Nonvolatile, Quad, 8-Bit DACs

16

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This initialization period takes about 80µs with the DAC

registers loading first and the mute/shutdown register

loading last. During this time, the DAC outputs are held

in the mute state and the serial interface is disabled.

Once the mute/shutdown register is loaded, the DAC

outputs are updated to their stored data and operating

states, and the serial interface is enabled.

Applications Information

DAC Linearity and Offset Voltage

The output buffer can have a negative input offset volt-

age that would normally drive the output negative, but

since there is no negative supply, the output remains at

GND (Figure 9). When linearity is determined using the

end-point method, it is measured between code 10

(0Ahex) and full-scale code (FFhex) after the offset and

gain error are calibrated out. With a single supply, neg-

ative offset causes the output not to change with an

input code transition near zero (Figure 9). Thus, the

lowest code that produces a positive output is the lower

endpoint.

External Voltage Reference

The MAX5105/MAX5106 have two reference inputs for

each DAC, REFH_, and REFL_. REFH_ sets the full-

scale voltage, while REFL_ sets the zero code output.

REFL2 and REFL3 are internally connected to GND in

the MAX5106. A 256k

Ω typical input impedance at

REFH_ is code independent. The output voltage from

these devices can be represented by a digitally pro-

grammable voltage source as follows:

where N is the decimal value of the DAC’s binary input

code.

Power Sequencing

The voltage applied to REFH_ and REFL_ should not

not possible, connect an external Schottky diode

ance with the absolute maximum ratings. Do not apply

signals to the digital inputs before the device is fully

powered up.

Power-Supply Bypassing and

Ground Management

Digital or AC transient signals on GND can create noise

at the analog output. Return GND to the highest-quality

located as close to the device as possible. Bypass

REF_ to GND with a 0.1µF capacitor. Carefully printed

circuit board ground layout minimizes crosstalk

between the DAC outputs and digital inputs.

Chip Information

TRANSISTOR COUNT: 32,000

PROCESS: CMOS