Issue 1- July 2005
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Zetex Semiconductors plc 2005
ZXCT1011
High-side low drift current monitor
Description
The ZXCT1011 is a high side current sense monitor. Using this type of device eliminates the need
to disrupt the ground plane when sensing a load current.
The ZXCT1011 takes the voltage developed across a current shunt resistor and translates it into a
proportional output current.
A user defined output resistor scales the output current into a ground referenced voltage.
A current reference resistor, external to the IC, results in an improved temperature coefficient
compared to the ZXCT1009.
The wide input voltage range of 20V down to as low as 2.5V make it suitable for a range of
applications. With a minimum operating current of just 4uA, combined with its SOT23-5 package
make it suitable for portable battery equipment too.
Features
Accurate high-side current sensing
2.5V to 20V supply range
4 A quiescent current
1% typical accuracy
Package SOT23-5
Temperature range -40 to 125C
Applications
Automotive current measurement
Battery management
DC motor and solenoid control
Over current monitor
Power management
Typical application circuit
Pin connections
Ordering information
Vin
Load
V
R
sense
ZXCT1011
V
sense+
I
out
GND
V
sense-
R
shunt
120
5
4
2
3
Rout
N/C
I
out
R
shunt
V
sense+
V
sense-
Order code
Pack
Part
mark
Reel Size
inches (mm)
Tape width
Quantity Per
reel
ZXCT1011E5TA
SOT23-5
1011
7 (180)
8mm
3,000
ZXCT1011
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Absolute maximum ratings
V
sense+
20 V
Voltage on any pin
0.6V and V
sense+
+0.5V
V
sense+
to V
sense-
2.5V
Operating temperature
-40 to 125C
Storage temperature
-55 to 150C
Maximum junction temperature
150C
Package power dissipation
300mW at T
A
= 25C (De-rate to zero at 150C)
Operation above the absolute maximum rating may cause device failure. Operation at the
absolute maximum ratings, for extended periods, may reduce device reliability.
Electrical characteristics
Test conditions T
A
= 25C, V
in
= 5V, R
shunt
= 120 . V
sense
=100mV. Unless otherwise stated.
Symbol Parameter
Conditions
Min
Typ.
Max
Units
V
in
*
NOTES:
* V
sense+
relative to I
out
.
Supply range
-
2.5
-
20
V
I
out
Output current
V
sense
= 0V
=10mV
=30mV
=100mV
=200mV
=500mV
1
84
273
0.97
1.95
4.85
4
116
320
1.00
2.00
5.00
15
124
330
1.03
2.05
5.15
A
A
A
mA
mA
mA
V
sense
Sense voltage
V
sense
= (V
sense+
) - (V
sense-
).
-
0
-
500
mV
I
sense -
V
sense-
input current
-
-
-
100
nA
Acc
Accuracy
R
sense
= 0.1
V
sense
= 100mV
-3
-
3
%
g
m
Transconductance
I
out
/V
sense
R
shunt
= 120
-
10
-
mA/V
Tc
Temperature coefficient
Temperature dependent measurements are extracted from characterization and simulation results.
-
-
30
150
ppm/
C
BW
**
** Where CL is the capacitance across R
out
.
Bandwidth
V
sense
= 10mV
CL = 5pF, R
out
= 1k
V
sense
= 100mV
CL = 5pF, R
out
= 1k
-
400
1.5
-
kHz
MHz
PSSR
Supply rejection
V
sense
= 200mV, R
out
=1k
-
68
-
dB
ZXCT1011
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Zetex Semiconductors plc 2005
Typical characteristics
T
A
=25C, R
shunt
= 120 unless otherwise stated.
ZXCT1011
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Zetex Semiconductors plc 2005
Typical characteristics
T
A
=25C, R
shunt
= 120 unless otherwise stated.
ZXCT1011
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Pin description
Application information
Design example
The following lines describe how to scale a load current to an output voltage.
V
sense
= (V
sense+
) - (V
sense-
) = I
load
x R
sense
Defining then
I
out
= Iq + V
sense
x g
m
since g
m
= 1.2 / R
shunt
I
out
= Iq + [ (V
sense
x 1.2) / R
shunt
]
= Iq + [ (1.2 x I
load
x R
sense
/ R
shunt
) ]
Note: Iq is embedded into the specification of the ZXCT1011 and therefore appears an offset error.
V
out
= (R
out
x I
offset
) + [(1.2 x R
out
x I
load
x R
sense
) / R
shunt
]
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 R
shunt
is considered. A 1% change in R
shunt
will cause a
1% change in output.
Consider the following: -
Pin no.
Pin name
Pin function
1
N/C
No connection
2
I
out
Output current - follows transconductance of sense voltage g
m
= 10mA/V
for R
shunt
=120
3
R
shunt
Trimming resistor Input. - used to trim gain value 60
R
shunt
240
4
V
sense-
Low side current sense input. connect to load/battery etc. Must be
lower than V
sense+
for correct operation. Cannot be grounded
without additional series resistor.
5
V
sense+
High side current sense input. Connect to supply rail. Must be
higher than V
sense+
for correct operation.
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