Nonvolatile, Quad, 8-Bit DACs with 2-Wire Serial

Interface

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17

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

with no negative supply, the output remains at GND

(Figure 10). Determine linearity using the end-point

method, measuring between code 10 (0A hex) and

code 240 (F0 hex) after calibrating the offset and gain

error (Figure 10).

External Voltage Reference

The MAX5115 features two reference inputs for each

DAC (REFH_ and REFL_). The MAX5116 uses a single

reference for all four DACs (REFH and REFL). REFH_

sets the full-scale voltage, while REFL_ sets the zero

code output. The MAX5115 has a 460k

Ω typical input

impedance that is independent of the code. The

MAX5116 has a 115k

Ω typical input impedance that is

independent of the code.

Power Sequencing

The voltage applied to REFH_ and REFL_ should not

not possible, connect an external Schottky diode

with the absolute maximum ratings. Do not apply signals

to the digital inputs before the device is fully powered.

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

REFH_ and REFL_ to GND with 0.1µF capacitors.

Careful PC board ground layout minimizes crosstalk

between the DAC outputs and digital inputs.

DAC

CODE

OUTPUT

VOLTAGE (V)

1111 1111

1000 0000

0000 0001

0000 0000

Table 9. Unipolar Code Output Voltage

O

DAC CODE

NEGATIVE

OFFSET

OUTPUT

VOLTAGE

Figure 10. Effect of Negative Offset (Single Supply)

255

256

×−

+

()

__

_

VV

V

REFH

REFL

REFL

128

256

×−

+

(

__

_

VV

V

REFH

REFL

REFL

256

−

+

()

__

_

VV

V

REFH

REFL

REFL