19-3378; Rev 2; 10/07 FireWire Current Limiter and Low-Drop ORing Switch Controller The MAX5943 is a fully integrated power-management IC for FireWire® applications. This device controls two external power n-channel MOSFETs to regulate current from the input power supply to the load and performs low-voltage-drop, power-supply ORing. The MAX5943 operates over a 7.5V to 37V input range and provides inrush and output current limit in addition to a diode ORing function suitable for FireWire applications. The MAX5943 FireWire/IEEE 1394™ protective circuit (Figure 12) is UL® recognized. The MAX5943 allows the safe insertion and removal of FireWire peripherals into a live FireWire port by providing inrush current control and an output current-limiting function. The ORing feature provides a very efficient way to protect the FireWire port when connected to another FireWire peripheral that sources a higher voltage. By turning off both external MOSFETS, the MAX5943 provides a true bidirectional load disconnect. A low-current shutdown mode disables the MAX5943, resulting in less than 10µA supply current. A pin-selectable input allows latched or autoretry fault management after a fault. The MAX5943A features a current-limit function that actively limits the current drawn by the load with a programmable timeout. The MAX5943B–MAX5943E do not actively limit the load current but provide a circuit-breaker function. See the Selector Guide for the default and programmable circuit-breaker timeouts. The MAX5943 operates over the -40°C to +85°C extended temperature range and is available in a 16-pin QSOP package. Applications FireWire Desktop/Notebook Port Features o Provides Safe Hot Swap for 7.5V to 37V Power Supplies o UL-Recognized FireWire/IEEE 1394 Protective Circuit o Low-Drop Power ORing with Ultra-Fast Turn-Off o Programmable Active Current Limit (MAX5943A) o Programmable Circuit Breaker (MAX5943B–MAX5943E) o ±5% Current-Limit Sensing Accuracy o Programmable Current-Limit/Circuit-Breaker Timeout o Fast Current-Limit Response to Output ShortCircuit Conditions (MAX5943A) o Drives External N-Channel Power MOSFETs o Overcurrent Fault Status Output o Latched or Autoretry Overcurrent Fault Management o 10µA Shutdown Current o ON/OFF Control Allows Undervoltage Lockout Programming o Fast Load Disconnect Control Through ON Input Ordering Information PART TEMP RANGE PIN-PACKAGE MAX5943AEEE -40°C to +85°C 16 QSOP MAX5943BEEE -40°C to +85°C 16 QSOP MAX5943CEEE -40°C to +85°C 16 QSOP MAX5943DEEE -40°C to +85°C 16 QSOP MAX5943EEEE -40°C to +85°C 16 QSOP FireWire Peripheral Device Current Limit Pin Configuration FireWire Hub Hot Swap TOP VIEW ON 1 16 IN FAULT 2 15 SENSE TIM 3 ILIM 4 Typical Operating Circuit and Selector Guide appear at end of data sheet. FireWire is a registered trademark of Apple Computers, Inc. IEEE 1394 is a trademark of the Institute of Electrical and Electronics Engineers trademark. UL is a registered trademark of Underwriters Laboratories, Inc. 14 GATE1 MAX5943 LATCH 5 13 N.C. 12 GATE2 OR_ADJ 6 11 OUT N.C. 7 10 N.C. ONQ1 8 9 GND QSOP ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX5943 General Description MAX5943 FireWire Current Limiter and Low-Drop ORing Switch Controller ABSOLUTE MAXIMUM RATINGS (Voltages referenced to GND, unless otherwise noted.) IN ............................................................................-0.3V to +80V OUT ........................................................................-0.3V to +80V SENSE to IN..............................................................-1V to +0.3V GATE1 to SENSE......................................................-0.3V to +8V GATE2 to OUT (internally clamped).........................-0.3V to +8V FAULT.....................................................................-0.3V to +85V ON, TIM, ILIM, LATCH, OR_ADJ, ONQ1 ..........-0.3V to (IN + 0.3V) Continuous Power Dissipation (TA = +70°C) 16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW Operating Temperature Range ...........................-40°C to +85°C Maximum Junction Temperature .....................................+150°C Storage Temperature Range .............................-60°C to +150°C ESD Rating (Human Body Model)......................................2000V Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN = 7.5V to 37V, GND = 0V, and TA = -40°C to +85°C, unless otherwise noted. Typical values are at VIN = 12V, TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 37 V 1.3 2.3 mA 5 10 µA 6.5 6.8 V SUPPLIES Supply Voltage Range VIN Supply Current IIN VON = 3V, no load Shutdown Current ISD VON = 0.4V IN Default Undervoltage Lockout VUVLO 7.5 VIN rising, ON = IN 6.2 IN Default Undervoltage Lockout Hysteresis ON Undervoltage Lockout Threshold 0.35 VON_REF VON rising 1.20 ON Undervoltage Lockout Threshold Hysteresis ON Input Bias Current 1.24 V 1.275 70 ION V mV 1 µA GATE2 (current-limit/circuit-breaker control) GATE2 Pullup Current IG2U (Note 2) GATE2 High Voltage VG2 VGATE2 - VOUT Current-Limit/Circuit-Breaker Threshold Voltage VTH VIN - VSENSE Fast Pulldown Current-Limit Threshold Voltage (MAX5943A) VTHF VIN - VSENSE (Note 3) 36 45 54 µA 7.5V ≤ VIN ≤ 8V 8V ≤ VIN ≤ 37V 4.25 4.5 5.5 5.5 6.5 6.5 V ILIM = GND 47.5 50 52.5 ILIM = floating 