ZXCT1011 View Datasheet(PDF) - Diodes Incorporated.

Part Name

Description

Manufacturer

ZXCT1011

High-side low drift current monitor

Diodes Incorporated. 

ZXCT1011

A 1 ampere load current is to be measured into a battery. The output signal required to an over

current controller needs to be 3.3V. What is a suitable value of Rout and what will the error due

to the supply current be?

Vin = 5.0V - 9.0V

Iload = 1.0A

Output signal required: 3.3V

Vin = 5.0V - 9.0V

Rshunt

120R

R sense

5

4

Vsense+ V sense-

3

R

shunt

ZXCT

1011

I out

2

3.3V

Iload = 1A

R load

Rout

Figure 1 ZXCT1011 to measure a 1.0 A load current

To obtain the highest accuracy, choose the of Rsense to give 100mV:

Rsense = 0.1/1.0 = 0.1⍀

The transconductance using a 120⍀ resistor will be 10mA/V.

Choose Rout to give Vout = 3.3V, when Vsense = 100mV

Rearranging equation 1 without the offset error gives:

Rout = (Vout x Rshunt) / (1.2 x ILoad x Rsense)

Rout = 3.3k⍀

Now consider the offset error for this resistor:

Offset due to supply current = Rout x 4x10-6µA = 13.2mV = 0.4%

Issue 1- July 2005

6

© Zetex Semiconductors plc 2005

www.zetex.com

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