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EVALUATION KIT AVAILABLE
1
TCM680
+5V TO 10V VOLTAGE CONVERTER
FEATURES
s s s s s 99% Voltage Conversion Efficiency 85% Power Conversion Efficiency Wide Voltage Range ......................... +2.0V to +5.5V Only 4 External Capacitors Required Space Saving 8-Pin SOIC Design
GENERAL DESCRIPTION
The TCM680 is a dual charge pump voltage converter that develops output voltages of +2VIN and - 2VIN from a single input voltage of +2.0V to +5.5V. Common applications include 10V from a single +5V logic supply, and 6V from a +3V lithium battery. The TCM680 is packaged in a space-saving 8-pin SOIC package and requires only four inexpensive external capacitors. The charge pumps are clocked by an on-board 8kHz oscillator. Low output source impedances (typically 150) provides maximum output currents of 10mA for each output. Typical power conversion efficiency is 85%. High efficiency, small installed size and low cost make the TCM680 suitable for a wide variety of applications that need both positive and negative power supplies derived from a single input voltage.
2 3 4 5 6 7
APPLICATIONS
s s s s s s s
10V From +5V Logic Supply 6V From a 3V Lithium Cell
Handheld Instruments Portable Cellular Phones LCD Display Bias Generator Panel Meters Operational Amplifier Power Supplies
PIN CONFIGURATIONS (DIP AND SOIC)
- C1 + C2 - C2 - VOUT 1 2 3 4 TCM680CPA TCM680EPA 8 7 6 5 + VOUT C1 +
ORDERING INFORMATION
Part No. TCM680COA TCM680CPA TCM680EOA TCM680EPA TC7660EV Package Temperature 8-Pin SOIC 0C to +70C 8-Pin Plastic DIP 0C to +70C 8-Pin SOIC - 40C to +85C 8-Pin Plastic DIP - 40C to +85C Charge Pump Family Evaluation Kit
VIN GND
C1- + C2 C-
2
1 2 3 4 TCM680COA TCM680EOA
8 7 6 5
+ VOUT + C1 VIN GND
V-
OUT
TYPICAL OPERATING CIRCUIT
2.0V+ C1 4.7F
- C1
+ C2 TCM680
C2 4.7F
+
- C2
GND
- VOUT
4.7F + C3
- VOUT = (- 2 x VIN)
GND
GND
TC660-2 9/4/96
8
4-13
TELCOM SEMICONDUCTOR, INC.
+5V TO 10V VOLTAGE CONVERTER
TCM680
ABSOLUTE MAXIMUM RATINGS*
VIN ..................................................................................................... +6.0V + VOUT .............................................................................................. +12.0V - V OUT ............................................................................................. - 12.0V - V OUT Short-Circuit Duration ............................ Continuous + VOUT Current ............................................................ 75mA VIN dV/dT .............................................................. 1V/sec Power Dissipation (TA 70C) Plastic DIP ...................................................... 730mW Small Outline .................................................. 470mW Storage Temperature ............................ - 65C to +150C Lead Temperature (Soldering, 10 sec) ................. +300C
*Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or other conditions above those indicated in the operation section of the specification is not implied. Exposure to the Absolute Maximum Ratings conditions for extended periods of time may affect device reliability.
ELECTRICAL CHARACTERISTICS: VIN = +5V, TA = +25C, test circuit Figure 1, unless otherwise indicated.
Symbol Parameter
Supply Voltage Range Supply Current
Test Conditions
MIN. TA MAX., RL = 2k VIN = 3V, RL = VIN = 5V, RL = VIN = 5V, 0C TA +70C, RL = VIN = 5V, - 40C TA +85C, RL = - + IL = 10mA, IL = 0mA, VIN = 5V - + IL = 5mA, IL = 0mA, VIN = 2.8V - + IL = 10mA, IL = 0mA, VIN = 5V: 0C TA +70C - 40C TA +85C + - IL = 10mA, IL = 0mA, VIN = 5V + - IL = 5mA, IL = 0mA, VIN = 2.8V + - IL = 10mA, IL = 0mA, VIN = 5V: 0C TA +70C - 40C TA +85C RL = 2k + VOUT, RL = - V OUT, RL =
Min
2.0 -- -- -- -- -- -- -- -- -- -- -- -- -- -- 97 97
Typ
1.5 to 5.5 0.5 1 -- -- 140 180 -- -- 140 180 -- -- 21 85 99 99
Max
5.5 1 2 2.5 3 180 250 220 250 180 250 220 250 -- -- -- --
Unit
V mA
Negative Charge Pump Output Source Resistance
Positive Charge Pump Output Source Resistance
FOSC PEFF VOUT EFF
Oscillator Frequency Power Efficiency Voltage Conversion Efficiency
kHz % %
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
8-Pin DIP/SOIC Symbol
1 2 3 4 5 6 7 8
- C1 + C2 - C2 - V OUT
VIN
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. Output. Positive output voltage (+2VIN)
C1
4.7F 1 2 - C1 + C2 + 8 VOUT + C1 7 + VOUT
C2
4.7F 6 3 C - TCM680 V IN 2 4 - V OUT GND 5
C4 10F
+ RL
GND VIN + C1 + VOUT
GND
C3 10F
- RL
- VOUT
Figure 1. Test Circuit 4-14
TELCOM SEMICONDUCTOR, INC.
