ZXCT1041EV1 User Guide issue 2

ZXCT1041 EV1
ZXCT1041EV1 EVALUATION BOARD USER GUIDE
DESCRIPTION
The ZXCT1041EV1 is intended for the evaluation of the
ZXCT1041 device. The ZXCT1041 is a high side bidirectional current monitor providing a fixed voltage gain
of 10.
The device produces a voltage output proportional to the
current sampled by a small inline sensing resistor, Rsense.
The voltage output is scaled by the choice of Rsense. As
delivered the board is set up to provide an out put of 1.5V
from a current of 1.5A using a 100 mΩ sampling resistor.
There is a second 25 mΩ resistor that can be selected
by means of a solder link and provides an output of
1.5V for a load current of 6A.
Additionally provision is made for a wire ended
sampling resistor of the users choice. An open
collector flag output indicates the direction of current
flow.
The printed circuit board is common to other devices in
the ZXCT family, for the ZXCT1041, the Vcc pin is not
used.
FEATURES
•
Supply Range 4.2 to 20V for 1.5V output.
•
Selectable current measurement range
•
5 Pin SOT23-5 package
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APPLICATIONS
•
Battery Charging
•
Power Supplies
•
Over Current Monitoring
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ZXCT1041 EV1 User Guide Rev2
ZXCT1041 EV1
ORDERING INFORMATION
ORDER NUMBER
ZXCT1041EV1
Please note evaluation boards are subject to availability and qualified leads.
PAD NAMES AND DEFINITIONS
.
NAME
DESCRIPTION
V1
Supply Voltage
Or
Connection to Load/Battery
Supply Voltage
Or
Connection to Load/Battery
V2
VOUT
Output Voltage
FLAG
GND
Flag Output
Indicates direction of current flow
0V / Ground
SL1,SL2
Solder Links
Vcc
Not used
Figure 1: ZXLD1350EV2 evaluation board
The ZXCT1041EV1 is configured as shown in figure 1; SL1 is shorted to output 1.5V for a 1.5A current flow. The
target applications are battery chargers, power supply units and other applications where bi-directional current
measurement is a requirement.
The input voltage range for the ZXCT1041EV1 is 20V down to a minimum of (2.7V +Vout). Eg if the required full scale
output voltage is 1.5 V the input range is 4.2V to 20V.
Note that the Flag output requires a pull-up resistor.
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ZXCT1041 EV1 User Guide Rev2
ZXCT1041 EV1
Figure 1 Schematic Diagram of ZXCT1041EV1
Sense resistor
The board has been designed with two selectable values of sense resistor.
chosen by using the solder links SL1 and SL2.
The value of the sense resistor can be
The board is also tracked for a user defined through hole resistor (R3).
The 100mΩ resistor (R1) is selected by shorting SL1 and opening SL2. This results in an output of 1.5V for a load
current of 1.5A (assuming that R3 is not fitted).
The 25mΩ resistor (R2) is selected by shorting SL2 and opening SL1, resulting in an output of 1.5A for a load current
of 6A (assuming that R3 is not fitted).
If both links are shorted the effective resistance is20mΩ giving an output of 1.5V for a current of 7.5A (assuming
that R3 is not fitted).
If both links are open only the optional leaded resistor R3 (if fitted ) is in circuit.
The maximum power dissipation rating of the resistor must be appropriate to the load current level.
N.B. The board is set by default with SL1 shorted and SL2 open, using the 100mΩ
Ω resistor.
For further information on choosing a value of sense resistor please refer to the ZXCT1041 datasheet .
Vout
If the preset selectable values of sense resistor are chosen, the device will output 1.5V for a 1.5A load current and
1.25V for a 5.0A load current. The output is directly proportional to the differential voltage across the sense pins of
the device. The ZXCT1041 will output the same voltage for current flow in either direction, but the level of the Flag
output will change.
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ZXCT1041 EV1 User Guide Rev2
ZXCT1041 EV1
Configuration table for ZXCT1041EV1
LOAD CURRENT
(A)
Rsense
(mΩ
Ω)
VOUT
(V)
SOLDER LINK
CONFIGURATION
1.5
100
1.5
Short SL1
6.0
25
1.5
Short SL2
7.5
20
1.5
Short SL1 & SL2
FLAG
The direction of current flow can be determined from the flag output pin. The flag output of the device is an open
collector output. On board the ZXCT1041EV1 is a 30kΩ resistor which is connected to V1, it may be connected to a
lower voltage eg 3V3 if that is appropriate in the application.
