16-Bit DACs with 32-Channel

Sample-and-Hold Outputs

10

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voltage at the ground-sense input. With a 2.5V refer-

ence, the nominal endpoints are -4.0535V and

+9.0535V (Table 1). Note that these are “virtual” inter-

nal endpoint voltages and cannot be reached with all

combinations of negative and positive power-supply

voltages. The nominal, useable DAC endpoint codes

for the selected power supplies may be calculated as:

200µV) (result

≥ 0)

200µV) (result

≤ 65535)

The resistive voltage-divider formed by the output resis-

Ground Sense

The MAX5631/MAX5632/MAX5633 include a ground-

sense input (GS), which allows the output voltages to

be referenced to a remote ground. The voltage at GS is

added to the output voltage with unity gain. Note that

the resulting output voltage must be within the valid

output voltage range set by the power supplies.

Output Clamp

The MAX5631/MAX5632/MAX5633 clamps the output

between two externally applied voltages. Internal

diodes at each channel restrict the output voltage to:

The clamping diodes allow the MAX5631/MAX5632/

MAX5633 to drive devices with restricted input ranges.

The diodes also allow the outputs to be clamped during

power-up or fault conditions. To disable output clamp-

clamping voltages beyond the maximum output voltage

range.

Serial Interface

The MAX5631/MAX5632/MAX5633 are controlled by an

SPI, QSPI, and MICROWIRE-compatible 3-wire inter-

face. Serial data is clocked into the 24-bit shift register

in an MSB-first format, with the 16-bit DAC data pre-

ceding the 5-bit SRAM address, 2-bit control, and a fill

0 (Figure 4). The input word is framed by

CS. The first

VV

V

V

V

CH

OUT

CL

+

−

07

07

..

_

Scaling Factor

R

RR

V

V

scaling factor

L

LO

OUT

CHOLD

=

+

=×

_

DATA

ADDRESS

CONTROL

D15 D14 D13 D12 D11 D10 D09 D08 D07 D06 D05 D04 D03 D02 D01

D0

A4

A3

A2

A1

A0

C1

C0

0

MSB

LSB

Figure 4. Input Word Sequence

Figure 3. Analog Block Diagram

GS

DAC

DATA

CH

OUT_

GAIN

AND

OFFSET

ONE OF 32 SHA CHANNELS

16-BIT

DAC

CL