DIODES ZXCT1020E5TA

ZXCT1020
ZXCT1020
Low offset current output current monitor
Description
The ZXCT1020 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 ZXCT1020 uses two external resistors to
set the overall voltage gain for applications
where improved accuracy at small sense
voltages is required. For fixed gain variants
Zetex offers the ZXCT1021 (G=10) and
ZXCT1022 (G=100).
The ZXCT1020 footprint follows that of the
ZXCT1021/2 with only 2 additional resistors
required:
Current output enables the user to set the gain
via these external resistors. Using two external
resistors to set the gain ensures optimal
versatility as the transconductance can be varied
to meet the output impedance requirements of
the load that the ZXCT1020 has to drive.
The very low offset voltage enables a typical
accuracy of 3% for sense voltages of only 10mV,
giving better tolerances for small sense
resistors necessary at higher currents.
One resistor between pins 1 and 4 for setting
transconductance, and the other between
pins 3 and 2 for setting overall gain.
The wide input voltage range of 20V down to as
low as 2.5V make it suitable for a range of
applications. With a minimum operating current
of just 25µA, combined with its SOT23-5
package make it suitable for portable battery
equipment too.
Features
Applications
•
Accurate high-side current sensing
•
Battery chargers
•
Versatile current output scaling
•
Over-current monitor
•
2.5V - 20V operating range
•
Motherboard power supply current measurement
•
25µA quiescent current
•
Level translating
•
1% typical accuracy
•
Programmable current source
•
SOT23-5 package
Pinout information
S+
1
Typical application circuit
5
R SH
GND
2
3
4
S(LOAD)
5
VB
S+ 1
OUT
IL
RS
S-
4
VB
+
Top view
VOUT
RG
3
2
ZXCT1020
GND
Ordering information
Order reference
Package
ZXCT1020E5TA
SOT23-5
Issue 1 - August 2007
© Zetex Semiconductors plc 2007
Device
marking
1020
Status
Preview
1
Reel size
(inches)
7
Quantity
per reel
3000
Tape width
(mm)
8
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ZXCT1020
Absolute maximum ratings
Voltage on VB with respect to GND pin
-0.5V to 20V
Voltage on S+(a), S-(b), OUT with respect to GND pin
-0.5V to VB+0.5V
VSENSE(c)
-0.5V to +2.5V(d)
Junction temperature
Storage temperature
Package power dissipation (Tamb = 25°C) SOT23-5
-40°C to125°C
-55°C to 150°C
300mW
NOTES:
(a) Subject to VSENSE+ never going 6V below VB.
(b) Subject to absolute maximum VSENSE not being exceeded.
(c) VSENSE is defined as the voltage difference across the sense resistor. and is the voltage across resistor RSH plus the
voltage between S+ and S-.
(d) VSENSE might need to be reduced when used with smaller values of RSH and at larger rails due to increased power dissipation.
Pin out information
Pin
1
Name
S+
Pin function
Positive sense input. Should be tied to positive side of sense resistor via
resistance (RSH) of the order of 150⍀ to 1.5k⍀.
2
3
GND
OUT
Ground and substrate connection of device.
Current output. A gain setting resistor (RG) referenced to GND should be
connected to this pin to set overall voltage gain of:
Gain = RG/RSH
The resistance, RG, placed on out will set the ZXCT1020 output impedance equal
to RG. When driving low impedance loads both RG and RSH should be reduced.
4
VB
5
S-
Input voltage pin. Provides bias to current monitor and should be tied to the
rail whose current is being monitored.
High impedance negative sense voltage input
Recommended operating conditions
Parameter
VSENSE+ Common-mode sense input range
VB
Bias pin input voltage range (*)
Min.
2.5
Max.
20
Units
V
2.5
20
V
VSENSE
Differential sense Input voltage range
0
1.5
V
VOUT
Output voltage range
0
VSENSE- - 1
V
RSH
Shunt resistor value
120
2000
⍀
TA
Ambient temperature range
-40
85
°C
NOTES:
(*) For best performance VB and VSENSE+ should be referred to the rail whose current is being measured.
Recommended resistor gain setting combinations
Gain
RSHUNT
RGAIN
10
20
50
100
1.5k⍀
750⍀
300⍀
150⍀
15k⍀
15k⍀
15k⍀
15k⍀
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ZXCT1020
Electrical characteristics
Tamb = 25°C, VSENSE+ = VB = 15V, VSENSE = 100mV, RG = 15k⍀, RSH = 1.5k⍀ unless otherwise stated.
Symbol Parameter
Conditions
Limits
Min.
VOUT
Output voltage
VSENSE = 0mV
Unit
Typ.
Max.
