ZXCT1020EV1 User Guide Issue1-2

ZXCT1020EV1
Evaluation Board
User Guide
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ZXCT1020EV1
Figure 1 Evaluation board components' layout
DESCRIPTION
The ZXCT1020EV1 evaluation board is intended for the evaluation of the ZXCT1020
device. 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.
It also has an externally programmable transconductance resistor, thus making it a
versatile device to use in many applications.
The device produces a current output that is proportional to the current sampled by a
small in-line sensing resistor, RS. The voltage output is scaled by the choice of RS (R1,
R2 on the evaluation board), RGT (R4 on the evaluation board) and the load resistor (R7
on the evaluation board).
The evaluation board is delivered with the values shown in Figure 2 below. As can be
seen, RS consists of two resistors (R1 and R2) which are configured in parallel such that
either one or both resistors could be connected by completing the solder-bridge link
next to each one. R2 (0.1R) is connected by default.
R3 consists of two pads with a hole in each pad and provides means for connecting an
external RS.
With the values shown the board produces an output of 1V/A
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ZXCT1020EV1
Evaluation Board
User Guide
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The printed circuit board is common to other devices in the ZXCT family and contains
redundant component positions which will not be discussed here as they are not
relevant.
RS
VSUPPLY (R1//R2 = 0.05R//0.1R)
ILOAD
V2
V1
RGT
(R4=1.5k)
5
1
4 S+
SVB ZXCT1020
GND
IOUT
2
3
IOUT
VOUT
RG
(R7 = 15k)
GND
GND
Figure 2 Equivalent circuit diagram for evaluation board ZXCT1020EV1
Operating voltage range: 2.5V to 20V
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ZXCT1020EV1
Evaluation Board
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ORDERING INFORMATION
ORDER NUMBER
ZXCT1020EV1
Please note evaluation boards are subject to availability and qualified leads.
PAD NAMES AND DEFINITIONS
NAME
DESCRIPTION/Usage
V1
V2
VOUT
FLAG
Supply Voltage
Connection to Load
GND
0V / Ground
SL1,SL2
Solder Links
VCC
Device pin S+ (connected to V1 via R4)
Output Voltage
Not used
The target applications are battery chargers, power supply units and other applications
where high side current measurement is a requirement.
The input voltage (voltage on V1) range for the ZXCT1020EV1 is ranges from 2.5V to
20V.
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ZXCT1020EV1 Summary
R3
R1 0.05R
SL1
ILOAD
V1
V2
SL2
R2 0.1R
R4
1.5k
5
1
S4 S+
VB ZXCT1020
IOUT
GND
2
3
VOUT
R7
15k
GND
GND
Figure 3 Actual circuit diagram for ZXCT1020EV1
Sense resistor
The board has been designed with two selectable values of sense resistor. The value
of the sense resistor can be chosen by using the solder links SL1 and SL2.
The board is also tracked for a user defined through hole resistor (R3).
The 50mΩ resistor (R1) is selected by shorting SL1 and opening SL2. This results in an
output of 0.5 V/A.
The 100mΩ resistor (R2) is selected by shorting SL2 and opening SL1, resulting in an
output of 1V/A.
If both links are shorted the effective resistance is 33.33mΩ giving an output of
333.3mV/A.
If both links are open, the optional leaded resistor R3 can be exclusively used as the
sense resistor. The maximum power dissipation rating of the resistor must be
appropriate to the load current level.
For further information on choosing a value of sense resistor please refer to the
ZXCT1020 datasheet.
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Configuration table for ZXCT1020EV1
LOAD
CURRENT
(A)
1.0
1.0
1.0
RSENSE
(mΩ
Ω)
VOUT
(V)
SOLDER LINK
CONFIGURATION
100
50
33.33
1.0
0.5
0.33
Short SL2
Short SL1
Short SL1 & SL2
Configuration for different LOAD currents.
The board can be configured for different load currents by changing the SMD resistors
or fitting a suitable wire ended resistor and opening both solder links. It is important to
ensure an appropriate value of RS is selected to obtain the desired accuracy for a given
output current.
