ZXCT1081
High voltage high-side current monitor
Description
The ZXCT1081 is a high side current sense
monitor with a gain of 10 and a voltage
output. Using this device eliminates the need
to disrupt the ground plane when sensing a
load current.
The wide input voltage range of 40V down to
as low as 3V make it suitable for a range of
applications; including systems operating
from industrial 24-28V rails and power
supplies.
The separate supply pin (V
to continue functioning under short circuit
conditions, giving an end stop voltage at the
output.
For automotive applications the ZXCT1081 has
a 60V transient capability and ambient
temperature range of -40°C to 125°C.
) allows the device
CC
Features
• 3V to 40V continuous high side voltage
• Accurate high-side current sensing
• Output voltage scaling x10
• 4.5V to 12V V
• Low quiescent current:
• 80µA supply pin
• 30µA I
CC
SENSE+
range
Applications
• Automotive current measurement
• Industrial applications current measurement
• Battery management
• Over current monitor
• Power management
• Power adapters
• SOT23-5 package
• -40°C to 125°C ambient temperature range
Pin connections Typical application circuit
V
CC
GND
OUT
V
1
2
3
5
SENSE-
4
SENSE+
IN
V
CC
1
4
SENSE+
V
cc
ZXCT1081
GND
2
R
SENSE
5
SENSE
OUT
3
-
V
OUT
Ordering information
Device Package Part mark Reel size
(inches)
ZXCT1081E5TA SOT23-5 1081 7 8 3000
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Tape width
(mm)
Quantity per
reel
Absolute maximum ratings
Continuous voltage on SENSE+ and SENSE- -0.6V and 45V
Transient voltage on SENSE+ and SENSE- -0.6V and 65V
Voltage on all other pins -0.6V and 14V
ZXCT1081
Differential sense voltage, V
800mV
SENSE
Operating temperature -40°C to 125°C
Storage temperature -55°C to 150°C
Maximum junction temperature 85°C
Package power dissipation 300mW at T
Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for
extended periods, may reduce device reliability.
= 25°C (de-rate to zero at 125°C)
A
Recommended operating conditions
Parameter Min. Max. Units
V
IN
V
CC
V
SENSE
V
OUT
T
J
Common-mode sense+ input range 3 40
V
Supply voltage range 4.5 12 V
Differential sense input voltage range 0 0.15 V
Output voltage range 0 1.5 V
Ambient temperature range -40 125 °C
Pin function table
Pin Name Description
1V
CC
This is the analogue supply and provides power to internal circuitry
2 GND Ground pin
3 OUT Output voltage pin. NMOS source follower with 20µA bias to ground
4 SENSE+ This is the positive input of the current monitor and has an input range from
40V (60V transient) down to 3V. The current through this pin varies with
differential sense voltage
5 SENSE- This is the negative input of the current monitor and has an input range
from 40V (60V transient) down to 3V
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Electrical characteristics
ZXCT1081
Test conditions TA = 25°C, VIN = 12V, VCC = 5 V, V
SENSE
(a)
= 100mV unless otherwise stated.
Symbol Parameter Conditions Min. Typ. Max. Units
I
CC
I
SENSE+
I
SENSE-
V
O(0)
V
O(10)
Gain
V
OUT
VCC supply current VCC = 12V 40 80 120 µA
SENSE+ input current 15 30 60 µA
SENSE- input current 10 40 80 nA
Zero V
SENSE
Output offset voltage
TC
(d)
⌬V
V
/⌬V
OUT
variation with
OUT
(a)
SENSE
error
(a)
(b)
(c)
V
SENSE
V
SENSE
V
SENSE
(a)
= 0V
(a)
= 10mV
(a)
= 10mV to 150mV
035mV
-30 +30 mV
9.95 10 10.05
30 ppm/°C
temperature
Acc Total output error -3 3 %
I
OH
I
OL
PSRR V
Output source current ⌬V
Output sink current ⌬V
supply rejection
CC
VCC = 4.5V to 12V 54 60 dB
= -30mV 1 mA
OUT
= +30mV 20 µA
OUT
ratio
CMRR Common-mode sense
= 40V to 3V 60 75 dB
V
IN
rejection ratio
BW -3dB small signal
bandwidth
V
SENSE
(a)
(AC)
= 10mV
PP
500 kHz
NOTES:
(a) V
(b) The ZXCT1081 operates from a positive power rail and the internal voltage-current converter current flow is
(c) For V
(d) Temperature dependent measurements are extracted from characterization and simulation results.
