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ISSUE 6 - AUGUST 2003
SEMICONDUCTORS
ZXCT1010
DESCRIPTION
The ZXCT1010 is a high side current sense monitor.
Using this device eliminates the need to disrupt the
ground plane when sensing a load current.
It is an enhanced version of the ZXCT1009 offering
reduced typical output offset and improved accuracy
at low sense voltage.
The wide input voltage range of 20V down to as low as
2.5V make it suitable for a range of applications. A
minimum operating current of just 4µA, combined
with its SOT23-5 package make suitable for portable
battery equipment.
FEATURES
•Low cost, accurate high-side current sensing.
•Output voltage scaling.
•Up to 2.5V sense voltage.
•2.5V – 20V supply range.
•300nA typical offset current.
•3.5µA 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
ENHANCED HIGH-SIDE CURRENT MONITOR
APPLICATION CIRCUIT
ORDERING INFORMATION
PART NUMBER PACKAGE PARTMARKING
ZXCT1010E5 SOT23-5 101
V
V
I
in
in
out
To Load
V
out
R
sense
R
out
Load
GND
ZXCT1010
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SEMICONDUCTORS
ZXCT1010
ABSOLUTE MAXIMUM RATINGS
Voltage on any pin -0.6V to 20V (relative to GND)
Continuous output current 25mA
Continuous sense voltage Vin + 0.5V > Vsense†> Vin – 5V
Operating Temperature -40 to 85°C
Storage Temperature -55 to 125°C
Package Power Dissipation (TA= 25°C)
SOT23-5 500mW
ELECTRICAL CHARACTERISTICS
Test Conditions TA= 25°C, Vin = 5V, Rout = 100Ω.
SYMBOL PARAMETER CONDITIONS LIMITS UNIT
Min Typ Max
Vin VCC Range 2.5 20 V
Iout1Output current Vsense =0V
Vsense = 10mV
Vsense = 100mV
Vsense = 200mV
Vsense =1V
0
85
0.975
1.95
9.7
0.3
100
1.00
2.00
10.0
10
115
1.025
2.05
10.3
µA
µA
mA
mA
mA
IqGround pin current Vsense = 0V 3.5 8 µA
Vsense2Sense Voltage 0 2500 mV
Isense Load pin
input current
100 nA
Acc Accuracy Rsense = 0.1Ω
Vsense = 200mV -2.5 2.5 %
Gm Transconductance,
Iout /V
sense
10000 µA/V
BW Bandwidth RF Pin = -20dBm3
Vsense = 10mV dc
Vsense = 100mV dc
300
2
kHz
MHz
1Includes input offset voltage contribution
2Vsense=Vin-Vload
3-20dBm=63mVp-p into 50Ω
ISSUE 6 - AUGUST 2003
SEMICONDUCTORS
ZXCT1010
3
TYPICAL CHARACTERISTICS
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SEMICONDUCTORS
ZXCT1010
PIN DESCRIPTION
Pin Name Pin Function
Vin Supply Voltage
Load Connection to load/battery
Iout Output current, proportional to Vin-Vload
GND Ground
SOT23-5
Package Suffix – E5
Top View
CONNECTION DIAGRAM
+
-
V
in
Load
I
out
100Ω
SCHEMATIC DIAGRAM
1
2
34
5
NC
GND
Iout
Load
VIN
ISSUE 6 - AUGUST 2003
SEMICONDUCTORS
ZXCT1010
5
The following lines describe how to scale a load
current to an output voltage.
Vsense = Vin -V
load
Vout = 0.01 x Vsense x Rout1
E.g.
A 1A current is to be represented by a 100mV output
voltage:
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 ohms.
2)Choose Rout to give Vout = 100mV, when Vsense =
100mV.
Rearranging 1for Rout gives:
Rout =V
out /(Vsense x 0.01)
Rout = 0.1 / (0.1 x 0.01) = 100 Ω
TYPICAL CIRCUIT APPLICATION
POWER DISSIPATION
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:
Pmax = (Tjmax – Tamb) / θja
The device power dissipation, PDis given by the
expression:
PD=Iout.(Vin-Vout) Watts
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.