37 39 41 ILIM = IN 55 58.5 61 ILIM = GND 70 75 80 ILIM = floating 54 59 64 ILIM = IN 83 88 93 mV mV GATE2 Pulldown Current (MAX5943A) IG2D VTH < (VIN - VSENSE) < VTHF, t < tILIM 335 435 535 µA GATE2 Fast Pulldown Current (MAX5943A) IG2DF (VIN - VSENSE) > VTHF, VGATE2 = VOUT + 4.5V 80 125 200 mA GATE2 Peak Pulldown Current (MAX5943A) IG2DP (VIN - VSENSE) = 1V 2 1.0 _______________________________________________________________________________________ A FireWire Current Limiter and Low-Drop ORing Switch Controller (VIN = 7.5V to 37V, GND = 0V, and TA = -40°C to +85°C, unless otherwise noted. Typical values are at VIN = 12V, TA = +25°C.) (Note 1) PARAMETER GATE2 Pulldown Current During Any GATE2 Turn-Off Condition SYMBOL IG2OFF CONDITIONS VGATE2 = VOUT + 4.5V (Note 4) MIN TYP MAX UNITS 80 125 200 mA 3 5 7 GATE1 (ORing control) OR_ADJ = GND ORing Switch Turn-On Current Threshold Voltage VOR ORing Switch Turn-On Current Threshold Voltage Hysteresis GATE1 Pullup Current (VIN - VSENSE) rising OR_ADJ = floating 5.5 7.5 9.5 OR_ADJ = IN 8.5 10.5 12.8 (VIN - VSENSE) falling IG1U 0.5 (Note 5) mV 36 45 54 7.5V ≤ VIN ≤ 8V 4.25 5.5 6.5 8V ≤ VIN ≤ 37V 4.5 5.5 6.5 2 3 GATE1 High Voltage VG1 VGATE1 - VSENSE GATE1 Turn-Off Switch OnResistance RG1 Measured between GATE1 and SENSE when (VIN - VSENSE) < VOR mV µA V Ω LOGIC INPUTS IIXL Current into or out of input for tri-state logic condition Current out of input for logic low IIH Current into input for logic high 20 VIL VON > VON_REF 0.7 V IIL LATCH, ONQ1 = GND, VON > VON_REF 1 µA LATCH, ONQ1 Input-Logic High Voltage VIH VON > VON_REF LATCH, ONQ1 Input Current IIH All voltages = VIN, VON > VON_REF 1 µA TIM, ILIM, LATCH, OR_ADJ, OUT, ONQ1 Shutdown Mode Input Current IIH_SD All voltages = VIN, VON ≤ 0.4V 1 µA 0.25 V 1 µA ILIM, OR_ADJ Input-Logic Tristate Current Tolerance (Note 6) LATCH, ONQ1 Input-Logic Low Voltage IIX -3 +3 20 1.8 FAULT Output Low Voltage VOL Low-impedance state, I FAULT = 5mA FAULT Output High Leakage Current IOH High-impedance state, V FAULT = 37V µA V 0.12 TIMING Current-Limit Timeout (MAX5943A) tILIM Current-limit mode (Note 7) TIM = IN 1.78 2.02 2.26 ms RTIM = 4kΩ 0.87 1.04 1.21 ms RTIM = 50kΩ 9.2 11.05 12.9 ms TIM = floating 120 175 225 ms _______________________________________________________________________________________ 3 MAX5943 ELECTRICAL CHARACTERISTICS (continued) MAX5943 FireWire Current Limiter and Low-Drop ORing Switch Controller ELECTRICAL CHARACTERISTICS (continued) (VIN = 7.5V to 37V, GND = 0V, and TA = -40°C to +85°C, unless otherwise noted. Typical values are at VIN = 12V, TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS Circuit-breaker mode, MAX5943B Circuit-breaker mode, MAX5943C Circuit-Breaker Timeout (MAX5943B–MAX5943E) (Note 7) tCB Circuit-breaker mode, MAX5943D Circuit-breaker mode, MAX5943E Automatic Restart Delay After Current-Limit/Circuit-Breaker Timeout tOFF LATCH = GND (Note 8) GATE1 Turn-Off Time (ORing Response Time) tOR Turn-Off Response Time tON_OFF Minimum Delay from ON Low to Low-Current Shutdown Mode tSD MIN TYP MAX UNITS 0.45 0.51 0.57 ms 27 32.5 38 µs RTIM = 50kΩ 228 345 403 µs TIM = floating 3.75 5.5 7 ms TIM = IN or TIM ≥ 3.4V 0.89 1.00 1.13 ms RTIM = 4kΩ 54 65 76 µs RTIM = 50kΩ 575 690 806 µs TIM = floating 7.5 10.9 14 ms TIM = IN 1.78 2.02 2.26 ms RTIM = 4kΩ 109 130 151 µs RTIM = 50kΩ 1.15 1.38 1.61 ms TIM = floating TIM = IN or TIM ≥ 3.4V RTIM = 4kΩ 15 21.9 28 ms TIM = IN or TIM ≥ 3.4V 3.56 4.05 4.52 ms RTIM = 4kΩ 217 260 303 µs RTIM = 50kΩ 2.3 2.76 3.23 ms TIM = floating 30 44 56 ms 128 x (tILIM OR tCB) ms From VOR trigger until (VGATE1 - VIN) < 1V, CGATE1 = 10nF 100 ns Time from VON < (VON_OFF - Hysteresis) until (VGATE2 - VOUT) < 1V, GATE2 = open (Note 9) 0.34 ON step from 1.3V to 0.4V 50 0.6 µs µs All min/max parameters are tested at +25°C and +85°C. Limits at -40°C are guaranteed by design. Measured at both VGATE2 = VOUT = 0V and VGATE2 = VOUT = VIN. The typical value of parameter VTHF is 1.5 x VTH. Current-Limit/Circuit-Breaker Timeout; IN or ON low. See the Typical Operating Circuit. Measured at VGATE1 = VSENSE. The tristate (“floating”) logic condition will be entered if the pin current is within these limits. RTIM is connected from TIM to GND. The maximum timeout period is enforced to prevent arbitrarily long operation in current-limit mode. Therefore, the relationship between resistor value and timeout changes for large values of RTIM. See Current-Limit Timeout vs. RTIM in the Typical Operating Characteristics for nominal values. Note 8: Parameter tOFF is a direct multiple of tILIM (or tCB), so the limits for tOFF track the limits for tILIM (or tCB). Note 9: If the ON voltage goes below VON_REF - Hysteresis, then GATE2 goes low immediately to disconnect power from the load quickly (within tON_OFF). Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: 4 _______________________________________________________________________________________ FireWire Current Limiter and Low-Drop ORing Switch Controller 1.5 TA = +25°C 1.4 1.3 1.2 1.1 TA = -40°C 1.0 10 15 20 25 30 35 2.0 1.5 1.0 0.5 0 10 15 20 25 30 35 VIN = 12V 58.5 58.0 57.5 VIN = 7.5V 42.0 41.5 41.0 40.5 10 35 60 ILIM = FLOATING 40.0 39.5 39.0 38.5 38.0 37.5 35 MAX5943A 10 1 MAX5943E 0.01 -15 10 35 60 1 85 10 100 1000 TEMPERATURE (°C) TEMPERATURE (°C) RTIM (kΩ) ORing THRESHOLD VOLTAGE vs. TEMPERATURE GATE CURRENTS vs. TEMPERATURE GATE1 DRIVE VOLTAGE vs. TEMPERATURE 46.5 GATE1 46.0 45.5 45.0 GATE2 OR_ADJ = GND 5.257 GATE1 DRIVE VOLTAGE (V) OR_ADJ = OPEN 5.260 MAX5943 toc09 47.0 GATE CURRENTS (μA) OR_ADJ = IN 85 60 0.1 -40 85 MAX5943 toc07 12.0 11.5 11.0 10.5 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 -15 10 TIMEOUT PERIOD vs. RTIM 37.0 36.5 36.0 -40 -15 100 TIMEOUT PERIOD (μs) VIN = 32V VIN = 7.5V VIN = 12V -40 MAX5943 toc05 CURRENT-LIMIT/CIRCUIT-BREAKER THRESHOLD VOLTAGE vs. TEMPERATURE THRESHOLD VOLTAGE (mV) CURRENT-LIMIT/CIRCUIT-BREAKER THRESHOLD VOLTAGE vs. TEMPERATURE 60.0 59.5 59.0 49.0 48.5 48.0 47.5 47.0 46.5 TEMPERATURE (°C) SUPPLY VOLTAGE (V) ILIM = IN 50.0 49.5 40 SUPPLY VOLTAGE (V) 62.0 61.5 61.0 60.5 VIN = 32V 50.5 46.0 5 57.0 56.5 56.0 ORing THRESHOLD VOLTAGE (mV) 3.0 2.5 40 MAX5943 toc04 THRESHOLD VOLTAGE (mV) 5 4.0 3.5 ILIM = GND 51.5 51.0 MAX5943 toc06 TA = +85°C 52.0 THRESHOLD VOLTAGE (mV) 1.7 5.5 5.0 4.5 MAX5943 toc08 SUPPLY CURRENT (mA) 1.8 6.0 MAX5943 toc02 1.9 SHUTDOWN SUPPLY CURRENT (μA) MAX5943 toc01 2.0 1.6 CURRENT-LIMIT/CIRCUIT-BREAKER THRESHOLD VOLTAGE vs. TEMPERATURE SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX5943 toc03 SUPPLY CURRENT vs. SUPPLY VOLTAGE 5.254 5.251 5.248 5.245 5.242 5.239 5.236 44.5 5.233 44.0 -40 -15 10 35 TEMPERATURE (°C) 60 85 5.230 -40 -15 10 35 TEMPERATURE (°C) 60 85 -40 -15 10 35 60 85 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX5943 Typical Operating Characteristics (VIN = +12V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VIN = +12V, TA = +25°C, unless otherwise noted.) ON LOW VOLTAGE vs. TEMPERATURE ON HIGH VOLTAGE vs. TEMPERATURE 1.258 ON HIGH VOLTAGE (V) 5.224 5.221 5.218 5.215 5.212 5.209 1.256 1.254 1.196 1.194 1.192 1.190 1.188 1.186 1.184 1.252 5.206 1.198 ON LOW VOLTAGE (V) 5.227 1.200 MAX5943 toc11 1.260 MAX5943 toc10 5.230 MAX5943 toc12 GATE2 DRIVE VOLTAGE vs. TEMPERATURE GATE2 DRIVE VOLTAGE (V) 1.182 5.203 1.180 1.250 5.200 -40 -15 10 35 -40 85 60 -15 10 FAULT LOW VOLTAGE vs. TEMPERATURE 180 60 -40 85 -15 10 MAX5943 toc14 IFAULT = 5mA 160 OR_ADJ = IN VIN 10V/div IIN 500mA/div 140 120 (VGATE - VSENSE) 5V/div 100 80 VOUT 5V/div 60 40 20 0 -40 -15 10 35 60 100μs/div 85 TEMPERATURE (°C) MAX5943A SHORT-CIRCUIT EVENT (VIN = 37V) TURN-OFF RESPONSE TIME MAX5943 toc15 MAX5943 toc16 VON 2V/div TIM = IN ILIM = GND VIN 50V/div IIN 1A/div IIN 1A/div VGATE2 10V/div VGATE2 50V/div VOUT 50V/div VFAULT 50V/div VOUT 10V/div 200ns/div 6 35 TEMPERATURE (°C) ORing THRESHOLD RESPONSE TIME MAX5943 toc13 200 35 TEMPERATURE (°C) TEMPERATURE (°C) FAULT LOW VOLTAGE (mV) MAX5943 FireWire Current Limiter and Low-Drop ORing Switch Controller 400μs/div _______________________________________________________________________________________ 60 85 FireWire Current Limiter and Low-Drop ORing Switch Controller MAX5943A SHORT-CIRCUIT RESPONSE (VIN = 8V) MAX5943A SHORT-CIRCUIT EVENT (VIN = 37V) MAX5943 toc18 MAX5943 toc17 VIN 10V/div ILIM = GND VIN 50V/div IIN 1A/div IIN 10A/div VGATE2 10V/div VGATE2 50V/div VOUT 10V/div VOUT 50V/div VFAULT 50V/div TIM = IN VFAULT 10V/div 400μs/div 100ns/div MAX5943E SHORT-CIRCUIT RESPONSE (VIN = 24V) MAX5943A SHORT-CIRCUIT RESPONSE (VIN = 8V) MAX5943 toc20 MAX5943 toc19 VIN 50V/div VIN 10V/div IIN 10A/div IIN 166A/div VGATE2 10V/div VGATE2 50V/div VOUT 10V/div VOUT 50V/div VFAULT 50V/div VFAULT 10V/div 200μs/div 100ns/div MAX5943E SHORT-CIRCUIT RESPONSE (VIN = 8V) ORing SWITCHOVER WAVEFORM MAX5943 toc22 MAX5943 toc21 VIN 10V/div VOUT 1V/div IIN 60A/div VGATE2 10V/div IIN1 500mA/div VOUT 10V/div TIM = IN IIN2 500mA/div VFAULT 10V/div 100μs/div VIN1 = 12V VIN2 = 128V 200μs/div VON2 RISING = 12V COUT = 0 _______________________________________________________________________________________ 7 MAX5943 Typical Operating Characteristics (continued) (VIN = +12V, TA = +25°C, unless otherwise noted.) MAX5943 FireWire Current Limiter and Low-Drop ORing Switch Controller Typical Operating Characteristics (continued) (VIN = +12V, TA = +25°C, unless otherwise noted.) ORing SWITCHOVER WAVEFORM (VIN2 FALLING BELOW VIN1) ORing SWITCHOVER WAVEFORM (VIN2 RISING ABOVE VIN1) MAX5943 toc24 MAX5943 toc23 VIN1 = 12V VIN2 = 13V VOUT 1V/div VOUT 1V/div IIN1 500mA/div IIN1 500mA/div IIN2 500mA/div IIN2 500mA/div 10μs/div VON2 RISING = 12V COUT = 0 VIN1 = 12V VIN2 = 13V MAX5943A HOT PLUG-IN LOAD CAPACITANCE INTO ACTIVE PORT (NO FAULT) 20μs/div VON2 FALLING = 12V COUT = 0 MAX5943A HOT PLUG-IN LOAD CAPACITANCE INTO ACTIVE PORT (CURRENT-LIMIT TIMEOUT) MAX5943 toc25 MAX5943 toc26 VFAULT 10V/div VFAULT 10V/div IIN 2A/div IIN 1A/div VGATE2 10V/div VGATE2 10V/div VOUT 10V/div VOUT 10V/div 400μs/div CLOAD = 220μF TIM = IN 8 400μs/div CLOAD = 470μF TIM = IN _______________________________________________________________________________________ FireWire Current Limiter and Low-Drop ORing Switch Controller PIN NAME FUNCTION On/Off-Control Input. ON sets the undervoltage lockout threshold and resets the part after a fault latch. Drive ON high to enable the device. Drive ON low to disable the device. Connect ON to IN for the default undervoltage lockout threshold. Connect a resistor-divider from IN to ON and GND to program the desired undervoltage lockout threshold. 