ZXCT1023
MICROPOWER FIXED GAIN OF 50 CURRENT MONITOR
ZXCT1023 1 of 6 MARCH 2009
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Ordering Information
Ord er R eferen ce Pack ag e Device
Marking Status Reel Size
(inches) Quantity
per Reel Tape
W
idth
(mm)
ZXCT1023DFGTA TDFN1218 1023 Active 7 3000 8
Description
The ZXCT1023 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 ZXCT1023 has a fixed internal gain of 50 and the only external
component required is the external current sense resistor; this
combined with its 1.2mm x 1.8mm TDFN package more than quarters
the solution size of the ZXCT1010.
The wide input voltage range of 20V down to as low as 2.5V makes it
suitable for a range of applications.
The combination of operation down to 2.5V and just 3.5µA quiescent
current makes it ideal for single cell Li-Ion/polymer battery
charge/discharge measurement applications.
Features
• Accurate high-side current sensing
• Fixed gain of 50 output scaling
• 2.5V – 20V operating range
• 3.5µA quiescent current
• TDFN1218 package
Applications
• Battery capacity measurement
• Battery chargers
• Over-current monitor
Pin Connections
TDFN1218-4L
Typical Operating Circuit
S+ S-
GND
VOUT
RG
RGT
RS
1
2
4
3
S+
S-
OUT
GND
Top View
ZXCT1023
MICROPOWER FIXED GAIN OF 50 CURRENT MONITOR
ZXCT1023 2 of 6 MARCH 2009
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Absolute maximum ratings
Voltage on S+1 .......................................-0.5V to 20V
Voltage on S-1,2, OUT1 .................. -0.5V to VS++0.5V
VSENSE
3 ............................................... -0.5V to +2.5V
Junction temperature ............................. -40 to125ºC
Storage temperature ............................. -55 to 150ºC
Package power dissipation (TA = 25ºC)
TDFN1812-4 ...................................................... mW
These are stress ratings only. Operation outside the absolute
maximum ratings may cause device failure. Operation at the
absolute maximum rating for extended periods may reduce
device reliability
Notes 1. Measured with respect to GND pin
2. Subject to absolute maximum VSENSE not being
exceeded.
3. VSENSE is defined as the voltage difference across
the sense resistor, RS.
4. The usable VSENSE range is limited by the output
voltage range; and as such will be reduced at lower
VS+ values.
Semiconductor devices are ESD sensitive and may be
damaged by exposure to ESD events. Suitable ESD
precautions should be taken when handling and
transporting these devices.
ESD ratings:
Human body model .............................. 2000V
Machine Model ........................................ TBD
Recommended operating conditions
Parameter MIN MAX Units
VS+
1
, Common-mode
sense input range 2.5 20 V
VSENSE, Differential Sense
Input voltage range 0 3804 mV
VOUT,Output Volta
g
e ran
g
e 0 VS- -1 V
TA, Ambient temperature
range -40 85 °C
Electrical characteristics
TA = 25°C, VS+ = 3.6V, VSENSE = 50mV, unless otherwise stated
Symbol Parameter Conditions Limits Unit
Min. Typ. Max.
VOUT Output voltage
VSENSE = 0mV 0.3 50 mV
VSENSE = 10mV 425 500 575
VSENSE = 30mV 1.41 1.5 1.59
V
VSENSE = 50mV 2.425 2.5 2.575
VSENSE = 100mV, VS+ = 20V 4.85 5 5.15
TC5 Output voltage
temperature coefficient 50 300 ppm
IQ Ground pin current VSENSE = 0V 3.5 8 μA
IS- SENSE- input current VSENSE = 0V 100 nA
Acc Accuracy VSENSE = 50mV -3 3 %
Gain VOUT/VSENSE V
SENSE = 50mV 50 V/V
ROUT Output resistance 15 kΩ
BW Bandwidth VSENSE (DC) = 10mV 300 kHz
VSENSE (DC) = 50mV 1 MHz
PSRR6 Power supply rejection
ratio VSENSE = 30mV, VS+ = 2.5 to 20V 50 60 dB
Notes 5. TC limits are determined by characterization.
