AD7476BRTZ-R23 datasheet(16/24 Pages) AD

16 / 24 page

AD7476/AD7477/AD7478

Rev. F | Page 16 of 24

To exit this mode of operation and power up the AD7476/

AD7477/AD7478 again, perform a dummy conversion. On the

falling edge of CS, the device begins to power up, and continues

to power up as long as CS is held low until after the falling edge

of the tenth SCLK. The device is fully powered up once 16

SCLKs have elapsed and, as shown in

, valid data

results from the next conversion. If

Figure 21

CS is brought high before

the tenth falling edge of SCLK, the AD7476/AD7477/AD7478

again goes back into power-down. This avoids accidental

power-up due to glitches on the CS line or an inadvertent burst

of eight SCLK cycles while CS is low. Although the device may

begin to power up on the falling edge of CS, it powers down

again on the rising edge of CS as long as it occurs before the

tenth SCLK falling edge.

Power-Down Mode

This mode is intended for use in applications where slower

throughput rates are required; either the ADC is powered

between each conversion, or a series of conversions can be

performed at a high throughput rate and the ADC is then

powered down for a relatively long duration between these

bursts of several conversions. When the AD7476/AD7477/

AD7478 is in power-down mode, all analog circuitry is

powered down.

To enter power-down, the conversion process must be

interrupted by bringing CS high any time after the second

falling edge of SCLK and before the tenth falling edge of SCLK,

as shown in

. Once

Figure 20

CS is brought high in this window

of SCLKs, the part enters power-down and the conversion

initiated by the falling edge of CS is terminated and SDATA

goes back into three-state.

If CS is brought high before the second SCLK falling edge, the

part remains in normal mode and does not power down. This

avoids accidental power-down due to glitches on the CS line.

4 LEADING ZEROS + CONVERSION RESULT

SCLK

SDATA

Figure 19. Normal Mode Operation

110

THREE-STATE

SCLK

SDATA

Figure 20. Entering Power-Down Mode

SCLK

SDATA

INVALID DATA

VALID DATA

THE PART BEGINS

TO POWER UP

THE PART IS FULLY POWERED

UP WITH VIN FULLY ACQUIRED

Figure 21. Exiting Power-Down Mode

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