www.austriamicrosystems.com

Revision 1.02

13 - 22

AS1524/AS1525

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

Input Bandwidth

The AS1524/AS1525 input tracking circuitry has a 20MHz small signal bandwidth, so it is possible to digitize high-

speed transient events and measure periodic signals with bandwidths exceeding the AS1524/AS1525 sampling rate

by using undersampling techniques.

Note: To avoid high-frequency signals being aliased into the frequency band of interest, anti-alias filtering is recom-

mended.

Analog Input Protection

more than 50mV for accurate conversions.

Note: If an off-channel analog input voltage exceeds the supply voltages, the input current should be limited to 2mA.

Internal Clock

The AS1524/AS1525 operate from an internal clock, which is accurate within 5% of the 4MHz clock rate. This results in

a worst-case conversion time of 3.7µs. The internal clock releases the system microprocessor from running the SAR

conversion clock and allows the conversion results to be read back at the processor’s convenience, at any clock rate

from 0 to 8MHz.

Output Data Format

Figure 19 on page 12 and Figure 20 on page 12 illustrate the conversion timing for the AS1524/AS1525. The 12-bit

conversion result is output in MSB-first format. Data on DOUT transitions on the falling edge of SCLK. All 12 bits must

be clocked out before CNVST transitions again.

For the AS1524, data is straight binary for unipolar mode and two’s complement for bipolar mode. For the AS1525,

data is always straight binary.

Transfer Function

Figure 21 on page 13 shows the unipolar transfer function for the AS1524/AS1525. Figure 22 on page 14 shows the

bipolar transfer function for the AS1524. Code transitions occur halfway between successive-integer LSB values.

Figure 21. AS1524/AS1525 Unipolar Transfer Function

11...111

11...110

11....101

00...011

00...010

00...001

00...000

Input Voltage (LSB)

0

1

2

3

FS-3/2 LSB FS

Full-Scale

Transition

Zero Scale = GND