3
15
mV
VSENSE = 30mV
291
300
309
mV
VSENSE = 100mV
0.98
1
1.02
V
VSENSE = 150mV
1.47
1.5
1.53
V
50
300
ppm
TC[1]
Output voltage temperature
coefficient
IQ
Ground pin current
VSENSE = 0V
25
35
␮A
IS-
S- input current
VSENSE = 0V
20
100
nA
I S+
S+ input current
VSENSE = 0V
100
Acc
Accuracy
VSENSE = 100mV
Gain
VOUT /VSENSE
VSENSE = 100mV
10
V/V
ROUT
Output resistance
RG not connected
370
M⍀
BW
Bandwidth
VSENSE (DC) = 10mV
300
kHz
VSENSE (DC) = 100mV
2
MHz
80
dB
PSRR
Power supply rejection ratio
Issue 1 - August 2007
© Zetex Semiconductors plc 2007
VSENSE+ = VB = 2.5 to 20V
3
-2
70
nA
2
%
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ZXCT1020
Typical characteristics
Test conditions unless otherwise stated: TA = 25°C, VB = VSENSE+ (via RSH) =15V, VSENSE = 100mV
RSH = 1.5k⍀, RG = 15k⍀.
Supply current v Temperature
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ZXCT1020
Test conditions unless otherwise stated: TA = 25°C, VB = VSENSE+ (via RSH) =15V, VSENSE = 100mV
Gain = 10, RG = 15k⍀.
°
°
°
°
°
°
°
°
°
°
°
°
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°
°
°
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ZXCT1020
Test conditions unless otherwise stated: TA = 25°C, VB = VSENSE+ (via RSH) =15V, VSENSE = 100mV
Gain = 20, RG = 15k⍀.
°
°
°
°
°
°
°
°
°
°
°
°
°
°
°
°
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ZXCT1020
Test conditions unless otherwise stated: TA = 25°C, VB = VSENSE+ (via RSH) =15V, VSENSE = 100mV
RG = 15k⍀.
°
°
°
°
Gain = 100
VSENSE = 10mV
°
°
°
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ZXCT1020
Typical AC characteristics
Test conditions unless otherwise stated: TA = 25°C, VB = VSENSE+ (via RSH) =15V, VSENSE = 100mV,
RG = 15k⍀.
Gain = 10
Gain = 50
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ZXCT1020
Test conditions unless otherwise stated: TA = 25°C, RG=15k, VB = VSENSE+ (via RSH) =15V,
VSENSE = 100mV unless otherwise stated.
Various gains with constant RG
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ZXCT1020
Test conditions unless otherwise stated: TA = 25°C, G=100, RG = 15k, VB = VSENSE+ (via RSH),
VSENSE = 100mV.
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ZXCT1020
Application information
The ZXCT1020 has a VB pin that is used to provide power to the current monitor. The maximum
voltage applied to the ZXCT1020 must be applied to this pin. The S+ and S- pins are used to
measure the current flowing to the load through the sense resistor. In normal use, the S+ is tied
to VB via a shunt resistor, RH making the ZXCT1020 essentially line powered.
The ZXCT1020 has a programmable gain set by the ratio of two external resistors RG and RSH.
RS
R SH
S(LOAD)
5
VB
S+ 1
IL
4
+
VOUT
RG
3
2
ZXCT1020
GND
RSH sets the transconductance whereas RG set the gain and results in an output voltage defined
as:
RG
V OUT = ---------- × V SENSE
R SH
Where VSENSE = RSENSE x IL
The ZXCT1020 has been tested to the same conditions as the ZXCT1021 giving an overall voltage
gain of 10. The gain of the ZXCT1020 can be adjusted simply by varying RG. So to achieve a gain
of 50 RG is increased from 15k⍀ to 75k⍀. An alternative is to decrease RSH from 1.5k⍀ to 300⍀.
Decreasing RSH increases the transconductance and, if for any given gain, reducing the RSH will
reduce the overall output impedance.
To achieve a gain of 100, for example, the following resistor values could be used:
RSH = 150 RG = 15k
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ZXCT1020
Intentionally left blank
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ZXCT1020
Package outline - SOT23-5
Dim.
A
A1
A2
b
C
D
E
E1
e
e1
L
a°
Millimeters
Min.
0.90
0.00
0.90
0.20
0.09
2.70
2.20
1.30
Inches
Max.
1.45
0.15
1.30
0.50
0.26
3.10
3.20
1.80
Min.
0.0354
0.00
0.0354
0.0078
0.0035
0.1062
0.0866
0.0511
0.95 REF
1.90 REF
0.10
0°
Max.
0.0570
0.0059
0.0511
0.0196
0.0102
0.1220
0.1181
0.0708
0.0374 REF
0.0748 REF
0.60
30°
0.0039
0°
0.0236
30°
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
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ZXCT1020
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
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.
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
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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.
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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
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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.
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© 2007 Published by Zetex Semiconductors plc
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