DIODES ZXCT1008FTA

ZXCT1008
AUTOMOTIVE HIGH-SIDE CURRENT MONITOR
DESCRIPTION
APPLICATIONS
The ZXCT1008 is a high side current sense monitor.
Using this device eliminates the need to disrupt the
ground plane when sensing a load current.
• Automotive current measurement
It takes a high side voltage developed across a current
shunt resistor and translates it into a proportional
output current.
• Over current monitor
• DC motor and solenoid control
• Power management
A user defined output resistor scales the output
current into a ground-referenced voltage.
The wide input voltage range of 20V down to as low as
2.5V make it suitable for a range of applications. The
ability to withstand high voltage transients and
reverse polarity connection, makes this part very
suitable for automotive and other transient rich
environments.
FEATURES
APPLICATION CIRCUIT
• Low cost, accurate high-side current sensing
• -40 to +125°C temperature range
• Up to 500mV sense voltage
• 2.5V – 20V supply range
• 4µA quiescent current
• 1% typical accuracy
• SOT23
ORDERING INFORMATION
DEVICE
REEL
SIZE
TAPE
WIDTH
QUANTITY PER
REEL
ZXCT1008FTA
7”
8mm
3,000 units
DEVICE MARKING
• 108
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ZXCT1008
ABSOLUTE MAXIMUM RATINGS
Voltage on any pin
Continuous output current, IOUT,
Continuous sense voltage, VSENSE†,
Operating temperature, TA,
Storage temperature
Package power dissipation (TA = 25°C)
-0.6V to 20V (relative to Iout)
10mA
-0.5V to +5V
-40 to 125°C
-55 to 150°C
450mW Derate to zero at 150°C
Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum
ratings, for extented periods, may reduce device reliability.
ELECTRICAL CHARACTERISTICS
Test Conditions TA = 25°C, Vin = 5V, Rout = 100Ω.
SYMBOL
PARAMETER
CONDITIONS
LIMITS
Min
V in
V CC range
I out 1
Output current
V sense †
Sense voltage
I sense -
V sense -
Acc
Accuracy
Typ
2.5
UNIT
Max
20
V
V sense =0V
1
4
15
µA
V sense =10mV
90
104
120
µA
V sense =100mV
0.975
1.0
1.025
mA
V sense =200mV
1.95
2.0
2.05
mA
V sense =500mV
4.8
5.0
5.2
mA
0
500
mV
100
nA
2.5
%
input current
R sense = 0.1Ω
-2.5
V sense =200mV
Gm
Transconductance,
Iout / V sense
BW
Bandwidth
10000
µA/V
V SENSE(DC) = 10mV, Pin = -40dBm ‡
300
kHz
VSENSE(DC) = 100mV, Pin = -20dBm ‡
2
MH
1
Includes input offset voltage contribution
†
VSENSE is defined as the differential voltage
VSENSE = VSENSE+ - VSENSE= VIN - VLOAD
= ILOAD x RSENSE
between VSENSE+ and VSENSE-.
‡ -20dBm=63mVp-p into 50Ω
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ZXCT1008
TYPICAL CHARACTERISTICS
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ZXCT1008
SCHEMATIC DIAGRAM
TYPICAL CHARACTERISTICS (Cont.)
PIN DESCRIPTION
Pin Name
Pin Function
V sense +
Supply voltage
V sense -
Connection to load/battery
I out
Output current, proportional to V in -V load
CONNECTION DIAGRAM
SOT23
Package Suffix – F
Top View
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ZXCT1008
POWER DISSIPATION
APPLICATIONS INFORMATION
The maximum allowable power dissipation of the
device for normal operation (Pmax), is a function of
the package junction to ambient thermal resistance
(θja), maximum junction temperature (Tjmax), and
ambient temperature (Tamb), according to the
expression:
The following lines describe how to scale a load
current to an output voltage.
Vsense = Vin - Vload
Vout = 0.01 x Vsense x Rout1
Pmax = (Tjmax – Tamb) / θja
E.g.
The device power dissipation, PD is given by the
expression:
A 1A current is to be represented by a 100mV output
voltage:
PD=Iout.(Vin-Vout) Watts
1) Choose the value of Rsense to give 50mV >
Vsense > 500mV at full load.
For example Vsense = 100mV at 1.0A.
Rsense = 0.1/1.0 => 0.1 Ω
2) Choose Rout to give Vout = 100mV,
when Vsense = 100mV.
