MCP4716 datasheet(63/70 Pages) MICROCHIP

63 / 70 page

 2012 Microchip Technology Inc.

DS25154A-page 63

MCP47A1

B.6

Total Unadjusted Error

The Total Unadjusted Error is the difference between

the ideal and measured VOUT voltage. Typically,

calibration of the output voltage is implemented to

improve system performance.

Total Unadjusted Error can be calculated, see

Equation B-4.

EQUATION B-4:

TOTAL UNADJUSTED

ERROR (LSb)

See

Figure 2-17

through

Figure 2-20

for

Total

Unadjusted Error characterization graphs.

B.7

Offset Error

The Offset error (see Figure B-2) is the deviation from

zero voltage output when the volatile DAC Register

value = 00h (zero scale voltage). This error affects all

codes by the same amount. The offset error can be

calibrated by software in application circuits.

FIGURE B-2:

OFFSET ERROR.

B.8

Offset Error Drift

The Offset error drift is the variation in offset error due

to a change in ambient temperature. The offset error

drift is typically expressed in ppm/oC.

B.9

Gain Error

The Gain error (see Figure B-3) is the difference

between the actual full-scale output voltage, from the

ideal output voltage of the DAC transfer curve. The

gain error is calculated after nullifying the offset error,

or full scale error minus the offset error.

The gain error indicates how well the slope of the actual

transfer function matches the slope of the ideal transfer

function. The gain error is usually expressed as percent

of full-scale range (% of FSR) or in LSb. The gain error

is not calibrated at the factory and most of the gain error

is contributed by the output buffer (op amp) saturation.

FIGURE B-3:

GAIN ERROR AND FULL-

SCALE ERROR EXAMPLE.

B.10

Gain Error Drift

The Gain error drift is the variation in gain error due to

a change in ambient temperature. The gain error drift is

typically expressed in ppm/oC.

ErrorLSb =

VIDEAL - VMEASURED

VLSb

Where:

VREF is the voltage on the VREF pin.

VMEASURED is the VOUT voltage for the same DAC

VIDEAL =

* DAC Code

VREF

VLSb =

VREF

Analog

Output

Ideal Transfer Function

Actual Transfer Function

DAC Input Code

Offset

Error

(ZSE)

Analog

Output

Actual Transfer Function

DAC Input Code

Gain Error

Ideal Transfer Function

after Offset Error is removed

Full-Scale

Error

Zero-Scale

Error

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