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AS1524/AS1525

Datasheet - A p p l i c a t i o n I n f o r m a t i o n

9 Application Information

Automatic Shutdown Mode

With CNVST low, the AS1524/AS1525 default to automatic shutdown (< 0.2µA) mode after power-up and between

conversions. After detecting a rising edge of CNVST, the AS1524/AS1525 powers up, sets DOUT low, and enters

track mode.

After detecting a falling edge of CNVST, the device enters hold mode and begins the conversion. A maximum of 3.7µs

later, the device completes conversion, enters shutdown, and MSB is available at DOUT.

External Reference

An external reference is required for the AS1524/AS1525. Use a 4.7µF bypass capacitor for best performance. The

Performing a Conversion

1. Use a general-purpose I/O line on the CPU to hold CNVST low between conversions.

2. Drive CNVST high to acquire AIN1(AS1525) or unipolar mode (AS1524). To acquire AIN2 (AS1525) or bipolar

mode (AS1524), drive CNVST low and high again.

3. Hold CNVST high for 1.4µs.

4. Drive CNVST low and wait approximately 3.7µs for conversion to complete. After 3.7µs, the MSB is available

at DOUT.

5. Activate SCLK for a minimum of 12 rising clock edges. DOUT transitions on SCLK’s falling edge and is avail-

able in MSB-first format. Observe the SCLK to DOUT valid timing characteristic. Clock data into the µP on

SCLK’s rising edge.

Standard Interface Connections

The AS1524/AS1525 serial interface is fully compatible with SPI, QSPI, and MICROWIRE. If a serial interface is avail-

able, establish the processor’s serial interface as a master so that the CPU generates the serial clock for the AS1524/

AS1525 and select a clock frequency up to 8MHz.

SPI and Microwire Interface

When using an SPI (Figure 23) or Microwire interface (Figure 24), set CPOL = CPHA = 0. Two 8-bit readings are nec-

essary to obtain the entire 12-bit result from the AS1524/AS1525. DOUT data transitions on the serial clock’s falling

edge and is clocked into the processor on SCLK’s rising edge. The first 8-bit data stream contains the first 8-bits of

DOUT starting with the MSB. The second 8-bit data stream contains the remaining four result bits. DOUT then goes

high impedance.

Figure 23. SPI Serial Interface Connections

AS1524/

AS1525

CPU

SSM

MISO

I/O

SCK

7

DOUT

6

CNVST

8

SCLK