DAC53508 datasheet(20/38 Pages) TI

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8.3.1.4 Output Amplifier

The output buffer amplifier generates rail-to-rail voltages on the output, giving a maximum output range of 0 V

to VDD. Equation 1 shows that the full-scale output range of the DAC output is determined by the voltage on the

VREFIN pin

8.3.2 Reference

The DACx3508 require an external reference to operate. However, the reference pin, VREFIN, and the supply

pin, VDD, can be tied together. The reference input pin voltage ranges from 1.8 V to VDD. The typical input

impedance of this pin when all the channels are powered on is 12.5 kΩ.

8.3.3 Power-On Reset (POR)

The DACx3508 family of devices includes a power-on reset (POR) function that controls the output voltage at

power up. After the VDD supply has been established, a POR event is issued. The POR causes all registers to

initialize to default values, and communication with the device is valid only after a 5-ms delay, when VDD reaches

DAC operating range. The default value for the DAC data registers is zero-code. The DAC output remains at the

power-up voltage until a valid command is written to a channel.

When the device powers up, a POR circuit sets the device to the default mode. The POR circuit requires specific

VDD levels, as indicated in Figure 8-2, to make sure that the internal capacitors discharge and reset the device

on power up. To make sure that a POR occurs, VDD must be less than 0.7 V for at least 1 ms. When VDD drops

to less than 1.7 V but remains greater than 0.7 V (shown as the undefined region), the device may or may

not reset under all specified temperature and power-supply conditions. In this case, initiate a POR. When VDD

remains greater than 1.7 V, a POR does not occur.

No power-on reset

Power-on reset

0.70

Undefined

0.00

1.70

1.80

5.50

VDD (V)

Specified supply

voltage range

Figure 8-2. Threshold Levels for VDD POR Circuit

8.3.4 Software Reset

A device software reset event is initiated by writing the reserved code 0x1010 to the SW_RST bit in the

STATUS_TRIGGER register.

DAC53508, DAC43508

SLASF08 – DECEMBER 2021

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DAC53508 Datasheet(PDF) 20 Page - Texas Instruments