19-0472; Rev 1; 7/97 Compact, Dual-Output Charge Pump ____________________________Features ♦ 1.11mm-High µMAX Package The internal oscillator is guaranteed to be between 20kHz and 38kHz, keeping noise above the audio range while consuming minimal supply current. A 75Ω output impedance permits useful output currents up to 20mA. The MAX865 comes in a 1.11mm-high, 8-pin µMAX package that occupies half the board area of a standard 8-pin SOIC. For a device with selectable frequencies and logic-controlled shutdown, refer to the MAX864 data sheet. ♦ +1.5V to +6.0V Input Voltage ________________________Applications Low-Voltage GaAsFET Bias in Wireless Handsets ♦ Compact: Circuit Fits in 0.08in2 ♦ Requires Only Four Capacitors ♦ Dual Outputs (positive and negative) ♦ 20kHz (min) Frequency (above the audio range) ______________Ordering Information PART TEMP. RANGE MAX865C/D MAX865EUA 0°C to +70°C -40°C to +85°C PIN-PACKAGE Dice 8 µMAX VCO and GaAsFET Supplies Split Supply from 3 Ni Cells or 1 Li+ Cell Low-Cost Split Supply for Low-Voltage Data-Acquisition Systems __________Typical Operating Circuit Split Supply for Analog Circuitry LCD Panels VIN (+1.5V to +6.0V) __________________Pin Configuration IN C1+ MAX865 TOP VIEW V+ +2*VIN V- -2*VIN C1- C1- 1 8 C1+ C2+ 2 7 V+ C2- 3 6 IN 5 GND MAX865 V- 4 C2+ C2GND µMAX GND GND +VIN to ±2VIN CONVERTER ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468. MAX865 _______________General Description The MAX865 is a CMOS charge-pump DC-DC converter in an ultra-small µMAX package. It produces positive and negative outputs from a single positive input, and requires only four capacitors. The charge pump first doubles the input voltage, then inverts the doubled voltage. The input voltage ranges from +1.5V to +6.0V. ABSOLUTE MAXIMUM RATINGS V+ to GND .................................................................+12V, -0.3V IN to GND .................................................................+6.2V, -0.3V V- to GND ..................................................................-12V, +0.3V V- Output Current .............................................................100mA V- Short-Circuit to GND ................................................Indefinite Continuous Power Dissipation (TA = +70°C) µMAX (derate 4.1mW/°C above +70°C) .......................330mW Operating Temperature Range MAX865EUA .....................................................-40°C to +85°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+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 = 5V, C1 = C2 = C3 = C4 = 3.3µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS Minimum Supply Voltage RLOAD = 10kΩ Maximum Supply Voltage RLOAD = 10kΩ MIN TYP 2.0 1.5 0.6 TA = -40°C to +85°C (Note 1) 19.5 TA = -40°C to +85°C (Note 1) Output Resistance Power Efficiency 24 V V 1.05 mA 32.5 18 IV+ = 1mA, IV- = 0mA TA = +25°C V+ = 10V (forced), IV- = 1mA TA = +25°C kHz 34 150 TA = TMIN to TMAX 200 280 75 Ω 100 TA = TMIN to TMAX 140 IL = 5mA Voltage Conversion Efficiency UNITS 1.15 TA = +25°C Oscillator Frequency MAX 6.0 TA = +25°C Supply Current 85 V+, RL = ∞ 95 99 V-, RL = ∞ 90 98 % % Note 1: These specifications are guaranteed by design and are not production tested. __________________________________________Typical Operating Characteristics (Circuit of Figure 1, VIN = 5V, TA = +25°C, unless otherwise noted.) 