If current is flowing from V1 to V2, the FLAG pin will be High, at the same potential as V1 or the supply connected to
the collector resistor on the Flag output.
If current is flowing in the reverse direction, i.e. from V2 to V1, the FLAG pin will be Low, typically 60mV.
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 Rsense is selected to obtain the
desired accuracy for a given output current.
The value of Vout is 10 times the voltage dropped across the sensing resistor, (providing that the input Voltage is
more than 2.7V higher than the Vout.)
Choosing a larger value for Rsense 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 Rsense. It also reduces the minimum voltage at which
the device will be linear as Vout +2.7V is the minimum input voltage for accurate results.
The ZXCT1041 is optimized for values of Vsense of either polarity between 0 and 800mV.
Example: Scaling for 1.5A load current and a 500mV output.
The ZXCT1041 has a fixed gain of 10. Vout = 10 x Vsense
To obtain a 500mV output, 50mV is required between Vsense+ and Vsense-.
The value for Rsense is thus 50mV /1.5A = 33mΩ.
Accuracy
2
The ZXCT1041 current monitor IC is a 2% accurate device. The accuracy of the output voltage will be influenced by
the tolerance of the external sense used. The ZXCT1041EV1 utilizes 1% accurate sense resistors.
2
Total error at +100mV sense voltage
COMPONENTS LIST
Ref
Value
Package
Part Number
R1
100mΩ
1206
LR1206-R10FI
R2
25mΩ
2512
LRF2512-R025FW
R3
30kΩ
0805
ZXCT
SOT235
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ZXCT1041E5
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Manufacturer
Welwyn
Welwyn
Generic
Notes
SMD Sense Resistor 1%
SMD Sense Resistor 1%
SMD 1% 0.125W
ZETEX
ZXCT1041 EV1 User Guide Rev2
ZXCT1041 EV1
SET-UP AND TEST
The board is preset to give an output |Voltage of 1.5V for a load current of 1.5A (SL1 is shorted to connect in
the 100mΩ
Ω (R1) sense resistor). To change the board to give an output Voltage of 1.5V for a current of 6.0A,
de-solder SL1 and short SL2. This connects the 25mΩ
Ω (R2) sense resistor.
1.0 Ampere load test
1.
2.
3.
4.
5.
6.
Ensure SL1 is shorted.
Connect a linear power supply of +15V between the V1 and GND terminals.
Set a load current of 1.5A between the V2 and GND terminals using a suitable load.
The load must be rated for at least 30W.
Check with a DVM the supply voltage is +15V between the V1 and GND terminals.
Measure VOUT with a DVM. The nominal output voltage should read 1.5V.
Measure the FLAG pin with a DVM, it should be High, approximately V1 15Vin this case.
1.0 Ampere load test
1.
2.
3.
4.
5.
7.
(forward current flow)
(reverse current flow)
Ensure SL1 is shorted.
Connect a linear power supply of +15V between the V2 and GND terminals.
Set a load current of 1.5A between the V1 and GND terminals using a suitable load.
The load must be rated for at least 30W.
Check with a DVM the supply voltage is +15V between the V2 and GND terminals.
Measure VOUT with a DVM. The nominal output voltage should read 1.5V.
Measure the FLAG pin with a DVM, it should be logic Low, less than 200mV
The device may also be evaluated with lower power loads and lower currents by increasing the value of
Rsense. As the device reacts only to the voltage across this resistor such tests are equally valid.
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ZXCT1041 EV1 User Guide Rev2
ZXCT1041 EV1
CONNECTION DIAGRAM
Forward Current flow
CURRENT MONITOR
EVALUATION BOARD
ZXCT1041EV1
FLAG
VOUT
V2
LOAD
V1
PSU
GND
GND
10 Ω
DVM
DVM
CONNECTION DIAGRAM……continued
Reverse Current flow
CURRENT MONITOR
EVALUATION BOARD
ZXCT1041EV1
FLAG
10 Ω
LOAD
VOUT
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V1
V2
PSU
GND
DVM
DVM
GND
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ZXCT1041 EV1 User Guide Rev2
ZXCT1041 EV1
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
Top Silk
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Top Copper
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ZXCT1041 EV1 User Guide Rev2
ZXCT1041 EV1
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 labeling 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”
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.
“Provisional version”
“Issue”
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© 2006 Published by Zetex Semiconductors plc.
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ZXCT1041 EV1 User Guide Rev2