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AS1520/AS1521

Reduced Power Mode

Reduced power mode is activated using bits PD1 and PD0 (see Table 12). When reduced power mode is asserted, the

AS1520/AS1521 completes any conversion in progress and enters reduced power mode.

The next start of conversion puts the AS1520/AS1521 into normal operation mode. The 8-bit control byte shifted into

the control register determines the next power mode. For example, if the 8-bit control byte contains PD1 = 0 and PD0

= 1, reduced power mode starts immediately after the conversion (see Figure 28).

The reduced-power mode achieves the lowest power consumption at speeds close to the maximum sample rate.

Figure 29 shows the AS1521 power consumption in reduced-power mode and normal operating mode (see Table 12

on page 19) with the internal reference and maximum clock speed.

Figure 28. Reduced-Power Mode Timing Waveforms (AS1521)

Note: The clock speed in reduced-power mode should be limited to 4.8MHz. Full power-down mode may provide

increased power savings in applications where the devices are inactive for long periods of time, where intermit-

tent bursts of high-speed conversions are required.

Figure 29. Normal Operation and Reduced Power Mode using Internal Reference (AS1521)

Full Power-Down Mode

Full power-down is activated using bits PD1 and PD0 (see Table 12). Full power-down mode offers the lowest power

consumption at up to 1000 conversions per-channel per-second. When full power-down is asserted, the AS1520/

AS1521 completes any conversion in progress and powers down into specified low-quiescent current state.

The start of the next conversion puts the AS1520/AS1521 into normal operation mode. The 8-bit control byte shifted

into the control register determines the next power mode. For example, if the 8-bit control byte contains PD1 = 0 and

PD0 = 0, full power-down mode starts immediately after the conversion (see Figure 30 on page 21)

DIN

1

11

1

1

1

00

0

Reduced-

Power Mode

Reduced-

Power Mode

Reduced-

Power Mode

2.50V (Always On)

2.2mA

2.2mA

2.2mA

0.4mA

0.4mA

0.4mA

REF

Normal Mode

Conversion

Reduced

Power Mode

Normal Mode

Conversion

Reduced

Power Mode

Normal Mode

Conversion

Reduced

Power Mode

0

500

1000

1500

2000

2500

3000

0.001

0.1

10

1000

Sampling Rate (ksps)

Reduced Power Mode

Normal Operation