AMC7812SPAPR datasheet(40/92 Pages) TI

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ToOutput

Amplifier

12-Bit

Resistor

String

OUT

DAC

Latch

DAC

Data

DACLoad

(1)

GainLogic

GainBits

Gain

AMC7812

SBAS513E – JANUARY 2011 – REVISED SEPTEMBER 2013

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DAC OPERATION

The AMC7812 contains 12 DACs that provide digital control with 12 bits of resolution using an internal or

external reference. The DAC core is a 12-bit string DAC and output buffer. The DAC drives the output buffer to

provide an output voltage. Refer to the DAC Configuration Register for details. Figure 91 shows a function block

diagram of the DAC architecture. The DAC Latch stores the code that determines the output voltage from the

DAC string. The code is transferred from the DAC-n-Data Register to the DAC Latch when the internal DAC-

Load signal is generated.

(1)

Internal DAC load is generated by writing '1' to ILDAC bit in synchronous mode. In asynchronous mode, the DAC

latch is transparent.

Figure 91. DAC Block Diagram

Resistor String

The resistor string structure is shown in Figure 92. It consists of a string of resistors, each of value R. The code

loaded to the DAC Latch determines at which node on the string the voltage is tapped off to be fed into the

output amplifier. The voltage is tapped off by closing one of the switches connecting the string to the amplifier.

This architecture is inherently monotonic, voltage out, and low glitch. It is also linear because all the resistors are

of equal value.

Figure 92. Resistor String

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