80 EFFICIENCY (%) V- 70 60 50 40 100 70 60 50 40 70 60 50 40 30 30 20 20 20 10 10 10 0 0 2 4 6 8 10 12 14 16 18 OUTPUT CURRENT (mA) V- 80 V- 30 0 V+ 90 EFFICIENCY (%) 80 2 V+ 90 MAX865-03 100 MAX865-02 V+ 90 MAX865-01 100 EFFICIENCY vs. OUTPUT CURRENT (VIN = 2V) EFFICIENCY vs. OUTPUT CURRENT (VIN = 3.3V) EFFICIENCY vs. OUTPUT CURRENT (VIN = 5V) EFFICIENCY (%) MAX865 Compact, Dual-Output Charge Pump 0 0 1 2 3 4 5 6 OUTPUT CURRENT (mA) 7 8 0 0.5 1.0 1.5 2.0 OUTPUT CURRENT (mA) _______________________________________________________________________________________ 2.5 Compact, Dual-Output Charge Pump (Circuit of Figure 1, VIN = 5V, TA = +25°C, unless otherwise noted.) OUTPUT VOLTAGE RIPPLE vs. PUMP CAPACITANCE VBOTH V+ AND V- LOADED EQUALLY 0 -2 C1 = C2 = C3 = C4 = 3.3µF VIN = 4.75V -4 V- -6 -8 2 4 6 8 10 250 200 F 150 D 100 MAX865-05 AE BC 50 VIN = 3.15V, V+ + |V-| = 10V 4 3 VIN = 1.90V, V+ + |V-| = 6V 2 1 14 12 0 5 0 10 15 20 25 30 35 40 45 50 5 0 10 15 20 25 30 35 40 45 50 PUMP CAPACITANCE (µF) PUMP CAPACITANCE (µF) OUTPUT RESISTANCE vs. TEMPERATURE SUPPLY CURRENT vs. SUPPLY VOLTAGE 300 MAX865-07 1000 C1 = C2 = C3 = C4 = 3.3µF 900 5 0 OUTPUT CURRENT (mA) 800 OUTPUT RESISTANCE (Ω) SUPPLY CURRENT (µA) 700 600 500 400 300 200 250 200 C1 = C2 = C3 = C4 = 3.3µF V-, VIN = 3.3V V-, VIN = 5.0V 150 100 V+, VIN = 3.3V V+, VIN = 5.0V 50 100 0 0 2.0 2.5 3.0 3.5 4.0 4.5 25 5 45 85 105 125 65 SUPPLY VOLTAGE (V) TEMPERATURE (°C) PUMP FREQUENCY vs. TEMPERATURE OUTPUT RESISTANCE vs. SUPPLY VOLTAGE 27 VIN = 5.0V VIN = 3.3V 23 250 OUTPUT RESISTANCE (Ω) 25 21 VIN = 2.0V 19 17 -55 -35 -15 5.0 5.5 6.0 MAX865-09 0 300 VIN = 4.75V, V+ + |V-| = 16V 6 C1 = C2 = C3 = C4 V+ -10 A: V+, IN = 4.75V, V+ + |V-| = 16V B: V+, IN = 3.15V, V+ + |V-| = 10V C: V+, IN = 1.90V, V+ + |V-| = 6V D: V-, IN = 4.75V, V+ + |V-| = 16V E: V-, IN = 3.15V, V+ + |V-| = 10V F: V-, IN = 1.90V, V+ + |V-| = 6V 200 15 V- 150 V+ 100 50 C1 = C2 = C3 = C4 = 3.3µF MAX865-10 2 7 MAX865-08 4 C1 = C2 = C3 = C4 350 OUTPUT CURRENT, V+ TO V- (mA) 6 PUMP FREQUENCY (kHz) OUTPUT VOLTAGE, V+, V- (V) 400 MAX865-04 V+ 8 OUTPUT VOLTAGE RIPPLE (mVp-p) 10 OUTPUT CURRENT vs. PUMP CAPACITANCE MAX865-06 OUTPUT VOLTAGE vs. OUTPUT CURRENT C1 = C2 = C3 = C4 = 3.3µF 0 -40 -20 0 20 40 60 TEMPERATURE (°C) 80 100 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 3 MAX865 ____________________________Typical Operating Characteristics (continued) MAX865 Compact, Dual-Output Charge Pump ____________________________Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = 5V, TA = +25°C, unless otherwise noted.) OUTPUT RIPPLE (C1 = C2 = C3 = C4 = 1µF) OUTPUT RIPPLE (C1 = C2 = C3 = C4 = 3.3µF) V- OUTPUT 20mV/div V- OUTPUT 10mV/div V+ OUTPUT 50mV/div V+ OUTPUT 10mV/div 10µs/div 10µs/div VIN = 4.75V, 1mA LOAD VIN = 4.75V, 1mA LOAD _____________________Pin Description PIN NAME FUNCTION 1 C1- Negative Terminal of the Flying Boost Capacitor 2 C2+ Positive Terminal of the Flying Inverting Capacitor 3 C2- Negative Terminal of the Flying Inverting Capacitor 4 V- 5 GND 6 IN Positive Power-Supply Input 7 V+ Output of the Boost Charge Pump 8 C1+ Output of the Inverting Charge Pump Ground VIN 3.3µF C1- C1+ IV+ C2+ MAX865 V+ C2- IN 3.3µF 3.3µF V- RL+ GND IV3.3µF Positive Terminal of the Flying Boost Capacitor RL- OUT- Figure 1. Test Circuit 4 OUT+ _______________________________________________________________________________________ Compact, Dual-Output Charge Pump and S7 open, switches S6 and S8 close, and the charge on capacitor C2 transfers to C4, generating the negative supply. The eight switches are CMOS power MOSFETs. Switches S1, S2, S4, and S5 are P-channel devices, while switches S3, S6, S7, and S8 are N-channel devices. The MAX865 contains all the circuitry needed to implement a voltage doubler/inverter. Only four external capacitors are needed. These may be polarized electrolytic or ceramic capacitors