APPLICATIONS INFORMATION
V
V
I
in
in
out
V
out
R
sense
R
out
R
load
Load
GND
ZXCT1010
ISSUE 6 - AUGUST 2003
SEMICONDUCTORS
ZXCT1010
6
Li-Ion Charger Circuit
The above figure shows the ZXCT1010 supporting
the Benchmarq bq2954 Charge Management IC.
Most of the support components for the bq2954 are
omitted for clarity. This design also uses the Zetex
FZT789A high current Super-PNP as the switching
transistor in the DC-DC step down converter and the
FMMT451 as the drive NPN for the FZT789A. The
circuit can be configured to charge up to four Li-Ion
cells at a charge current of 1.25A. Charge can be
terminated on maximum voltage, selectable
minimum current, or maximum time out. Switching
frequency of the PWM loop is approximately 120kHz.
100Ω
0.2Ω
100Ω
FZT789A
BC81725 1kΩ
BAS16
10µH
FMMT451
140µH
ZHCS1000
220Ω
SNS pin
MOD pin
Charger Input To Battery +
bq2954
5V
ZXCT1010
support components omitted for clarity
+
-
Vin Load
Iout
APPLICATIONS INFORMATION (Continued) Bi-Directional Current Sensing
The ZXCT1010 can be used to measure current
bi-directionally, if two devices are connected as
shown below.
If the voltage V1 is positive with respect to the
voltage V2 the lower device will be active, delivering
a proportional output current to Rout. Due to the
polarity of the voltage across Rsense, the upper
device will be inactive and will not contribute to the
current delivered to Rout. When V2 is more positive
than V1, current will be flowing in the opposite
direction, causing the upper device to be active
instead.
Non-linearity will be apparent at small values of
Vsense due to offset current contribution. Devices
can use separate output resistors if the current
direction is to be monitored independently.
Bi-directional Transfer Function
Iout
3
Load 5
Vin
4
R
Iout 3
Load
5Vin 4
V
1
V
V
2
sense
out
R
out
-400 -200 0 200 400
0
1
2
3
4
5
Output Current (mA)
Sense Voltage (mV)
Output Current v Sense Voltage
ISSUE 6 - AUGUST 2003
SEMICONDUCTORS
ZXCT1010
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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.
The figure opposite shows a PCB layout suggestion.
The resistor section is 25mm x 0.25mm giving
approximately 150mΩusing 1oz copper. The data
for the normalised graph was obtained using a 1A
load current and a 100Ωoutput resistor. An
electronic version of the PCB layout is available at
www.zetex.com/isense
APPLICATIONS INFORMATION (Continued)
Layout shows area of shunt
resistor compared to SOT23-5
package. Not actual size
Actual Size
ZXCT1010
SEMICONDUCTORS
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ISSUE 6 - AUGUST 2003
Europe
Zetex plc
Fields New Road
Chadderton
Oldham, OL9 8NP
United Kingdom
Telephone (44) 161 622 4444
Fax: (44) 161 622 4446
hq@zetex.com
Zetex GmbH
Streitfeldstraße19
D-81673 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 Hwy
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
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
© Zetex plc 2003
PACKAGE DIMENSIONS SOT23-5
DIM Millimetres Inches
MIN MAX MIN MAX
A 0.90 1.45 0.035 0.057
A1 0.00 0.15 0.00 0.006
A2 0.90 1.3 0.035 0.051
b 0.35 0.50 0.014 0.020
C 0.09 0.20 0.0035 0.008
D 2.80 3.00 0.110 0.118
E 2.60 3.00 0.102 0.118
E1 1.50 1.75 0.059 0.069
e 0.95 REF 0.037 REF
e1 1.90 REF 0.075 REF
L 0.10 0.60 0.004 0.024
a°010010
