MCP47DA1 datasheet(71/76 Pages) MICROCHIP

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DS25118D-page 71

MCP47DA1

B.13

Settling Time

The Settling time is the time delay required for the VOUT

voltage to settle into its new output value. This time is

measured from the start of code transition, to when the

VOUT voltage is within the specified accuracy.

In the MCP47DA1, the settling time is a measure of the

time delay until the VOUT voltage reaches within 0.5

LSb of its final value, when the volatile DAC register

changes from 40h to 50h.

See Figure 2-89 through Figure 2-92 for Settling Time

oscilloscope screen captures.

B.14

Major-Code Transition Glitch

Major-code transition glitch is the impulse energy

injected into the DAC analog output when the code in

the DAC register changes state. It is normally specified

as the area of the glitch in nV-Sec, and is measured

when the digital code is changed by 1 LSb at the major

carry transition (Example: wiper code changes from

“011111” to “100000”, or from “100000” to

“011111”).

B.15

Digital Feedthrough

The Digital feedthrough is the glitch that appears at the

analog output caused by coupling from the digital input

pins of the device. The area of the glitch is expressed

in nV-Sec, and is measured with a full-scale change

(Example: all 0s to all 1s and vice versa) on the digital

input pins. The digital feedthrough is measured when

the DAC is not writing to the output register.

B.16

Power-Supply Rejection Ratio

(PSRR)

PSRR indicates how the output of the DAC is affected

by changes in the supply voltage. PSRR is the ratio of

the change in VOUT to a change in VDD for full-scale

output of the DAC. The VOUT is measured while the

VDD is varied +/- 10%, and expressed in dB or µV/V.

B.17

Ratiometric Temperature

Coefficient

The ratiometric temperature coefficient quantifies the

error in the ratio of the resistor setting (Resistance from

VREF pin to wiper position (RVREF-W) and the wiper

position to Ground (RW-VSS) due to temperature drift.

This error also includes the drift of the output driver

over temperature. This is typically the critical error

when using a DAC.

See Figure 2-56 through Figure 2-66 for Tempco

characterization graphs.

B.18

Absolute Temperature Coefficient

The absolute temperature coefficient quantifies the

error in the end-to-end output voltage (Nominal output

voltage VOUT) due to temperature drift. For a DAC, this

error is typically not an issue, due to the ratiometric

aspect of the output.

Note:

Due to the three resistor implementation

of the MCP47DA1 (R1, RAB, and R2), R1,

RAB and R2 are implemented so that they

have a common tempco over-process.

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