AD4680 datasheet(20/29 Pages) AD

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AD4680/AD4681

Data Sheet

Rev. 0 | Page 20 of 29

POWER MODES

The AD4680/AD4681 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 AD4680/AD4681. Set PMODE

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

Normal Mode

Keep the AD4680/AD4681 in normal mode to achieve the

fastest throughput rate. All blocks within the AD4680/AD4681

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

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

AD4680/AD4681 are not converting, the devices are in static

mode, and power consumption is automatically reduced. Addi-

tional current is required to perform a conversion, therefore,

power consumption on the AD4680/AD4681 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 AD4680/AD4681 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 AD4680/AD4681 to exit shutdown mode.

To enter shutdown mode, write to the PMODE bit in the

CONFIGURATION1 register. The AD4680/AD4681 shut

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, suffi-

cient 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 AD4680/AD4681 have a buffered 2.5 V internal reference

primarily used as a reference voltage for device operation. When

using the buffered internal 2.5 V reference externally via the

REFIO pin, the internal 2.5 V reference must use an external

buffer before connecting to the external circuitry. 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 or 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 AD4680/AD4681 have two reset modes, a soft reset and a

hard reset. A reset is initiated by writing to the reset 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 regulator 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.

tRESET

SDI

SOFTWARE RESET

Figure 37. Software Reset Operation

DIAGNOSTIC SELF TEST

The AD4680/AD4681 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 AD4680/AD4681 registers to the default status.

tSTARTUP

SHUTDOWN

MODE

NORMAL

MODE

ACCURATE

CONVERSION

SDI

SHUTDOWN

NORMAL

Figure 38. Shutdown Mode Operation

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