MCP6V5XTESLASHMS datasheet(27/50 Pages) MICROCHIP

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DS20006136B-page 27

MCP6V51/2/4

4.3.11.3

Miscellaneous Effects

Keep the resistances seen by the input pins as small,

and as near to equal as possible, to minimize bias

current related offsets.

Make the (trace) capacitances seen by the input pins

small and equal. This is helpful in minimizing switching

glitch induced offset voltages.

Bending a coax cable with a radius that is too small

causes a small voltage drop to appear on the center

conductor (the triboelectric effect). Make sure the

bending radius is large enough to keep the conductors

and insulation in full contact.

Mechanical stresses can make some capacitor types

(such as some ceramics) to output small voltages. Use

more appropriate capacitor types in the signal path and

minimize mechanical stresses and vibration.

Humidity can cause electrochemical potential voltages

to appear in a circuit. Proper PCB cleaning helps, as

does the use of encapsulants.

4.4

Typical Applications

4.4.1

LOW-SIDE CURRENT SENSE

The Common-Mode input range of the MCP6V51/2/4

typically extends to 0.3V below ground (VSS), which

makes this amplifier a good choice for low-side current

sense application, especially where operation on

higher supply voltages is required. One such example

is shown in Figure 4-11. Here, the Load Current (IL)

ranges from 0A to 1.5A, which results in a voltage drop

across the shunt resistor of 0 to 75 mV. The gain on the

MCP6V51/2/4 is set to 201 V/V, which gives an output

voltage range of about 0V to +15V.

FIGURE 4-11:

Low-Side Current Sense for

1.5A Maximum Load Current.

This circuit example can be adapted to a wide range of

similar applications:

• For VDD voltages from 4.5V up to 45V

• Adjusting the shunt resistor and/or gain for higher

or lower load currents.

Because the MCP6V51/2/4 has a very low offset drift

and virtually no 1/f noise, very small shunt resistor

values can be selected, which helps in mediating the

heating and size problems that may arise in such

applications.

4.4.2

WHEATSTONE BRIDGE

Many sensors are configured as Wheatstone bridges.

Strain gauges and pressure sensors are two common

examples. These signals can be small and the

Common-Mode noise large. Amplifier designs with

high differential gain are desirable.

Figure 4-12 shows how to interface to a Wheatstone

bridge with a minimum of components. Because the

circuit is not symmetric, the ADC input is single-ended

and there is a minimum of filtering; the CMRR is good

enough for moderate Common-Mode noise.

FIGURE 4-12:

Simple Design.

8.2 nF

VOUT

40 VDD

RSHUNT

0.05Ω

20 kΩ

100Ω

MCP6V51

–

40 VDD

Load

VDD

R R

100R

0.01C

ADC

+5V

0.2R

1 kΩ

MCP6V51

–

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