AMC7832IPAP datasheet(25/74 Pages) TI2

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AMC7832

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SLAS836 – MARCH 2014

8.3 Feature Description

8.3.1 Digital-to-Analog Converters (DACs)

The AMC7832 features an analog control system centered on twelve, 12-bit DACs that operate from the device

internal reference. Each DAC core consists of a string DAC and output voltage buffer.

The resistor string structure consists of a series of resistors, each of value R. The code loaded to the DAC

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 has inherent

monotonicity, voltage output, and low glitch. It is also linear because all the resistors are of equal value.

8.3.1.1 DAC Output Range and Clamp Configuration

The twelve DACs are split into four total groups: two groups of two DACs (DAC groups B and C) and two groups

of four DACs (DAC groups A and D). All of the DACs in a given group share the same output range and clamp

voltage value however these settings can be set independently for each DAC group. After power-on or a reset

event, the DAC output are directed automatically to their corresponding clamp value and all DAC buffer and

active registers are set to their default values.

The output range for each DAC group is configured as either positive or negative through its corresponding

VRANGE terminal. The VRANGE terminals can be driven directly by the REF_OUT1 and REF_OUT2 +2.5-V

outputs. When a DAC group is in positive output range the DAC Range register (address 0x1E) can be set to

specify an output range of 0 to +5-V instead of the default range of 0 to +10-V.

Additionally the power-on-reset and clamp voltage value of each DAC group is set by its corresponding AVSS

terminal. It is imperative that the clamp voltage setting for a DAC group matches its operating voltage range. The

recommended connections for AVSS are: AGND for the positive output ranges, in which case the clamp voltage

is 0-V; and -12-V for the negative output range, in which case the clamp voltage is AVSS + 2-V.

The full-scale output range for each DAC group is limited by the power supplies AVCC and its corresponding

AVSS. The maximum and minimum outputs cannot exceed AVCC or be lower than AVSS, respectively.

Table 1. DAC Group Configuration

POSITIVE OUTPUT RANGE

NEGATIVE OUTPUT RANGE

VRANGE = GND

VRANGE = +2.5-V

OUTPUT

CLAMP

DAC

DACs

POLARITY

VOLTAGE

VALID CLAMP

GROUP

OUTPUT

SELECTION

OUTPUT RANGE

VOLTAGE

RANGE

CONNECTION

DAC_A8

DAC_A9

0 to +5-V

VRANGEA

AVSSA

GND

-10 to 0-V

-12-V

DAC_A10

0 to +10-V

DAC_A11

DAC_B6

0 to +5-V

VRANGEB

AVSSB

GND

-10 to 0-V

-12-V

DAC_B7

0 to +10-V

DAC_C0

0 to +5-V

VRANGEC

AVSSC

GND

-10 to 0-V

-12-V

DAC_C1

0 to +10-V

DAC_D2

DAC_D3

0 to +5-V

VRANGED

AVSSD

GND

-10 to 0-V

-12-V

DAC_D4

0 to +10-V

DAC_D5

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