+5V TO 10V VOLTAGE CONVERTER
1
TCM680
VIN = +5V - + SW1 + - + C1 SW2 -5V - C2 SW4 - + C3 SW3 C4 VDD VSS
DETAILED DESCRIPTION Phase 1
VSS charge storage - The positive side of capacitors C1 + and C2 are connected to +5V at the start of this phase. C1 is - then switched to ground and the charge in C1 is transferred - + to C2 . Since C2 is connected to +5V, the voltage potential across capacitor C2 is now 10V.
VIN = +5V - + SW1 + - + C1 SW2 -5V - C2 SW4 - + C3 SW3
2 3 4 5 6 7
Figure 4. Charge Pump - Phase 3
C4 VDD VSS
Phase 4
VDD transfer - The fourth phase of the clock connects the negative terminal of C2 to ground, and transfers the generated 10V across C2 to C4, the VDD storage capacitor. Again, simultaneously with this, the positive side of capacitor C1 is switched to +5V and the negative side is connected to ground, and the cycle begins again.
+5V - SW1 + - C1 SW2 SW3 + - SW4 -10V C2 + C4 VDD VSS - + C3
Figure 2. Charge Pump - Phase 1
Phase 2
VSS transfer - Phase two of the clock connects the negative terminal of C2 to the VSS storage 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.
+5V
Figure 5. Charge Pump - Phase 4
- SW1 + - C1 SW2 + - SW4 -10V SW3 C2 + C4 VDD VSS - + C3
MAXIMUM OPERATING LIMITS
The TCM680 has on-chip zener diodes that clamp VIN + - to 5.8V, V OUT to 11.6V, and V OUT to -11.6V. Never exceed the maximum supply voltage or excessive current will be shunted by these diodes, potentially damaging the chip. The TCM680 will operate over the entire operating temperature range with an input voltage of 2V to 5.5V.
Figure 3. Charge Pump - Phase 2
Phase 3
VDD charge storage - The third phase of the clock is identical to the first phase - the charge transferred in C1 produces -5V in the negative terminal of C1, which is applied + to the negative side of capacitor C2. Since C2 is at +5V, the voltage potential across C2 is 10V.
8
4-15
TELCOM SEMICONDUCTOR, INC.
+5V TO 10V VOLTAGE CONVERTER
TCM680
EFFICIENCY CONSIDERATIONS
Theoretically a charge pump can approach 100% efficiency under the following conditions: * The charge Pump switches have virtually no offset and extremely low on resistance * Minimal power is consumed by the drive circuitry * The impedances of the reservoir and pump capacitors are negligible For the TCM680, efficiency is as shown below: Efficiency V+ = VDD /(2VIN) VDD = 2VIN - V+ DROP + + V+ DROP = (I OUT)(R OUT) Efficiency V- = VSS /(- 2VIN) VSS = 2VIN - V- DROP - - V- DROP = (I OUT)(R OUT)
+ - - Power Loss = (V+ DROP)(I OUT) + (V DROP)(I OUT)
Capacitor Selection
The TCM680 requires only 4 external capacitors for operation. These can be inexpensive polarized aluminum electrolytic types. For the circuit in Figure 6 the output characteristics are largely determined by the external capacitors. An expression for ROUT can be derived as shown below: R+ OUT = 4(RSW1 + RSW2 + ESRC1 + RSW3 + RSW4 + ESRC2) +4(RSW1 + RSW2 + ESRC1 + RSW3 + RSW4 + ESRC2) +1/(fPUMP x C1) + 1/(fPUMP x C2) + ESRC4 R- OUT = 4(RSW1 + RSW2 + ESRC1 + RSW3 + RSW4 + ESRC2) +4(RSW1 + RSW2 + ESRC1 + RSW3 + RSW4+ ESRC2) +1/(fPUMP x C1) + 1/(fPUMP x C2) + ESRC3 Assuming all switch resistances are approximately equal... R+ OUT = 32RSW + 8ESRC1 + 8ESRC2 + ESRC4 +1/(fPUMP x C1) + 1/(fPUMP x C2) R- OUT = 32RSW + 8ESRC1 + 8ESRC2 + ESRC3 +1/(fPUMP x C1) + 1/(fPUMP x C2) ROUT is typically 140 at +25C with VIN = +5V and C1 and C2 as 4.7F low ESR capacitors. The fixed term (32RSW) is about 130. 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 0.5 ESR). C1 and C4 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 and C4. Typically the larger the value of C3 and C4 the less the ripple for a given load current. The formula for VRIPPLE(p-p) is given below:
+ V+ RIPPLE(p-p) = {1/[2(fPUMP /3) x C4] + 2(ESRC4)}(I OUT) - V- RIPPLE(p-p) = {1/[2(fPUMP /3) x C3] + 2(ESRC3)}(I OUT)
There will be a substantial voltage difference between (V+ OUT - VIN) and VIN for the positive pump and between V+ and V OUT if the impedances of the pump capacitors C1 OUT - and C2 are high with respect to the output loads. Larger values of reservoir capacitors C3 and C4 will reduce output ripple. Larger values of both pump and reservoir capacitors improve the efficiency. See "Capacitor Selection" in Applications Section.