= "V
SENSE
unidirectional; these result in the output offset voltage for V
SENSE
used. V
O(10)
" - "V
SENSE+
> 10mV, the internal voltage-current converter is fully linear. This enables a true offset to be defined and
is expressed as the variance about an output voltage of 100mV>
SENSE-
"
= 0V always being positive.
SENSE
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Typical characteristics
ZXCT1081
Test conditions unless otherwise stated: TA = 25°C, VCC = 5V, V
SENSE+
=12V, V
SENSE
= 100mV
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Typical characteristics
ZXCT1081
Test conditions unless otherwise stated: TA = 25°C, VCC = 5V, V
SENSE+
=12V, V
SENSE
= 100mV
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© Zetex Semiconductors plc 2007
Typical characteristics
ZXCT1081
Test conditions unless otherwise stated: TA = 25°C, VCC = 5V, V
SENSE+
=12V, V
SENSE
= 100mV
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© Zetex Semiconductors plc 2007
Typical characteristics
ZXCT1081
Test conditions unless otherwise stated: TA = 25°C, VCC = 5V, V
SENSE+
=12V, V
SENSE
= 100mV
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© Zetex Semiconductors plc 2007
ZXCT1081
V
OUTILRSENSE
R
G
R
SH
-----------
1
× I
LRSENSE
× 10×==
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 V
pin can be used independently of SENSE+.
CC
Figure 1 shows the basic configuration of the ZXCT1081.
Input
SENSE
+
R
SENSE
SENSE
Load
-
ZXCT1081
R
SH
V
CC
A1
G
OUT
M1
+1A2
R
GND
Figure 1 Typical configuration of ZXCT1081
Load current from the input is drawn through R
inputs of the ZXCT1081.
The internal amplifier forces V
across internal resistance RSH causing a current to flow
SENSE
through MOSFET M1. This current is then converted to a voltage by R
R
and RSH creates the fixed gain of 10. The output is then buffered by the unity gain buffer.
G
The gain equation of the ZXCT1081 is:
developing a voltage V
SENSE
SENSE
. A ratio of 10:1 between
G
across the
The maximum recommended differential input voltage, V
withstand voltages up to 800m⍀. This can be increased further by the inclusion of a resistor, R
, is 150mV; it will however
SENSE
LIM
between SENSE- pin and the load; typical value is of the order of 10k .
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© Zetex Semiconductors plc 2007
,
R
V
OUT
V
SENSE
()xG V
O10()
+=
I
L
V
OUTVO10()
–()
GxR
SENSE
-------------------------------------------=
SENSE
ZXCT1081
R
LIM
C
D
SENSE
+
SENSE
-
ZXCT1081
Figure 2 Protection/error sources for ZXCT1081
Capacitor C
provides high frequency transient decoupling when used with R
D
are of the order 10pF
For best performance R
minimizing any series resistance with R
When choosing appropriate values for R
should be connected as close to the SENSE+ (and SENSE ) pins;
SENSE
SENSE
SENSE
.
a compromise must be reached between in-line
signal loss (including potential power dissipation effects) and small signal accuracy.
Higher values for R
gives better accuracy at low load currents by reducing the inaccuracies
SENSE
due to internal offsets. For best operation the ZXCT1081 has been designed to operate with
V
of the order of 50mV to 150mV.
SENSE
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.
