32-Channel, 16-Bit, Voltage-Output

DACs with Serial Interface

16

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Detailed Description

The MAX5732–MAX5735 are 32-channel, 16-bit, volt-

age-output DACs (Figure 1). The devices accept a 3V

external reference input at REF. An internal offset DAC

allows all outputs to be offset (see Table 1). The devices

provide a ground-sensing function that allows the output

voltages to be referenced to a remote ground.

A 33MHz SPI-/QSPI/-MICROWIRE- and DSP-compatible

serial interface controls the MAX5732–MAX5735 (Figure 2).

Each DAC includes a double-buffered input structure to

minimize the digital noise feedthrough from the digital

inputs to the outputs, and allows for synchronous or

asynchronous updating of the outputs. The two buffers

are organized as an input register followed by a DAC

register that stores the contents of the output. Input reg-

isters update the DAC registers independently or simul-

taneously with a single software or hardware command.

The MAX5732–MAX5735 also have a DOUT that allows

for read-back or daisy chaining multiple devices.

The MAX5732–MAX5735 analog and digital sections

have separate power inputs. Separate power inputs are

also provided for the output buffer amplifiers.

Proprietary deglitch circuits prevent output glitches at

power-up and eliminate the need for power sequenc-

ing. A software-shutdown mode allows efficient power

management. The MAX5732–MAX5735 consume 50µA

of supply current in shutdown.

All DACs provide buffered outputs that can drive 10k

Ω

in parallel with 100pF. The MAX5732 has a 0 to +5V

output range; the MAX5733 has a 0 to +10V output

range; the MAX5734 has a -2.5V to +7.5V output range;

and the MAX5735 has a -5V to +5V output range.

The MAX5732–MAX5735 are available in a 56-pin 8mm

x 8mm thin QFN package and are specified over the

extended -40°C to +85°C temperature range.

External Reference Input (REF)

The REF voltage sets the full-scale output voltage for all

32 DACs. REF accepts a +3V ±3% input. Reference

voltages outside these limits can result in a degradation

of device performance.

REF is a buffered input. The typical input impedance is

10M

Ω, and it does not vary with code. Use a high-

accuracy, low-noise voltage reference such as the

MAX6126AASA30 (3ppm/°C temp drift and 0.02% initial

accuracy) to improve static accuracy. REF does not

accept AC signals.

Ground Sense (GS)

The MAX5732–MAX5735 include a GS that allows the

output voltages to be referenced to a remote ground.

resulting output voltage must be within the valid output-

voltage range set by the power supplies. See the

Output Amplifiers (OUT0–OUT31) section for the effect

of the GS inputs on the DAC outputs.

Offset DAC

The MAX5732–MAX5735 feature an offset DAC that

determines the output voltage range. While each part

number has an output voltage range associated with it,

SCLK

XX

1

2

3

32

X

DIN

D0

C0

C1

C2

CS

(DSP MODE)

CS

(

µC MODE)

Figure 2. Serial-interface Timing