6. PSRR is defined as change in output voltage per change in S+ voltage, VS+.
ZXCT1023
MICROPOWER FIXED GAIN OF 50 CURRENT MONITOR
ZXCT1023 3 of 6 MARCH 2009
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Typical DC characteristics
V
SENSE
= 0V, V
S+
= 3.6V
0
0.5
1
1.5
2
2.5
2 4 6 8 10 12 14 16 18 20
V
S+
(V)
I
S+
(µA)
T
A
= -40°C
T
A
= 0°C
T
A
= 85°C
Vs+ = 3.6v
Relative to gain = 50
-2%
-1%
0%
1%
2%
3%
0 1020304050
V
SENSE
(mV)
Differential Gain Error
T
A
= 85°C
T
A
= -40°C
T
A
= 0°C
T
A
= 25°C
S+ input current vs Supply voltage Normalised gain error Vs Sense voltage
V
S+
= 3.6V
-40°C
25°C
85°C
20
30
40
50
60
70
0246810
V
SENSE
(mV)
Differential Gain (ΔV
OUT
/ΔV
SENSE
)
T
A
= 0°C V
S+
= 3.6V
0
0.5
1
1.5
2
2.5
3
3.5
0 102030405060
V
SENSE
(mV)
V
OUT
(V)
T
A
= 85°C
T
A
= 25°C
T
A
= 0°C
T
A
= -40°C
Differential gain Vs Sense voltage Output Voltage Vs Sense voltage
T
A
= 25°C
V
SENSE
= 10mV
V
SENSE
= 30mV
V
SENSE
= 50mV
0
0.5
1
1.5
2
2.5
3
2 4 6 8 10 12 14 16 18 20
V
S+
(V)
V
OUT
(V)
V
S+
=3.6V
w.r.t. V
OUT
at 25°C
V
SENSE
= 10mV, 30mV, 50mV
10mV
30mV
30mV
50mV
50mV
-0.6%
-0.4%
-0.2%
0.0%
0.2%
0.4%
0.6%
-40 -15 10 35 60 85
Temperature (°C)
ΔVOUT %Error
Output voltage VS+ Input voltage Relative output voltage change Vs Temperature
ZXCT1023
MICROPOWER FIXED GAIN OF 50 CURRENT MONITOR
ZXCT1023 4 of 6 MARCH 2009
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Typical AC characteristics
-20
-10
0
10
20
30
40
10E+0 100E+0 1E+3 10E+3 100E+3 1E+6 10E+6
frequency (Hz)
Gain (dB)
V
SENSE
= 50mV
V
SENSE
= 10mV
V
S+
=3.6V
T
A
=25°C
T
A
= 25°C
V
SENSE
= 50mV
0
10
20
30
40
50
60
70
0.01 0.1 1 10 100 1000
Frequency (kHz)
PSRR (dB)
V
S+
= 10V
V
S+
=
Small signal frequency response Power supply rejection ratio
-5
0
5
10
15
20
25
0 50 100 150 200 250 300
Time (µs)
Input (mV)
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
Output (V)
Input Output
V
S+
=3.6V, T
A
= 25°C
V
SENSE
= 20mV
-10
0
10
20
30
40
50
60
0 50 100 150 200
Time (µs)
Input (mV)
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Output (V)
Input
Output
V
S+
=3.6V, T
A
= 25°C
V
SENSE
= 50mV
l
Large signal pulse response 20mV Large signal pulse response 50mV
49
50
51
52
53
54
55
56
0 50 100 150 200
time (µs)
Sense voltage (mV)
2.45
2.50
2.55
2.60
2.65
2.70
2.75
2.80
Output voltage (V)
Input
Output
V
S+
=3.6V, T
A
=25°C
V
SENSE
= 50mV(DC) + 5mV
44
45
46
47
48
49
50
51
0 25 50 75 100 125 150
time (µs)
V
SENSE
(mV)
2.20
2.25
2.30
2.35
2.40
2.45
2.50
2.55
V
OUT
(V)
Input
Output
V
S+
=3.6V, T
A
=25°C
V
SENSE
= 50mV(DC) - 5mV pulse
Small signal positive pulse response Small signal negative pulse response
Pin out information
Package Name Pin function
1 OUT
Voltage output. The output voltage is referenced to GND.
The overall voltage gain of
V
OUT = 50 x VSENSE where VSENSE = VS+ - VS-
2 GND Ground and substrate connection of device.
NC No connection
3 S- High impedance negative sense voltage input
4 S+ Positive sense input. Also acts as power supply pin to ZXCT1023
ZXCT1023
MICROPOWER FIXED GAIN OF 50 CURRENT MONITOR
ZXCT1023 5 of 6 MARCH 2009
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Application informatio n
The ZXCT1023 is line powered (derives its power from the rail being sensed) this reduces the number of
pins used and PCB trace routing. The fixed gain of 50 reduces the PCB area by reducing the number of
external components. The only external component required is the sense resistor. This coupled with the
1.2mm x 1.8mm TDFN package makes the solution size very small.
The fixed gain of 50 has been chosen to meet the normal requirements of most applications.
The ZXCT1023 has its gain setting resistor, RG, set at 15kΩ which further reduces power consumption at
larger VSENSE.
Application Examples
Please refer to Zetex AN39 for sample applications.
Package Outline
TDFN1812-4 package
S+ S-
GND
V
OU
T
RG
RGT
RS
ZXCT1023
MICROPOWER FIXED GAIN OF 50 CURRENT MONITOR
ZXCT1023 6 of 6 MARCH 2009
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