LMP8480MMX-SSLASHNOPB datasheet(12/24 Pages) TI

12 / 24 page

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

VSENSE (V)

VCC> 14V

VCC = +4.5V to +76V

0.1 PF

VOUT

To Load

+4.0V

+76V

RSENSE

ISENSE

ADC

RSN

RSP

GND

LMP8480

VIN+

VIN- VREF

VSENSE

VCC

LMP8480, LMP8481

SNVS829A – JUNE 2012 – REVISED AUGUST 2012

www.ti.com

UNI-DIRECTIONAL VS. BI-DIRECTIONAL OPERATION

Uni-directional operation is where the load current only flows in one direction (VSENSE is always positive).

Application examples would be PA monitoring, non-inductive load monitoring and laser or LED drivers. This

allows the output zero reference to be true zero volts on the output. The LMP8480 is designed for unidirectional

applications where the setting of VREF is not required. See the UNI-DIRECTIONAL OPERATION for more

details.

Bi-directional operation is where the load current can flow in both directions (VSENSE can be positive or

negative). Application examples would be battery charging or regenerative motor monitoring. The LMP8481 is

designed for bidirectional applications and has a pair of VREF pins to allow the setting of the output zero

reference level (VREF). See the BI-DIRECTIONAL OPERATION (LMP8481 ONLY) section for more details.

UNI-DIRECTIONAL OPERATION

The LMP8480 is designed for unidirectional current sense applications. The output of the amplifier will be equal

to the differential input voltage times the fixed device gain.

Figure 8. Uni-Directional Application with LMP8480

Figure 9. Uni-Directional Transfer Function for Gain-of-20 option

The output voltage can be calculated from:

VOUT = ( (VRSP – VRSN) * Av )

(1)

It should be noted that the minimum “zero” reading will be limited by the lower output swing and input offset.

The LMP8480 is functionally identical to the LMP8481, but with the VREFA and VREFB nodes grounded internally.

The LMP8481 can replace the LMP8480 if both the VREF inputs (pins 6 & 7) are grounded.

BI-DIRECTIONAL OPERATION (LMP8481 ONLY)

Bi-directional operation is required where the measured load current can be positive or negative. Because VSENSE

can be positive or negative, and the output cannot swing negative, the “zero” output level must be level-shifted

above ground to a known zero reference point. The LMP8481 allows for the setting this reference point.

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LMP8480MMX-S/NOPB Datasheet(PDF) 12 Page - Texas Instruments

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