ADMOS AMS682CS

Advanced
Monolithic
Systems
AMS682
INVERTING VOLTAGE DOUBLER
FEATURES
APPLICATIONS
• 99.9% Voltage Conversion Efficiency
• 92% Power Conversion Efficiency
• Wide Input Voltage Range +2.4V to 5.5V
• 185µ
µ A Supply Current
• Available in SO-8 and PDIP Packages
• Only 3 external Capacitors Required
• 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 140Ω), 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 -40°C to 85°C while AMS682C is operating over a
0°C to 70°C 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
OPERATING
8 LEAD PDIP
AMS682EP
AMS682CP
TEMPERATURE RANGE
-40 to 85° C
0 to 70° C
TYPICAL OPERATING CIRCUIT
VIN
PIN CONFIGURATIONS
+2.4V < VIN < +5.5V
C1
C2
+
C1 +
-
C1 -
+
C2 +
-
C2 -
8-LEAD DIP/ 8-LEAD SOIC
VIN
ON/OFF
VOUT = -(2 X VIN)
VOUT
GND
VOUT
+
COUT
C-2
1
C+2
2
C-2
VOUT
8
ON/OFF
7
C+1
3
6
VIN
4
5
GND
AMS682
GND
All Caps = 3.3µF
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 70°C)
Plastic DIP
SOIC
+5.8V
1V/µsec
-11.6V
Continuous
730mW
470mW
Operating Temperature Range
AMS682E
AMS682C
Storage temperature
Soldering information
Lead Temperature (Soldering 10sec)
-40°C to 85°C
0°C to 70°C
-85°C to +150°C
+300°C
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at VIN =+5V and TA = +25°C test circuit figure 1, unless otherwise specified.
Parameter
Conditions
Min
AMS682
Typ
Units
Max
Supply Voltage Range
VIN
RL=2kΩ
2.4

5.5
V
Supply Current
IIN
RL = ∞

185
300
µA
VOUT Source Resistance
RL = ∞


400
-
I L = 10mA

140
180
-
I L =10mA

170
230
I L = 5mA , VIN = 2.8V

ROUT
Source Resistance
-
Oscillator Frequency
FOSC
Power Efficiency
PEFF
Voltage Conversion Efficiency
VOUTEFF
Ω
320

