ZXCT1050

ZXCT1050
Precision wide input range current monitor
Description
The ZXCT1050 is a wide input range current
monitor, which operates over a range of input
voltages from ground up to VCC-2V. As a
result the ZXCT1050 can be used on the high
or low side of the load.
The very low offset voltage enables a typical
accuracy of 1% for sense voltages of only 30mV,
giving better tolerances for small sense
resistors necessary at higher currents.
The ZXCT1050 provides variable gain by
using two external resistors. The first of
which sets the transconductance and the
second setting the overall gain.
Features
Applications
•
Accurate down to end current sensing
•
Power supply
•
Output voltage scaling x10
•
DC motor and solenoid control
•
0 to VCC-2V sense input range
•
Battery management
•
2.7 to 20V supply range
•
Over current monitor
•
50µA quiescent current
•
Power management
•
SOT23-5 package
•
Short circuit detection
Pin connections
VCC 1
Typical application circuit
5
RSENSE
IN
SENSE-
RSHUNT
GND 2
SENSE+
OUT 3
4
SENSE+
VCC
SENSE-
ZXCT1050
Load
OUT
OUT
RGAIN
Ordering information
Order code
ZXCT1050E5TA
Pack
Part mark
Reel size
(inches)
Tape width
(mm)
Quantity
per reel
SOT23-5
1050
7
8
3000
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ZXCT1050
Absolute maximum ratings
VCC max.
20V
Voltage on SENSE- and SENSE+
-0.6 to VCC
Voltage on all other pins
-0.6V and VCC +0.6V
VSENSE = ‘(VSENSE+) - (VSENSE-)’
500mV
Operating temperature
-40 to 125°C
Storage temperature
-55 to 150°C
Maximum junction temperature
150°C
Package power dissipation
300mW* at TA = 25°C (De-rate to zero for TJ = 150°C)
Operation above the absolute maximum rating may cause device failure. Operation at the absolute
maximum ratings, for extended periods, may reduce device reliability.
Recommended operating conditions
VSENSE+
Parameter
Common-mode sense input range
Min.
0
Max.
VCC-2
VCC
Supply voltage range
2.7
20
Units
V
V
VSENSE
Differential sense input voltage range
10
300
mV
VOUT
Output voltage range
0
VCC-2
V
TA
Ambient temperature range
-40
125
°C
Recommended resistor gain setting combinations
Gain
RSH
RG
10
20
50
100
20
50
100
7.5k⍀
7.5k⍀
7.5k⍀
7.5k⍀
3.75k⍀
1.5k⍀
750⍀
3.75k⍀
7.5k⍀
18.7k⍀
37.5k⍀
3.75k⍀
3.75k⍀
3.75k⍀
Pin function table
PIN
1
Name
VCC
Description
This is the analog supply and provides power to internal circuitry.
2
3
GND
OUT
4
SENSE+
Ground pin.
Output pin. A resistor, RGAIN, connected from this pin pin down to ground
develops an output voltage.
This is the positive input of the current monitor and has an input range from
0V up to VCC – 2V.
5
SENSE-
This is the negative input of the current monitor and has an input range from
0V up to VCC – 2V. The current through this pin varies with differential sense
voltage. A resistor, RSHUNT, from this pin to the rail being sensed set the
transconductance of the current monitor.
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ZXCT1050
Electrical characteristics
Test conditions TA = 25°C, VSENSE+ = 10V, VCC = 12V, VSENSE = 100mV, RSH = 7.5k⍀, RG = 3.75k⍀.
Symbol
Parameter
Conditions
Min.
Typ.
Max.
IQ
VCC pin current
VSENSE = 0V
VOUT
Output voltage
VSENSE = 0V
=30mV
=100mV
=150mV
45
70
µA
3
300
1.00
1.50
15
315
1.03
1.55
mV
mV
V
V
ISENSE+
VSENSE+ input current VSENSE = 0V
60
150
nA
ISENSE-
VSENSE- input current VSENSE = 0V
15
150
nA
VOUT TC
VOUT variation with
temperature
300
ppm/°C
Gain
VOUT/VSENSE
Accuracy
Total output error
BW
Bandwidth
0
285
0.97
1.45
See note (*)
Units
10
-3
VSENSE(DC)
= 10mV
VSENSE(AC)
= 10mVPP
CL = 5pF,
VSENSE(DC)
= 100mV
3
%
300
kHz
0.8
MHz
PSRR
Power supply
rejection ratio
VCC = 2.7V to 20V
VSENSE+ = 0.7V
60
dB
CMRR
Common mode
rejection ratio
VCC = 20V
VSENSE+ = 0 to 18V
70
dB
NOTES:
(*) Temperature dependent measurements are extracted from characterisation and simulation results.
