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Threshold

Detector

Node 512

REF −

REF+

512

To Output

Latches

REF+

REF+

REF+

REF+

1

2

4

8

16

128

256

1

REF+

REF+

REF −

REF −

REF −

REF −

REF −

REF −

REF −

REF −

CHIP-SELECT OPERATION

REFERENCE VOLTAGE INPUTS

TLC1542I,, TLC1542M,, TLC1542Q

TLC1542C, TLC1543C, TLC1543I, TLC1543Q

SLAS052G – MARCH 1992 – REVISED JANUARY 2006

Figure 1. Simplified Model of the Successive-Approximation System

The trailing edge of CS starts all modes of operation, and CS can abort a conversion sequence in any mode. A

high-to-low transition on CS within the specified time during an ongoing cycle aborts the cycle, and the device

returns to the initial state (the contents of the output data register remain at the previous conversion result).

Exercise care to prevent CS from being taken low close to completion of conversion because the output data

can be corrupted.

There are two reference inputs used with the device: REF+ and REF-. These voltage values establish the upper

and lower limits of the analog input to produce a full-scale and zero reading respectively. The values of REF+,

REF-, and the analog input should not exceed the positive supply or be lower than GND consistent with the

specified absolute maximum ratings. The digital output is at full scale when the input signal is equal to or higher

than REF+ and at zero when the input signal is equal to or lower than REF-.

7

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