AD5721 datasheet(23/31 Pages) AD

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Data Sheet

AD5761/AD5721

Rev. C | Page 23 of 31

Asynchronous DAC Update

In asynchronous DAC update mode, LDAC is held high while

data is being clocked into the input shift register. The DAC output

is asynchronously updated by taking LDAC low after SYNC is

taken high. The update then occurs on the falling edge of LDAC.

Reset Function (RESET)

The AD5761/AD5721 can be reset to its power-on state by two

means: either by asserting the RESET pin or by using the software

full reset registers (see Table 26).

Asynchronous Clear Function (CLEAR)

The CLEAR pin is a falling edge active input that allows the output

to be cleared to a user defined value. The clear code value is

programmed by writing to Bit 10 and Bit 9 in the control register

(see Table 11 and Table 12). It is necessary to maintain CLEAR low

for a minimum amount of time to complete the operation (see

Figure 2). When the CLEAR signal is returned high, the output

remains at the clear value until a new value is loaded to the

DAC register.

Alert Function (ALERT)

When the ALERT pin is asserted low, a readback from the

control register is required to clarify whether a short-circuit

or brownout condition occurred, depending on the values of

Bit 12 and Bit 11, SC and BO bits, respectively (see Table 15

and Table 16). If neither of these conditions occurred, the

temperature exceeded approximately 150°C.

The ALERT pin is low during power-up, a software full reset, or

a hardware reset. After the first write to the control register to

configure the DAC, the ALERT pin is asserted high.

In the event of the die temperature exceeding approximately 150°C,

the ALERT pin is low and the value of the ETS bit determines the

state of the digital supply of the device, whether the internal

digital supply is powered on or powered down. If the ETS bit is

set to 0, the internal digital supply is powered on when the internal

die temperature exceeds approximately 150°C. If the ETS bit is

set to 1, the internal digital supply is powered down when the

internal die temperature exceeds approximately 150°C and the

device becomes nonfunctional (see Table 11 and Table 12).

The AD5761/AD5721 temperature at power-up must be less

than 150°C for proper operation of the devices.

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