MCP6C04 datasheet(14/54 Pages) MICROCHIP

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MCP6C04

DS20006179A-page 14

 2019 Microchip Technology Inc.

The impedance at VREF (shown here as RWR) needs to

have a magnitude less than 1Ω, for gain accuracy in the

signal bandwidth. The magnitude needs to be < 50Ω,

when f < 1 MHz, to maintain good stability.

1.6

Explanation of DC Error

Specifications

1.6.1

LINEAR RESPONSE MODEL

When the inputs and the output are in their normal

ranges, and the nonlinear errors are negligible, the out-

put voltage (VOUT) is:

EQUATION 1-3:

VDM is the input voltage. VE is the sum of input offset

errors (due to VOS, PSRR, CMRR, CMRR2, TC1, TC2,

etc.). gE is the Gain Error (GDM is the nominal gain).

1.6.2

INPUT OFFSET RELATED ERRORS

When VDM = 0V, the linear response model for VOUT

becomes:

EQUATION 1-4:

The input offset error (VE) is extracted from input offset

measurements

(see

Section 1.5.1

“VOS

Test

Circuit”):

EQUATION 1-5:

We usually assume gE =0, in Equation 1-5, when

extracting VE. The result is accurate enough, since gE

is so low.

VE has several terms, that assume a linear response to

changes in VDD, VSS, VIP and VREF.

VOS’s dependence on temperature (TA) is a quadratic

polynomial (VOS, TC1 and TC2). The aging specs

(ΔVOS and ΔTC1) are not included, for simplicity.

EQUATION 1-6:

1.6.3

INPUT OFFSET’S COMMON-MODE

VOLTAGE NONLINEARITY

The input offset error (VE) changes nonlinearly with VIP.

Figure 1-12 shows the MCP6C04’s VE vs. VIP, as well

as a linear fit line (VE_LIN), that goes through the center

point (VC, V2) and has the same slope as the end

points.

FIGURE 1-12:

Input Offset Error vs.

Common-Mode Input Voltage.

VOUT

VREF GDM 1gE

() VDM VE

()

VOUT

VREF GDM 1gE

()VE

VOUT VREF

–

GDM 1gE

()

---------------------------------

Where:

PSRR, CMRR and CMRR2 are in units of V/V

ΔTA is in units of °C

VDM =0

VOS

ΔVDD ΔVSS

–

PSRR

------------------------------------

ΔVIP

CMRR

----------------

ΔVREF

CMRR2

-------------------

ΔTATC1 ΔTA

TC2

VE,VE_LIN (V)

VIP (V)

VIPL

VIPH

VE_LIN

ΔVE

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