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Part: TC682
Category:
RF & Microwaves
-> Frequency Doublers
Description: Inverting Voltage Doubler
Company: TelCom Semiconductor
Datasheet: Download TC682 datasheet File size : 235 kB
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Datasheet text preview:
EVALUATION KIT AVAILABLE
1
TC682
INVERTING VOLTAGE DOUBLER
FEATURES
s s s s s s 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 Space-Saving 8-Pin SOIC and 8-Pin Plastic DIP Packages
GENERAL DESCRIPTION
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 140), provides 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). The minimum external parts count and small physical size of the TC682 make it useful in many medium-current, dual voltage analog power supplies.
2 3 4 5 6 7
8 7 NC C1+ VIN GND
TC682-2 8/21/96
APPLICATIONS
s s s s s s s 10V from +5V Logic Supply 6V from a Single 3V Lithium Cell Portable Handheld Instruments Cellular Phones LCD Display Bias Generator Panel Meters Operational Amplifier Power Supplies
ORDERING INFORMATION
Part No.
TC 6 8 2 C O A TC682CPA TC 6 8 2 E O A TC682EPA TC7660EV
Package
8-Pin SOIC 8-Pin Plastic DIP 8-Pin SOIC 8-Pin Plastic DIP Evaluation Kit for Charge Pump Family
Temp. Range
0°C to +70°C 0°C to +70°C 40°C to +85°C 40°C to +85°C
TYPICAL OPERATING CIRCUIT
VIN
+2.4V < VIN < +5.5V
PIN CONFIGURATIONS
C1+ C1 C2+ C2 TC682 VOUT GND VOUT = (2 x VIN ) VOUT + COUT
C1 1 C2+ 2 C2 3 VOUT 4 TC682COA TC682EOA
VIN
C1 C2+ C2 VOUT 1 2 3 4
8-Pin DIP
8 7 TC682CPA TC682EPA 6 5 NC C1+ VIN GND
+ C1
+ C2
8-Pin SOIC
GND
All Caps = 3.3µF
6 5
8
4-21
TELCOM SEMICONDUCTOR, INC.
INVERTING VOLTAGE DOUBLER
TC682
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
*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.
ELECTRICAL CHARACTERISTICS: Over Operating Temperature Range, VIN = +5V, test circuit Figure 1,
unless otherwise indicated. Symbol
VIN IIN ROUT
Parameter
Supply Voltage Range Supply Current VOUT Source Resistance Source Resistance Oscillator Frequency Power Efficiency Voltage Conversion Efficiency
Test Conditions
RL = 2k RL = , TA = 25°C RL = IL = 10mA, TA = 25°C IL = 10mA IL = 5mA, VIN = 2.8V RL = 2k, TA = 25°C VOUT, RL =
Min
2.4 -- -- -- -- -- -- 90 99
Typ
-- 185 -- 140 -- 170 12 92 99.9
Max
5.5 300 400 180 230 320 -- -- --
Unit
V µA
F OSC PEFF VOUT EFF
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
Pin No. 8-Pin DIP/SOIC Symbol Description
1 2 3 4 5 6 7 8
C1 + C2 C2
VIN (+5V) 7 1 2 3 C1+ C1
6 VIN + C1
VOUT GND VIN + C1 N/C
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 No Connection
TC682 + C2 C2+ C2 V OUT GND 5 GND 4 C + OUT RL VOUT
All Caps = 3.3µF
Figure 1. TC682 Test Circuit
4-22
TELCOM SEMICONDUCTOR, INC.
INVERTING VOLTAGE DOUBLER
1
TC682
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 TC682, efficiency is as shown below:
DETAILED DESCRIPTION Phase 1
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.
VIN = +5V
2 3 4 5 6
SW1 + + C1 SW2 5V
SW3 C2 SW4 +
VOUT C3
Voltage Efficiency = VOUT / ( 2VIN) VOUT = 2VIN + VDROP VDROP = (IOUT) (ROUT) Power Loss = IOUT (VDROP)
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.
+5V
There will be a substantial voltage difference between V UT and 2 VIN if the impedances of the pump capacitors O 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 Selection" in Applications section.
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).
SW1 + C1 SW2 +
SW3 VOUT C2 + 10V
C2 22µF 3 C 2 4 22µF 1 C1 C1+ 7
SW4
C3
C1
2 C+ 2
TC682
VIN GND
Figure 3. Charge Pump Phase 2
6 5
VIN GND C3 22µF VOUT
7
MAXIMUM OPERATING LIMITS
The TC682 has on-chip zener diodes that clamp VIN to approximately 5.8V, and VOUT to 11.6V. Never exceed the maximum supply voltage or excessive current will be shunted by these diodes, potentially damaging the chip. The TC682 will operate over the entire operating temperature range with an input voltage of 2V to 5.5V. TELCOM SEMICONDUCTOR, INC.
V OUT
Figure 4. Inverting Voltage Doubler 4-23
8
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