19-4241; Rev 0; 8/08 30mA Inverting Charge Pump in SOT23 for EMI-Sensitive Automotive Applications The MAX16945 ultra-small, monolithic, CMOS chargepump voltage inverter accepts an input voltage ranging from +1.4V to +5.5V. This device features an ultra-low 12Ω output resistance, permitting loads of up to 30mA at +105°C with maximum efficiency. The MAX16945 operates at a frequency of 125kHz, allowing use of small external components. Its small external components, micropower shutdown mode, and wide temperature range make this device ideal for both automotive and industrial applications. Oscillator control circuitry and four power MOSFET switches are included on-chip. The MAX16945 comes in a 6-pin SOT23 package and operates over -40°C to +105°C. Features ♦ +1.4V to +5.5V Input Voltage Range ♦ 30mA Guaranteed Output Current at +105°C ♦ Slew-Rate Limited to Reduce EMI ♦ 0.1µA Logic-Controlled Shutdown ♦ Low 12Ω Output Resistance ♦ Startup Current Limited ♦ 6-Pin SOT23 Package Ordering Information Applications Automotive and Industrial Equipment PART TEMP RANGE PIN-PACKAGE Small LCD Panels MAX16945TGUT# -40°C to +105°C 6 SOT23 Negative Supply from +5V or +3.3V Logic Supplies #Denotes a RoHS-compliant device that may include lead that is exempt under RoHS requirements. GaAsFET Bias Supplies Note: The MAX16945 requires a special solder temperature profile described in the Absolute Maximum Ratings section. Handy-Terminals, PDAs Pin Configuration Typical Operating Circuit 1μF TOP VIEW INPUT 1.5V TO 5.5V C1+ C1OUT IN MAX16945 SHDN ON OFF NEGATIVE OUTPUT -1 ✕ VIN 60mA OUT 1 IN 2 C1- 3 MAX16945 6 C1+ 5 SHDN 4 GND 1μF GND SOT23 ________________________________________________________________ Maxim Integrated Products 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. 1 MAX16945 General Description MAX16945 30mA Inverting Charge Pump in SOT23 for EMI-Sensitive Automotive Applications ABSOLUTE MAXIMUM RATINGS IN to GND .................................................................-0.3V to +6V C1+, SHDN to GND .......................................0.3V to (VIN +0.3V) C1- to GND...............................................(VOUT - 0.3V) to +0.3V OUT to GND .............................................................+0.3V to -6V OUT Output Current............................................................90mA OUT Short Circuit to GND..............................................Indefinite Continuous Power Dissipation (TA = +70°C) 6-Pin SOT23 (derate 7.4mW/°C above +70°C) (Note 1) .....595mW Junction-to-Case Thermal Resistance (θJC) (Note 1) 6-Pin SOT23 ................................................................39°C/W Junction-to-Ambient Thermal Resistance (θJA) (Note 1) 6-Pin SOT23 ..............................................................134°C/W Operating Temperature Range .........................-40°C to +105°C Junction Temperature. .....................................................+150°C Storage Temperature Range ............................-65°C to +150°C Lead Temperature.......................................................... (Note 2) Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial. Note 2: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device can be exposed to during board-level solder attach and rework. Maxim recommends the use of the solder profiles recommended in the industry-standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection reflow processes. Preheating, per this standard, is required. Hand or wave soldering is not recommended. 