APPLICATIONS Positive and negative Converter
The most common application of the TCM680 is as a dual charge pump voltage converter which provides positive and negative outputs of two times a positive input voltage. The simple circuit of Figure 6 performs this same function using the TCM680 and external capacitors, C1, C2, C3 and C4.
C1
22F 1 C1- + 8 VOUT +7 C1 C4 22F VIN GND C3 22F - VOUT + VOUT
2 C+ 2 C2 22F
6 3 C - TCM680 V IN 2 4 - V OUT GND 5
For a 10F (0.5 ESR) capacitor for C3, C4, fPUMP = 21kHz and IOUT = 10mA the peak-to-peak ripple voltage at the output will be less than 100mV. In most applications (IOUT < = 10mA) 10-20F output capacitors and 1-5F pump capacitors will suffice. Table 2 shows VRIPPLE for different values of C3 and C4 (assume 1 ESR).
Figure 6. Positive and Negative Converter 4-16
TELCOM SEMICONDUCTOR, INC.
+5V TO 10V VOLTAGE CONVERTER
1
TCM680
Paralleling Devices
Table 1. ROUT vs. C1 ,C2 C1, C2 (F)
0.1 0.47 1 3.3 4.7 10 22 100
ROUT ()
1089 339 232 165 157 146 141 137
Paralleling multiple TCM680s reduces the output resistance of both the positive and negative converters. The effective output resistance is the output resistance of a single device divided by the number of devices. As illustrated in Figure 7, each requires separate pump capacitors C1 and C2, but all can share a single set of reservoir capacitors.
2 3 4 5
5V Regulated Supplies From A Single 3V Battery
Figure 8 shows a complete 5V power supply using one 3V battery. The TCM680 provides +6V at V+ , which is OUT regulated to +5V by the TC55, and -5V by the negative LDO. The input to the TCM680 can vary from 3V to 6V without affecting regulation appreciably. With higher input voltage, more current can be drawn from the outputs of the TCM680. With 5V at VIN, 10mA can be drawn from both regulated outputs simultaneously. Assuming 150 source resistance for both converters, with (I+ + IL) = 20mA, the positive charge L pump will droop 3V, providing +7V for the negative charge pump.
Table 2. VRIPPLE (p-p) vs. C3, C4 (IOUT = 10mA) C3, C4 (F)
0.47 1 3.3 4.7 10 22 100
VRIPPLE (mV)
1540 734 236 172 91 52 27
VIN
+ 10F -
+ C1 - C1
VIN 10F
+ -
+ C1 - C1
VIN
6
- VOUT NEGATIVE SUPPLY - + - COUT
TCM680
+ 10F - C2 + - VOUT GND + 10F - C-
2
TCM680
C2 +
C2
-
GND
22F
7
GND
Figure 7. Paralleling TCM680 for Lower Output Source Resistance
8
4-17
TELCOM SEMICONDUCTOR, INC.
+5V TO 10V VOLTAGE CONVERTER
TCM680
- + +
10F
+ COUT
22F
TC55RP5002Exx VIN VOUT VSS + 1F - GROUND - VSS VIN
22F
C1
+
VIN
VOUT +6V
+
+5 SUPPLY
- + 3V - +
10F
C1- C2 + TCM680 -6V - + C- OUT
1F + VOUT -5 SUPPLY
-
C2- GND
- VOUT
NEGATIVE LDO
TC54VC2702Exx VIN VSS VOUT LOW BATTERY
Figure 8. Split Supply Derived from 3V Battery
4-18
TELCOM SEMICONDUCTOR, INC.
+5V TO 10V VOLTAGE CONVERTER
1
TCM680
TYPICAL CHARACTERISTICS
- V+ OUT or V OUT Output Resistance vs. VIN
300
+ - VOUT or VOUT vs. Load Current
10.0
2 3
C1 - C4 = 10F
VIN = 5V
OUTPUT RESISTANCE ()
250
200
VOUT (V)
9.0
8.0 150
ROUT
7.0
100
1
2
3 VIN (V)
4
5
6
0
5
10 LOAD CURRENT (mA)
15
Supply Current vs. VIN
1.4 1.2 1.0 0.8
+ - Output Voltage vs. Output Current From VOUT to VOUT
10.0
4 5
VIN = 5V
SUPPLY CURRENT (mA)
VOUT (V)
9.0
NO LOAD
0.6 0.4 0.2
8.0
1
2
3 VIN (V)
4
5
6
7.0
0
6 8 4 2 + - OUTPUT CURRENT (mA) From VOUT TO VOUT
10
6 7
Output Source Resistance vs. Temperature
180
OUTPUT SOURCE RESISTANCE ()
VIN = 5V IOUT = 10mA
160
ROUT
140
120
100 -50
0 50 TEMPERATURE (C)
100
8
4-19
TELCOM SEMICONDUCTOR, INC.

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