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AD5671R/AD5675R

Data Sheet

Rev. B | Page 28 of 32

HARDWARE RESET (RESET)

The RESET pin is an active low reset that allows the outputs to

be cleared to either zero scale or midscale. The clear code value

is user selectable via the RSTSEL pin. Keep RESET low for a

minimum time (see Table 5) to complete the operation. When

the RESET signal is returned high, the output remains at the

cleared value until a new value is programmed. While

the RESET pin is low, the outputs cannot be updated with a new

value. A software executable reset function is also available that

resets the DAC to the power-on reset code. Command 0110 is

designated for this software reset function. Any events

on LDAC or RESET during power-on reset are ignored.

RESET SELECT PIN (RSTSEL)

The AD5671R/AD5675R contain a power-on reset circuit that

controls the output voltage during power-up. By connecting the

RSTSEL pin low, the output powers up to zero scale. Note that

this power-up is outside the linear region of the DAC; by

connecting the RSTSEL pin high, VOUT powers up to midscale.

The output remains powered up at this level until a valid write

sequence is made to the DAC.

INTERNAL REFERENCE AND AMPLIFIER GAIN

SELECTION

The on-chip reference is on at power-up by default. To reduce

the supply current, turn off this reference by setting the software

programmable bit, DB0, in the internal reference and gain setup

The state of Bit DB2 in the internal reference and gain setup

LFCSP package (see Table 16 and Table 17). Ignore Bit DB2 for

the TSSOP package. Command 0111 is reserved for setting up the

internal reference and amplifier gain.

Table 16. Internal Reference and Gain Setup Register

Bit

Description

DB2

Amplifier gain setting

DB2 = 0; amplifier gain = 1 (default)

DB2 = 1; amplifier gain = 2

DB1

Reserved; set to 0

DB0

Internal reference

DB0 = 0; reference is on (default)

DB1 = 1; reference is off

SOLDER HEAT REFLOW

As with all IC reference voltage circuits, the reference value

experiences a shift induced by the soldering process. Analog

Devices, Inc., performs a reliability test called precondition to

mimic the effect of soldering a device to a board. The output

voltage specification quoted previously includes the effect of

this reliability test.

Figure 64 shows the effect of solder heat reflow (SHR) as

measured through the reliability test (precondition).

Figure 64. Solder Heat Reflow Reference Voltage Shift

LONG-TERM TEMPERATURE DRIFT

Figure 65 shows the change in VREF value after 1000 hours in the

life test at 150°C.

Figure 65. Reference Drift Through to 1000 Hours

2.497

2.498

2.499

2.500

2.501

2.502

VREF (V)

POSTSOLDER

HEAT REFLOW

PRESOLDER

HEAT REFLOW

2.498

2.499

2.500

2.501

2.502

0 HOURS

168 HOURS

500 HOURS

1000 HOURS

VREF (V)

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