UM0971 datasheet(19/45 Pages) STMICROELECTRONICS

19 / 45 page

UM0971

Board description

Doc ID 17701 Rev 1

19/45

Equation 7

With the resistor values actually used in the circuit schematic, it is:

●

R1=5100

●

R2=920

●

R3=470

●

r= 1000

●

R= 5100

Therefore getting:

●

Vbias=1.7534

and:

●

G=1.944

This means that the maximum instantaneous current amplifiable without distortion is 8 A

(corresponding to Vout = 3.3 V). The user can modify the maximum current value by

changing the shunt resistor values.

Table 8 lists the involved jumper and their positions for AC current reading configuration:

Note:

The resistor R2 value of 920

Ω in the circuit schematic is made up of the sum of two

resistors: one of 100

Ω, belonging to the low-pass filter across the shunt resistor and the

second of 820

Ω belonging to the amplifier network.

2.6.2

Unipolar current reading configuration

The details of the single-shunt current sensing (also referred to as direct DC current)

configuration are shown in Figure 12. This configuration is used when sampling is done on

positive current on the shunt resistor. The only positive value read on the shunt resistor

allows the setting of a higher gain for the op amp than the one set in AC reading mode.

Table 8.

AC current jumper configuration

Jumper

Position

J10

Present

J11

Between 1-2

J12

Present

--------

⎝⎠

⎛⎞

⋅

-------------------------------------------------------

------------

⋅

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