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 µA quiescent current
■
1% typical accuracy
■
Package SOT23-5
■
Temperature range -40 to 125°C
Applications
■
Automotive current measurement
■
Battery management
■
DC motor and solenoid control
■
Over current monitor
■
Power management
Typical application circuit
Vin
R
sense
Load
Pin connections
N/C
R
shunt
120
Ω
3
5
V
sense+
V
sense+
4
V
sense-
I
out
R
shunt
V
ZXCT1011
I
out
2
Rout
V
sense-
GND
Ordering information
Order code
ZXCT1011E5TA
Pack
SOT23-5
Part
mark
1011
Reel Size
inches (mm)
7 (180)
Tape width
8mm
Quantity Per
reel
3,000
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ZXCT1011
Absolute maximum ratings
V
sense+
Voltage on any pin
V
sense+
to V
sense-
Operating temperature
Storage temperature
Maximum junction temperature
Package power dissipation
20 V
0.6V and V
sense+
+0.5V
2.5V
-40 to 125°C
-55 to 150°C
150°C
300mW at T
A
= 25°C (De-rate to zero at 150°C)
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
= 25°C, V
in
= 5V, R
shunt
= 120 . V
sense
=100mV. Unless otherwise stated.
Symbol Parameter
V
in*
I
out
Supply range
Output current
Conditions
-
V
sense
= 0V
=10mV
=30mV
=100mV
=200mV
=500mV
Min
2.5
1
84
273
0.97
1.95
4.85
0
-
-3
-
-
-
Typ.
-
4
116
320
1.00
2.00
5.00
-
-
-
10
30
400
1.5
Max
20
15
124
330
1.03
2.05
5.15
500
100
3
-
150
-
Units
V
µA
µA
µA
mA
mA
mA
mV
nA
%
mA/V
ppm/° C
kHz
MHz
V
sense
I
sense -
Acc
g
m
Tc
BW
**
Sense voltage
†
V
sense-
input current
Accuracy
Transconductance
I
out
/V
sense
-
-
R
sense
= 0.1
V
sense
= 100mV
R
shunt
= 120
Temperature coefficient
‡
-
Bandwidth
V
sense
= 10mV
CL = 5pF, R
out
= 1k
V
sense
= 100mV
CL = 5pF, R
out
= 1k
V
sense
= 200mV, R
out
=1k
PSSR
Supply rejection
-
68
-
dB
NOTES:
* V
sense+
relative to I
out
.
† V
sense
= (V
sense+
) - (V
sense-
).
‡ Temperature dependent measurements are extracted from characterization and simulation results.
** Where CL is the capacitance across R
out
.
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ZXCT1011
Typical characteristics
T
A
=25°C, R
shunt
= 120
unless otherwise stated.
Issue 1- July 2005
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ZXCT1011
Typical characteristics
T
A
=25°C, R
shunt
= 120
unless otherwise stated.
Issue 1- July 2005
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ZXCT1011
Pin description
Pin no.
1
2
Pin name
N/C
I
out
R
shunt
V
sense-
Pin function
No connection
Output current - follows transconductance of sense voltage g
m
= 10mA/V
for R
shunt
=120
Trimming resistor Input. - used to trim gain value 60
R
shunt
240
3
4
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.
High side current sense input. – Connect to supply rail. Must be
higher than V
sense+
for correct operation.
5
V
sense+
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
since
I
out
= Iq + V
sense
x g
m
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.
∴
out
= (R
out
x I
offset
) + [(1.2 x R
out
x I
load
x R
sense
) / R
shunt
]
V
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: -
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