with values ranging from 1µF to 100µF. Figure 2a shows the ideal operation of the positive voltage doubler. The on-chip oscillator generates a 50% duty-cycle clock signal. During the first half cycle, switches S2 and S4 open, switches S1 and S3 close, and capacitor C1 charges to the input voltage (V IN). During the second half cycle, switches S1 and S3 open, switches S2 and S4 close, and capacitor C1 is level shifted upward by VIN. Assuming ideal switches and no load on C3, charge transfers into C3 from C1 such that the voltage on C3 will be 2VIN, generating the positive supply output (V+). Charge-Pump Output The MAX865 is not a voltage regulator: the output source resistance of either charge pump is approximately 150Ω at room temperature with VIN = +5V, and V+ and V- will approach +10V and -10V, respectively, when lightly loaded. Both V+ and V- will droop toward GND as the current draw from either V+ or V- increases, since V- is derived from V+. Treating each converter separately, the droop of the negative supply (VDROOP-) is the product of the current draw from V(IV-) and the source resistance of the negative converter (RS-): Figure 2b illustrates the ideal operation of the negative converter. The switches of the negative converter are out of phase with the positive converter. During the second half cycle, switches S6 and S8 open and switches S5 and S7 close, charging C2 from V+ (pumped up to 2VIN by the positive charge pump) to GND. In the first half of the clock cycle, switches S5 a) VDROOP- = I V - x RS The droop of the positive supply (V DROOP+ ) is the product of the current draw from the positive supply (I LOAD+ ) and the source resistance of the positive b) V+ S1 C1+ V+ S2 S5 C2+ S6 GND IN C3 C1 IV+ RL+ C2 IV- RL- C4 S3 S4 S7 IN GND C1- S8 V- GND C2- Figure 2. Idealized Voltage Quadrupler: a) Positive Charge Pump; b) Negative Charge Pump _______________________________________________________________________________________ 5 MAX865 _______________Detailed Description MAX865 Compact, Dual-Output Charge Pump converter (RS+), where ILOAD+ is the combination of IVand the external load on V+ (IV+): ( ) VDROOP+ = ILOAD+ x RS+ = I V+ + I V - x RS+ Determine V+ and V- as follows: V+ = 2VIN - VDROOP+ V - = (V+ - VDROOP ) = -(2VIN - VDROOP+ - VDROOP- ) The output resistance for the positive and negative charge pumps are tested and specified separately. The positive charge pump is tested with V- unloaded. The negative charge pump is tested with V+ supplied from an external source, isolating the negative charge pump. Current draw from either V+ or V- is supplied by the reservoir capacitor alone during one half cycle of the clock. Calculate the resulting ripple voltage on either output as follows: VRIPPLE = 1 2 ILOAD (1 / fPUMP ) (1 / CRESERVOIR ) where ILOAD is the load on either V+ or V-. For the typical fPUMP of 30kHz with 3.3µF reservoir capacitors, the ripple is 25mV when ILOAD is 5mA. Remember that, in most applications, the total load on V+ is the V+ load current (I V+) and the current taken by the negative charge pump (IV-). Efficiency Considerations Theoretically, a charge-pump voltage multiplier can approach 100% power efficiency under the following conditions: • The charge-pump switches have virtually no offset and extremely low on-resistance. • The drive circuitry consumes minimal power. • The impedances of the reservoir and pump capacitors are negligible. For the MAX865, the energy loss per clock cycle is the sum of the energy loss in the positive and negative converters, as follows: LOSSCYCLE = LOSSPOS + LOSSNEG = + 1 2 1 2 2 C1 ( V + ) − 2( V + ) ( VIN ) 2 2 C2 ( V + ) − ( V − ) The average power loss is simply: PLOSS = LOSSCYCLE x fPUMP Resulting in an efficiency of: ( η = Total Output Power / Total Output Power − PLOSS VIN 3.3µF 3.3µF 1 2 3.3µF C1C2- MAX865 C1+ V+ 8 1 C1- 7 2 C2+ MAX865 V+ C2- IN 3.3µF 3 4 C2V- IN GND 6 3 5 4 V- C1+ GND 8 7 OUT+ 3.3µF 6 IN 5 GND 3.3µF OUT- Figure 3. Paralleling MAX865s 6 _______________________________________________________________________________________ ) Compact, Dual-Output Charge Pump Charge-Pump Capacitor Selection To maintain the lowest output resistance, use capacitors with low effective series resistance (ESR). The chargepump output resistance is a function of C1, C2, C3, and C4’s ESR. Therefore, minimizing the charge-pump capacitors’ ESR minimizes the total output resistance. __________Applications Information Paralleling Devices Paralleling multiple MAX865s (Figure 3) reduces the output resistance of both the positive and negative converters. The effective output resistance is the output resistance of one device divided by the number of devices. Separate C1 and C2 charge-pump capacitors are required for each MAX865, but the reservoir capacitors C3 and C4 can be shared. Heavy Output Current Loads When under heavy loads, where V+ is sourcing current into V- (i.e., load current flows from V+ to V-, rather than from supply to ground), do not allow the V- supply to pull above ground. In applications where large currents flow from V+ to V-, use a Schottky diode (1N5817) between GND and V-, with the anode connected to GND (Figure 4). Positive and Negative Converter Layout and Grounding The MAX865 is most commonly used as a dual chargepump voltage converter that provides positive and negative outputs of two times a positive input voltage. The Typical Operating Circuit shows that only four external components are needed: capacitors C1 and C3 for the positive pump, C2 and C4 for the negative pump. In most applications, all four capacitors are low-cost, 3.3µF polarized electrolytics. For applications where PC board space is at a premium and very low currents are being drawn from the MAX865, 1µF capacitors may be used for the pump capacitors C1 and C2, with 1µF reservoir capacitors C3 and C4. Capacitors C2 and C4 must be rated at 12V or greater. 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 • Use a ground plane. GND MAX865 V- Figure 4. A Schottky diode protects the MAX865 when large currents flow from V+ to V-. _______________________________________________________________________________________ 7 MAX865 A substantial voltage difference exists between (V+ VIN) and VIN for the positive pump, and between V+ and V- if the impedances of the pump capacitors (C1 and C2) are large with respect to their output loads. Larger values of reservoir capacitors (C3 and C4) reduce output ripple. Larger values of both pump and reservoir capacitors improve power efficiency. Compact, Dual-Output Charge Pump MAX865 ___________________Chip Topography TRANSISTOR COUNT: 80 SUBSTRATE CONNECTED TO V+ C1- C1+ C2+ V+ 0.084" (2.13mm) IN C2- V- GND 0.058" (1.47mm) ________________________________________________________Package Information DIM C α A 0.101mm 0.004 in e B A1 L A A1 B C D E e H L α INCHES MAX MIN 0.044 0.036 0.008 0.004 0.014 0.010 0.007 0.005 0.120 0.116 0.120 0.116 0.0256 0.198 0.188 0.026 0.016 6° 0° MILLIMETERS MIN MAX 0.91 1.11 0.10 0.20 0.25 0.36 0.13 0.18 2.95 3.05 2.95 3.05 0.65 4.78 5.03 0.41 0.66 0° 6° 21-0036D E H 8-PIN µMAX MICROMAX SMALL-OUTLINE PACKAGE D 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 © 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.