OPAX196 datasheet(28/52 Pages) TI2

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ILOAD (A)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

ILOAD (A)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0.02

0.04

0.06

0.08

0.1

Gain

OUT MAX

OUT MIN

IN MAX

IN MIN

Gain

SHUNT MAX

SHUNT

LOAD MAX

100mV

100m

OUT

LOAD

SHUNT

Gain

OPA196, OPA2196, OPA4196

SBOS869 – JULY 2017

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Product Folder Links: OPA196 OPA2196 OPA4196

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Typical Applications (continued)

8.2.1.2 Detailed Design Procedure

The transfer function of the circuit in Figure 46 is given in Equation 1:

(1)

The load current (ILOAD) produces a voltage drop across the shunt resistor (RSHUNT). The load current is set from

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

defined using Equation 2.

(2)

Using Equation 2, RSHUNT is calculated to be 100 mΩ. The voltage drop produced by ILOAD and RSHUNT is

amplified by the OPA196 to produce an output voltage of 0 V to 4.9 V. The gain needed by the OPA196 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

is used to size the resistors, RF and RG, to set the gain of the OPA196 to 49 V/V.

(4)

Choosing RF as 360 kΩ, RG is calculated to be 7.5 kΩ. RF and RG were chosen as 360 kΩ and 7.5 kΩ because

they are standard value resistors that create a 49:1 ratio. Other resistors that create a 49:1 ratio can also be

used. Figure 2 shows the measured transfer function of the circuit shown in Figure 46.

8.2.1.3 Application Curves

Figure 47. Low-Side, Current-Sense, Transfer Function

Figure 48. Low-Side, Current-Sense, Full-Scale Error

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