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 (Circuit of Figure 1, C1 = C2 =2.2µF, VIN = VSHDN = +5V, VGND = 0, TA = 0°C to +105°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS Supply Voltage Range RL = 5kΩ Quiescent Supply Current TA = +25°C (Note 3) Shutdown Supply Current VSHDN = 0 MIN TYP 1.4 5.5 TA = 0°C to +105°C 1.5 5.5 950 1700 TA = +25°C 0.002 1 TA = 0°C to +105°C 0.03 Short-Circuit Current Output shorted to ground, TA = +25°C Oscillator Frequency TA = +25°C 70 125 Voltage Conversion Efficiency IOUT = 0, TA = +25°C 99 99.9 Output Resistance IOUT = 30mA (Note 4) OUT-to-GND Shutdown Resistance VSHDN = 0, OUT is internally pulled to GND in shutdown SHDN Input Logic-High SHDN Input Logic-Low SHDN Bias Current Wake-Up Time from Shutdown 2 MAX TA = +25°C 170 TA = +25°C 12 TA = 0°C to +105°C 2.5V ≤ VIN ≤ 5.5V 25 8.5 2.5V ≤ VIN ≤ 5.5V 0.6 0.2 = GND or IN IOUT = 15mA TA = +25°C TA = 0°C to +105°C -100 µA kHz Ω Ω V VIN - 0.2 VIN(MIN) ≤ VIN ≤ 2.5V SHDN µA % 2.0 VIN(MIN) ≤ VIN ≤ 2.5V V mA 180 36 3 UNITS +0.05 10 100 _______________________________________________________________________________________ +100 V nA µs 30mA Inverting Charge Pump in SOT23 for EMI-Sensitive Automotive Applications (Circuit of Figure 1, C1 = C2 =2.2µF, VIN = VSHDN = +5V, VGND = 0, TA = 0°C to +105°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS Supply Voltage Range MIN RL = 5kΩ TYP MAX UNITS 5.5 V 1.6 Output Current Continuous, long-term Quiescent Supply Current (Note 3) Oscillator Frequency µA 200 kHz IOUT = 30mA (Note 5) 36 Ω OUT-to-GND Shutdown Resistance VSHDN = 0, OUT is internally pulled to GND in shutdown 8.5 Ω Input Logic-High SHDN Input Logic-Low 2.5V ≤ VIN ≤ 5.5V 125 mARMS Output Resistance SHDN 60 60 1800 2.1 VIN(MIN) ≤ VIN ≤ 2.5V V VIN - 0.2 2.5V ≤ VIN ≤ 5.5V 0.6 VIN(MIN) ≤ VIN ≤ 2.5V 0.2 V Note 3: The MAX16945 may draw high supply current during startup, up to the minimum operating supply voltage. To guarantee proper startup, the input supply must be capable of delivering 90mA more than the maximum load current. Note 4: Output resistance is guaranteed with capacitor ESR of 0.3Ω or less. Note 5: All specifications from -40°C to +105°C are guaranteed by design, not production tested. Typical Operating Characteristics (Circuit of Figure 1, C1 = C2 = 2.2µF, VIN = VSHDN = +5V, VGND = 0, TA = +25°C, unless otherwise noted.) OUTPUT VOLTAGE vs. OUTPUT CURRENT 80 EFFICIENCY (%) VIN = +2V -1.5 -2.0 -2.5 VIN = +3.3V -3.0 VIN = +3.3V 70 60 VIN = +2V 50 40 30 -3.5 -4.0 25 20 15 10 0 0 10 30 5 10 -5.0 0 35 20 VIN = +5V -4.5 MAX16945 toc03 90 40 OUTPUT IMPEDANCE (Ω) -1.0 VIN = +5V MAX16945 toc02 -0.5 OUTPUT VOLTAGE (V) 100 MAX16945 toc01 0 OUTPUT IMPEDANCE vs. INPUT VOLTAGE EFFICIENCY vs. OUTPUT CURRENT 5.0 5.5 _______________________________________________________________________________________ 3 20 30 OUTPUT CURRENT (mA) 40 50 0 10 20 30 OUTPUT CURRENT (mA) 40 50 1.5 2.0 2.5 3.0 3.5 4.0 4.5 INPUT VOLTAGE (V) MAX16945 ELECTRICAL CHARACTERISTICS Typical Operating Characteristics (continued) (Circuit of Figure 1, C1 = C2 = 2.2µF, VIN = VSHDN = +5V, VGND = 0, TA = +25°C, unless otherwise noted.) SUPPLY CURRENT vs. SUPPLY VOLTAGE 1.0 500 VIN = +5V 400 VIN = +3.3V 300 VIN = +2V 200 0.5 100 0 MAX16945 toc06 600 35 OUTPUT IMPEDANCE (Ω) 1.5 40 MAX16945 toc05 700 SUPPLY CURRENT (nA) 2.0 OUTPUT IMPEDANCE vs. TEMPERATURE SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE MAX16945 toc04 2.5 SUPPLY CURRENT (mA) 30 VIN = +2V 25 20 VIN = +3.3V 15 VIN = +5V 10 5 0 0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 SUPPLY VOLTAGE (V) TEMPERATURE (°C) TEMPERATURE (°C) PUMP FREQUENCY vs. TEMPERATURE OUTPUT NOISE AND RIPPLE MAX16945 toc08 MAX16945 toc07 120 119 PUMP FREQUENCY (kHz) MAX16945 30mA Inverting Charge Pump in SOT23 for EMI-Sensitive Automotive Applications 118 117 116 10mV/div 115 114 113 112 111 110 2μs/div -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) STARTUP FROM SHUTDOWN MAX16945 toc09 SHDN 5V/div VOUT 2V/div 40μs/div 4 _______________________________________________________________________________________ 30mA Inverting Charge Pump in SOT23 for EMI-Sensitive Automotive Applications (Circuit of Figure 1, C1 = C2 = 2.2µF, VIN = VSHDN = +5V, VGND = 0, TA = +25°C, unless otherwise noted.) OUTPUT RIPPLE vs. CAPACITANCE OUTPUT CURRENT