1 ON 2 FAULT 3 TIM Current-Limit/Circuit-Breaker Timeout Adjustment Input. Connect TIM to IN for the default timeout period or connect a resistor from TIM to GND to program the current-limit/circuit-breaker timeout period. 4 ILIM Current-Limit/Circuit-Breaker Threshold Input. Leave ILIM open for a 40mV circuit-breaker threshold, connect to GND for a 50mV circuit-breaker threshold, or connect to IN for a 60mV circuit-breaker threshold (see the Current Limiting section). 5 LATCH Latch or Autoretry Fault Management Selection Input. Connect LATCH to IN to select latch-off mode after a current-limit/circuit-breaker timeout. Connect LATCH to GND for autorestart mode after a currentlimit/circuit-breaker timeout. 6 OR_ADJ ORing Switch Turn-On Current Threshold Adjustment Input. Select one of three ORing switch turn-on threshold settings: connect OR_ADJ to GND, connect OR_ADJ to IN, or leave OR_ADJ floating (see the Power-Supply ORing section). 7, 10, 13 N.C. 8 ONQ1 Current-Fault, Active-Low, Open-Drain Output. FAULT asserts and latches low after a current-limit/circuitbreaker fault has exceeded the current-limit/circuit-breaker timeout period (see the FAULT section). No Connection. Not internally connected. ORing Switch Manual Turn-On Input. Drive ONQ1 low to enable power-supply ORing. Drive ONQ1 high to set GATE1 high to allow reverse current flow. ONQ1 is disabled when VIN is below the UVLO threshold, VON is below the VON_REF threshold, and after a current/circuit-breaker fault. 9 GND Ground 11 OUT Output Voltage Sense. Connect to the output. 12 GATE2 Current-Limiter Switch Gate Drive Output. Connect GATE2 to the gate of the 2nd n-channel MOSFET. GATE2 is a charge pump with a 45µA pullup current to 5.5V (typ) above OUT when active (see the Typical Operating Circuit). 14 GATE1 ORing Switch Gate-Drive Output. Connect GATE1 to the gate of the 1st n-channel MOSFET. GATE1 is a charge pump with a 45µA pullup current to 5.5V (typ) above SENSE when active (see the Typical Operating Circuit). 15 SENSE Current-Sense Negative Input. Connect a current-sense resistor, RSENSE, from IN to SENSE (see the Typical Operating Circuit). 16 IN Input Power and Current-Sense Positive Input. Connect IN to the positive terminal of the current-sense resistor and to the power source (see the Typical Operating Circuit). _______________________________________________________________________________________ 9 MAX5943 Pin Description MAX5943 FireWire Current Limiter and Low-Drop ORing Switch Controller POWER SOURCE RSENSE Q1 SENSE GATE1 Q2 GATE2 OUT ONQ1 OR COMPARATOR THRESHOLD OR_ADJ + - SENSE GATE1 GATE1 DRIVE GATE2 OUT GATE2 DRIVE + CIRCUIT-BREAKER (CURRENT-LIMIT) THRESHOLD ILIM - FAULT TIMEOUT TIM + (FAST CURRENTLIMIT THRESHOLD) - X128 UVLO COMPARATOR + 6.5V ON AUTORETRY TIMEOUT PERIOD + 1.24V - ON COMPARATOR + 0.4V SHUTDOWN MODE - CP1 CP2 GATE CHARGE PUMPS FAULT MANAGEMENT LATCH OR AUTORETRY LATCH FAULT MAX5943A–MAX5943E GND ( ) MAX5943A ONLY. Figure 1. MAX5943 Functional Diagram Detailed Description The MAX5943 performs hot-swapping, power-supply ORing, and current limiting for FireWire power-supply applications. The MAX5943 incorporates two MOSFET drivers (GATE1 and GATE2) to control two external n-channel power MOSFETs to perform low-voltage-drop power-supply ORing (GATE1) and hot swapping and current limiting (GATE2) from the input power supply to the load. A sense resistor provides accurate currentlimiting/circuit-breaker function. GATE1 and GATE2 provide true load disconnect to prevent current flowing from either direction between IN and OUT. The MAX5943 remains in low-current shutdown mode when VON is below the 0.4V threshold. Low-current shutdown mode disables the MAX5943, resulting in less than 10µA supply current. Shutdown places all 10 logic inputs in a high-impedance state allowing the inputs to be connected to IN without drawing additional current from the supply. When the input supply voltage (VIN) is above 7.5V and VON is above the VON_REF threshold, the MAX5943 turns on, sourcing 45µA current from GATE2 (current regulation) to enhance Q2 slowly. For the MAX5943A, if the voltage across the current-sense resistor, VIS, is greater than the programmed current-limit threshold, the MAX5943A regulates the GATE2 voltage to limit the load current at the current-limit level so that VIS is equal to VTH. In normal operation, VIS drops below VTH and GATE2 rises to approximately 5.5V above OUT. Since the MAX5943B–MAX5943E do not regulate the load current, a capacitor can be added from GATE2 to GND to limit inrush current during startup (see the Applications Information section). ______________________________________________________________________________________ FireWire Current Limiter and Low-Drop ORing Switch Controller Current Limiting/Circuit Breaker Current Limiting (MAX5943A Only) The MAX5943A limits the load current by monitoring the voltage across RSENSE at all times and by regulating the current to the load as necessary to keep VIS to its programmable current-limit threshold voltage (VTH). Set the maximum current limit (ILIMIT) by placing the appropriate sense resistor between IN and SENSE, where ILIMIT = VTH/RSENSE. When the load current is less than