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Advanced Monolithic Systems
FEATURES
* 99.9% Voltage Conversion Efficiency * 92% Power Conversion Efficiency * Wide Input Voltage Range +2.4V to 5.5V * 185A Supply Current * Available in SO-8 and PDIP Packages * Only 3 external Capacitors Required
AMS682
INVERTING VOLTAGE DOUBLER
APPLICATIONS
* Portable Handheld Instrumentation * Cellular Phones * Panel Meters * -10V from +5V logic Supply * -6V from a Single 3V Lithium Cell * LCD Display Bias Generator * Operational Amplifiers Power Supplies
GENERAL DESCRIPTION
The AMS682 is a CMOS charge pump converter that provides an inverted doubled output from a single positive supply. Requiring only three external capacitors for full circuit implementation the device has an on -board 12kHz (typical) oscillator which provides the clock. Low output source impedance (typically 140), provides output current up to 10mA. The AMS682 features low quiescent current and high efficiency, making it the ideal choice for a wide variety of applications that require a negative voltage derived from a single positive supply. The compact size and minimum external parts count of the AMS682 makes it useful in many medium current, dual voltage analog power supplies. The AMS682E is operational in the full industrial temperature range of -40C to 85C while AMS682C is operating over a 0C to 70C temperature range. The AMS682E/AMS682C are available in surface mount 8-Pin SOIC (SO-8) and 8-Pin Plastic DIP (PDIP) packages.
ORDERING INFORMATION:
PACKAGE TYPE 8 LEAD SOIC AMS682ES AMS682CS 8 LEAD PDIP AMS682EP AMS682CP OPERATING TEMPERATURE RANGE -40 to 85 C 0 to 70 C
TYPICAL OPERATING CIRCUIT
VIN +2.4V < VIN < +5.5V
VIN ON/OFF
PIN CONFIGURATIONS
8-LEAD DIP/ 8-LEAD SOIC
C-2 1 2 8 7 ON/OFF C+1 VIN GND
+ C1 + C2 -
C1 + C1 C2 + C2 -
VOUT = -(2 X VIN)
VOUT GND + COUT
C+2 C-2 VOUT
AMS682
3 4 6 5
VOUT
GND All Caps = 3.3F
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS682
ABSOLUTE MAXIMUM RATINGS
VIN VIN V/T VOUT VOUT Short Circuit Duration Power Dissipation (TA 70C) Plastic DIP SOIC +5.8V 1V/sec -11.6V Continuous 730mW 470mW Operating Temperature Range AMS682E AMS682C Storage temperature Soldering information Lead Temperature (Soldering 10sec) -40C to 85C 0C to 70C -85C to +150C +300C
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at VIN =+5V and TA = +25C test circuit figure 1, unless otherwise specified. Parameter
Supply Voltage Range Supply Current
Conditions
VIN IIN
-
Min
2.4
AMS682 Typ
185 140 170
Max
5.5 300 400 180 230 320
Units
V A
RL=2k RL = RL =
VOUT Source Resistance Source Resistance
ROUT
I L = 10mA I L =10mA I L = 5mA , VIN = 2.8V
-
Oscillator Frequency Power Efficiency Voltage Conversion Efficiency
FOSC PEFF VOUTEFF RL = 2k VOUT RL=
12 92 99.9

kHz % %
90 99
PIN DESCRIPTION
PIN NO 8-PIN DIP/SOIC 1 2 3 4 5 6 7 8
SYMBOL C1C2+ C2VOUT GND VIN C1+ ON/OFF
DESCRIPTION Input. Capacitor C1 negative terminal. Input. Capacitor C2 positive terminal. Input. Capacitor C2 negative terminal Output. Negative output voltage (-2VIN) Input. Device ground. Input. Power supply voltage. Input. Capacitor C1 positive terminal. ON/OFF Oscilator.
VIN
(+5V)
+ C1 + C2 -
7 1 2 3
6 VIN 8 C1 + ON/OFF C1C2 + C2V-OUT 4 GND 5
V-OUT
+ COUT RL
GND
All Caps = 3.3F
Figure 1. AMS682 Test Circuit
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS682
DETAILED DESCRIPTION
Phase 1
EFFICIENCY CONSIDERATIONS
Theoretically a charge pump voltage multiplier can approach 100% efficiency under the following conditions: * The charge pump switches have virtually no offset and are extremely low on resistance. * Minimal power is consumed by the drive circuitry. * The Impedances of the reservoir and pump capacitors are negligible. For the AMS682, efficiency is as shown below:
VSS charge storage- before this phase of the clock cycle, capacitor C1 is already charged to +5V. C1+ is then switched to ground and the charge in C1- is transferred to C2-. Since C2+ is at +5V, the voltage potential across capacitor C2 is now -10V.