vs. CAPACITANCE 40 VIN = +4.375V, VOUT = -4V 30 MAX16945 toc11 200 OUTPUT RIPPLE (mV) 50 OUTPUT CURRENT (mA) 250 MAX16945 toc10 60 VIN = +2.825V, VOUT = -2.5V 20 VIN = +1.7V, VOUT = -1.5V VIN = +4.375V, VOUT = -4V 150 VIN = +2.825V, VOUT = -2.5V 100 VIN = +1.7V, VOUT = -1.5V 50 10 0 0 0 1 2 3 4 5 6 7 8 9 0 10 1 2 3 Pin Description PIN NAME 1 OUT 2 IN FUNCTION Inverting Charge-Pump Output Power-Supply Voltage Input. Input range is 1.4V to 5.5V. 3 C1- 4 GND Ground SHDN Shutdown Input. Drive SHDN high for normal operation; drive SHDN low for shutdown mode. OUT is actively pulled to ground during shutdown. 5 6 C1+ Negative Terminal of the Flying Capacitor Positive Terminal of the Flying Capacitor 4 5 6 7 8 9 10 CAPACITANCE (μF) CAPACITANCE (μF) C1 INPUT 1.5V TO 5.5V 2 3 C1- 6 C1+ IN OUT C3 RL MAX16945 ON OFF 5 SHDN NEGATIVE OUTPUT -1 ✕ VIN 1 C2 GND 4 Figure 1. Typical Application Circuit S1 S2 IN C1 Detailed Description The MAX16945 capacitive charge pump inverts the voltage applied to its input. For highest performance, use low-ESR capacitors. During the first half-cycle, switches S2 and S4 open, switches S1 and S3 close, and capacitor C1 charges to the voltage at IN (Figure 2). During the second halfcycle, S1 and S3 open, S2 and S4 close, and C1 is level shifted downward by VIN volts. This connects C1 in parallel with the reservoir capacitor C2. If the voltage across C2 is smaller than the voltage across C1, charge flows from C1 to C2 until the voltage across C2 reaches -VIN. The absolute value of the inverting output S3 S4 C2 VOUT = -(VIN) Figure 2. Ideal Voltage Inverter voltage is always smaller than the value of the input voltage due to the losses of the flying capacitor C1 and the resistance of the switches S1–S4. _______________________________________________________________________________________ 5 MAX16945 Typical Operating Characteristics (continued) MAX16945 30mA Inverting Charge Pump in SOT23 for EMI-Sensitive Automotive Applications Efficiency Considerations Shutdown The efficiency of the MAX16945 is dominated by its quiescent supply current (IQ) at low output current, and by its output impedance (ROUT) at higher output current. Efficiency is calculated as follows: The MAX16945 has a logic-controlled shutdown input. Driving SHDN low places the device in a low-power shutdown mode. The charge-pump switching halts, supply current is reduced to 2nA, and OUT is actively pulled to ground through a 3Ω resistance. Driving SHDN high will restart the charge pump. The switching frequency and capacitor values determine how soon the device will reach 90% of the input voltage. η≅ ⎛ I ⎞ OUT x ROUT ⎜1 − ⎟ VIN IOUT + IQ ⎝ ⎠ IOUT where the output impedance is roughly approximated by: 1 ROUT ≅ + 2RSW + 4ESRC1 + ESRC2 fOSC x C1 ( ) The first term is the effective resistance of an ideal switched-capacitor circuit (Figures 3a and 3b), and RSW is the sum of the charge pump’s internal switch resistances (typically 4Ω to 5Ω at VIN = +5V). The typical output impedance is more accurately determined from the Typical Operating Characteristics. fOSC V+ VOUT C2 C1 RL Figure 3a. Switched-Capacitor Model V+ VOUT 1 fOSC ✕ C1 C2 RL Figure 3b. Equivalent Circuit Current Limit The MAX16945 limits its input current upon startup to 170mA (typ). This prevents low-current or higher output impedance input supplies (such as alkaline cells) from being overloaded when power is applied or when the device awakes from shutdown. 