ILIMIT, GATE2 rises to VG2 (5.5V) to fully enhance MOSFET Q2 (see the Typical Operating Circuit). When the load current attempts to draw more than ILIMIT, the MAX5943A’s GATE2 pulldown current (IG2D) regulates the current through Q2 causing OUT to act as a constant-current source. The output current is limited to the programmed ILIMIT. If the current-limit condition persists after the current-limit timeout (tILIM) period has expired, GATE2’s strong pulldown current (IG2 OFF) quickly turns off GATE2 to disconnect the load from the power supply. FAULT then asserts low (Figure 2a). If the current-limit duration is less than tILIM, GATE2 pulls to VG2 (Figure 2b). During an output short circuit or a gross overload, the load current overshoots and causes VIS to exceed the fast pulldown current-limit threshold voltage (VTHF). The MAX5943A responds with much stronger GATE2 pulldown currents (IG2DP and/or IG2DF) to quickly bring the load current back down to the programmed current limit. MAX5943 The MAX5943 current-limit/circuit-breaker timeout is programmable by connecting an external resistor from TIM to GND. The MAX5943A has a default 2ms currentlimit timeout. The MAX5943B, MAX5943C, MAX5943D, and MAX5943E have 0.5ms, 1ms, 2ms, and 4ms default circuit-breaker timeouts, respectively. GATE1 controls the MAX5943 ORing function. Initially, GATE1 is off (ONQ1 = low) and the load current conducts through the body diode of Q1. GATE1 rises to 5.5V above SENSE when VIS exceeds VOR, thereby enhancing Q1 and reducing the voltage drop, power dissipation, and heat generation in the power-supply path. When a voltage greater than VIN is connected at OUT, the higher voltage source commences, providing current to the load. The MAX5943 rapidly turns off GATE1 upon VIS falling below VOR - hysteresis, thus blocking the higher voltage from back-driving V IN . GATE1 also turns off when the load current drops, causing VIS to fall below the VOR hysteresis. VFAULT ILIMIT tILIM IOUT VIN VGATE1 VGATE2 ILIMIT x RLOAD VOUT (a) VFAULT < tILIM ILIMIT IOUT VGATE1 VGATE2 ILIMIT x RLOAD VOUT (b) Figure 2. MAX5943A Current-Limit Timing Diagram ______________________________________________________________________________________ 11 MAX5943 FireWire Current Limiter and Low-Drop ORing Switch Controller MAX5943B–MAX5943E Circuit Breaker The MAX5943B–MAX5943E provide a circuit-breaker function that protects against excessive load currents and short-circuit conditions. The load current is monitored by sensing the voltage across an external sense resistor (R SENSE ) and disconnects the load from the power source when the voltage across RSENSE, VIS, exceeds the programmed circuit-breaker thresholds (VTH) for longer than the circuit-breaker timeout period, tCB. Unlike the MAX5943A, when an output short circuit or overcurrent occurs, the MAX5943B–MAX5943E keep GATE2 fully enhanced. The short-circuit current is limited only by the input source impedance, RSENSE, Q1’s RDS(ON), Q2’s RDS(ON), and any parasitic impedance in the power path. If the excessive current condition persists (as indicated by VIS > VTH) for longer than tCB, GATE2 turns off with a strong pulldown (IG2 OFF) to quickly disconnect the power source from the load and FAULT asserts low (Figure 3). Exercise caution when using the MAX5943B–MAX5943E. Unlike the MAX5943A, the MAX5943B–MAX5943E do not limit the load current during tCB. High current during tCB may cause damage to external devices connected in the power path. Current-Limit/Circuit-Breaker Thresholds The MAX5943 allows three selectable current-limit/circuit-breaker thresholds (V TH ). Choose the voltage threshold by connecting ILIM to the appropriate level; see Table 1. Table 1. Current-Limit/Circuit-Breaker Trip Threshold Level ILIM CONNECTION VTH (mV) Open 40 GND 50 IN 60 Current-Limit/Circuit-Breaker Timeout Period (tILIM/tCB) The MAX5943’s current-limit/circuit-breaker timeout function disconnects power from the load if the currentlimit or circuit-breaker threshold voltage exceeds its maximum limit for a programmable amount of time. Connect TIM to IN for the MAX5943 default timeout periods (see Table 2). Adjust the fault timeout period (tILIM/ tCB) by connecting a resistor (RTIM) from TIM to GND (see the Typical Operating Characteristics ). Calculate the fault-limit timeout period using the following equation: tILIM (ms) = t CB (ms) = 0.25 × R TIM (kΩ) K where RTIM is in kΩ, tILIM/tCB is in ms, and K = 1 for MAX5943A, K = 32 for MAX5943B, K = 16 for MAX5943C, K = 8 for MAX5943D, and K = 4 for the MAX5943E. VFAULT ILIMIT Table 2. MAX5943_ Timeout Periods tCB DEFAULT TIMEOUT, TIM = IN (ms) PROGRAMMABLE TIMEOUT RANGE (4kΩ < RTIM < 50kΩ) MAXIMUM TIMEOUT, TIM = FLOATING (ms) MAX5943A 2 1.04ms to 11.05ms 175 MAX5943B 0.5 32.5µs to 345µs 4.8 MAX5943C 1 65µs to 690µs 9.6 MAX5943D 2 130µs to 1.38ms 19.2 MAX5943E 4 260µs to 2.76ms 38.4 IOUT VIN PART VGATE1 VGATE2 VG2 VOUT VG2 Figure 3. MAX5943B–MAX5943E Circuit-Breaker Timing Diagram 12 ______________________________________________________________________________________ FireWire Current Limiter and Low-Drop ORing Switch Controller Power-Supply ORing (ONQ1 = Low) GATE1 controls the MAX5943 ORing function. The MAX5943 accomplishes a very-low-voltage-drop diode