TC682COA [TELCOM]
INVERTING VOLTAGE DOUBLER; 反相电压倍增
| 型号： | TC682COA |
| 厂家： | 
TELCOM SEMICONDUCTOR, INC |
| 描述： | INVERTING VOLTAGE DOUBLER |
| 文件： | 总6页 (文件大小：82K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
4
EVALUATION
KIT
AVAILABLE
TC682
INVERTING VOLTAGE DOUBLER
FEATURES
GENERAL DESCRIPTION
■ 99.9% Voltage Conversion Efficiency
■ 92% Power Conversion Efficiency
■ Wide Input Voltage Range ...............+2.4V to +5.5V
■ Only 3 External Capacitors Required
■ 185µA Supply Current
The TC682 is a CMOS charge pump converter that
provides an inverted doubled output from a single positive
supply. An on-board 12kHz (typical) oscillator provides the
clock and only 3 external capacitors are required for full
circuit implementation.
Low output source impedance (typically 140Ω), pro-
vides output current up to 10mA. The TC682 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 (for
example: generation of – 6V from a 3V lithium cell or – 10V
generated from a +5V logic supply).
■ Space-Saving 8-Pin SOIC and 8-Pin Plastic DIP
Packages
APPLICATIONS
■ – 10V from +5V Logic Supply
■ – 6V from a Single 3V Lithium Cell
■ Portable Handheld Instruments
■ Cellular Phones
■ LCD Display Bias Generator
■ Panel Meters
The minimum external parts count and small physical
size of the TC682 make it useful in many medium-current,
dual voltage analog power supplies.
■ Operational Amplifier Power Supplies
ORDERING INFORMATION
Part No.
Package
Temp. Range
T
C682COA
TC682CPA
C682EOA
8-Pin SOIC
0°C to +70°C
0°C to +70°C
8-Pin Plastic DIP
8-Pin SOIC
TYPICAL OPERATING CIRCUIT
T
– 40°C to +85°C
– 40°C to +85°C
TC682EPA
8-Pin Plastic DIP
TC7660EV
Evaluation Kit for
Charge Pump Family
+2.4V < V < +5.5V
IN
V
IN
PIN CONFIGURATIONS
8-Pin DIP
V
IN
+
C
C
+
–
1
–
+
–
NC
C
C
C
C
C
1
2
3
4
8
7
6
5
1
1
2
2
–
1
+
C
1
TC682
V
TC682CPA
TC682EPA
+
–
V
C
C
+
–
IN
2
V
= – (2 x V
V
)
IN
OUT
2
V
GND
OUT
OUT
OUT
2
GND
C
OUT
8-Pin SOIC
+
GND
–
C
C
C
NC
1
2
3
4
8
7
6
5
1
2
2
All Caps = 3.3µF
+
–
+
C
1
TC682COA
TC682EOA
V
IN
V
GND
OUT
TC682-2 8/21/96
TELCOM SEMICONDUCTOR, INC.
4-21
INVERTING VOLTAGE DOUBLER
TC682
*This is a stress rating only and functional operation of the device at these
or any other conditions above 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.
ABSOLUTE MAXIMUM RATINGS*
VIN .......................................................................... +5.8V
VIN dV/dT ............................................................. 1V/µsec
VOUT ......................................................................– 11.6V
VOUT Short-Circuit Duration ............................ Continuous
Power Dissipation (TA ≤ 70°C)
Plastic DIP ........................................................... 730mW
SOIC ...............................................................470mW
Storage Temperature Range ................ – 65°C to +150°C
Lead Temperature (Soldering, 10 sec) ................. +300°C
ELECTRICAL CHARACTERISTICS: Over Operating Temperature Range, VIN = +5V, test circuit Figure 1,
unless otherwise indicated.
