C1

POWER

SWITCH

INDUCTIVE

LOAD

24V

+IN

-IN

+

-

Preamplifier

Output Buffer

Gain = K2

A1

A2

Gain = 10

OFFSET

Internal

Resistor

100 k:

OUT

Level

shift

1

5

3

4

7

8

LMP8601/

LMP8601Q

ADC

LMP8601, LMP8601-Q1

SNOSAR2E – SEPTEMBER 2008 – REVISED MARCH 2013

www.ti.com

Figure 40. Reduce Error When Driving ADCs

The external capacitor absorbs the charge that flows when the ADC sampling capacitor is connected. The

external capacitor should be much larger than the sample and hold capacitor at the input of the ADC and the RC

time constant of the external filter should be such that the speed of the system is not affected.

LOW SIDE CURRENT SENSING APPLICATION

Figure 41 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

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 LMP8601/LMP8601Q and because of the high AC common mode rejection ratio, the

LMP8601/LMP8601Q is very well suited for this application.

Figure 41. Low Side Current Sensing Application

18

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