V =+5V IN
SW1 + C1 SW2 -5V + -
SW3 VOUT C2 SW4 C3 +
Voltage Efficiency = VOUT / (-2VIN ) VOUT = -2VIN + VDROP VDROP = (IOUT) (R OUT) Power Loss = IOUT (VDROP)
Figure 2. Charge Pump - Phase 1
Phase 2
There will be a substantial voltage difference between VOUT and 2VIN if the impedances of the pump capacitors C1 and C2 are high with respect to their respective output loads. If the values of the reservoir capacitor C3 are larger the output ripple will be reduced. The efficiency will be improved if both pump and reservoir capacitors have larger values. ( See "Capacitor Selection" in Application Section.)
VSS transfer- phase two of the clock connects the negative terminal of C2 to the negative side of reservoir capacitor C3 and the positive terminal of C2 to the ground, transferring the generated -10V to C3. Simultaneously, the positive side of capacitor C1 is switched to +5V and the negative side is connected to ground. C2 is then switched to VCC and GND and Phase 1 begins again.
V =+5V IN
APPLICATIONS
Negative Doubling Converter
The AMS682 is most commonly used as a charge pump voltage converter which provides a negative output of two times a positive input voltage (Fig.4)
V OUT
SW1 + C1 SW2 + SW4
SW3 C2 C3 +
C1 + 22F
1 2
-10V
C2 + 22F
C1- ON/OFF C2+ C2C1+ VIN
8 7 6 5 + C3 22F GND
3 4
VIN
Figure 3. Charge Pump - Phase 2
V-OUT GND
MAXIMUM OPERATING LIMITS
The AMS682 has on-chip zener diodes that clamp VIN to approximately 5.8V, and V-OUT to -11.6V. Exceeding the maximum supply voltage will potentially damage the chip. With an input voltage of 2V to 5.5V the AMS682 will operate over the entire operating temperature range.
V-OUT
Figure 4. Inverting Voltage Doubler
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS682
APPLICATIONS (Continued)
Capacitor Selection Paralleling devices
The output resistance of the AMS682 is determined in part by the ESR of the capacitors used. An expression for ROUT is derived as shown below: ROUT = 2( RSW1+RSW2+ESRC1+ RSW3+RSW4+ESRC2) +2(RSW1+RSW2+ESRC1+ RSW3+RSW4+ESRC2) +1/ (fPUMP X C1) +1/ (fPUMP X C2) + ESRC3 Assuming all switch resistances are approximately equal: ROUT = 16 RSW+ 4ESRC1+ 4ESRC2+ ESRC3 +1/ (fPUMP X C1) +1/ (fPUMP X C2)
Paralleling multiple AMS682 reduces the output resistance of the converter. The effective output resistance is the output resistance of one device divided by the number of devices. Figure 5 illustrates how each device requires separate pump capacitors C1 and C2, but all can share a single reservoir capacitor.
-5V Regulated Supply From A Single 3V Battery
ROUT is typically 140 at +25C with VIN =+5V and 3.3F low ESR capacitors. The fixed term (16RSW) is about 8090. Increasing or decreasing values of C1 and C2 will affect efficiency by changing ROUT. Table 1 shows ROUT for various values of C1 and C2 (assume 0.5 ESR). C1 must be rated at 6VDC or greater while C2 and C3 must be rated at 12VDC or greater. Output voltage ripple is affected by C3. Typically the larger the value of C3 the less the ripple for a given load current. The formula for p-p VRIPPLE is : VRIPPLE = [1/[2(fPUMP X C3)]+2(ESRC3)] (IOUT) For a 10F (0.5 ESR), fPUMP = 10kHz and IOUT=10mA the peak -to-peak ripple voltage at the output will be less than 60mV. In most applications (IOUT 10mA) a 10-20F capacitor and 1-5F pump capacitors will be sufficient. Table 2 shows VRIPPLE for different values of C3 (assume 1 ESR).