Symbol Parameter
Test Conditions
Min
Typ
Max
Unit
VIN
IIN
Supply Voltage Range
RL = 2kΩ
2.4
—
5.5
V
Supply Current
RL = ∞, TA = 25°C
RL = ∞
—
—
185
—
300
400
µA
ROUT
VOUT Source Resistance
Source Resistance
IL– = 10mA, TA = 25°C
—
—
—
140
—
170
180
230
320
Ω
IL– = 10mA
IL– = 5mA, VIN = 2.8V
FOSC
PEFF
Oscillator Frequency
Power Efficiency
—
90
99
12
92
—
—
—
kHz
%
RL = 2kΩ, TA = 25°C
VOUT, RL = ∞
VOUT EFF Voltage Conversion Efficiency
99.9
%
TelCom Semiconductor reserves the right to make changes in the circuitry or specifications detailed in this manual at any time without notice. Minimums
and maximums are guaranteed. All other specifications are intended as guidelines only. TelCom Semiconductor assumes no responsibility for the use
of any circuits described herein and makes no representations that they are free from patent infringement.
PIN DESCRIPTION
Pin No.
V
IN
8-Pin DIP/SOIC Symbol Description
(+5V)
6
1
2
3
4
C1–
Input. Capacitor C1 negative
terminal.
V
IN
7
1
+
–
+
–
C
C
1
C2+
Input. Capacitor C2 positive
terminal.
C
C
1
1
C2–
Input. Capacitor C2 negative
terminal
TC682
V
2
3
+
–
+
–
C
C
2
2
VOUT
Output. Negative output voltage
(– 2VIN)
4
–
V
OUT
OUT
2
GND
5
–
+
5
6
7
GND
VIN
C1+
Input. Device ground.
C
R
L
OUT
Input. Power supply voltage.
GND
Input. Capacitor C1 positive
terminal
All Caps = 3.3µF
8
N/C
No Connection
Figure 1. TC682 Test Circuit
4-22
TELCOM SEMICONDUCTOR, INC.
INVERTING VOLTAGE DOUBLER
4
TC682
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.
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.
• Minimal power is consumed by the drive circuitry
• The impedances of the reservoir and pump capaci-
tors are negligible.
For the TC682, efficiency is as shown below:
Voltage Efficiency = VOUT / (– 2VIN)
VIN = +5V
VOUT = – 2VIN + VDROP
VDROP = (IOUT) (ROUT
)
SW1
SW3
VOUT
+
–
+
–
C
1
C
2
Power Loss
= IOUT (VDROP)
–
+
C
3
SW2
SW4
There will be a substantial voltage difference between
V–OUT and 2 VIN if the impedances of the pump capacitors
C1 and C2 are high with respect to their respective output
loads.
Larger values of reservoir capacitor C3 will reduce
output ripple. Larger values of both pump and reservoir
capacitors improve the efficiency. See "Capacitor Selec-
tion" in Applications section.
–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 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.
APPLICATIONS
Negative Doubling Converter
The most common application of the TC682 is as a
charge pump voltage converter which provides a negative
output of two times a positive input voltage (Figure 4).
+5V
SW1
SW3
VOUT
+
–
+
–
C
1
C
2
22µF
22µF
C1
–
+
C
1
2
–
+
3
C1
SW2
SW4
–10V
+
7
C1
C2
C2
TC682
6
5
–
3
4
VIN
VIN
C2
Figure 3. Charge Pump – Phase 2
–
VOUT
GND
GND
MAXIMUM OPERATING LIMITS
C3
The TC682 has on-chip zener diodes that clamp VIN to
approximately5.8V, andVO– UT to–11.6V. Neverexceedthe
maximumsupplyvoltageorexcessivecurrentwillbeshunted
by these diodes, potentially damaging the chip. The TC682
willoperateovertheentireoperatingtemperaturerangewith
an input voltage of 2V to 5.5V.
22µF
–
VOUT
Figure 4. Inverting Voltage Doubler
TELCOM SEMICONDUCTOR, INC.
4-23
INVERTING VOLTAGE DOUBLER
TC682
Table 2. VRIPPLE Peak- to-Peak vs. C3 (IOUT = 10mA)
Capacitor Selection
The output resistance of the TC682 is determined, in
part, by the ESR of the capacitors used. An expression for
ROUT is derived as shown below:
C3 (µF)
VRIPPLE (mV)
0.50
1.00
1020
520
172
120
70
3.30
ROUT = 2(RSW1 + RSW2 + ESRC1 + RSW3 + RSW4 + ESRC2
)
+2(RSW1 + RSW2 + ESRC1 + RSW3 + RSW4 + ESRC2
+1/(fPUMP x C1) +1/(fPUMP x C2)
+ESRC3
)
5.00
10.00
22.00
100.00
43
25
Assuming all switch resistances are approximately
equal...
