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ZXCT1081E5TA

P1-P3P4-P6P7-P9P10-P11
ZXCT1081
ZXCT1081
Document number: DS32102 Rev. 1 - 2
7 of 11
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March 2010
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Typical Operating Conditions (Cont.)
ZXCT1081
ZXCT1081
Document number: DS32102 Rev. 1 - 2
8 of 11
www.diodes.com
March 2010
© Diodes Incorporated
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Product Line o
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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
-
+1A2
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 800mΩ.
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
ZXCT1081
ZXCT1081
Document number: DS32102 Rev. 1 - 2
9 of 11
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March 2010
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R
SENSE
C
D
R
LIM
ZXCT1081
SENSE
+
SENSE
-
Figure 2 Protection/Error Sources for ZXCT1081
Capacitor CD provides high frequency transient decoupling when used with R
LIM
; typical values are of the order 10pF.
For best performance R
SENS
E should be connected as close to the SENSE+ (and SENSE ) pins; minimizing any series
resistance with R
SENSE
.
When choosing appropriate values for R
SENSE
a compromise must be reached between in-line signal loss (including
potential power dissipation effects) and small signal accuracy.
Higher values for R
SENSE
gives better accuracy at low load currents by reducing the inaccuracies due to internal offsets. For
best operation the ZXCT1081 has been designed to operate with V
SENSE
of the order of 50mV to 150mV.
Current monitors' basic configuration is that of a unipolar voltage to current to voltage converter powered from a single
supply rail. The internal amplifier at the heart of the current monitor may well have a bipolar offset voltage but the output
cannot go negative; this results in current monitors saturating at very low sense voltages.
As a result of this phenomenon the ZXCT1081 has been specified to operate in a linear manner over a V
SENSE
range of
10mV to 150mV range, however it will still be monotonic down to V
SENSE
of 0V.
It is for this very reason that Zetex has specified an input offset voltage (V
O(10)
) at 10mV. The output voltage for any V
SENSE
voltage from 10mV to 150mV can be calculated as follows:
V
OUT
= (V
SENSE
) xG + V
O(10)
Alternatively the load current can be expressed as:
I
L
=
V
OUT
– V
O
(
10
)
GxR
SENSE
P1-P3P4-P6P7-P9P10-P11

ZXCT1081E5TA

Mfr. #:
Buy ZXCT1081E5TA
Manufacturer:
Diodes Incorporated
Description:
Current & Power Monitors & Regulators 7-40V Input 80uA
Lifecycle:
New from this manufacturer.
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