ORing function using an n-channel power MOSFET, Q1. Initially, GATE1 is off (ONQ1 = low) and the load current conducts through the body diode of Q1 (Figure 4). GATE1 rises to 5.5V above SENSE when VIS exceeds VOR, enhancing Q1. Q1’s low RDS(ON) provides a verylow-voltage drop across its source to drain, reducing voltage drop, power dissipation, and heat generation in the power-supply path created by a traditional diode. The MAX5943 continuously monitors the load current by the voltage drop, VIS, across the current-sensing resistor. Q1 turns off rapidly when VIS decreases below VOR minus its hysteresis. Set the MAX5943 ORing threshold (VOR) by connecting OR_ADJ to GND for a 5mV threshold, or to IN for a 10mV threshold, or leave it open for a 7.5mV threshold. Connect ONQ1 to GND for normal ORing function. Drive ONQ1 high to force Q1 on, regardless of the load current condition, as long as the voltages at IN and ON exceed V UVLO and V ON_REF , respectively, and the device is not in a current fault shutdown. When a higher voltage supply is connected at OUT (Figure 5), the sense voltage drops below the programmable ORing threshold. The MAX5943 immediately turns off Q1, blocking reverse current flow from OUT to IN. The power is then routed from the higher supply input to the load (Figure 6). + VIN VIS RSENSE IINA = 0 VINA TO FireWire PORT RSENSE FROM BATTERY SOURCE VINB > VINA ILOAD ON IN SENSE GATE1 GND IINB VINB MAX5943 OR_ADJ GATE2 OUT GATE2 OUT ONQ1 RSENSE FROM POWER SOURCE ON IN SENSE GATE1 GND MAX5943 OR_ADJ ONQ1 Figure 5. MAX5943 ORing Controller Rerouting Load Current VINA IINA IINB TO FireWire PORT VOUT Q1 ON IN SENSE GND GATE1 MAX5943 OR_ADJ Q2 GATE2 OUT VINB ONQ1 Figure 4. Q1 Current Path During Inital Startup VINB > VINA Figure 6. MAX5943 Power Switch Over ORing Timing Diagram ______________________________________________________________________________________ 13 MAX5943 Timing accuracy is guaranteed for RTIM ranging from 4kΩ to 50kΩ. Large RTIM values can be used, which reduces timing accuracy. A maximum timeout period is enforced to prevent arbitrarily long operation in currentlimit/circuit-breaker conditions. Long durations in current-limit/circuit-breaker mode may produce excessive heating and electrical stresses in RSENSE, Q1, Q2, and any other components in the power path. Use component values rated to handle electrical stresses during the timeout period. MAX5943 FireWire Current Limiter and Low-Drop ORing Switch Controller Reverse Current Override (ONQ1 = High) Drive ONQ1 high to disable the power-supply ORing function. Disabling the MAX5943 ORing function allows reverse current flow through the power-supply system. When ONQ1 is high, GATE1 remains fully enhanced as long as VIN is greater than VUVLO, VON is above the VON_REF threshold, and the MAX5943 is not in a current-limit or circuit-breaker fault condition. The MAX5943 reverse-current flow feature permits a higher voltage source connected to one port to route power to another port, as long as the voltage at IN remains above the minimum 7.5V operating range (see Figure 7). PORT1 TIM IN ON ONQ1 ILIM SENSE GATE1 LATCH MAX5943 GND OR_ADJ GATE2 OUT FAULT PORT2 TIM IN ON ONQ1 SENSE GATE1 ILIM MAX5943 LATCH GND GATE2 OUT FAULT OR_ADJ Figure 7. MAX5943 Operating in Reverse-Current Mode (Routing Power from Port 1 to Port 2) Undervoltage Lockout The MAX5943 operates from 7.5V to 37V and has a default 6.5V undervoltage lockout threshold. The external MOSFETs remain off as long as VIN > 6.5V and VON < VON_REF. The turn-on threshold is programmable by connecting a resistor-divider at ON. When VON > 1.24V and VIN > 7.5V, GATE2 is enhanced to 5.5V, with respect to OUT and the MAX5943 goes into normal operation. Program the MAX5943’s turn-on voltage using the following formula: ⎛ VTURN _ ON ⎞ R1 = ⎜ − 1⎟ × R2 1.24 ⎝ ⎠ VIN IN R1 MAX5943 ON R2 GND Figure 8. Setting the MAX5943 Turn-On Voltage When operating the MAX5943, ON must remain above its 1.24V threshold. If VON falls below its 1.24V threshold, the power-supply MOSFETs (Q1 and Q2) turn off immediately (less than 1µs). This allows the power supply to disconnect in the event of a fault condition detected by the system, such as shorting of the output to a different power-supply voltage or a FireWire signal pin. If possible transient conditions exist at the main power-supply line (IN), place an RC filter at ON to reject transient voltage dips and to prevent unnecessary power-supply interruptions. The MAX5943 remains in low-current shutdown mode when VON is below the 0.4V threshold. Low-current shutdown mode disables the MAX5943 resulting in less than 10µA supply current. Shutdown places all logic inputs in a high-impedance state allowing the inputs to be connected to IN without drawing additional current from the supply. An internal delay, tSD, allows Q1 and Q2 to be turned off before the MAX5943 enters lowcurrent shutdown mode. Fault Status Output (FAULT) FAULT is a high-voltage open-drain output that pulls low when a current-limit/circuit-breaker fault shutdown has occurred. FAULT remains low until the next startup cycle. VIN IN LATCH R1 MAX5943 ON R2 GND where VTURN_ON is the desired turn-on voltage of the MAX5943. Choose an R2 value in the 1kΩ range to minimize error due to the ON bias current. 