ROUT = 16RSW + 4ESRC1 + 4ESRC2 + ESRC3
+1/(fPUMP x C1) +1/(fPUMP x C2)
Paralleling Devices
Paralleling multiple TC682s reduces the output resis-
tance of the converter. The effective output resistance is the
output resistance of a single device divided by the number
of devices. As illustrated in Figure 5, each requires separate
pump capacitors C1 and C2, but all can share a single
reservoir capacitor.
ROUT is typically 140Ω at +25°C with VIN = +5V and
3.3µF low ESR capacitors. The fixed term (16RSW) is about
80-90Ω. It can be seen easily that increasing or decreasing
values of C1 and C2 will affect efficiency by changing ROUT
.
However, be careful about ESR. This term can quickly
become dominant with large electrolytic capacitors. 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.
–5V Regulated Supply From A Single
3V Battery
Figure 6 shows a – 5V power supply using one 3V
battery. The TC682 provides – 6V at VO– UT, which is regu-
lated to – 5V by the negative LDO. The input to the TC682
can vary from 3V to 5.5V without affecting regulation appre-
ciably. A TC54 device 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 TC682. 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 droop 1.5V.
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 given below:
VRIPPLE = {1/[2(fPUMP x C3)] + 2(ESRC3)} (IOUT
)
For a 10µF (0.5Ω ESR) capacitor for C3, fPUMP = 10kHz
and IOUT = 10mA the peak-to-peak ripple voltage at the
output will be less then 60mV. In most applications (IOUT
<
= 10mA) a 10-20µF capacitor and 1-5µF pump capacitors
will suffice. Table 2 shows VRIPPLE for different values of C3
(assume 1Ω ESR).
Table 1. ROUT vs. C1, C2
C1, C2 (µF)
ROUT (Ω)
0.05
0.10
4085
2084
510
285
145
125
105
94
0.47
1.00
3.30
5.00
10.00
22.00
100.00
87
4-24
TELCOM SEMICONDUCTOR, INC.
INVERTING VOLTAGE DOUBLER
4
TC682
VIN
VIN
VIN
+
+
C1
C1
+
+
–
10µF
10µF
–
–
–
C1
C1
TC682
GND
TC682
+
+
C2
C2
–
+
10µF
+
VOUT
NEGATIVE
SUPPLY
–
VOUT
10µF
–
–
–
–
C2
C2
GND
–
+
–
22µF
COUT
GND
Figure 5. Paralleling TC682 for Lower Output Source Resistance
VIN
+
C1
+
–
10µF
–
C1
+
–
3V
GROUND
TC682
+
–
+
C2
1µF
+
VSS
10µF
–
–
–
2
VOUT
–5 SUPPLY
VOUT
VIN
C
GND
NEGATIVE LDO
REGULATOR
–
+
22µF
–
COUT
TC54VC2702Exx
VOUT
VIN
LOW BATTERY
VSS
Figure 6. Negative Supply Derived from 3V Battery
TELCOM SEMICONDUCTOR, INC.
4-25
INVERTING VOLTAGE DOUBLER
TC682
TYPICAL CHARACTERISTICS (FOSC = 12kHz)
V
vs. Load Current
Output Resistance vs. V
IN
OUT
240
–7.5
–8.0
V
= 5V
IN
C1– C3 = 3.3µF
220
200
180
160
–8.5
–9.0
–9.5
140
120
–10.0
–10.5
1
2
3
5
6
0
5
10
15
4
V
(V)
IN
LOAD CURRENT (mA)
Supply Current vs. V
IN
Output Source Resistance vs. Temperature
= 5V
200
180
300
250
200
150
V
I
IN
NO LOAD
= 10mA
OUT
160
140
120
100
80
100
50
–50
0
50
100
1
2
3
5
6
4
V
(V)
TEMPERATURE (°C)
IN
Output Ripple vs. Output Current
200
V
= 5V
IN
150
100
C3 =10µF
C3 =100µF
50
0
0
20
10
5
15
OUTPUT CURRENT (mA)
4-26
TELCOM SEMICONDUCTOR, INC.
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