TLV914X datasheet(28/48 Pages) TI1

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

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

using Equation 2:

RSHUNT = VSHUNT_MAX

ILOAD_MAX = 100mV1A = 100mΩ

(2)

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

amplified by the TLV9141 to produce an output voltage of 0V to 4.9V. The gain needed by the TLV9141 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 49V/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 TLV9141 to 49V/V.

Gain = 1 + RFRG

(4)

Choosing RF as 5.76kΩ, RG is calculated to be 120Ω. RF and RG were chosen as 5.76kΩ and 120Ω because

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

used. However, excessively large resistors can generate thermal noise that exceeds the intrinsic noise of the op

amp. Figure 7-2 shows the measured transfer function of the circuit shown in Figure 7-1.

7.2.1.3 Application Curve

ILOAD (A)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Figure 7-2. Low-Side, Current-Sense, Transfer Function

7.3 Power Supply Recommendations

The TLV914x is specified for operation from 2.7V to 18V (±1.35V to ±9V); many specifications apply from –40°C

to 125°C or with specific supply voltages and test conditions.

CAUTION

Supply voltages larger than 20V can permanently damage the device; see Absolute Maximum

Ratings.

Place 0.1µF bypass capacitors close to the power-supply pins to reduce errors coupling in from noisy or

high-impedance power supplies. For more detailed information on bypass capacitor placement, refer to Layout.

TLV9141, TLV9142, TLV9144

SBOSAM4 – DECEMBER 2024

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