Issue 9 - July 2007 1 www.zetex.com
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ZXCT1021
Low offset high-side current monitor
Description
Ordering information
The ZXCT1021 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 ZXCT1021 provides a fixed gain of 10 for
applications where minimal sense voltage is
required.
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
• Output voltage scaling
• 2.5V – 20V supply range
•25A quiescent current
• 1% typical accuracy
• SOT23-5 package
Applications
• Battery chargers
• Smart battery packs
• DC motor control
• Over current monitor
• Power management
• Level translating
• Programmable current source
Pinout information Typical application circuit
Order reference Package Device
marking
Status Reel size
(inches)
Quantity
per reel
Tape width
(mm)
ZXCT1021E5TA SOT23-5 1021 Released 7 3000 8
NC
GND
V
OUT
V
SENSE
-
V
SENSE
+
Pinout - top view
ZXCT1021
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© Zetex Semiconductors plc 2007
Absolute maximum ratings
Pinout information
Voltage on any pin
with respect to END pin
-0.6V to 20V
VSENSE -0.6V to VIN +0.5V
Operating temperature -40 to 85°C
Storage temperature -55 to 150°C
Package power dissipation (Tamb = 25°C)
SOT23-5 300mW
Pin name Pin function
N/C Not internally connected
GND Ground
VOUT Voltage output referenced to GND. Intended to drive high impedance loads
VSENSE-High impedance negative sense voltage input
VSENSE+ Supply and positive sense voltage input
ZXCT1021
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© Zetex Semiconductors plc 2007
Electrical characteristics test conditions Tamb = 25°C, VIN = 15V
Symbol Parameter Conditions Limits Unit
Min. Typ. Max.
VIN VCC range 2.5 20 V
VOUT Output voltage VSENSE = 30mV 291 300 309 mV
VSENSE = 100mV 0.98 1.00 1.02 V
VSENSE = 150mV 1.47 1.50 1.53 V
ROUT Output resistance 10 15 20 k⍀
TC (*)
NOTES:
(*) TC limits are determined by characterization
Output voltage
temperature coefficient
50 300 ppm
IQGround pin current VSENSE = 0V 25 35 A
VSENSE (†)
(†) VSENSE = VIN - VLOAD
Sense voltage VIN = 20V 0 1.5 (‡)
(‡) This will be reduced at lower VIN voltages due to clipping of output voltage.
V
ILOAD VSENSE- load pin
input current
VSENSE = 0V 100 nA
Acc Accuracy VSENSE = 100mV -2 2 %
Gain VOUT / VSENSE VSENSE = 100mV 9.8 10 10.2 V/V
BW Bandwidth VSENSE = 10mV 300 kHz
VSENSE = 100mV 2 MHz
ZXCT1021
Issue 9 - July 2007 6 www.zetex.com
© Zetex Semiconductors plc 2007
Application information
The ZXCT1021 has a fixed dc voltage gain of 100. No external scaling resistors are required for
the output. Output voltage is simply defined as:
VOUT = 10 x VSENSE (V)
Where VSENSE = VIN - VLOAD
PCB trace shunt resistor for low cost solution
Figure 1 shows a PCB layout suggestion for a low cost solution where a PCB resistive trace in
replacement for a conventional shunt resistor, can be used. The resistor section is 25mm x
0.25mm giving approximately 150m⍀ using 1 oz copper. Smaller resistances can be used if
required.
Total circuit solution: 1 component. Shows area of 150m⍀
sense resistor compared to SOT23 package.
Practical tolerance of the PCB resistor will be around 5%
depending on manufacturing methods.
VIN
VOUT
GND
Figure 1 PCB layout suggestion
Load
ZXCT1021/2
ZXCT1021
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© Zetex Semiconductors plc 2007
Package outline - SOT23-5
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
DIM Millimeters Inches
Min. Max. Min. Max.
A 0.90 1.45 0.0354 0.0570
A1 0.00 0.15 0.00 0.0059
A2 0.90 1.30 0.0354 0.0511
b 0.20 0.50 0.0078 0.0196
C 0.09 0.26 0.0035 0.0102
D 2.70 3.10 0.1062 0.1220
E 2.20 3.20 0.0866 0.1181
E1 1.30 1.80 0.0511 0.0708
e 0.95 REF 0.0374 REF
e1 1.90 REF 0.0748 REF
L 0.10 0.60 0.0039 0.0236
a° 0° 30° 0° 30°
ZXCT1021
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© Zetex Semiconductors plc 2007
Zetex sales offices
Europe
Zetex GmbH
Kustermann-park
Balanstraße 59
D-81541 München
Germany
Telefon: (49) 89 45 49 49 0
Fax: (49) 89 45 49 49 49
europe.sales@zetex.com
Americas
Zetex Inc
700 Veterans Memorial Highway
Hauppauge, NY 11788
USA
Telephone: (1) 631 360 2222
Fax: (1) 631 360 8222
usa.sales@zetex.com
Asia Pacific
Zetex (Asia Ltd)
3701-04 Metroplaza Tower 1
Hing Fong Road, Kwai Fong
Hong Kong
Telephone: (852) 26100 611
Fax: (852) 24250 494
asia.sales@zetex.com
Corporate Headquarters
Zetex Semiconductors plc
Zetex Technology Park, Chadderton
Oldham, OL9 9LL
United Kingdom
Telephone: (44) 161 622 4444
Fax: (44) 161 622 4446
hq@zetex.com
© 2007 Published by Zetex Semiconductors plc
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Applications disclaimer
The circuits in this design/application note are offered as design ideas. It is the responsibility of the user to ensure that the circuit is fit for
the user’s application and meets with the user’s requirements. No representation or warranty is given and no liability whatsoever is
assumed by Zetex with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights
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opportunity or consequential loss in the use of these circuit applications, under any circumstances.
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1. are intended to implant into the body
or
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the
labelling can be reasonably expected to result in significant injury to the user.
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Semiconductor devices are susceptible to damage by ESD. Suitable precautions should be taken when handling and transporting devices.
The possible damage to devices depends on the circumstances of the handling and transporting, and the nature of the device. The extent
of damage can vary from immediate functional or parametric malfunction to degradation of function or performance in use over time.
Devices suspected of being affected should be replaced.
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Zetex Semiconductors is committed to environmental excellence in all aspects of its operations which includes meeting or exceeding
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Product status key:
“Preview” Future device intended for production at some point. Samples may be available
“Active” Product status recommended for new designs
“Last time buy (LTB)” Device will be discontinued and last time buy period and delivery is in effect
“Not recommended for new designs”
Device is still in production to support existing designs and production
“Obsolete” Production has been discontinued
Datasheet status key:
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may change in any manner without notice.
“Provisional version” This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance.
However, changes to the test conditions and specifications may occur, at any time and without notice.
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specifications may occur, at any time and without notice.
