LMP8276 datasheet(4/5 Pages) NSC

4 / 5 page

Application Note (Continued)

This represents a value that the LMP8271 and LMP8276

have not been optimized and trimmed for and may very well

be above the limits indicated in the electrical characteristics

tables.

Midrail Offset Adjustment Pin

The external midrail offset adjustment pin enables the user

to utilize this device for bidirectional current sensing. If the

offset pin, pin 7, is connected to ground then the LMP8271,

LMP8276 are capable of sensing positive signals. When the

offset pin is connected to V

S then 1/2VS is added to the

output and under this condition the amplifier can sense both

positive and negative signals. If this offset pin is connected

to any voltage between ground and V

S, then the output is

increased by a voltage equal to half of that offset, e.g. If the

offset is connected to V

X, then the output increases by

1/2V

X. The following figure shows how this works:

Note that the offset pin, pin 7, needs to be connected at all

times. If the pin is left floating, the LMP8271 and LMP8276

will be operating in an undefined mode. Also pin 7 should be

driven from a low impedance source.

20130806

FIGURE 2.

LMP8276 数据表(PDF) 4 Page - National Semiconductor (TI)