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ZXCT1050
Typical characteristics
ICC Supply Current (A)
ICC Supply Current (A)
RG = 3.75k⍀, RSH = 7.5k⍀ unless otherwise stated.
Supply Current v Input Voltage
IS- Sense Current (A)
ICC Supply Current (A)
Supply Current v Supply Voltage
Sense- Current v Supply Voltage
IS- Sense Current (A)
Percentage Change IS- (%)
Supply Current v Sense Voltage
Sense- Current v Temperature
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Sense- Current v Sense Voltage
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ZXCT1050
Typical characteristics
10
1
ΔVOUT Output Voltage (mV)
VOUT - Output Voltage (V)
RG = 3.75k⍀, RSH = 7.5k⍀ unless otherwise stated.
100m
10m
1E-3
0.01
0.1
5
0
-5
-40 -20
0
20
40
60
80 100 120
Temperature Characteristic
10.1
Incremental Gain
VOUT - Output Voltage (mV)
1100
1050
1000
950
900
-20
-15
-10
-5
0
5
10
μ
15
10.0
9.9
20
18
16
14
12
10
8
6
4
2
0
-2
-4
-6
-8
0
2
4
6
8
10 12
14 16
18 20
Common Mode Characteristic
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50m
100m
150m
Incremental Gain v Sense Voltage
ΔVOUT - Output Voltage (mV)
ΔVOUT - Output Voltage (mV)
VOUT v Load Current
0
12
8
4
0
-4
-8
-12
0
5
10
15
20
Supply Characteristic
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ZXCT1050
Typical characteristics
RG = 3.75k⍀, RSH = 7.5k⍀ unless otherwise stated.
Referred
to 1V
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ZXCT1050
Applications information
The ZXCT1050 is a current output version of the ZXCT1051 and as such uses a separate power
supply pin. All biasing for the internal amplifiers comes from its separate VCC input and is not ‘line
powered’, unlike the ZXCT1021.
This means that at very small sense voltages the ZXCT1050 draws very little current (<1␮A) from
the lines being sensed.
The separate VCC pin enables the ZXCT1050 to be operated at sense line voltages down to 0V,
where the ZXCT1021 would switch off. This feature enables the ZXCT1050 to be used to sense the
currents flowing through lines that have been shorted to ground.
VRAIL
R SH
R SENSE
IL
SENSE+ (4)
(5) SENSE-
VCC
(1)
Load
Q1
Out
(3)
ZXCT1050
GND
RG
GND (2)
Basic operation
Load current, IL, from VRAIL is drawn through RSENSE developing a voltage VSENSE across the
sense inputs of the ZXCT1050.
The internal amplifier forces VSENSE across external resistance RSH (internal on the ZXCT1051)
causing a current to flow through transistor Q1 and out of the output pin, OUT. This current is then
converted to a voltage by a resistor, RG, between OUT and GND.
The overall gain of the ZXCT1050 is determined by the following expression:
RG
GAIN = 20 × ---------R SH
A ratio of 1:2 between RSH and RG creates the fixed gain of 10 with an output impedance equal to
RG (see electrical characteristics for output current-voltage characteristics).
The ZXCT1050 has both RG and RSH external. This allows RG and RSH to be varied so that the
required gain can be achieved at the required output impedance.
For low power applications both RG and RSH can be increased whereas for driving low impedance
RG and RSH can be decreased.
The maximum recommended value for RG is 40k⍀ and the maximum recommended value for
RSH is 10k⍀. Large values of RSH start increasing the effective input offset error, while large values
of RG can created load errors and reduce bandwidths.
The maximum differential input voltage, VSENSE, is 150mV (IL * RSENSE); however voltages up to
500mV will not damage it. This can be increased further by the inclusion of a resistor, RLIM,
between the SENSE+ pin and the rail being sensed, VRAIL.
For best performance RSENSE should be connected as close to the SENSE+ and SENSE- pins thus
minimizing any series resistance with RSENSE.
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ZXCT1050
Intentionally left blank
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ZXCT1050
Package outline - SOT23-5
DIM
A
A1
A2
b
c
D
E
E1
e
e1
L
L2
a°
Millimeters
Min.
0.01
0.84
0.30
0.12
Inches
Max.
1.00
0.10
0.90
0.45
0.20
Min.
0.0003
0.0330
0.0118
0.0047
2.90 BSC
2.80 BSC
1.60 BSC
0.95 BSC
1.90 BSC
0.30
0.114 BSC
0.110 BSC
0.062 BSC
0.0374 BSC
0.0748 BSC
0.50
0.0118
0.25 BSC
4°
Max.
0.0393
0.0039
0.0354
0.0177
0.0078
0.0196
0.010 BSC
12°
4°
12°
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
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ZXCT1050
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.
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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.
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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.
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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.
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© 2007 Published by Zetex Semiconductors plc
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