ZXCT1011 datasheet(5/8 Pages) ZETEX

5 / 8 page

ZXCT1011

Issue 1- July 2005

www.zetex.com

Pin description

Application information

Design example

The following lines describe how to scale a load current to an output voltage.

Vsense = (Vsense+) - (Vsense-) = Iload x Rsense

Defining then

Iout = Iq + Vsense x gm

since

gm= 1.2 / Rshunt

Iout

= Iq + [ (Vsense x 1.2) / Rshunt ]

= Iq + [ (1.2 x Iload x Rsense / Rshunt) ]

Note: Iq is embedded into the specification of the ZXCT1011 and therefore appears an offset error.

∴V

out = (Rout x Ioffset) + [(1.2 x Rout x Iload x Rsense) / Rshunt]

The output current of the ZXCT1011 is directly related to the size of the trimming resistor used. It

is important to ensure the tolerance of Rshunt is considered. A 1% change in Rshunt will cause a

1% change in output.

Consider the following: -

Pin no.

Pin name

Pin function

N/C

No connection

2Iout

Output current - follows transconductance of sense voltage gm = 10mA/V

for Rshunt=120

3Rshunt

Trimming resistor Input. - used to trim gain value 60

Rshunt

240

4Vsense-

Low side current sense input. – connect to load/battery etc. Must be

lower than Vsense+ for correct operation. Cannot be grounded

without additional series resistor.

5Vsense+

High side current sense input. – Connect to supply rail. Must be

higher than Vsense+ for correct operation.

ZXCT1011 Datasheet(PDF) 5 Page - Zetex Semiconductors