DAC7562SDGST datasheet(30/63 Pages) TI2

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REFIN

REFOUT

Reference

Enable

DAC7562, DAC7563, DAC8162

DAC8163, DAC8562, DAC8563

SLAS719E – AUGUST 2010 – REVISED JUNE 2015

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Feature Description (continued)

8.3.2 Internal Reference

The DAC756x, DAC816x, and DAC856x devices include a 2.5-V internal reference that is disabled by default.

The internal reference is externally available at the VREFIN/VREFOUT pin. The internal reference output voltage is

2.5 V and can sink and source up to 20 mA.

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

The internal reference of the DAC756x, DAC816x, and DAC856x devices is a bipolar transistor-based precision

band-gap voltage reference. Figure 90 shows the basic band-gap topology. Transistors Q1 and Q2 are biased

such that the current density of Q1 is greater than that of Q2. The difference of the two base-emitter voltages

(VBE1 – VBE2) has a positive temperature coefficient and is forced across resistor R1. This voltage is amplified and

added to the base-emitter voltage of Q2, which has a negative temperature coefficient. The resulting output

voltage is virtually independent of temperature. The short-circuit current is limited by design to approximately

100 mA.

Figure 90. Band-Gap Reference Simplified Schematic

8.3.3 Power-On Reset

8.3.3.1 Power-On Reset to Zero-Scale

The DAC7562, DAC8162, and DAC8562 devices contain a power-on-reset circuit that controls the output voltage

during power up. All device registers are reset as shown in Table 4. At power up, all DAC registers are filled with

zeros and the output voltages of all DAC channels are set to zero volts. Each DAC channel remains that way

until a valid load command is written to it. The power-on reset is useful in applications where it is important to

know the state of the output of each DAC while the device is in the process of powering up. No device pin should

be brought high before applying power to the device. The internal reference is disabled by default and remains

that way until a valid reference-change command is executed.

8.3.3.2 Power-On Reset to Mid-Scale

The DAC7563, DAC8163, and DAC8563 devices contain a power-on reset circuit that controls the output voltage

during power up. At power up, all DAC registers are reset to mid-scale code and the output voltages of all DAC

channels are set to VREFIN / 2 volts. Each DAC channel remains that way until a valid load command is written to

it. The power-on reset is useful in applications where it is important to know the state of the output of each DAC

while the device is in the process of powering up. No device pin should be brought high before applying power to

the device. The internal reference is powered off or down by default and remains that way until a valid reference-

change command is executed. If using an external reference, it is acceptable to power on the VREFIN pin either at

the same time as or after applying AVDD.

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Product Folder Links: DAC7562 DAC7563 DAC8162 DAC8163 DAC8562 DAC8563

DAC7562SDGST Datasheet(PDF) 30 Page - Texas Instruments

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