TLV9001UIDBVR datasheet(27/70 Pages) TI1

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0.2

0.4

0.6

0.8

LOAD (A)

C219

Gain

OUT MAX

OUT MIN

IN MAX

IN MIN

Gain

SHUNT MAX

SHUNT

LOAD MAX

100mV

100m

OUT

LOAD

SHUNT

Gain

TLV9001, TLV9001S, TLV9002, TLV9002S, TLV9004, TLV9004S

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SBOS833G – OCTOBER 2017 – REVISED SEPTEMBER 2018

Product Folder Links: TLV9001 TLV9001S TLV9002 TLV9002S TLV9004 TLV9004S

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Typical Application (continued)

9.2.1.1 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

9.2.1.2 Detailed Design Procedure

The transfer function of the circuit in Figure 37 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

shown 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 TLV900x to produce an output voltage of approximately 0 V to 4.9 V. The gain needed by the

TLV900x 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 TLV900x 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 38 shows the

measured transfer function of the circuit shown in Figure 37. 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.

9.2.1.3 Application Curve

Figure 38. Low-Side, Current-Sense Transfer Function

TLV9001UIDBVR Datasheet(PDF) 27 Page - Texas Instruments

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