TC7135(2002) View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

TC7135
(Rev.:2002)

4-1/2 Digit A/D Converter

Microchip Technology 

5.3 BUSY Output

At the beginning of the signal integration phase, BUSY

goes high and remains high until the first clock pulse

after the integrator zero crossing. BUSY returns to the

logic "0" state after the measurement cycle ends in an

overrange condition. The internal display latches are

loaded during the first clock pulse after BUSY and are

latched at the clock pulse end. The BUSY signal does

not go high at the beginning of the measurement cycle,

which starts with the auto zero cycle.

5.4 OVERRANGE Output

If the input signal causes the reference voltage integra-

tion time to exceed 20,000 clock pulses, the OVER-

RANGE output is set to a logic "1." The overrange

output register is set when BUSY goes low and is reset

at the beginning of the next reference integration

phase.

5.5 UNDERRANGE Output

If the output count is 9% of full scale or less (-1800

counts), the underrange register bit is set at the end of

BUSY. The bit is set low at the next signal integration

phase.

5.6 POLARITY Output

A positive input is registered by a logic "1" polarity sig-

nal. The polarity bit is valid at the beginning of refer-

ence integrate and remains valid until determined

during the next conversion.

The polarity bit is valid even for a zero reading. Signals

less than the converter's LSB will have the signal polar-

ity determined correctly. This is useful in null

applications.

5.7 Digit Drive Outputs

Digit drive signals are positive-going signals. The scan

sequence is D5 to D1. All positive pulses are 200 clock

pulses wide, with the exception D5, which is 201 clock

pulses wide.

All five digits are scanned continuously, unless an

overrange condition occurs. In an overrange condition,

all digit drives are held low from the final STROBE

pulse until the beginning of the next reference integrate

phase. The scanning sequence is then repeated. This

provides a blinking visual display indication.

5.8 BCD Data Outputs

The binary coded decimal (BCD) bits B8, B4, B2, and B1

are positive-true logic signals. The data bits become

active at the same time as the digit drive signals. In an

overrange condition, all data bits are at a logic "0" state.

© 2002 Microchip Technology Inc.

TC7135

DS21460B-page 11

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