TC7662BEPA データシートの表示（PDF） - TelCom Semiconductor Inc => Microchip

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TC7662BEPA

CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER

TelCom Semiconductor Inc => Microchip 

CHARGE PUMP DC-TO-DC

VOLTAGE CONVERTER

1

Regulated Negative Voltage 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 over-

come 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. Direct feedback is advisable,

since the TC7662B’s output does not respond instanta-

neously to change in input, but only after the switching delay.

The circuit shown supplies enough delay to accommodate

the TC7662B, while maintaining adequate feedback. An

increase in pump and storage capacitors is desirable, and

the values shown provide an output impedance of less than

5Ω to a load of 10mA.

TC7662B

+5 LOGIC SUPPLY

TTL DATA

INPUT

+

1µF

–

16

4

15

1

8

2

7

3 TC7662B 6

4

5

1µF

+

12 11

IH5142

13 14

+5V

-5V

1

3

RS232

DATA

OUTPUT

2

3

+8V

56k

50k

100k

50k

+8V

–

+

+

100µF -

1

8

2

7

3 TC7662B 6

4

5

–

10µF

+

V+

VOUT

800k

250K

VOLTAGE

ADJUST

100µF

Figure 12. Regulating the Output Voltage

Figure 13. RS232 Levels from a Single 5V Supply

4

5

6

7

TELCOM SEMICONDUCTOR, INC.

8

4-89

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