Diodes ZXCT1081 - Manual (Page 8)

ZXCT1081
ZXCT1081
Document number: DS32102 Rev. 1 - 2
8 of 11
www.diodes.com
March 2010
© Diodes Incorporated
A Product Line of
Diodes Incorporated
Application Information
The ZXCT1081 has been designed to allow it to operate with 5V supply rails while sensing common mode signals up to
40V. This makes it well suited to a wide range of industrial and power supply monitoring applications that require the
interface to 5V systems while sensing much higher voltages.
To allow this its VCC pin can be used independently of SENSE+.
Figure 1 shows the basic configuration of the ZXCT1081.
ZXCT1081
OUT
GND
V
CC
R
SH
R
G
M1
R
SENSE
Input Load
SENSE+ SENSE-
+1 A2
A1
Figure 1 Typical Configuration of ZXCT1081
Load current from the input is drawn through R
SENSE
developing a voltage V
SENSE
across the inputs of the ZXCT1081.
The internal amplifier forces V
SENSE
across internal resistance R
SH
causing a current to flow through MOSFET M1. This
current is then converted to a voltage by R
G
. A ratio of 10:1 between R
G
and R
SH
creates the fixed gain of 10. The output is
then buffered by the unity gain buffer.
The gain equation of the ZXCT1081 is:
V
OUT
= I
L
R
SENSE
x 1 = x R
SENSE
x 10
The maximum recommended differential input voltage, V
SENSE
, is 150mV; it will however withstand voltages up to 800m Ω.
This can be increased further by the inclusion of a resistor, R
LIM
, between SENSE- pin and the load; typical value is of the
order of 10k .
R
G
R
SH