AMC7812B datasheet(40/92 Pages) TAOS

40 / 92 page

ToOutput

Amplifier

12-Bit

Resistor

String

OUT

DAC

Latch

DAC

Data

DACLoad

(1)

GainLogic

GainBits

Gain

AMC7812B

SBAS625A – SEPTEMBER 2013 – REVISED SEPTEMBER 2013

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DAC OPERATION

The device 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 the 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. The resistor string 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. The resistor string architecture is

also linear because all the resistors are of equal value.

Figure 92. Resistor String

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