Rearranging 1 for Rout gives:
Rout = Vout /(Vsense x 0.01)
Rout = 0.1 / (0.1 x 0.01) = 100 Ω
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ZXCT1008
Where Rload represents any load including DC
motors, a charging battery or further circuitry that
requires monitoring, Rsense can be selected on
specific requirements of accuracy, size and power
rating.
TYPICAL AUTOMOTIVE CIRCUIT APPLICATION
An additional resistor, Rlim can be added in series
with Rout (figure 1.0), to limit the current from Iout.
Any circuit connected to Vout will be protected from
input voltage transients. This can be of particular
use in automotive applications where load dump
and other common transients need to be
considered. The zener Z1 provides additional
protection for local dump, reverse battery and high
voltage transient incidents.
Assuming the worst case condition of Vout = 0V;
providing a low impedance to a transient, the
minimum value of Rlim is given by:Rlim(min) =
Vpk − Vmax
Ipk
Vpk = Peak transient voltage to be withstood
Vmax = Maximum working Voltage = 20V
Ipk = Peak output current = 40mA
Figure 1.0
ZXCT1009 with additional current limiting Resistor Rlim
and zener Z1
The maximum value of Rlim is set by Vin(min),
Vout(max) and the dropout voltage (see transfer
characteristic on page 3) of the ZXCT1009 :Rlim(max) =
Rout [Vin(min) − (Vdp + Vout (max))]
Vout (max)
Vin(min) = Minimum Supply Operating Voltage
Vdp = Dropout Voltage
Vout (max) = Maximum Operating Output Voltage
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ZXCT1008
APPLICATIONS INFORMATION
PCB trace shunt resistor for low
cost solution.
The figure below shows output characteristics of the
device when using a PCB resistive trace for a low cost
solution in replacement for a conventional shunt
resistor. The graph shows the linear rise in voltage
across the resistor due to the PTC of the material and
demonstrates how this rise in resistance value over
temperature compensates for the NTC of the device.
ZXCT1009
ZXCT1009
Vout
Vin
Vout
The figure opposite shows a PCB layout suggestion.
The resistor section is 25mm x 0.25mm giving
approximately 150mΩ using 1oz copper. The data
for the normalised graph was obtained using a 1A
load current and a 100Ω output resistor. An
electronic version of the PCB layout is available at
www.zetex.com/isense
Load
Rout
Rout
Vin
GND
Actual Size
Load
GND
Layout shows area of shunt
resistor compared to SOT23
package. Not actual size
Voltage across
Copper Sense
Resistor
Normalised Voltage
1.4
1.2
VOUT with Copper
Sense Resistor
1.0
VOUT with Ideal
Sense Resistor
0.8
-40
-20
0
20
40
60
80
100 120 140
Temperature (°C)
Effect of Sense Resistor Material
on Temperature Performance
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ZXCT1008
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 labeling 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"Device is still in production to support existing designs and production
"Obsolete"Production has been discontinued
Datasheet status key:
"Draft version"This term denotes a very early datasheet version and contains highly provisional
information, which 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.
"Issue"This term denotes an issued datasheet containing finalized specifications. However, changes to specifications may occur, at any time and
without notice.
ISSUE 4 - JULY 2007
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ZXCT1008
PACKAGE OUTLINE
E
e
e1
b
3 leads
L1
D
E1
A
A1
L
c
Controlling dimensions are in millimeters. Approximate conversions are given in inches
PACKAGE DIMENSIONS
Millimeters
DIM
Inches
Millimeters
DIM
Max.
Min.
Max.
A
ᎏ
1.12
ᎏ
0.044
A1
0.01
0.10
0.0004
0.004
E
2.10
2.64
0.083
0.104
b
0.30
0.50
0.012
0.020
E1
1.20
1.40
0.047
0.055
C
0.085
0.120
0.003
0.008
L
0.25
0.62
0.018
0.024
D
2.80
3.04
0.0110
0.120
L1
0.45
0.62
0.018
0.024
ᎏ
ᎏ
ᎏ
ᎏ
ᎏ
e
0.95 NOM
0.0375 NOM
e1
Min.
Max.
Inches
Min.
1.90 NOM
Max.
Max.
0.075 NOM
© Zetex Semiconductors plc 2007
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These offices are supported by agents and distributors in major countries world-wide.
This publication is 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. The Company
reserves the right to alter without notice the specification, design, price or conditions of supply of any product or service.
For the latest product information, log on to www.zetex.com
ISSUE 4 - JULY 2007
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