ZXCT1022EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1022EV1-UG 1.0 25 March 2008 1 of 8 DESCRIPTION The ZXCT1022EV1 evaluation board is intended for the evaluation of the ZXCT1022 device. The ZXCT1022 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 ZXCT1022 provides a fixed gain of 100 for applications where minimal sense voltage is required. 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. The wide input voltage range of 20V down to as low as 2.5V makes it suitable for a range of applications. It requires no additional components thus making it a versatile device with minimal components count. The evaluation board is delivered with the values shown in Figure 1 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 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. FEATURES • High side current sensing • Supply Range 2.5V to 20V. • Fixed gain of 100 • 1% typical accuracy • 5 Pin SOT23-5 package ZDB341R2 APPLICATIONS • Battery Charging • Power Supplies • Over Current Monitoring • Automotive current measurement Doc: Issue: Date: Page: ZXCT1022EV1 Evaluation Board User Guide RS (R1//R2 = 0.05R//0.005R) V1 VSUPPLY ZXCT1022EV1-UG 1.0 25 March 2008 2 of 8 ILOAD V2 5 4 S+ SVCC ZXCT1022 VOUT GND 2 3 VOUT GND GND Figure 1 Equivalent circuit diagram for evaluation board ZXCT1022EV1 Figure 2 Evaluation board components' layout ZDB341R2 ZXCT1022EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1022EV1-UG 1.0 25 March 2008 3 of 8 ORDERING INFORMATION ORDER NUMBER ZXCT1022EV1 Please note evaluation boards are subject to availability and qualified leads. PAD NAMES AND DEFINITIONS NAME DESCRIPTION V1 V2 VOUT FLAG Supply Voltage Connection to Load GND 0V / Ground SL1,SL2 Solder Links VCC Not used 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 ZXCT1022EV1 is from 2.5V to 20V. ZDB341R2 ZXCT1022EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1022EV1-UG 1.0 25 March 2008 4 of 8 ZXCT1022EV1 Summary R3 R1 0.005R SL1 ILOAD V1 V2 SL2 R2 0.05R 5 4 S+ SVCC ZXCT1022 VOUT GND 2 3 VOUT GND GND Figure 3 Actual circuit diagram for ZXCT1022EV1 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 5mΩ resistor (R1) is selected by shorting SL1 and opening SL2. This results in an output of 0.5 V/A. The 50mΩ resistor (R2) is selected by shorting SL2 and opening SL1, resulting in an output of 5V/A. If both links are shorted the effective resistance is 4.54mΩ giving an output of 454 mV/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 ZXCT1022 datasheet. ZDB341R2 ZXCT1022EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1022EV1-UG 1.0 25 March 2008 5 of 8 Configuration table for ZXCT1022EV1 LOAD CURRENT (A) 1.0 1.0 1.0 RSENSE (mΩ Ω) VOUT (V) SOLDER LINK CONFIGURATION 5 50 4.54 0.5 5 0.454 Short SL1 Short SL2 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 VOUT is the voltage dropped across the sensing resistor multiplied by a hundred. 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. The ZXCT1022 is optimized for values of VSENSE between 10mV and 100mV. Accuracy The ZXCT1022 has a typical 3% accuracy for a VSENSE of between 10mV and 100mV. The accuracy of the output voltage will be influenced by the tolerance of the external sense used. The ZXCT1022EV1 utilizes 1% sense resistors. ZDB341R2 ZXCT1022EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1022EV1-UG 1.0 25 March 2008 6 of 8 COMPONENTS LIST Ref R1 R2 R5,R6 ZXCT Value 5mΩ 50mΩ 0R Package Part Number Manufacturer Notes 1206 1206 Link SOT23-5 LR1206-R005FI LR1206-R050FI Welwyn Welwyn SMD Sense Resistor 1% SMD Sense Resistor 1% ZXCT1022E5 ZETEX SET-UP AND TEST The board is preset to give an output Voltage of 5V for a load current of 1A - SL2 is shorted to connect in the 50mΩ (R2) sense resistor. To change the board to give an output Voltage of 0.5V for a current of 1.0A, de-solder SL2 and short SL1. This connects the 5mΩ (R1) sense resistor. Required Equipment 1. 2. 3. 1 x 10R 5W resistor (load). 1 x adjustable bench PSU’s. 2 x DVM’s (one for voltage measurement and one for current measurement) 500mA load test 1. Ensure SL2 is shorted. 2. Connect the bench power supply, PSU1, between the V1 and GND terminals. 3. Connect a resistor in series with an ammeter set to 1A or 2A range between the V2 and GND terminals - 10R 5W suggested. If using a different value, make sure its power rating is P ≥ 2(I2*R). Make sure PSU1 is set to zero volts to start with. 4. Switch on PSU1 and adjust until the ammeter reads 500 mA ±2 mA, 5. Measure VOUT with a DVM. The output voltage should read 2.5V ± 0.1 V. ZDB341R2 Doc: Issue: Date: Page: ZXCT1022EV1 Evaluation Board User Guide ZXCT1022EV1 VCC FLAG VOUT DVM V1 10R 5W V2 A PSU2 GND GND Figure 4 Test diagram for ZXCT1022EV1 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 Top Copper ZXCT1022EV1-UG 1.0 25 March 2008 7 of 8 ZXCT1022EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1022EV1-UG 1.0 25 March 2008 8 of 8 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. 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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. 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