MCP48FVB21 datasheet(77/84 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS20005466A-page 77

MCP48FVBXX

B.4

Full-Scale Error (EFS)

The Full-Scale Error (see Figure B-3) is the error on

the VOUT pin relative to the expected VOUT voltage

(theoretical) for the maximum device DAC register

code (code FFFh for 12-bit, code 3FFh for 10-bit, and

code FFh for 8-bit) (see Equation B-2). The error is

dependent on the resistive load on the VOUT pin (and

where that load is tied to, such as VSS or VDD). For

loads (to VSS) greater than specified, the full-scale

error will be greater.

The error in bits is determined by the theoretical voltage

step size to give an error in LSb.

EQUATION B-2:

FULL-SCALE ERROR

B.5

Zero-Scale Error (EZS)

The Zero-Scale Error (see Figure B-2) is the difference

between the ideal and the measured VOUT voltage with

the DAC register code equal to 000h (Equation B-3).

The error is dependent on the resistive load on the

VOUT pin (and where that load is tied to, such as VSS or

VDD). For loads (to VDD) greater than specified, the

zero-scale error will be greater.

The error in bits is determined by the theoretical voltage

step size to give an error in LSb.

EQUATION B-3:

ZERO-SCALE ERROR

B.6

Total Unadjusted Error (ET)

The Total Unadjusted Error (ET) is the difference

between the ideal and measured VOUT voltage.

Typically, calibration of the output voltage is

implemented to improve system performance.

The error in bits is determined by the theoretical voltage

step size to give an error in LSb.

Equation B-4 shows the Total Unadjusted Error

calculation.

EQUATION B-4:

TOTAL UNADJUSTED

ERROR CALCULATION

EFS =

VOUT(@FS) - VIDEAL(@FS)

VLSb(IDEAL)

Where:

EFS is expressed in LSb.

VOUT(@FS) = The VOUT voltage when the DAC

VIDEAL(@FS) = The ideal output voltage when the

DAC register code is at full-scale.

VLSb(IDEAL) = The theoretical voltage step size.

EZS =

VOUT(@ZS)

VLSb(IDEAL)

Where:

EZS is expressed in LSb.

VOUT(@ZS) =The VOUT voltage when the DAC

VLSb(IDEAL) = The theoretical voltage step size.

Where:

ET is expressed in LSb.

VOUT_Actual(@code) = The measured DAC output

voltage at the specified code.

VOUT_Ideal(@code) = The calculated DAC output

voltage at the specified code.

( code * V

LSb(Ideal) )

VLSb(Ideal) =VREF/# Steps

12-bit = VREF/4096

10-bit = VREF/1024

8-bit = VREF/ 256

ET =

( VOUT_Actual(@code) - VOUT_Ideal(@Code) )

VLSb(Ideal)

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