The value of IOUT is the voltage dropped across the sensing resistor divided by RGT.
Choosing a larger value for RS gives a higher output voltage for a given current resulting
in better resolution but at the expense of increased voltage drop and higher dissipation
in RS.
Increasing the value of the gain resistor, R7, also increases the sensitivity but at the
expense of a higher output impedance. The criterion for minimum input voltage still
applies.
The maximum practical value of the gain resistor is limited by the output conductance of
the ZXCT1020 and the output voltage that can be tolerated - in practice the gain
resistance should not be greater than about 40k.
The ZXCT1020 is optimized for values of VSENSE around 100mV.
Accuracy
The ZXCT1020 has a typical 2% accuracy for a VSENSE of 100mV. The accuracy of the
output voltage will be influenced by the tolerance of the external sense used. The
ZXCT1020EV1 utilizes 1% sense resistors.
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COMPONENTS LIST
Ref
Value
Package
Part Number
Manufacturer
Notes
R1
R2
R4
R5,R6
R7
I/O’s
ZXCT
50mΩ
100mΩ
1.5k
0R
15k
2512
2512
0805
Link/0805
0805
Test loops
SOT23-5
LR2512-R050FW
LR2512-R100FW
Welwyn
Welwyn
SMD Sense Resistor 1%
SMD Sense Resistor 1%
100-108
ZXCT1020E5
Hughes
ZETEX
Rapid 17-1835
SET-UP AND TEST
The board is preset to give an output Voltage of 1V for a load current of 1A (SL2 is
shorted to connect in the 100mΩ (R2) sense resistor). To change the board to give an
output Voltage of 1V for a current of 2.0A, de-solder SL2 and short SL1. This connects
the 50mΩ (R1) sense resistor.
Required Equipment
1.
2.
3.
1 x 10R 5W resistor (load).
1 x adjustable bench PSU.
2 x DVMs (one for voltage measurement and one for current measurement)
500mA load test
1. Ensure SL2 is shorted.
2. Connect a resistor in series with the ammeter between the V2 and GND terminals (10R 5W resistor is suggested, if using a different value, make sure it’s power rating
is P ≥ 2*I2*R).
3. Set ammeter to a suitable range for measuring up to 500mA or 600mA.
4. Set the current limit of PSU1 to 600mA, and set the voltage to 0V.
5. Connect PSU1 to V1.
6. Switch on PSU1 and increase the voltage until the ammeter reads 500mA ± 2mA
7. Measure VOUT with a DVM. The output voltage should read 0.5V ± 25mV.
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ZXCT1020EV1
VCC
FLAG
VOUT
DVM
V1
10R 5W
V2
A
PSU1
GND
GND
Figure 4 Test diagram for ZXCT1020EV1
EVALUATION BOARD
CURRENT MONITOR
EVALUATION BOARD
www.zetex.com
Vcc
FLAG
ZXCT
R4 C1
R5
V1
R7 R8
Vout
R6
R1
SL1
R2
SL2
V2
R3
SL3
GND
GND
Refer to 'User Guide'
for details.
Bare board: ZDB341R2
Copyright Zetex PLC 2006
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ZXCT1020EV1
Evaluation Board
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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
All products are sold subjects to Zetex’ terms and conditions of sale, and this disclaimer (save in the event of a conflict between the two 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.
Quality of product
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 regionally
authorized distributors. For a complete listing of authorized distributors please visit: www.zetex.com/salesnetwork
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”
“Active”
“Last time buy (LTB)”
“Not recommended for new designs”
“Obsolete”
Datasheet status key:
“Draft version”
“Provisional version”
“Issue”
Future device intended for production at some point. Samples may be available
Product status recommended for new designs
Device will be discontinued and last time buy period and delivery is in effect
Device is still in production to support existing designs and production
Production has been discontinued
This term denotes a very early datasheet version and contains highly provisional
information, which may change in any manner without notice.
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.
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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© 2006 Published by Zetex Semiconductors plc.
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