Zetex ZXCT1041 EV1 User manual

ZXCT1041 EV1
Zdb341R2. 26-Feb-07 1/8 ZXCT1041 EV1 User Guide Rev2
ZXCT1041EV1 EVALUATION BOARD USER GUIDE
DESCRIPTION
The ZXCT1041EV1 is intended for the evaluation of the
ZXCT1041 device. The ZXCT1041 is a high side bi-
directional 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, R
sense
.
The voltage output is scaled by the choice of R
sense
. As
delivered the board is set up to provide an out put of 1.5V
from a current of 1.5A using a 100 mΩsampling resistor.
There is a second 25 mΩresistor 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
APPLICATIONS
•Battery Charging
•Power Supplies
•Over Current Monitoring

ZXCT1041 EV1
Zdb341R2. 26-Feb-07 2/8 ZXCT1041 EV1 User Guide Rev2
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
V2
Supply Voltage
Or
Connection to Load/Battery
VOUT
Output Voltage
FLAG
Flag Output
Indicates direction of current flow
GND
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.

ZXCT1041 EV1
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Figure 1 Schematic Diagram of ZXCT1041EV1
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 100mΩresistor (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 25mΩresistor (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 is20mΩgiving 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
ΩΩ
Ωresistor.
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.

ZXCT1041 EV1
Zdb341R2. 26-Feb-07 4/8 ZXCT1041 EV1 User Guide Rev2
Configuration table for ZXCT1041EV1
LOAD CURRENT
(A) R
sense
(mΩ
ΩΩ
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 30kΩresistor 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 R
sense
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 R
sense
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 R
sense
. 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 V
sense
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. V
out
= 10 x V
sense
To obtain a 500mV output, 50mV is required between V
sense+
and V
sense-.
The value for R
sense
is thus 50mV /1.5A = 33mΩ.
Accuracy
The ZXCT1041 current monitor IC is a 2%
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 Manufacturer Notes
R1 100mΩ1206 LR1206-R10FI
Welwyn SMD Sense Resistor 1%
R2 25mΩ2512 LRF2512-R025FW
Welwyn SMD Sense Resistor 1%
R3 30kΩ0805
Generic
SMD 1% 0.125W
ZXCT SOT235 ZXCT1041E5 ZETEX

ZXCT1041 EV1
Zdb341R2. 26-Feb-07 5/8 ZXCT1041 EV1 User Guide Rev2
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
ΩΩ
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
ΩΩ
Ω(R2) sense resistor.
1.0 Ampere load test (forward current flow)
1. Ensure SL1 is shorted.
2. Connect a linear power supply of +15V between the V1 and GND terminals.
3. 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.
4. Check with a DVM the supply voltage is +15V between the V1 and GND terminals.
5. Measure VOUT with a DVM. The nominal output voltage should read 1.5V.
6. Measure the FLAG pin with a DVM, it should be High, approximately V1 15Vin this case.
1.0 Ampere load test (reverse current flow)
1. Ensure SL1 is shorted.
2. Connect a linear power supply of +15V between the V2 and GND terminals.
3. 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.
4. Check with a DVM the supply voltage is +15V between the V2 and GND terminals.
5. Measure VOUT with a DVM. The nominal output voltage should read 1.5V.
7. 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
R
sense.
As the device reacts only to the voltage across this resistor such tests are equally valid.

ZXCT1041 EV1
Zdb341R2. 26-Feb-07 6/8 ZXCT1041 EV1 User Guide Rev2
CONNECTION DIAGRAM
Forward Current flow
PSU
DVM
GND
V1 V2
VOUT
GND
LOAD
ZXCT1041EV1
FLAG
10Ω
DVM
CURRENT MONITOR
EVALUATIONBOARD
CONNECTION DIAGRAM……continued
Reverse Current flow
PSU
DVM
GND
V1 V2
VOUT
GND
LOAD
ZXCT1041EV1
FLAG
10Ω
DVM
CURRENT MONITOR
EVALUATION BOARD

ZXCT1041 EV1
Zdb341R2. 26-Feb-07 7/8 ZXCT1041 EV1 User Guide Rev2
EVALUATION BOARD
CURRENT MONITOR
EVALUATION BOARD
Vcc
GNDGND
Vout
FLAG
SL1
SL2
R1
R2
SL3
ZXCT
R3
V1 V2
R5
Refer to'User Guide'
for details.
Bare board: ZDB341R2 Copyright Zetex PLC 2006
R4 C1 R7
www.zetex.com
R6
R8
Top Silk Top Copper

ZXCT1041 EV1
Zdb341R2. 26-Feb-07 8/8 ZXCT1041 EV1 User Guide Rev2
Definitions
Product change
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Customers are solely responsible for obtaining the latest relevant information before placing orders.
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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
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applications, under any circumstances.
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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
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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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