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AD7380/AD7381

Data Sheet

Rev. 0 | Page 20 of 31

POWER MODES

The AD7380/AD7381 have two power modes, normal mode

and shutdown mode. These modes of operation provide flexible

power management options, allowing optimization of the

power dissipation and throughput rate ratio for different

application requirements.

Program the PMODE bit in the CONFIGURATION1 register to

configure the power modes in the AD7380/AD7381. Set PMODE

to Logic 0 for normal mode and Logic 1 for shutdown mode.

Normal Mode

Keep the AD7380/AD7381 in normal mode to achieve the

fastest throughput rate. All blocks within the AD7380/AD7381

remain fully powered at all times, and an ADC conversion can

be initiated by a falling edge of CS, when required. When the

AD7380/AD7381 are not converting, the devices are in static

mode, and power consumption is automatically reduced.

Additional current is required to perform a conversion,

therefore, power consumption on the AD7380/AD7381 scales

with throughput.

Shutdown Mode

When slower throughput rates and lower power consumption

are required, use shutdown mode by either powering down the

ADC between each conversion or by performing a series of

conversions at a high throughput rate and then powering down

the ADC for a relatively long duration between these burst

conversions. When the AD7380/AD7381 are in shutdown

mode, all analog circuitry powers down, including the internal

reference, if enabled. The serial interface remains active during

shutdown mode to allow the AD7380/AD7381 to exit shutdown

mode.

To enter shutdown mode, write to the PMODE bit in

theCONFIGURATION1 register. The AD7380/AD7381 shuts

down and current consumption reduces.

To exit shutdown mode and return to normal mode, set the

PMODE bit in the CONFIGURATION1 register to Logic 0. All

leaving shutdown mode. After exiting shutdown mode,

sufficient time must be allowed for the circuitry to turn on

before starting a conversion. If the internal reference is enabled,

the reference must be allowed to settle for accurate conversions to

happen.

INTERNAL AND EXTERNAL REFERENCE

The AD7380/AD7381 have a 2.5 V internal reference.

Alternatively, if a more accurate reference or higher dynamic

range is required, an external reference can be supplied. An

externally supplied reference can be in the range of 2.5 V to 3.3 V.

Reference selection, internal/external, is configured by the

REFSEL bit in the CONFIGURATION1 register. If REFSEL is

set to 0, the internal reference buffer is enabled. If an external

reference is preferred, the REFSEL bit must be set to 1, and an

external reference must be supplied to the REFIO pin.

SOFTWARE RESET

The AD7380/AD7381 have two reset modes, a soft reset and a

hard reset. A reset is initiated by writing to the RESET[7:0] bits

in the CONFIGURATION2 register.

A soft reset maintains the contents of the configurable registers

but refreshes the interface and the ADC blocks. Any internal

state machines are reinitialized, and the oversampling block and

FIFO are flushed. The ALERT register is cleared. The reference

and LDO remain powered.

A hard reset, in addition to the blocks reset by a soft reset, resets

all user registers to the default status, resets the reference buffer,

and resets the internal oscillator block.

DIAGNOSTIC SELF-TEST

The AD7380/AD7381 run a diagnostic self test after a power-on

reset (POR) or after a software hard reset to ensure correct

configuration is loaded into the device.

The result of the self test is displayed in the SETUP_F bit in the

ALERT register. If the SETUP_F bit is set to Logic 1, the

diagnostic self test has failed. If the test fails, perform a software

hard reset to reset the AD7380/AD7381 registers to the default

status.

tSTARTUP

POWER-DOWN

MODE

NORMAL

MODE

ACCURATE

CONVERSION

SDI

SHUTDOWN

NORMAL

Figure 35. Shutdown Mode Operation

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