AN795

© 2002 Microchip Technology, Inc.

DS00795A-page 4

13-BIT A/D CONVERTER

A 13-bit binary A/D converter can be built by combining the TC9400 V/F converter with a counter, latch, and time base. When the V/F

converter is set up for 10kHz full scale, a 1-second time base will provide one conversion per second.

4-DIGIT VOLTMETER WITH OPTOISOLATED INPUT

The use of a frequency counter will give a display of the V/F converter's frequency, which is directly proportional to the input voltage.

When the V/F converter is running at 10kHz full scale, a 1-second time base will give 4-digit resolution with 1 reading per second.

The optoisolator is used for transmitting the frequency, so there is no DC path to the frequency counter. This is especially useful in

medical applications, where a voltage probe should not be directly connected to the human body.

LONG-TERM INTEGRATOR WITH INFINITE HOLD

This system will integrate an input signal for minutes or days, and hold its output indefinitely. The data is held in a digital counter and

stays there until the counter is reset. Typical applications involve controlling the amount of surface metal deposited in a plating system

or how much charge a battery has taken on.

TC9400

V/F

Gate

Reset

Latch

Time

Base

13-bit Latch

13-bit Binary Counter

121110 9 8 7654 321 0

Bit

1MΩ

TC9400

V/F

Battery or

Transformer

Isolated

Supply

Frequency Counter

+

1M

Ω

TC9400

V/F

Digital Display

Reset

α

t

o

∫

Binary

or BCD

Counter

D/A

Converter

FIGURE 7: 13-Bit A/D converter.

FIGURE 8: 4-Digit voltmeter with optoisolated input.

FIGURE 9: Long-term integrator with infinite hold.