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AS1526/AS1527

8 Detailed Description

The AS1526/AS1527 analog-to-digital converters have two modes of operation:

!

Normal A/D Conversion Mode – Pulling pin SHDNN high or leaving it open puts the device into normal A/D conver-

sion mode.

!

≤

3.6V).

Note:

Pulling pin CSN low starts a conversion. The conversion result is available at pin DOUT in unipolar serial for-

mat (see Timing and Control on page 12).

Figure 23 shows a basic configuration for the AS1526/AS1527. The integrated input track/hold circuitry and a succes-

sive-approximation register (SAR) circuitry convert analog input signals to a digital 10-bit output. No external-hold

capacitor is needed for the track/hold circuit.

The AS1526 internal reference is trimmed to 2.5V; the AS1527 requires an external reference. Both devices can

SCLK, CSN, and DOUT) and provides a simple microprocessor interface.

Figure 23. Operational Diagram

Analog Input

Figure 24 illustrates the integrated comparator sampling architecture. The full scale input voltage is set by the voltage

at pin REF.

Figure 24. Equivalent Input Circuit

AS1526/

AS1527

+2.7 to +3.6V

AS1526 – 4.7µF

AS1527 – 0.1µF

Reference Input

Required for AS1527,

Optional for AS1526

0.1µF

4.7µF

+

6

DOUT

5

GND

1

7

CSN

8

SCLK

3

SHDNN

2

AIN

4

REF

+

–

+

Comparator

14pF

13pF

–

REF

AIN

+

13pF

–

Sample

Switch

GND

S&H and DAC