Figure 6 shows a -5V power supply using one 3V battery. The AMS682 provides -6V at V-OUT , which is regulated to -5V by the negative LDO. The AMS682 input can vary from 3V to 5.5V without affecting regulation significantly. A voltage detector is connected to the battery to detect undervoltage. This unit is set to detect at 2.7V. With higher input voltage, more current can be drawn from the outputs of the AMS682. With 5V at VIN , 10mA can be drawn from the regulated output. Assuming 150 source resistance for the converter, with IL=10mA, the charge pump will drop 1.5V.
Table 1. ROUT vs. C1, C2 C1, C2 (F) 0.05 0.10 0.47 1.00 3.30 5.00 10.00 22.00 100.00
ROUT ( ) 4085 2084 510 285 145 125 105 94 87
Table 2. VRIPPLE Peak-to-Peak vs. C3 (IOUT =10mA) VRIPPLE (mV) C3(F) 0.50 1020 1.00 520 3.30 172 5.00 120 10.00 70 22.00 43 100.00 25
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS682
APPLICATIONS (Continued)
VIN
+ 10F + VIN C1+ C1C2+ C2GND
10F
10F
+ + -
VIN C1+ C1C2+ C2GND
V-OUT
10F
V-OUT C-OUT 22F
NEGATIVE SUPPLY
+
GND
Figure 5. Paralleling AMS682 for Lower Output Source Resistance
+ 10F + 3V 10F + -
VIN C1+ C1C2+ C2- V-OUT GND VIN VSS VOUT
+ -
GROUND 1F -5 SUPPLY
+
22F C-OUT
NEG. LDO
VOLTAGE DETECT. VIN VOUT VSS
LOW BATTERY
Figure 6. Negative Supply Derived from 3V Battery
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS682
TYPICAL PERFORMANCE CHARACTERISTICS (FOSC = 12kHz)
VOUT vs. Load Current
240
-7.5 -8.0 -8.5 VIN = 5V
Output Resistance vs. VIN OUTPUT RESISTANCE()
C1-C3 = 3.3F 220 200 180 160 140 120
VOUT (V)
-9.0 -9.5 -10.0 -10.5 0 5 10 15
1
2
3
4
5
6
LOAD CURRENT Output Source Resistance vs. Temperature OUTPUT SOURCE RESISTANCE ) (
200 180 160 140 120 100 80 -50 0 50 100 VIN = 5V IOUT = 10mA 300 NO LOAD
VIN (V) Supply Current vs. V IN
SUPPLY CURRENT (A)
250
200
150
100 50 1 2 3 VIN (V) 4 5 6
TEMPERATURE (C) Output Ripple vs. Output Current OUTPUT RIPPLE (mV PK-PK)
200
150
VIN = 5V C3 = 10 F
100
50
C3 = 100F
0 0 5 10 15 20
OUTPUT CURRENT (mA)
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS682
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted.
8 LEAD SOIC PLASTIC PACKAGE (S)
0.189-0.197* (4.801-5.004) 8 7 6 5
0.228-0.244 (5.791-6.197)
0.150-0.157** (3.810-3.988)
1
2
3
4
0.053-0.069 (1.346-1.752) 0.004-0.010 (0.101-0.254) 0.008-0.010 (0.203-0.254)
0.010-0.020 x 45 (0.254-0.508) 0-8 TYP
0.014-0.019 (0.355-0.483)
0.050 (1.270) TYP
0.016-0.050 (0.406-1.270)
S (SO-8 ) AMS DRW# 042293
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
8 LEAD PLASTIC DIP PACKAGE (P)
0.400* (10.160) MAX 8 7 6 5
0.2550.015* (6.4770.381)
1
2
3
4
0.045-0.065 (1.143-1.651)
0.1300.005 (3.3020.127)
0.300-0.325 (7.620-8.255)
0.065 (1.651) TYP 0.005 (0.127) MIN 0.1000.010 (2.5400.254) 0.125 (3.175) MIN 0.0180.003 (0.4570.076) 0.015 (0.380) MIN
0.009-0.015 (0.229-0.381) 0.325 +0.025 -0.015 (8.255 +0.635 -0.381
)
P (8L PDIP ) AMS DRW# 042294
*DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTUSIONS. MOLD FLASH OR PROTUSIONS SHALL NOT EXCEED 0.010" (0.254mm)
Advanced Monolithic Systems, Inc.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140

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