0

1

2

3

4

5

0

0.2

0.4

0.6

0.8

1

I

C219

F

G

R

Gain

1

R

_

_

_

_

OUT MAX

OUT MIN

IN MAX

IN MIN

V

V

Gain

V

V

_

_

SHUNT MAX

SHUNT

LOAD MAX

V

100mV

R

100m

I

1A

:

OUT

LOAD

SHUNT

V

I

R

Gain

u

u

17

LMV321A, LMV358A, LMV324A

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SBOS923B – DECEMBER 2017 – REVISED JUNE 2018

Product Folder Links: LMV321A LMV358A LMV324A

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Typical Application (continued)

8.2.1.1 Design Requirements

The design requirements for this design are:

•

Load current: 0 A to 1 A

•

Output voltage: 4.9 V

•

Maximum shunt voltage: 100 mV

8.2.1.2 Detailed Design Procedure

The transfer function of the circuit in is given in Equation 1:

(1)

0 A to 1 A. To keep the shunt voltage below 100 mV at maximum load current, the largest shunt resistor is

shown using Equation 2:

(2)

amplified by the LMV3xxA to produce an output voltage of approximately 0 V to 4.9 V. The gain needed by the

LMV3xxA to produce the necessary output voltage is calculated using Equation 3:

(3)

Using Equation 3, the required gain is calculated to be 49 V/V, which is set with resistors RF and RG. Equation 4

sizes the resistors RF and RG, to set the gain of the LMV3xxA to 49 V/V.

(4)

Selecting RF as 57.6 kΩ and RG as 1.2 kΩ provides a combination that equals 49 V/V. Figure 33 shows the

measured transfer function of the circuit shown in Figure 32.

8.2.1.3 Application Curve

Figure 33. Low-Side, Current-Sense Transfer Function