TC826 データシートの表示（PDF） - Microchip Technology

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TC826

Analog-to-Digital Converter with Bar Graph Display Output

Microchip Technology 

TC826

The differential input voltage must be within the device

Common mode range when the converter and mea-

sured system share the same power supply common

(ground). If the converter and measured system do not

share the same power supply common, -IN should be

tied to analog common. This is the usual connection for

battery operated systems. Polarity is determined at the

end of signal integrate signal phase. The sign bit is a

true polarity indication, in that signals less than 1LSB

are correctly determined. This allows precision null

detection limited only by device noise and system

noise.

4.1.3 REFERENCE INTEGRATE CYCLE

The final phase is reference integrate or de-integrate.

-IN is internally connected to analog common and +IN

is connected with the correct polarity to cause the inte-

grator output to return to zero. The time required for the

output to return to zero is proportional to the input sig-

nal and is between 0 and 40 counts. The digital reading

displayed is:

EQUATION 4-2:

20 =

VIN

VREF

FIGURE 4-2:

CONVERSION HAS THREE PHASES

Integrator

Output

Auto-Zero Phase (AZ) Signal Integrate

Phase (SI)

Reference Integrate Phase (RI)

(De-integrate)

Sign Bit Determined

Analog Common

Potential

Internal

System

Clock (FSYS)

Internal Data

Latch Update

Signal

True Zero

Crossing

Zero Crossing

Detected

Number of Counts

Proportional to

VIN

TI

TD ≈ VIN

19 Counts

Minimum

20

Counts

One Conversion Cycle = 80 Counts

41 Counts

Maximum

1

(TCONV = 80 X

)

FSYS

© 2002 Microchip Technology Inc.

DS21477B-page 9

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