MCP6C04 datasheet(32/54 Pages) MICROCHIP

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MCP6C04

DS20006179A-page 32

 2019 Microchip Technology Inc.

4.0

DEVICE OPERATION

This chapter includes additional information on basic

operations and major functions.

4.1

Basic Performance

4.1.1

IDEAL PERFORMANCE

Figure 4-1 shows the basic circuit; inputs, supplies and

output. When the inputs (VIP, VIM, VDD, VSS and VREF)

and output (VOUT) are in their specified ranges, and the

part is nearly ideal, the output voltage is:

EQUATION 4-1:

FIGURE 4-1:

Basic Circuit.

For normal operation, keep:

•VIP between VIPL and VIPH

•VDM between VDML and VDMH

•VREF between VRL and VRH

•VOUT between 0.1V to VDD – 0.1V, usually

-VOL and VOH are hard limits

4.1.2

ANALOG ARCHITECTURE

Figure 4-2 shows the block diagram for these high-side

current sense amplifiers, without any details on offset

correction.

FIGURE 4-2:

MCP6C04 Block Diagram.

The input (differential) signal is applied to GM1. Due to

its architecture, the MCP6C04’s signal inputs are best

described by VIP and VDM. The inverting input is then:

EQUATION 4-2:

The negative feedback loop includes GM2, RM3, RF and

RG. These blocks set the DC open-loop gain (AOL) and

the nominal differential gain (GDM):

EQUATION 4-3:

AOL is very high, so the current into RM3 (I1 +I2) is

nearly zero. This makes the differential inputs to GM1

and GM2 equal in magnitude and opposite in polarity.

Ideally, this gives:

EQUATION 4-4:

For an ideal part, within the operating ranges, changing

VIP, VSS or VDD produces no change in VOUT. VREF

shifts VOUT as needed in the design.

The different GDM options change GM1, GM2, RF, RG

and the internal compensation capacitor. This results in

the performance trade-offs highlighted in Table 1.

4.1.3

DC PERFORMANCE

4.1.3.1

DC Voltage Errors

Section 1.6, Explanation of DC Error Specifications

covers some DC specifications. The input offset error

(with temperature coefficients), gain error and

nonlinearities are discussed in detail.

Plots in Section 2.1, DC Precision and Section 2.2,

Other DC Voltages and Currents give useful

information.

In this data sheet, CMRR is based on changes in VIP

(i.e., CMRR = ΔVIP/ΔVOS). This is accurate since VDM

is relatively small. This CMRR describes the rejection

of errors at the high voltage supply, without any

contribution from VDM.

VOUT VREF GDMVDM

≈

Where:

GDM = Differential-Mode Gain

VIP = Common-Mode Input (and HV supply)

VDM = Differential-Mode Input (VIP –VIM)

VDD

U1 (DUT)

MCP6C04

VOUT

VSS

VIP

VIM

VREF

VFG

VOUT

VREF

RM3

GM2

VDD

VSS

GM1

VIP

VIM

VIP VDM

–

AOL

GM2RM3

GDM

1RF RG

⁄

VFG VREF

–

VDM

VOUT

VREF GDMVDM

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