-page 24 Receive 1-byte Data from Previously Set Pointer. © 2005 Microchip Technology Inc. MCP9805 6.0 APPLICATIONS INFORMATION 6.1 Connecting to the Serial Bus The SDA and SCLK serial interface pins are open-drain pins that require pull-up resistors. This configuration is shown in Figure 6-1. Microcontroller VDD MCP9805 R R R SDA SCLK Event Master FIGURE 6-1: Interface. Slave Pull-up Resistors On Serial The number of devices connected to the bus is limited only by the maximum rise and fall times of the SDA and SCLK lines. Unlike I2C specifications, SMBus does not specify a maximum bus capacitance value. Rather, the SMBus specification requires that the maximum current through the pull-up resistor be 350 µA and minimum 100 µA. Because of this, the value of the pull-up resistors will vary depending on the system’s bias voltage (VDD). The pull-up resistor values for a 3.3 V system ranges 9 kΩ to 33 kΩ. Minimizing bus capacitance is still very important as it directly affects the rise and fall times of the SDA and SCLK lines. Although SMBus specifications only require the SDA and SCLK lines to pull-down 350 µA, with a maximum voltage drop of 0.4 V, the MCP9805 is designed to meet a maximum voltage drop of 0.4 V, with 3 mA of current. This allows lower pull-up resistor values to be used, allowing the MCP9805 to handle higher bus capacitance. In such applications, all devices on the bus must meet the same pull-down current requirements. A possible configuration using multiple devices on the SMBus is shown in Figure 6-2. 6.2 Layout Considerations The MCP9805 does not require any additional components besides the master controller in order to measure temperature. However, it is recommended that a decoupling capacitor of 0.1 µF to 1 µF be used between the VDD and GND pins. A high-frequency ceramic capacitor is recommended. It is necessary for the capacitor to be located as close as possible to the power and ground pins of the device in order to provide effective noise protection. 6.3 Thermal Considerations A potential for self-heating errors can exist if the MCP9805 SDA, SCLK and Event lines are heavily loaded with pull-ups (high current). Typically, the self-heating error is negligible because of the relatively small current consumption of the MCP9805. A temperature accuracy error of approximately 0.5°C could result from self-heating if the communication pins sink/source the maximum current specified. For example, if the Event output is loaded to maximum IOL, Equation 6-1 can be used to determine the effect of self-heating. EQUATION 6-1: T Δ EFFECT OF SELF-HEATING = θ JA ( V DD • I DD + V OL_Event • I OL_Event + VOL_SDA • IOL_SDA ) Where: TΔ = TJ - TA TJ = Junction Temperature TA = Ambient Temperature θJA = Package Thermal Resistance VOL_Event, SDA = Event and SDA Output VOL (0.4 Vmax) IOL_Event, SDA = Event and SDA Output IOL (3 mAmax) At room temperature (TA = +25°C) with maximum IDD = 500 µA and VDD = 3.6V, the self-heating due to power dissipation TΔ is 0.2°C for the DFN-8 package and 0.5°C for the TSSOP-8 package. SDA SCLK MCP9805 24LCS52 Temperature Sensor FIGURE 6-2: SMBus. EEPROM Multiple Devices on DIMM © 2005 Microchip Technology Inc. DS21977B-page 25 MCP9805 7.0 PACKAGING INFORMATION 7.1 Package Marking Information 8-Lead DFN (MC) XXX YWW NN ABA 536 56 8-Lead TSSOP (ST) XXXX 805B 0536 NNN 256 e3 * DS21977B-page 26 Example: YYWW Legend: XX...X Y YY WW NNN Note: Example: Customer-specific information Year code (last digit of calendar year) Year code (last 2 digits of calendar year) Week code (week of January 1 is week ‘01’) Alphanumeric traceability code Pb-free JEDEC designator for Matte Tin (Sn) This package is Pb-free. The Pb-free JEDEC designator ( e3 ) can be found on the outer packaging for this package. In the event the full Microchip part number cannot be marked on one line, it will be carried over to the next line, thus limiting the number of available characters for customer-specific information. © 2005 Microchip Technology Inc. MCP9805 8-Lead Plastic Dual Flat No-Lead Package (MC) 2x3x0.9 mm Body (DFN) – Saw Singulated b D p n L K E2 E EXPOSED METAL PAD (NOTE 2) PIN 1 ID INDEX AREA (NOTE 1) 2 DETAIL ALTERNATE CONTACT CONFIGURATION TOP VIEW A1 Units n MILLIMETERS* INCHES MIN Number of Pins BOTTOM VIEW EXPOSED TIE BAR (NOTE 3) A A3 Dimension Limits 1 D2 NOM MAX MIN MAX NOM 8 8 Pitch e Overall Height A .031 .035 .039 0.80 0.90 1.00 Standoff A1 .000 .001 .002 0.00 0.02 0.05 Contact Thickness A3 .008 REF. 0.20 REF. Overall Length D .079 BSC 2.00 BSC Overall Width E .118 BSC 0.50 BSC .020 BSC 3.00 BSC Exposed Pad Length D2 .051 – .069 1.30** – 1.75 Exposed Pad Width E2 .059 – .075 1.50** – 1.90 L .012 K .008 b .008 Contact Length § Contact-to-Exposed Pad Contact Width § .016 .020 – .010 – .012 * Controlling Parameter ** Not within JEDEC parameters § Significant Characteristic Notes: 1. Pin 1 visual index feature may vary, but must