LMP8602MASLASHNOPB datasheet(28/42 Pages) TI1

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RSENSE

POWER

SWITCH

INDUCTIVE

LOAD

24V

+IN

-IN

Preamplifier

Output Buffer

Gain = K2

Gain = 10

OFFSET

Internal

Resistor

100 k:

OUT

Level

shift

LMP8601, LMP8601-Q1

LMP8602, LMP8602-Q1

LMP8603, LMP8603-Q1

SNOSAR2H – SEPTEMBER 2008 – REVISED APRIL 2016

www.ti.com

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

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Typical Applications (continued)

8.2.2 Low-Side, Current-Sensing Application

Figure 62 illustrates a low-side, current-sensing application with a low-side driver. The power transistor is pulse

width modulated to control the average current flowing through the inductive load which is connected to a

relatively high battery voltage. The current through the load is measured across a shunt resistor RSENSE in series

with the load. When the power transistor is on, current flows from the battery through the inductive load, the

shunt resistor and the power transistor to ground. In this case, the common-mode voltage on the shunt is close

to ground. When the power transistor is off, current flows through the inductive load, through the shunt resistor

and through the freewheeling diode. In this case the common-mode voltage on the shunt is at least one diode

voltage drop above the battery voltage. Therefore, in this application the common-mode voltage on the shunt is

varying between a large positive voltage and a relatively low voltage. Because the large common-mode voltage

range of the LMP860x and LMP860x-Q1 and because of the high ac common-mode rejection ratio, the LMP860x

and LMP860x-Q1 are very well suited for this application.

RSENSE = 0.01 Ω, K2 = 2, VOUT = 0.2 V/A

Figure 62. Low-Side Current-Sensing Application

For this application, the following example can be used for the calculation of the sense voltage (VSENSE):

When using a sense resistor, RSENSE, of 0.01 Ω and a current, ILOAD, of 1 A, the sense voltage at the input pins of

the LMP860x and LMP860x-Q1 is:

VSENSE = RSENSE × ILOAD = 0.01 Ω × 1 A = 0.01 V

(35)

With the gain of 20 for the LMP8601, the result is an output of 0.2 V. Or in other words, VOUT = 0.2 V/A. The

result is the same for the LMP8601-Q1.

For the LMP8602 and LMP8602-Q1 with a gain of 50, the output is 0.5 V/A.

For the LMP8603 and LMP8603-Q1 with a gain of 100, the output is 1 V/A.

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