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OPA196 Datasheet, PDF (28/47 Pages) Texas Instruments – 36-V, Low-Power, Low Offset Voltage, Rail-to-Rail Operational Amplifier | |||
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OPA196, OPA2196, OPA4196
SBOS869 â JULY 2017
www.ti.com
Typical Applications (continued)
8.2.1.2 Detailed Design Procedure
The transfer function of the circuit in Figure 46 is given in Equation 1:
VOUT ILOAD uRSHUNT u Gain
(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.
RSHUNT
VSHUNT _ MAX
ILOAD _ MAX
100mV 100m:
1A
(2)
Using Equation 2, RSHUNT is calculated to be 100 mâ¦. 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:
Gain VOUT _ MAX VOUT _ MIN
VIN _ MAX VIN _ MIN
(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.
Gain 1 RF
RG
(4)
Choosing RF as 360 kâ¦, RG is calculated to be 7.5 kâ¦. RF and RG were chosen as 360 k⦠and 7.5 k⦠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
5
0.1
4
0.08
3
0.06
2
0.04
1
0.02
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
ILOAD (A)
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
ILOAD (A)
Figure 47. Low-Side, Current-Sense, Transfer Function
Figure 48. Low-Side, Current-Sense, Full-Scale Error
28
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Product Folder Links: OPA196 OPA2196 OPA4196
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