12

kHz
RL = 2kΩ
90
92

%
VOUT RL= ∞
99
99.9

%
PIN DESCRIPTION
PIN NO
8-PIN DIP/SOIC
1
2
3
SYMBOL
DESCRIPTION
C1-
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.
C2+
C2-
4
VOUT
5
6
7
GND
VIN
C1+
8
ON/OFF
Advanced Monolithic Systems, Inc.
VIN
(+5V)
+
C1
-
7
1
2
+
C2
GND
-
3
6
VIN
8
C1 + ON/OFF
C1C2 +
C2-
V-OUT 4
GND
5
V-OUT
+
COUT
RL
All Caps = 3.3µF
Figure 1. AMS682 Test Circuit
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS682
DETAILED DESCRIPTION
EFFICIENCY CONSIDERATIONS
Phase 1
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.
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.
For the AMS682, efficiency is as shown below:
VIN =+5V
SW3
SW1
VOUT
+
-
C1
SW2
+
-
C2
Power Loss
-
C3
+
SW4
Voltage Efficiency = VOUT / (-2VIN )
VOUT = -2VIN + VDROP
VDROP = (IOUT) (R OUT)
-5V
Figure 2. Charge Pump - Phase 1
Phase 2
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.
= IOUT (VDROP)
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.)
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)
VIN =+5V
SW3
SW1
VOUT
+
-
C1
SW2
+
-
C2
-
C3
+
SW4
C1
+
22µF
-10V
C2
Figure 3. Charge Pump - Phase 2
+
22µF
1
C1- ON/OFF
8
2
C2+
C1+
7
C2-
VIN
3
4
V-OUT GND
VIN
6
5
+ C3
22µF
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.
Advanced Monolithic Systems, Inc.
GND
V-OUT
Figure 4. Inverting Voltage Doubler
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:
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.
ROUT = 2( RSW1+RSW2+ESRC1+ RSW3+RSW4+ESRC2)
+2(RSW1+RSW2+ESRC1+ RSW3+RSW4+ESRC2)
+1/ (fPUMP X C1) +1/ (fPUMP X C2) + ESRC3
-5V Regulated Supply From A Single 3V Battery
Assuming all switch resistances are approximately equal:
ROUT = 16 RSW+ 4ESRC1+ 4ESRC2+ ESRC3
+1/ (fPUMP X C1) +1/ (fPUMP X C2)
ROUT is typically 140Ω at +25°C with VIN =+5V and 3.3µF
low ESR capacitors. The fixed term (16RSW) is about 8090Ω. 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
0.5Ω 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 :
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 150Ω source resistance for the converter,
with IL=10mA, the charge pump will drop 1.5V.
VRIPPLE = [1/[2(fPUMP X C3)]+2(ESRC3)] (IOUT)
For a 10µF (0.5Ω 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 10-20µF
capacitor and 1-5µF pump capacitors will be sufficient. Table
2 shows VRIPPLE for different values of C3 (assume 1Ω ESR).
Table 1. ROUT vs. C1, C2
C1, C2 (µ
µ F)
0.05
0.10
0.47
1.00
3.30
5.00
10.00
22.00
100.00
ROUT (Ω
Ω)
4085
2084
510
285
145
125
105
94
87
Advanced Monolithic Systems, Inc.
Table 2. VRIPPLE Peak-to-Peak vs. C3 (IOUT =10mA)
VRIPPLE (mV)
C3(µ
µ F)
0.50
1020
1.00
520
3.30
172
5.00
120
10.00
70
22.00
43
100.00
25
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
AMS682
APPLICATIONS (Continued)
VIN
10µF
VIN
C1+
+
-
10µF
10µF
C1C2+
+
C2GND
-
V-OUT
10µF
+
VIN
C1+
+
C1C2+
-
C2GND
NEGATIVE
SUPPLY
V-OUT
-
C-OUT 22µF
+
GND
Figure 5. Paralleling AMS682 for Lower Output Source Resistance
+
VIN
C1+
+
C1C2+
-
C2- V-OUT
GND
10µF
+
3V
-
10µF
VIN
+
22µF
C-OUT
VSS
VOUT
+
-
GROUND
1µF
-5 SUPPLY
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)
240
VIN = 5V
OUTPUT RESISTANCE(Ω)
-8.0
Output Resistance vs. VIN
VOUT vs. Load Current
-7.5
VOUT (V)
-8.5
-9.0
-9.5
-10.0
C1-C3 = 3.3µF
220
200
180
160
140
120
-10.5
0
5
10
1
15
2
3
LOAD CURRENT
180
5
6
5
6
Supply Current vs. VIN
300
VIN = 5V
IOUT = 10mA
NO LOAD
SUPPLY CURRENT (µA)
OUTPUT SOURCE RESISTANCE Ω)
(
Output Source Resistance vs. Temperature
200
4
VIN (V)
160
140
120
100
80
250
200
150
100
50
-50
100
50
0
1
3
2
4
VIN (V)
TEMPERATURE (°C)
OUTPUT RIPPLE (mV PK-PK)
Output Ripple vs. Output Current
200
VIN = 5V
150
C3 = 10 µF
100
C3 = 100µF
50
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
0.010-0.020
x 45°
(0.254-0.508)
0.053-0.069
(1.346-1.752)
0.004-0.010
(0.101-0.254)
0.014-0.019
(0.355-0.483)
0.008-0.010
(0.203-0.254)
0.050
(1.270)
TYP
0°-8° 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
1
2
3
4
0.255±0.015*
(6.477±0.381)
0.045-0.065
(1.143-1.651)
0.300-0.325
(7.620-8.255)
0.130±0.005
(3.302±0.127)
0.065
(1.651)
TYP
0.005
(0.127)
MIN
0.100±0.010
(2.540±0.254)
0.125
(3.175)
MIN
0.009-0.015
(0.229-0.381)
0.015
(0.380)
MIN
0.018±0.003
(0.457±0.076)
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