LMP8481 datasheet(14/29 Pages) TI

14 / 29 page

LMP8480, LMP8481

SNVS829C – MARCH 1999 – REVISED SEPTEMBER 2015

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Feature Description (continued)

A typical surface mount sense resistor tempco is in the 50 ppm to 500 ppm/°C range offering more measurement

consistency and accuracy over the copper trace. Special low-tempco resistors are available in the 0.1 to 50 ppm

range, but at a higher cost.

8.3.4 VREFA and VREFB Pins (LMP8481 Only)

The voltage applied to the VREFA and VREFB pins controls the output zero reference level. Depending on how the

pins are configured, the output reference level can be set to GND, or VCC/2, or external VREF/2, or the average of

two different input references.

The reference inputs consist of a pair of divider resistors with equal values to a common summing point, VREF' as

shown in Figure 23. Assuming VSENSE is zero, the output will be at the same value as VREF'.

Figure 23. VREF Input Resistor Network

VREF' is the voltage at the resistor tap-point that will be directly applied to the output as an offset. With the two

VREF inputs tied together, the output zero voltage will have a 1:1 ratio relationship with VREF.

VOUT = ( (VRSP – VRSN) ×Av ) + VREF’

(4)

Where:

VREF’ = VREFA = VREFB (Equal Inputs)

(5)

or:

VREF’ = ( VREFA + VREFB ) / 2 (Different Inputs)

(6)

8.3.4.1 One-to-One (1:1) Reference Input

To directly set the reference level, the two inputs are connected to the external reference voltage. The applied

VREF will be reflected 1:1 on the output.

Figure 24. Applying 1:1 Direct Reference Voltage

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LMP8481 Datasheet(PDF) 14 Page - Texas Instruments