TLV9041UIDBVR datasheet(28/67 Pages) TI

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9.2.1.1 Design Requirements

The design requirements for this design are:

• Load current: 0 A to 1 A

• Maximum output voltage: 4.9 V

• Maximum shunt voltage: 100 mV

9.2.1.2 Detailed Design Procedure

The transfer function of the circuit in Figure 9-1 is given in Equation 1.

OUT

LOAD

SHUNT

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

shown using Equation 2.

SHUNT

MAX

SHUNT

LOAD

MAX

100mV

100m

(2)

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

amplified by the TLV904x to produce an output voltage of approximately 0 V to 4.9 V. The gain needed by the

TLV904x to produce the necessary output voltage is calculated using Equation 3.

OUT

MAX

OUT

MIN

MAX

MIN

Gain

(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 TLV904x to 49 V/V.

Gain

(4)

Selecting RF as 57.6 kΩ and RG as 1.2 kΩ provides a combination that equals 49 V/V. Figure 9-2 shows the

measured transfer function of the circuit shown in Figure 9-1. Notice that the gain is only a function of the

feedback and gain resistors. This gain is adjusted by varying the ratio of the resistors and the actual resistors

values are determined by the impedance levels that the designer wants to establish. The impedance level

determines the current drain, the effect that stray capacitance has, and a few other behaviors. There is no

optimal impedance selection that works for every system; you must choose an impedance that is ideal for your

system parameters.

TLV9041, TLV9042, TLV9044

SBOS836E – MARCH 2020 – REVISED AUGUST 2021

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