14 Figure 9. Resetting MAX5943 After a Latched Fault Condition ______________________________________________________________________________________ FireWire Current Limiter and Low-Drop ORing Switch Controller To prevent the MAX5943B–MAX5943E from starting up in a fault condition set: VTH IINRUSH < RSENSE RSENSE + Q1 Q2 1kΩ CGATE IC ILOAD 45μA IN SENSE GATE1 GATE2 OUT COUT LOAD VIN MAX5943B–MAX5943E GND - Applications Information Figure 10. Controlling the MAX5943B–MAX5943E Inrush Current Startup Consideration Optimizing for Short-Circuit Conditions MAX5943A During startup, a large capacitor at OUT may result in a charging current equivalent to the current limit. Choose a current-limit timeout that will allow a successful startup. The timeout can be approximated using the following equation: C × VIN tILIM > OUT ILIMIT − ILOAD Choosing RSENSE Select a sense resistor that causes the circuit-breaker voltage drop at a current-limit/circuit-breaker level above the maximum normal operating current. Typically, set the overload current at 1.2 to 1.5 times the full load current. \where ILIMIT is the programmed current limit, COUT is the capacitor at OUT, VIN is the supply voltage, and ILOAD is the load current during startup. With IN = 12V, C OUT = 330µF, I LIMIT = 1.5A, and I LOAD = 0, the MAX5943 commences by charging the output capacitor with 1.5A for approximately 2.7ms. Therefore, the MAX5943A current-limit timeout period (tILIM) should be greater than 2.7ms for a successful startup. Otherwise, the MAX5943A powers up in fault management mode by exceeding the current-limit timeout period. PRSENSE = I2LIMIT x RSENSE where PRSENSE is the power dissipated across RSENSE during a current-limit/circuit-breaker fault. Under short-circuit conditions, it is imperative that the appropriate sense resistor is utilized. Operating the MAX5943B–MAX5943E at high input voltages can cause very large currents during the circuit-breaker timeout period. The peak current will be limited by the saturation current of Q2 or the series resistance in the power path (RTOTAL). Using a 30mΩ on-resistance MOSFET at GATE1 and GATE2 and a 30mΩ sense resistor results in a short-circuit current approximately equal to: ISC = VIN/RTOTAL MAX5943B–MAX5943E The MAX5943B–MAX5943E do not control the inrush current during startup. Inrush current control can be implemented by placing a resistor and capacitor at GATE2 (Figure 10) to slowly ramp up the gate voltage, thus limiting the inrush current. The inrush current can be approximated using the following formula: IINRUSH = COUT × IG2U + ILOAD CGATE2 Where I G2U is GATE2’s 45µA sourcing current and ILOAD is the load current at startup. Choose the sense-resistor power rating to accommodate an overcurrent condition: where: RTOTAL = RSENSE + 2 x (RON) = 30mΩ + 2 x (30mΩ) = 90mΩ For example, an input voltage of 20V produces a current at approximately 222A (or ISAT of Q2, whichever is less) in the power path for the circuit-breaker timeout period. Choose an RSENSE capable of handling the high power dissipation during a short-circuit event. ______________________________________________________________________________________ 15 MAX5943 Fault Management The MAX5943 offers either latch or autoretry fault management configurable by the LATCH input. Connect LATCH to IN for latch fault management or connect LATCH to GND for autoretry fault management. In latch fault management, FAULT latches low, GATE1 and GATE2 latch off indefinitely. Cycle ON low and then high to unlatch and restart the MAX5943. However, the MAX5943 will not enter a startup cycle until tOFF has expired. Figure 9 illustrates a way to reset the MAX5943 after a fault using a pushbutton switch. In autoretry fault management, the MAX5943_ attempt to restart after a tOFF of 128 x tILIM (or 128 x tCB) limiting the duty cycle of the MOSFETs to 1/129 under continuous fault conditions. FAULT deasserts every time a restart attempt is made. MOSFET Selection Select external MOSFETs according to the application current level. The MOSFETs’ on-resistance (RDS(ON)) should be chosen low enough to have minimum voltage drop at full load to limit the MOSFET power dissipation. High RDS(ON) also causes large output ripple if there is a pulsating load. Determine the device power rating to accommodate startup, a short-circuit condition, and when the device is in autoretry mode. During normal operation, the external MOSFETs dissipate little power. The power dissipated in normal operation is: P = ILOAD2 x RDS(ON) For the MAX5943B–MAX5943E, a short-circuit event results in high power dissipated in both Q1 and Q2 during the timeout period (Figure 13) where the total power dissipated in either MOSFET is: P = ISC2 x RDS(ON) where: ISC = VIN/REQ and REQ = RSENSE +RDS(ON1) + RDS(ON2) VIN The most power dissipation occurs during a short-circuit event, resulting in high power dissipated in Q2 (Figure 11) during the timeout period for the MAX5943A, where the power dissipated across Q2 is: PQ2 = (VIN - VIS – VQ1 ) x ILIMIT VIS + IN - + VQ1 - + VQ2 - SENSE GATE1 GATE2 OUT MAX5943A Figure 11. Power Dissipated Across MOSFETs During a ShortCircuit Fault for MAX5943A N1 Si2318DS N2A Si7222DN L1 FERRITE 250Ω N2B TP3 PORT 0 1 3 