MICRO

CONTROLLER

+IN

-IN

REFS

REFF

FB

OUT

+5V

1

2

3

4

5

6

7

VHSER/VLPAR

V

-

VLSER/VHPAR

SCK/G2

SDI/G1

SDO/G0

8

9

10

11

12

13

14

V

+

LMP8358

CSB/SHDN

+3.3V

EMI

ADC161S626

CSB

SCLK

DOUT

+5V

0.1 PF

+5V

MICRO

CONTROLLER

+3.3V

+

-

R

C

+

0.1 PF

10 PF

10k

10k

100pF

+5V

8k

2k

0.1 PF

+

0.1 PF

10 PF

+

0.1 PF

10 PF

LMP7701

LMP8358

SNOSB09B – APRIL 2010 – REVISED MARCH 2013

www.ti.com

negative input of the ADC and the REFF and REFS pins of the LMP8358 can be set to +2.5V to set the signal at

the center of the supply. A resistor divider supplies +2.5V to the positive input of an LMP7701 set up in a buffer

should all be set to the same voltage as the microcontroller, +3.3V in this example. The VLSER/VHPAR pin

should be connected to ground. The resistor and capacitor between the LMP8358 and the ADC161S626 serve a

dual purpose. The capacitor is a charge reservoir for the sampling capacitor of the ADC. The resistor provides

isolation for the LMP8358 from the capacitive load. The values listed in the ADC161S626 datasheet are 180

Ω for

the resistor and the 470pF for the capacitor. These two components also form a low pass filter of about 1.9MHz.

If a filter is needed to attenuate disturbance from the internal auto

−zeroing at 12kHz and the ping−pong

frequency at 50kHz of the LMP8358 these values could be changed to 7870

Ω and 0.01µF which will make a filter

with a corner of about 2kHz.

Figure 61. Differential Bridge Sensor

32

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