AD7380 datasheet(20/31 Pages) AD

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AD7381-4

Data Sheet

Rev. 0 | Page 20 of 31

INTERNAL/EXTERNAL REFERENCE

The AD7381-4 has a 2.5 V internal reference with a buffer.

Alternatively, if a more accurate reference or dynamic range is

required, an external 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 Configuration 1 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 AD7381-4 has two reset modes: a soft reset and a hard

reset. A reset is initiated by writing to the reset bits in the

Configuration 2 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 indication 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 35. Software Reset Operation

DIAGNOSTIC SELF TEST

The AD7381-4 runs a diagnostic self test after a POR or after a

software hard reset to ensure the correct configuration is

loaded into the device.

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

alert indication 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 AD7381-4 registers to the default status.

SHUTDOWN

NORMAL

SDI

tSTARTUP

SHUTDOWN MODE

NORMAL MODE

ACCURATE CONVERSION

Figure 36. Shutdown Mode Operation

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