Datasheet

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TC7662B

TC7662B-8 9/11/96

EVALUATION

KIT

AVAILABLE

CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER

FEATURES

■ Wide Operating Voltage Range: 1.5V to 15V

■ Boost Pin (Pin 1) for Higher Switching Frequency

■ High Power Efficiency is 96%

■ Easy to Use – Requires Only 2 External Non-Critical

Passive Components

■ Improved Direct Replacement for Industry Stan-

dard ICL7660 and Other Second Source Devices

APPLICATIONS

■ Simple Conversion of +5V to ±5V Supplies

■ Voltage Multiplication V

OUT

= ±nV

■ Negative Supplies for Data Acquisition Systems

and Instrumentation

■ RS232 Power Supplies

■ Supply Splitter, V

OUT

= ±V

GENERAL DESCRIPTION

The TC7662B is a pin-compatible upgrade to the Indus-

try standard TC7660 charge pump voltage converter. It

converts a +1.5V to +15V input to a corresponding – 1.5 to

– 15V output using only two low-cost capacitors, eliminating

inductors and their associated cost, size and EMI.

The on-board oscillator operates at a nominal fre-

quency of 10kHz. Frequency is increased to 35kHz when

pin 1 is connected to V

, allowing the use of smaller external

capacitors. Operation below 10kHz (for lower supply current

applications) is also possible by connecting an external

capacitor from OSC to ground (with pin 1 open).

The TC7662B is available in both 8-pin DIP and 8-pin

small outline (SO) packages in commercial and extended

temperature ranges.

FUNCTIONAL BLOCK DIAGRAM

TC7662B

GND

INTERNAL

VOLTAGE

REGULATOR

OSCILLATOR

VOLTAGE–

LEVEL

TRANSLATOR

÷ 2

CAP

OSC

LOGIC

NETWORK

OUT

CAP

–

BOOST

TC7662BCPA

TC7662BEPA

BOOST

CAP

GND

CAP

–

OUT

LOW

VOLTAGE (LV)

OSC

TC7662BCOA

TC7662BEOA

BOOST

CAP

GND

CAP

–

OUT

LOW

VOLTAGE (LV)

OSC

PIN CONFIGURATION (DIP AND SOIC)

ORDERING INFORMATION

Temperature

Part No. Package Range

TC7662BCOA 8-Pin SOIC 0°C to +70°C

TC7662BCPA 8-Pin Plastic DIP 0°C to +70°C

TC7662BEOA 8-Pin SOIC – 40°C to +85°C

TC7662BEPA 8-Pin Plastic DIP – 40°C to +85°C

TC7660EV Evaluation Kit for

Charge Pump Family

Summary of content (11 pages)

PAGE 1
EVALUATION KIT AVAILABLE TC7662B CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER FEATURES GENERAL DESCRIPTION ■ ■ ■ ■ The TC7662B is a pin-compatible upgrade to the Industry standard TC7660 charge pump voltage converter. It converts a +1.5V to +15V input to a corresponding – 1.5 to – 15V output using only two low-cost capacitors, eliminating inductors and their associated cost, size and EMI. The on-board oscillator operates at a nominal frequency of 10kHz.
PAGE 2
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER TC7662B Operating Temperature Range C Suffix .................................................. 0°C to +70°C E Suffix ............................................. – 40°C to +85°C Storage Temperature Range ................ – 65°C to +150°C Lead Temperature (Soldering, 10 sec) ................. +300°C ABSOLUTE MAXIMUM RATINGS* Supply Voltage ...................................................... +16.5V LV, Boost and OSC Inputs Voltage (Note 1) V+<5.5V .................
PAGE 3
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER TC7662B DETAILED DESCRIPTION THEORETICAL POWER EFFICIENCY CONSIDERATIONS The TC7662B contains all the necessary circuitry to complete a negative voltage converter, with the exception of two external capacitors which may be inexpensive 1µF polarized electrolytic types. The mode of operation of the device may be best understood by considering Figure 2, which shows an idealized negative voltage converter.
PAGE 4
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER TC7662B voltage and temperature (See the Output Source Resistance graphs), typically 23Ω at +25°C and 5V. Careful selection of C1 and C2 will reduce the remaining terms, minimizing the output impedance. High value capacitors will reduce the 1/(fPUMP x C1) component, and low ESR capacitors will lower the ESR term.
PAGE 5
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER TC7662B Paralleling Devices Changing the TC7662B Oscillator Frequency Any number of TC7662B voltage converters may be paralleled to reduce output resistance (Figure 5). The reservoir capacitor, C2, serves all devices, while each device requires its own pump capacitor, C1. The resultant output resistance would be approximately: It may be desirable in some applications (due to noise or other considerations) to increase the oscillator frequency.
PAGE 6
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER TC7662B V+ V+ C1 + 1 8 2 7 3 TC7662B 4 COSC 6 1 8 2 7 TC7662B 3 5 VOUT + + C1 C2 D1 6 4 VOUT = – (V+– VF) 5 D2 + C3 VOUT = (2 V +) – (2 VF) + C2 Figure 8. Lowering Oscillator Frequency + C4 Positive Voltage Doubling Figure 10. Combined Negative Converter and Positive Doubler The TC7662B may be employed to achieve positive voltage doubling using the circuit shown in Figure 9.
PAGE 7
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER TC7662B Regulated Negative Voltage Supply +5 LOGIC SUPPLY In some cases, the output impedance of the TC7662B can be a problem, particularly if the load current varies substantially. The circuit of Figure 12 can be used to overcome this by controlling the input voltage, via an ICL7611 low-power CMOS op amp, in such a way as to maintain a nearly constant output voltage.
PAGE 8
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER TC7662B TYPICAL CHARACTERISTICS 1000 VOLTAGE CONVERSION EFFICIENCY (%) Supply Current vs. Temperature (with Boost Pin = VIN) 800 VIN = 12V IDD (µA) 600 400 200 VIN = 5V 0 -40 -20 0 20 40 60 80 Voltage Conversion 101.0 100.5 Without Load 100.0 99.5 10K Load 99.0 98.5 TA = 25°C 98.0 100 1 2 3 4 5 6 7 8 9 10 11 12 TEMPERATURE (°C) INPUT VOLTAGE VIN (V) Output Source Resistance vs. Supply Voltage Output Source Resistance vs.
PAGE 9
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER TC7662B TYPICAL CHARACTERISTICS (cont.) Unloaded Osc Freq vs. Temperature with Boost Pin = VIN Unloaded Osc Freq vs.
PAGE 10
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER TC7662B PACKAGE DIMENSIONS (Cont.) 8-Pin SOIC .157 (3.99) .150 (3.81) .244 (6.20) .228 (5.79) Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging .050 (1.27) TYP. .197 (5.00) .189 (4.80) .069 (1.75) .053 (1.35) .010 (0.25) .007 (0.18) 8° MAX. .020 (0.51) .010 (0.25) .013 (0.33) .004 (0.10) .050 (1.27) .016 (0.
PAGE 11
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER TC7662B WORLDWIDE SALES AND SERVICE AMERICAS New York Corporate Office 150 Motor Parkway, Suite 202 Hauppauge, NY 11788 Tel: 631-273-5305 Fax: 631-273-5335 2355 West Chandler Blvd. Chandler, AZ 85224-6199 Tel: 480-792-7200 Fax: 480-792-7277 Technical Support: 480-792-7627 Web Address: http://www.microchip.com Rocky Mountain 2355 West Chandler Blvd.