be located within the hatched area. 2. Exposed pad may vary according to die attach paddle size. 3. Package may have one or more exposed tie bars at ends. BSC: Basic Dimension. Theoretically exact value shown without tolerances. See ASME Y14.5M REF: Reference Dimension, usually without tolerance, for information purposes only. See ASME Y14.5M JEDEC Equivalent MO-229 VCED-2 DWG No. C04-123 © 2005 Microchip Technology Inc. 0.30 0.20 0.20 0.40 0.50 – – 0.25 0.30 Revised 09-12-05 DS21977B-page 27 MCP9805 8-Lead Plastic Thin Shrink Small Outline (ST) – 4.4 mm Body (TSSOP) E E1 p D 2 1 n B α A c β φ L Units Dimension Limits A2 A1 MILLIMETERS* INCHES MIN NOM MAX MIN NOM MAX Pitch n p Overall Height A .039 .041 .043 1.00 1.05 1.10 Molded Package Thickness A2 .033 .035 .037 0.85 0.90 0.95 Number of Pins 8 8 .026 0.65 Standoff A1 .002 .004 .006 0.05 0.10 0.15 Overall Width E .246 .251 .256 6.25 6.38 6.50 Molded Package Width E1 .169 .173 .177 4.30 4.40 4.50 Molded Package Length D .114 .118 .122 2.90 3.00 3.10 Foot Length L φ .020 .024 .028 0.50 0.60 0.70 Foot Angle Lead Thickness c .004 .006 .008 0.09 0.15 0.20 Lead Width B α .007 .010 .012 0.19 0.25 0.30 Mold Draft Angle Top Mold Draft Angle Bottom β 0° 4° 8° 0° 4° 8° 0° 5° 10° 0° 5° 10° 0° 5° 10° 0° 5° 10° * Controlling Parameter Notes: Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed .005" (0.127mm) per side. JEDEC Equivalent: MO-153 Drawing No. C04-086 DS21977B-page 28 Revised 07-21-05 © 2005 Microchip Technology Inc. MCP9805 APPENDIX A: REVISION HISTORY Revision B (September 2005) • Added the text “for Mobile Platform Memory Module Thermal Sensor” to first bullet under Features section. Revision A (September 2005) • Original Release of this Document. © 2005 Microchip Technology Inc. DS21977B-page 29 MCP9805 NOTES: DS21977B-page 30 © 2005 Microchip Technology Inc. MCP9805 PRODUCT IDENTIFICATION SYSTEM To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office. PART NO. –X X /XX Device Grade Temperature Range Package Examples: a) b) Device: MCP9805: Digital Temperature Sensor MCP9805T: Digital Temperature Sensor (Tape and Reel) Grade: B B B = ±1°C (max.) from +75°C to +95°C, ±2°C (max.) from +40°C to +125°C, and ±3°C (max.) from -20°C to +125°C Temperature Range: E = -40°C to +125°C Package: MC = Dual Flat No Lead (2x3 mm Body), 8-lead ST = Plastic Thin Shrink Small Outline (4x4 mm Body), 8-lead © 2005 Microchip Technology Inc. c) MCP9805T-BE/MC: Tape and Reel, Extended Temp., 8LD DFN pkg. MCP9805-BE/ST: Extended Temp., 8LD TSSOP pkg. MCP9805T-BE/ST: Tape and Reel, Extended Temp., 8LD TSSOP pkg. DS21977B-page 31 MCP9805 NOTES: DS21977B-page 32 © 2005 Microchip Technology Inc. Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property. • Microchip is willing to work with the customer who is concerned about the integrity of their code. • Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as “unbreakable.” Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act. Information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. Microchip disclaims all liability arising from this information and its use. Use of Microchip’s products as critical components in life support systems is not authorized except with express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights. Trademarks The Microchip name and logo, the Microchip logo, Accuron, dsPIC, KEELOQ, microID, MPLAB, PIC, PICmicro, PICSTART, PRO MATE, PowerSmart, rfPIC, and SmartShunt are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. AmpLab, FilterLab, Migratable Memory, MXDEV, MXLAB, PICMASTER, SEEVAL, SmartSensor and The Embedded Control Solutions Company are registered trademarks of Microchip Technology Incorporated in the U.S.A. Analog-for-the-Digital Age, Application Maestro, dsPICDEM, dsPICDEM.net, dsPICworks, ECAN, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP, ICEPIC, Linear Active Thermistor, MPASM, MPLIB, MPLINK, MPSIM, PICkit, PICDEM, PICDEM.net, PICLAB, PICtail, PowerCal, PowerInfo, PowerMate, PowerTool, rfLAB, rfPICDEM, Select Mode, Smart Serial, SmartTel, Total Endurance and WiperLock are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. SQTP is a service mark of Microchip Technology Incorporated in the U.S.A. All other trademarks mentioned herein are property of their respective companies. © 2005, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved. Printed on recycled paper. Microchip received ISO/TS-16949:2002 quality system certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona and Mountain View, California in October 2003. The Company’s quality system processes and procedures are for its PICmicro® 8-bit MCUs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory and analog products. In addition, Microchip’s quality system for the design and manufacture of development systems is ISO 9001:2000 certified. © 2005 Microchip Technology Inc. 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