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LMP8601, LMP8601-Q1

LMP8602, LMP8602-Q1

LMP8603, LMP8603-Q1

www.ti.com

SNOSAR2H – SEPTEMBER 2008 – REVISED APRIL 2016

Product Folder Links: LMP8601 LMP8601-Q1 LMP8602 LMP8602-Q1 LMP8603 LMP8603-Q1

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Copyright © 2008–2016, Texas Instruments Incorporated

(1)

The OFFSET pin must be driven from a very low-impedance source (< 10

Ω) because the OFFSET pin internally connects directly to the

resistive feedback networks of the two gain stages. When the OFFSET pin is driven from a relatively large impedance (for example, a

resistive divider between the supply rails), accuracy decreases.

7.3 Feature Description

7.3.1 Offset Input Pin

The OFFSET pin allows the output signal to be level-shifted to enable bidirectional current sensing. The output

signal is bidirectional and mid-rail referenced when the offset pin is connected to the positive supply rail. With the

offset pin connected to ground, the output signal is unidirectional and ground-referenced.

The signal on the A1 and OUT pins is ground-referenced when the offset pin is connected to ground. This means

that the output signal can only represent positive values of the current through the shunt resistor, so only

currents flowing in one direction can be measured.

When the offset pin is tied to the positive supply rail, the signal on the A1 and OUT pins is referenced to a mid-

rail voltage which allows bidirectional current sensing. The operation of the amplifier will be fully bidirectional and

symmetrical around 0 V differential at the input pins. The signal at the output will follow this voltage difference

When the offset pin is connected to an external voltage source, the output signal will be level shifted to that

applying twice that voltage to the OFFSET pin.

NOTE

The OFFSET pin must be driven from a very low-impedance source (< 10

Ω). This low

source impedance is required because the OFFSET pin internally connects directly to the

resistive feedback networks of the two gain stages. When the OFFSET pin is driven from

a relatively large impedance (for example, a resistive divider between the supply rails),

accuracy decreases.

Examples:

•

10 mV results in 2.7 V at the output pin. Similarly, –10 mV at the input results in 2.3 V at the output pin.

•

LMP8602, LMP8602-Q1: A 5-V supply, a gain of 50x, and a differential input signal of 10 mV results in 3.0 V

at the output pin. Similarly, –10 mV at the input results in 2.0 V at the output pin.

•

LMP8603, LMP8603-Q1: A 5-V supply, a gain of 100x, and a differential input signal of 10 mV results in 3.5 V