DAC80504 datasheet(23/50 Pages) TI2

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VREFOUT (V)

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2.4975 2.4980 2.4985 2.4990 2.4995 2.5000 2.5005 2.5010

D061

Presolder Heat Reflow

Postsolder Heat Reflow

DAC80504, DAC70504, DAC60504

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SBAS871C – AUGUST 2017 – REVISED JANUARY 2019

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8.3.2 Internal Reference

The DACx0504 includes a 2.5 V precision bandgap reference enabled by default. Operation from an external

reference is supported by disabling the internal reference in the CONFIG register. The internal reference is

externally available at the REF pin.

A minimum 150 nF capacitor is recommended between the reference output and GND for noise filtering.

8.3.2.1 Reference Divider

The reference voltage to the device, either from the internal reference or an external one can be divided by a

factor of two by tying the REFDIV pin high at power-up or by setting the REF-DIV bit in the GAIN register to 1

during normal operation. The reference voltage divider provides additional flexibility in setting the full-scale output

voltage for each DAC output and must be configured to make certain that there is sufficient headroom from VDD

to the DAC operating reference voltage (VREF/DIV). See the Recommended Operating Conditions table for more

information.

Improper configuration of the reference divider issues a reference alarm condition. In this case, the reference

buffer is shut down, and all the DAC outputs go to 0 V. The DAC data registers are unaffected by the alarm

condition thus enabling the DAC output to return to normal operation once the reference divider is configured

correctly. The reference alarm status can be read from the REF-ALM bit in the STATUS register. Additionally by

setting ALM-EN = 1 and ALM-SEL = 1 in the CONFIG register, the SDO/ALARM pin is configured as a reference

alarm pin.

8.3.2.2 Solder Heat Reflow

A known behavior of IC reference voltage circuits is the shift induced by the soldering process. Figure 58 shows

the effect of solder heat reflow for the DACx0504 internal reference.

Figure 58. Solder Heat Reflow Reference Voltage Shift

DAC80504 датащи(PDF) 23 Page - Texas Instruments