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AS1536/AS1537

Datasheet - D e t a i l e d D e s c r i p t i o n

8 Detailed Description

The AS1536/AS1537 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 13).

Figure 23 shows a basic configuration for the AS1536/AS1537. The integrated input track/hold circuitry and a succes-

sive-approximation register (SAR) circuitry convert analog input signals to a digital 12-bit output. No external-hold

capacitor is needed for the track/hold circuit.

The AS1536 internal reference is trimmed to 2.5V; the AS1537 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

AS1536/

AS1537

+2.7V to +5.25V

AS1536 – 4.7µF

AS1537 – 0.1µF

Reference Input

Required for AS1537,

Optional for AS1536

0.1µF

4.7µF

+

6

DOUT

5

GND

1

VDD

7

CSN

8

SCLK

3

SHDNN

2

AIN

4

REF

+

–

+

Comparator

14pF

13pF

–

REF

AIN

+

13pF

–

Sample

Switch

GND

S&H and DAC