6 Capacitor Selection The charge-pump output resistance is a function of the ESR of C1 and C2. To maintain the lowest output resistance, use capacitors with low ESR. Flying Capacitor (C1) Increasing the flying capacitor’s value reduces the output resistance. Above a certain point, increasing C1’s capacitance has negligible effect because the output resistance is then dominated by internal switch resistance and capacitor ESR. Output Capacitor (C2) Increasing the output capacitor’s value reduces the output ripple voltage. Decreasing its ESR reduces both output resistance and ripple. Lower capacitance values can be used with light loads if higher output ripple can be tolerated. Use the following equation to calculate the peak-to-peak ripple: VRIPPLE = REQUIV REQUIV = Applications Information IOUT + 2 × IOUT × ESRC2 2(fOSC )C2 Input Bypass Capacitor (C3) If necessary, bypass the incoming supply to reduce its AC impedance and the impact of the MAX16945’s switching noise. An input bypass capacitor (C3) with a value equal to that of C1 is recommended. Voltage Inverter The most common application for these devices is a charge-pump voltage inverter (Figure 1). This application requires only two external components, capacitors C1 and C2, plus an input bypass capacitor C3, if necessary. See the Capacitor Selection section for suggested capacitor sizes. _______________________________________________________________________________________ 30mA Inverting Charge Pump in SOT23 for EMI-Sensitive Automotive Applications Combined Doubler/Inverter In the circuit of Figure 6, capacitors C1 and C2 form the inverter, while C3 and C4 form the doubler. C1 and C3 are the pump capacitors; C2 and C4 are the reservoir capacitors. Because both the inverter and doubler use part of the charge-pump circuit, loading either output causes both outputs to decline toward GND. Make sure the sum of the currents drawn from the two outputs does not exceed 30mA. SHDN 2 3 C1 4 3 +VIN 2 C1 4 3 MAX16945 4 C1 6 1 MAX16945 6 1 6 1 VOUT = -VIN VOUT C2 D2 C2 5 C2 D1, D2 = 1N4148 2 D1 MAX16945 … 5 +VIN 5 … C4 C3 SHDN VOUT = (2VIN) (VFD1) - (VFD2) VOUT = -nVIN Figure 4. Cascading MAX16945s to Increase Output Voltage Figure 6. Combined Doubler and Inverter Paralleling Devices Heavy Load Connected to a Positive Supply Paralleling multiple MAX16945s reduces the output resistance. Each device requires its own charge-pump capacitor (C1), but the reservoir capacitor (C2) serves all devices (Figure 5). Increase C2’s value by a factor of n, where n is the number of parallel devices. Figure 5 shows the equation for calculating output resistance. Under heavy loads, where a higher supply is sourcing current into OUT, the OUT supply must not be pulled above ground. Applications that sink heavy current into OUT require a Schottky diode (1N5817) between GND and OUT, with the anode connected to OUT (Figure 7). +VIN … GND 2 2 3 C1 3 MAX16945 4 C1 1 6 … 5 SHDN MAX16945 MAX16945 1 VOUT 1 Figure 7. Heavy Load Connected to a Positive Supply 5 VOUT = -VIN V+ RL OUT 4 6 4 Layout and Grounding C2 ROUT OF SINGLE DEVICE ROUT = NUMBER OF DEVICES Figure 5. Paralleling MAX16945s to Reduce Output Resistance Good layout is important, primarily for good noise performance. To ensure good layout, mount all components as close together as possible, keep traces short to minimize parasitic inductance and capacitance, and use a ground plane. Chip Information PROCESS: BiCMOS _______________________________________________________________________________________ 7 MAX16945 Cascading Devices Two devices can be cascaded to produce an even larger negative voltage (Figure 4). The unloaded output voltage is normally -2 x VIN, but this is reduced slightly by the output resistance of the first device when multiplied by the quiescent current of the second. When cascading more than two devices, the output resistance rises dramatically. The maximum load current and startup current of the nth cascaded circuit must not exceed the maximum output current capability of the (n-1)th circuit to ensure proper startup. MAX16945 30mA Inverting Charge Pump in SOT23 for EMI-Sensitive Automotive Applications Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 6 SOT23 U6F-6 21-0058 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. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
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