1
ISSUE 3 - APRIL 2001
ZXCT1009
DESCRIPTION
The ZXCT1009 is a high side current sense monitor.
Using this device eliminates the need to disrupt the
ground plane when sensing a load current.
It takes a high side voltage developed across a current
shunt resistor and translates it into a proportional
output current.
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. A
minimum operating current of just 4A, combined
with its SOT23 package make it a unique solution,
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.
4A quiescent current.
1% typical accuracy.
SOT23 & SM8
packages.
APPLICATIONS
Battery Chargers
Smart Battery Packs
DC Motor control
Over current monitor
Power Management
Level translating
Programmable current source
HIGH-SIDE CURRENT MONITOR
APPLICATION CIRCUIT
V
in
To Load
V
out
R
sense
R
out
ZXCT
1009
8 leaded SOT223
ORDERING INFORMATION
PART NUMBER
PACKAGE
PARTMARKING
ZXCT1009F
SOT23
109
ZXCT1009T8
SM8
ZXCT1009
SM8 due for release May 2001
Sampling April 2001
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ISSUE 3 - APRIL 2001
ZXCT1009
ABSOLUTE MAXIMUM RATINGS
Voltage on any pin
-0.6V to 20V (relative to I
out
)
Continuous output current
25mA
Continuous sense voltage
V
in
+ 0.5V > V
sense
> V
in
5V
Operating Temperature
-40 to 85
C
Storage Temperature
-55 to 125
C
Package Power Dissipation
(T
A
= 25
C)
SOT23
450mW
SM8
2W
ELECTRICAL CHARACTERISTICS
Test Conditions T
A
= 25
C, V
in
= 5V, R
out
= 100
.
SYMBOL
PARAMETER
CONDITIONS
LIMITS
UNIT
Min
Typ
Max
V
in
V
CC
Range
2.5
20
V
I
out
1
Output current
V
sense
=0V
V
sense
=10mV
V
sense
=100mV
V
sense
=200mV
V
sense
=1V
1
90
0.975
1.95
9.6
4
104
1.002
2.0
9.98
15
120
1.025
2.05
10.2
A
A
mA
mA
mA
V
sense
Sense Voltage
0
2500
mV
I
sense
Load pin
input current
100
nA
Acc
Accuracy
R
sense
= 0.1
V
sense
=200mV
-2.5
2.5
%
Gm
Transconductance,
I
out
/ V
sense
10000
A/V
BW
Bandwidth
RF P
in
= -20dBm
V
sense
= 10mV dc
V
sense
= 100mV dc
300
2
kHz
MHz
1
Includes input offset voltage contribution
V
sense
=V
in
-V
load
-20dBm=63mVp-p into 50
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ISSUE 3 - APRIL 2001
ZXCT1009
PIN DESCRIPTION
Pin Name
Pin Function
V
in
Supply Voltage
Load
Connection to load/battery
I
out
Output current, proportional to V
in
-V
load
SM8
Package Suffix T8
Top View
SOT23
Package Suffix F
Top View
I
out
Load
V
in
3
2
1
Iout
Load
N/C
V
in
N/C
N/C
N/C
N/C
5
6
7
8
4
3
2
1
CONNECTION DIAGRAMS
+
-
V
in
Load
I
out
100
SCHEMATIC DIAGRAM
ISSUE 3 - APRIL 2001
ZXCT1009
5
The following lines describe how to scale a load
current to an output voltage.
V
sense
= V
in
- V
load
V
out
= 0.01 x V
sense
x R
out
1
E.g.
A 1A current is to be represented by a 100mV output
voltage:
1)Choose the value of R
sense
to give 50mV > V
sense
>
500mV at full load.
For example V
sense
= 100mV at 1.0A. R
sense
= 0.1/1.0
=> 0.1 ohms.
2)Choose R
out
to give V
out
= 100mV, when V
sense
=
100mV.
Rearranging
1
for R
out
gives:
R
out
= V
out
/(V
sense
x 0.01)
R
out
= 0.1 / (0.1 x 0.01) = 100
V
in
Vin
Iout
Load
V
out
R
sense
R
load
R
out
ZXCT1009
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
(
ja), maximum junction temperature (Tjmax), and
ambient temperature (Tamb), according to the
expression:
P
max
= (Tj
max
T
amb
) /
ja
The device power dissipation, P
D
is given by the
expression:
P
D
=I
out
.(V
in
-V
out
) Watts
SM8
SOT23
Where R
load
represents any load including DC motors,
a charging battery or further circuitry that requires
monitoring, R
sense
can be selected on specific
requirements of accuracy, size and power rating.
APPLICATIONS INFORMATION
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