ZXCT1020
ZXCT1020
Low offset current output current monitor
Description
The ZXCT1020 is a precision high-side current
sense monitor. Using this type of device
eliminates the need to disrupt the ground
plane when sensing a load current.
The ZXCT1020 uses two external resistors to
set the overall voltage gain for applications
where improved accuracy at small sense
voltages is required. For fixed gain variants
Zetex offers the ZXCT1021 (G=10) and
ZXCT1022 (G=100).
The ZXCT1020 footprint follows that of the
ZXCT1021/2 with only 2 additional resistors
required:
One resistor between pins 1 and 4 for setting
transconductance, and the other between
pins 3 and 2 for setting overall gain.
Current output enables the user to set the gain
via these external resistors. Using two external
resistors to set the gain ensures optimal
versatility as the transconductance can be varied
to meet the output impedance requirements of
the load that the ZXCT1020 has to drive.
The very low offset voltage enables a typical
accuracy of 3% for sense voltages of only 10mV,
giving better tolerances for small sense
resistors necessary at higher currents.
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 25µA, combined with its SOT23-5
package make it suitable for portable battery
equipment too.
Features
•
•
•
•
•
•
Accurate high-side current sensing
Versatile current output scaling
2.5V - 20V operating range
25µA quiescent current
1% typical accuracy
SOT23-5 package
Applications
•
•
•
•
•
Battery chargers
Over-current monitor
Motherboard power supply current measurement
Level translating
Programmable current source
Pinout information
S+
GND
OUT
1
5
Typical application circuit
S-
R
S
R
SH
V
B
S+
1
4
I
L
S-
(LOAD)
5
2
3
4
V
B
-
+
Top view
V
OUT
R
G
3
2
ZXCT1020
GND
Ordering information
Order reference
ZXCT1020E5TA
Issue 1 - August 2007
© Zetex Semiconductors plc 2007
Package
SOT23-5
Device
marking
1020
Status
Preview
1
Reel size
(inches)
7
Quantity
per reel
3000
Tape width
(mm)
8
www.zetex.com
ZXCT1020
Absolute maximum ratings
Voltage on V
B
with respect to GND pin
Voltage on S+
(a)
, S-
(b)
, OUT with respect to GND pin
V
SENSE(c)
Junction temperature
Storage temperature
Package power dissipation (T
amb
= 25°C) SOT23-5
-0.5V to 20V
-0.5V to V
B
+0.5V
-0.5V to +2.5V
(d)
-40°C to125°C
-55°C to 150°C
300mW
NOTES:
(a) Subject to V
SENSE
+ never going 6V below V
B
.
(b) Subject to absolute maximum V
SENSE
not being exceeded.
(c) V
SENSE
is defined as the voltage difference across the sense resistor. and is the voltage across resistor R
SH
plus the
voltage between S+ and S-.
(d) V
SENSE
might need to be reduced when used with smaller values of R
SH
and at larger rails due to increased power dissipation.
Pin out information
Pin
1
2
3
Name
S+
GND
OUT
Pin function
Positive sense input. Should be tied to positive side of sense resistor via
resistance (R
SH
) of the order of 150 to 1.5k .
Ground and substrate connection of device.
Current output. A gain setting resistor (R
G
) referenced to GND should be
connected to this pin to set overall voltage gain of:
Gain = R
G
/R
SH
The resistance, R
G
, placed on out will set the ZXCT1020 output impedance equal
to R
G
. When driving low impedance loads both R
G
and R
SH
should be reduced.
Input voltage pin. Provides bias to current monitor and should be tied to the
rail whose current is being monitored.
High impedance negative sense voltage input
4
5
V
B
S-
Recommended operating conditions
Parameter
V
SENSE+
Common-mode sense input range
V
B
Bias pin input voltage range
(*)
V
SENSE
V
OUT
R
SH
T
A
Differential sense Input voltage range
Output voltage range
Shunt resistor value
Ambient temperature range
Min.
2.5
2.5
0
0
120
-40
Max.
20
20
1.5
V
SENSE-
- 1
2000
85
°C
Units
V
V
V
V
NOTES:
(*) For best performance V
B
and V
SENSE+
should be referred to the rail whose current is being measured.
Recommended resistor gain setting combinations
Gain
10
20
50
100
Issue 1 - August 2007
© Zetex Semiconductors plc 2007
R
SHUNT
1.5k
750
300
150
2
R
GAIN
15k
15k
15k
15k
www.zetex.com
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