ZXCT1050EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1050EV1-UG 1.1 29 February 2008 1 of 8 DESCRIPTION The ZXCT1050EV1 evaluation board is intended for the evaluation of the ZXCT1050 device. The ZXCT1050 is a wide input common mode range current monitor. Because this wide input common mode range includes ground, the device is able to measure short circuit currents. 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 inline sensing resistor, RS. The voltage output is scaled by the choice of RS (R1, R2 on the evaluation board), RGT (R6 on the evaluation board) and the load resistor (R7 // R8 on the evaluation board). 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 • VCC range 2.7V to 20V • Supply Range 0V to VCC – 2V. • Selectable current measurement range • 5 Pin SOT23-5 package ZDB341R2 APPLICATIONS • Battery Charging • Power Supplies • Over Current Monitoring • Low/High side current monitoring ZXCT1050EV1 Evaluation Board User Guide RS V1 VSUPPLY (R1//R2 = 0.05R//0.1R) Doc: Issue: Date: Page: ZXCT1050EV1-UG 1.1 29 February 2008 2 of 8 ILOAD V2 RGT (R6 = 7.5k) 5 4 VCC S1 S+ VCC ZXCT1050 GND IOUT 2 3 IOUT VOUT RG (R7//R8 = 7.5k // 7.5k) GND GND Figure 1 Equivalent circuit diagram for evaluation board ZXCT1050EV1 ZXCT1050EV1 Figure 2 Evaluation board components' layout ZDB341R2 ZXCT1050EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1050EV1-UG 1.1 29 February 2008 3 of 8 ORDERING INFORMATION ORDER NUMBER ZXCT1050EV1 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 Device supply Output Voltage Not used The target applications are battery chargers, power supply units and other applications where high side current measurement is a requirement along with ability to measure down to 0V. The input voltage (voltage on V1) range for the ZXCT1050EV1 is from zero up to VCC 2 volts. VCC, ranges from 2.7V to 20V. ZDB341R2 Doc: Issue: Date: Page: ZXCT1050EV1 Evaluation Board User Guide ZXCT1050EV1-UG 1.1 29 February 2008 4 of 8 ZXCT1050EV1 Summary R3 R1 0.05R SL1 ILOAD V1 V2 SL2 R2 0.1R R6 7.5k 5 4 VCC S1 S+ VCC ZXCT1050 GND IOUT 2 3 VOUT R7 7.5k GND R8 7.5k GND Figure 3 Actual circuit diagram for ZXCT1050EV1 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 ZXCT1050 datasheet. ZDB341R2 ZXCT1050EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1050EV1-UG 1.1 29 February 2008 5 of 8 Configuration table for ZXCT1050EV1 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//R8, 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 ZXCT1050 and the output voltage that can be tolerated - in practice the gain resistance should not be greater than about 40k. The ZXCT1050 is optimized for values of VSENSE between 10mV and 300mV. Accuracy The ZXCT1050 has a typical 1% accuracy for a VSENSE of 30mV. The accuracy of the output voltage will be influenced by the tolerance of the external sense used. The ZXCT1050EV1 utilizes 1% sense resistors. ZDB341R2 ZXCT1050EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1050EV1-UG 1.1 29 February 2008 6 of 8 COMPONENTS LIST Ref Value Package Part Number Manufacturer Notes R1 R2 R5 R6 R7, R8 ZXCT 50mΩ 100mΩ 0R 7.5k 7.5k 2512 1206 Link 0805 0805 SOT23-5 LR1206-R050FI LRF2512-R100FW Welwyn Welwyn SMD Sense Resistor 1% SMD Sense Resistor 1% ZXCT1050E5 ZETEX 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). 2 x adjustable bench PSU’s. 2 x DVM’s (one for voltage measurement and one for current measurement) 500mA load test 1. 2. 3. 4. Ensure SL2 is shorted. Power VCC at 15V ±0.2V with a linear bench supply, PSU1. Connect another linear power supply, PSU2, between the V1 and GND terminals. 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 PSU2 is set to zero volts to start with. 5. Switch on PSU1, followed by PSU2. 6. Adjust PSU2 until the ammeter reads 500 mA ±2 mA, 7. Measure VOUT with a DVM. The output voltage should read 0.5V ± 25mV. ZDB341R2 Doc: Issue: Date: Page: ZXCT1050EV1 Evaluation Board User Guide ZXCT1050EV1-UG 1.1 29 February 2008 7 of 8 ZXCT1050EV1 VCC FLAG VOUT DVM V1 10R 5W V2 A PSU1 PSU2 GND GND Figure 4 Test diagram for ZXCT1050EV1 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 ZXCT1050EV1 Evaluation Board User Guide Doc: Issue: Date: Page: ZXCT1050EV1-UG 1.1 29 February 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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