; typical values
LIM
As a result of this phenomenon the ZXCT1081 has been specified to operate in a linear manner
over a V
range of 10mV to 150mV range, however it will still be monotonic down to
SENSE
VSENSE
of 0V.
It is for this very reason that Zetex has specified an input offset voltage (V
output voltage for any V
voltage from 10mV to 150mV can be calculated as follows:
SENSE
) at 10mV. The
O(10)
Alternatively the load current can be expressed as:
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© Zetex Semiconductors plc 2007
Package details - SOT23-5
DIM Millimeters Inches
Min. Max. Min. Max.
A - 1.00 - 0.0393
A1 0.01 0.10 0.0003 0.0039
A2 0.84 0.90 0.0330 0.0354
b 0.30 0.45 0.0118 0.0177
c 0.12 0.20 0.0047 0.0078
D 2.90 BSC 0.114 BSC
E 2.80 BSC 0.110 BSC
E1 1.60 BSC 0.062 BSC
e 0.95 BSC 0.0374 BSC
e1 1.90 BSC 0.0748 BSC
L 0.30 0.50 0.0118 0.0196
L2 0.25 BSC 0.010 BSC
a° 4° 12° 4° 12°
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
ZXCT1081
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ZXCT1081
Intentionally left blank
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ZXCT1081
Definitions
Product change
Zetex Semiconductors reserves the right to alter, without notice, specifications, design, price or conditions of supply of any product or
service. Customers are solely responsible for obtaining the latest relevant information before placing orders.
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
arising from such use or otherwise. Zetex does not assume any legal responsibility or will not be held legally liable (whether in contract,
tort (including negligence), breach of statutory duty, restriction or otherwise) for any damages, loss of profit, business, contract,
opportunity or consequential loss in the use of these circuit applications, under any circumstances.
Life support
Zetex products are specifically not authorized for use as critical components in life support devices or systems without the express written
approval of the Chief Executive Officer of Zetex Semiconductors plc. As used herein:
A. Life support devices or systems are devices or systems which:
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.
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to
cause the failure of the life support device or to affect its safety or effectiveness.
Reproduction
The product specifications contained in this publication are issued to provide outline information only which (unless agreed by the
company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a
representation relating to the products or services concerned.
Terms and Conditions
All products are sold subjects to Zetex’ terms and conditions of sale, and this disclaimer (save in the event of a conflict between the two
when the terms of the contract shall prevail) according to region, supplied at the time of order acknowledgement.
For the latest information on technology, delivery terms and conditions and prices, please contact your nearest Zetex sales office.
Quality of product
Zetex is an ISO 9001 and TS16949 certified semiconductor manufacturer.
To ensure quality of service and products we strongly advise the purchase of parts directly from Zetex Semiconductors or one of our
regionally authorized distributors. For a complete listing of authorized distributors please visit: www.zetex.com/salesnetwork
Zetex Semiconductors does not warrant or accept any liability whatsoever in respect of any parts purchased through unauthorized sales channels.
ESD (Electrostatic discharge)
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.
Green compliance
Zetex Semiconductors is committed to environmental excellence in all aspects of its operations which includes meeting or exceeding
regulatory requirements with respect to the use of hazardous substances. Numerous successful programs have been implemented to
reduce the use of hazardous substances and/or emissions.
All Zetex components are compliant with the RoHS directive, and through this it is supporting its customers in their compliance with
WEEE and ELV directives.
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”
“Obsolete” Production has been discontinued
Datasheet status key:
“Draft version” This term denotes a very early datasheet version and contains highly provisional information, which
“Provisional version” This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance.
“Issue” This term denotes an issued datasheet containing finalized specifications. However, changes to
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
© 2006 Published by Zetex Semiconductors plc
Device is still in production to support existing designs and production
may change in any manner without notice.
However, changes to the test conditions and specifications may occur, at any time and without notice.
specifications may occur, at any time and without notice.
Americas
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Hauppauge, NY 11788
USA
Telephone: (1) 631 360 2222
Fax: (1) 631 360 8222
usa.sales@zetex.com
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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
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