ZXCT1012 EV1 ZXCT1012EV1 EVALUATION BOARD USER GUIDE DESCRIPTION The ZXCT1012EV1 is intended for the evaluation of the ZXCT1012 device. The ZXCT1012 is a high side current monitor providing a fixed transconductance gain of 10mS (mA/V). The device produces a current output proportional to the current sampled by a small inline sensing resistor, Rsense. The voltage output is scaled by the choice of Rsense and the load resistor R7. As delivered the board is set up to provide an out put of 1.5V from a current of 300mA using a 200 mΩ sampling resistor and a 2.49k load resistor. FEATURES • Supply Range 4.2 to 20V for 1.5V output. • Selectable current measurement range • 5 Pin SOT23-5 package Zdb341R2. 08-May-07 There is a second (50mΩ) resistor that can be selected by means of a solder link and provides an output of 1.5V for a load current of 1.2A. 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 ZXCT1012, neither the FLAG pin nor the Vcc pin is used. APPLICATIONS • Battery Charging • Power Supplies • Over Current Monitoring 1/6 ZXCT1012 EV1 User Guide Rev2 ZXCT1012 EV1 ORDERING INFORMATION ORDER NUMBER ZXCT1012EV1 Please note evaluation boards are subject to availability and qualified leads. PAD NAMES AND DEFINITIONS . NAME DESCRIPTION V1 Supply Voltage V2 Connection to Load VOUT Output Voltage FLAG Not used GND 0V / Ground SL1,SL2 Solder Links Vcc Not used The ZXCT1012EV1 is configured as shown in figure 1; SL1 is shorted to output 1.5V for a 300mA current flow. The target applications are battery chargers, power supply units and other applications where current measurement is a requirement. The input voltage range for the ZXCT1012EV1 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. Zdb341R2. 08-May-07 2/6 ZXCT1012 EV1 User Guide Rev2 ZXCT1012 EV1 ZXCT1012EV1 Schematic R3 SL1 R1 200m R2 V1 SL2 V2 50m Vsense+ Vsense- ZXCT1012 Vout GND Vout R7 2.49k GND 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 200mΩ resistor (R1) is selected by shorting SL1 and opening SL2. This results in an output of 1.5V for a load current of 300mA (assuming that R3 is not fitted). The 50mΩ resistor (R2) is selected by shorting SL2 and opening SL1, resulting in an output of 1.5V for a load current of 1.2A (assuming that R3 is not fitted). If both links are shorted the effective resistance is 40mΩ giving an output of 1.5V for a current of 1.5A (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 200mΩ Ω resistor. For further information on choosing a value of sense resistor please refer to the ZXCT1012 datasheet . Vout If the preset selectable values of sense resistor are chosen, the device will produce 0.6mA for a 300mA load current or 0.6mA for a 3.0A load current, depending on which link is closed. The current output is directly proportional to the differential voltage across the sense pins of the device. The output Voltage is then proportional to the value of the load resistor R7. As supplied R7 = 2.49K giving 1.5V for a current of 0.6mA. Zdb341R2. 08-May-07 3/6 ZXCT1012 EV1 User Guide Rev2 ZXCT1012 EV1 Configuration table for ZXCT1012EV1 LOAD CURRENT (A) Rsense (mΩ Ω) VOUT (V) SOLDER LINK CONFIGURATION 0.3 200 1.5 Short SL1 1.2 50 1.5 Short SL2 1.5 40 1.5 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 Rsense is selected to obtain the desired accuracy for a given output current. The value of Iout is 10 µ A times the voltage dropped across the sensing resistor in mV , (providing that the voltage on V1 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. Increasing the value of the load resistor R7 also increases the sensitivity but at the expense of larger output impedance. The criterion for minimum input voltage still applies. The maximum practical value of R7 is limited by the output conductance of the ZXCT1012 and the output voltage that can be tolerated - in practice R7 should not be greater than about 5k. The ZXCT1012 is optimized for values of Vsense between 1mV and 150mV but may be used up to 800mV. Example: Scaling for 1.5A load current and a 500mV output. The ZXCT1012 has a fixed tranconductance gain of 10mS. Iout = Vsense/100. Using the fitted value of R7 (2.49k) an output current of 200uA would be required to produce 500mV output Voltage. Vsense must then be 200uA *100 = 20mV required between Vsense+ and Vsense-. The value for Rsense is thus 20mV /1.5A = 13mΩ. Accuracy 1 The ZXCT1012 current monitor IC is a 1% accurate device. The accuracy of the output voltage will be influenced by the tolerance of the external sense used. The ZXCT1012EV1 utilizes 1% accurate sense resistors. 1 Total error at +100mV sense voltage COMPONENTS LIST Ref Value Package Part Number Manufacturer R1 200mΩ 1206 LR1206-R20FI R2 50mΩ 2512 LRF2512-R050FW Welwyn Welwyn ZXCT R7 SOT235 0805 ZXCT1012E5 ZETEX 2.49kΩ Zdb341R2. 08-May-07 4/6 Notes SMD Sense Resistor 1% SMD Sense Resistor 1% ZXCT1012 EV1 User Guide Rev2 ZXCT1012 EV1 SET-UP AND TEST The board is preset to give an output Voltage of 2.5V for a load current of 500mA (SL1 is shorted to connect in the 500mΩ Ω (R1) sense resistor). To change the board to give an output Voltage of 2.5V for a current of 2.0A, de-solder SL1 and short SL2. This connects the 50mΩ Ω (R2) sense resistor. 500mA load test 1. 2. 3. 4. 5. Ensure SL1 is shorted. Connect a linear power supply of +10V between the V1 and GND terminals. Set a load current of 500mA between the V2 and GND terminals using a suitable load. The load must be rated for at least 5W . Check with a DVM the supply voltage is +10V between the V1 and GND terminals. Measure VOUT with a DVM. The nominal output voltage should read 2.5V. 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. CONNECTION DIAGRAM 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 Zdb341R2. 08-May-07 Top Copper 5/6 ZXCT1012 EV1 User Guide Rev2 ZXCT1012 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. 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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” Europe Americas Asia Pacific Corporate Headquarters Zetex GmbH Kustermann-park Balanstraße 59 D-81541 München Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 [email protected] Zetex Inc 700 Veterans Memorial Highway Hauppauge, NY 11788 USA Zetex (Asia Ltd) 3701-04 Metroplaza Tower 1 Hing Fong Road, Kwai Fong Hong Kong Zetex Semiconductors plc Zetex Technology Park, Chadderton Oldham, OL9 9LL United Kingdom Telephone: (1) 631 360 2222 Fax: (1) 631 360 8222 [email protected] Telephone: (852) 26100 611 Fax: (852) 24250 494 [email protected] Telephone (44) 161 622 4444 Fax: (44) 161 622 4446 [email protected] © 2006 Published by Zetex Semiconductors plc. Zdb341R2. 08-May-07 6/6 ZXCT1012 EV1 User Guide Rev2