5 J3 R3 1kΩ DMMT3906 Q1B Q1A R4 1kΩ C3 1μF C4 0.1μF R7 100kΩ J1 VIN GND NC 9 10 11 OUT 12 GATE2 13 N.C. GATE1 14 R6 100kΩ IN SENSE 16 R2 0.020Ω 1% TP1 VIN 0.25W 15 R5 100kΩ U1 TP5 ON TP2 GND TP6 VPULLUP R8 100kΩ 8 N.C. OR_ADJ 6 LATCH 5 ILIM 4 TIM 3 J2 GND 2 ON C2 0.01μF FAULT C1 1μF ONQ1 MAX5943AEEE 7 R1 200kΩ 1 MAX5943 FireWire Current Limiter and Low-Drop ORing Switch Controller TP4 FAULT Figure 12. UL-Recognized Single-Port FireWire Protective Circuit 16 ______________________________________________________________________________________ PORT 0 2 4 6 FireWire Current Limiter and Low-Drop ORing Switch Controller ISC RSENSE VIN IN RDS(ON)1 thereof, that are UL recognized. The circuit is further described in Application Note 3984—UL Recognized, IEEE 1394 Single- and Dual-Port FireWire Protective Circuits available at www.maxim-ic.com/appnotes.cfm/ appnote_number/3984. The circuit provides: • 2.5A (adjustable) current limiting to the load at initial connection or in overload fault condition • 2ms (adjustable) current-limit timeout before load disconnect for excessive load current • Automatic-restart attempts after a fault shutdown condition • <0.8% current-limited duty cycle in continuous fault condition • 6.5V undervoltage shutdown protection • Low-drop ORing in multiple power-source applications, and • Fault reporting RDS(ON)1 SENSE GATE1 GATE2 OUT MAX5943B–MAX5943E Figure 13. Power Dissipated Across MOSFETs During a ShortCircuit Fault for MAX5943B–MAX5943E CPA SENSE PHY POWER OUT FB VIN BST ON LX MAX5033 GND IN4148 IN4148 VD SGND IN4148 15mΩ CABLE POWER SOURCE TIM IN ON ILIM SI7958DP SENSE GATE1 MAX5943A LATCH GND ONQ1 30mΩ SI7958DP GATE2 OUT FAULT INA ONA SI7958DP SENSEA GATE1A ONQ1 OR_ADJ SI7958DP PORT 0 GATE2A OUTA FAULTA GND MAX5944 FAULTB ONB INB 15mΩ BATTERYPOWER SOURCE SI7958DP SENSEB GATE1B SI7958DP 30mΩ TIM IN ON ILIM CABLE NOT ON SLEEP SENSE GATE1 MAX5943A LATCH GND ONQ1 GATE2B OUTB IRF7478 PORT 1 IRF7478 IN4148 GATE2 OUT FAULT OR_ADJ CURRENT-LIMIT SENSE PORT 1 PORT 0 SENSE SENSE Figure 14. Two-Port FireWire Power Provider Using MAX5943A and MAX5944 ______________________________________________________________________________________ 17 MAX5943 The programmable timeout of the MAX5943 allows the use of MOSFETs with low power ratings. A MOSFET typically withstands single-shot pulses with higher dissipation than the specified package rating. A single-port FireWire protective circuit employing the MAX5943A has been UL recognized as a result of extensive safety testing by Underwriters Laboratories. It is the circuits themselves, not any individual component MAX5943 FireWire Current Limiter and Low-Drop ORing Switch Controller FireWire Power Management The MAX5943 serves to regulate and protect FireWire power over a system interface. The MAX5943 programmable features make it suitable for both power provider and power receiver applications. Figure 14 shows a high-end two-port FireWire power management system using two MAX5943As and a dual-channel MAX5944 FireWire current-limiting IC. Transient Protection If IN or OUT experiences a fast voltage transient, the drain-to-gate parasitic capacitance of Q1 and/or Q2 may be sufficient to briefly enhance one of the transistors, allowing current glitch. If the circuit is subjected to large transients, connect capacitors from the gate to source across the appropriate MOSFET, preventing the parasitic capacitance from turning on the device. Typical Operating Circuit Caution: The additional gate-to-source capacitance causes the turn-off time of the MOSFETs to increase due to the additional charge of the capacitor. Use the minimum capacitor value to prevent currents from flowing in hot-plug situations. Typical Application Circuit FireWire PORT SUPPLY + 30mΩ SI7958DP SI7958DP Q1 1kΩ 10kΩ VIN = 12V Q2 4kΩ TIM IN SENSE GATE1 FAULT ON 7.15kΩ TO FireWire PORT GATE2 OUT MAX5943A ILIM LATCH GND OR_ADJ ONQ1 - FireWire PORT SUPPLY + TO FireWire PORT VIS RSENSE Q1 R1 Selector Guide Q2 R3 TIM IN SENSE GATE1 FAULT ON R2 GATE2 OUT PART CURRENT LIMITER/ CIRCUIT BREAKER MAX5943A Current limit DEFAULT PROGRAMMABLE TIMEOUT TIMEOUT RANGE (ms) MAX5943A ILIM LATCH GND OR_ADJ ONQ1 MAX5943 EQUIVALENT CIRCUIT VERY-LOW-DROP ORing DIODE 2 1.04ms to 11.05ms 32.5µs to 345µs MAX5943B Circuit breaker 0.5 MAX5943C Circuit breaker 1 65µs to 690µs MAX5943D Circuit breaker 2 130µs to 1.38ms MAX5943E Circuit breaker 4 260µs to 2.76ms LOAD DISCONNECT SWITCH Chip Information CURRENT-LIMIT/CIRCUIT-BREAKER AND INRUSH CONTROL 18 TRANSISTOR COUNT: 2324 PROCESS: BiCMOS ______________________________________________________________________________________ FireWire Current Limiter and Low-Drop ORing Switch Controller QSOP.EPS ______________________________________________________________________________________ 19 MAX5943 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) MAX5943 FireWire Current Limiter and Low-Drop ORing Switch Controller Revision History REVISION NUMBER REVISION DATE 0 8/04 Initial release 1 1/05 Corrected Table 2 and Figures 10, 11, and 12 2 10/07 DESCRIPTION PAGES CHANGED — Added FireWire/IEEE and UL information, inserted new Figure 12, and updated Package Outline 12, 15, 16, 17 1, 16, 17, 18, 20 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.