Diodes ZXCT1012 - Manual (Page 6)

ZXCT1012
REDUCED HEIGHT MICRO-POWER CURRENT MONITOR
ZXCT1012
Document number: DS33444 Rev. 2 - 2
6 of 9
www.diodes.com
September 2011
© Diodes Incorporated
Applications Information (cont.)
The following lines describe how to scale a load current to an output voltage.
V
SENSE
= R
SENSE
* I
LOAD
equation (1)
I
OUT
= 10mA/V x V
SENSE
equation (2)
V
OUT
= I
OUT
x R
OUT
equation (3)
Design example
In the circuit below a 1A current is to be represented by a 100mV output voltage (V
OUT
):
A) To be within recommended values choose the value of R
SENSE
to give:
50mV > V
SENSE
> 200mV at full load.
For example set V
SENSE
= 100mV at 1.0A.
From equation (1)
R
SENSE
= 0.1V/1.0A = 0.1 Ω
B) Now choose R
OUT
to give:
V
OUT
= 100mV, when V
SENSE
= 100mV.
From equation (2)
I
OUT
= 10mA/V x 0.1 = 1mA
Rearranging equation (3) for R
OUT
gives:
R
OUT
= V
OUT
/I
OUT
= 0.1/0.001 = 100 Ω
ZXCT1012
R
SENSE V
IN
V
OUT
R
OUT
R
LOAD
SENSE+ SENSE-
OUT GND
= 0.1 / (0.1 x 0.01) = 100 Ω
Typical Circuit Application
Where R
LOAD
represents any load including DC motors, a charging battery or further circuitry that requires monitoring, R
SENSE
can be selected on specific requirements of accuracy, size and power rating.