Evaluates: MAX9918/MAX9919/MAX9920 19-4552 Rev 0 4/09 MAX9918 Evaluation Kit General Description Features The MAX9918 evaluation kit (EV kit) provides a proven Wide -20V to +75V Input Range Independent of design to evaluate the MAX9918 wide input range, preci- Supply Voltage sion unidirectional/bidirectional, current-sense amplifier Operates Off a Single +5V Supply in an 8-pin SO package. The EV kit features Kelvin con- nections for force and sense at the amplifier inputs and a Unidirectional or Bidirectional Operation very precise current-sense resistor with a tolerance of Lead(Pb)-Free and RoHS Compliant 0.5%. Various test points are included for additional evaluation. Proven PCB Layout The MAX9918 EV kit PCB comes with a MAX9918ASA+ Fully Assembled and Tested installed. Contact the factory for free samples of the pin- compatible MAX9919FASA+, MAX9919NASA+, and MAX9920ASA+ to evaluate these devices. Ordering Information PART TYPE MAX9918EVKIT+ EV Kit +Denotes lead(Pb)-free and RoHS compliant. Component List DESIGNATION QTY DESCRIPTION DESIGNATION QTY DESCRIPTION 0.1F 10%, 16V X7R ceramic R2 1 88.7k 0.1% resistor (0805) C1 1 capacitor (0603) 0.05 0.5%, 0.5W 4-terminal TDK C1608X7R1C104K R3 1 current-sense resistor (1206) 10F 20%, 6.3V X5R ceramic Ohmite LVK12R050DER C2 1 capacitor (0805) TP1TP5 5 Red test points TDK C2012X5R0J106M Precision bidirectional current-sense JU1 1 3-pin header U1 1 amplifier (8 SO) Maxim MAX9918ASA+ JU2 1 2-pin header P1, P2 2 Binding posts 2 Shunts 1 PCB: MAX9918 Evaluation Kit+ R1 1 1k 0.1% resistor (0805) Component Supplier SUPPLIER PHONE WEBSITE TDK Corp. 847-803-6100 www.component.tdk.com Note: Indicate that you are using the MAX9918 when contacting this component supplier. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.MAX9918 Evaluation Kit Additional Evaluation Quick Start 1) Turn off the electronic load, remove the shunt from Required Equipment JU2, and apply +2.5V on REFIN (TP3). This is for MAX9918 EV kit bidirectional operation. +5V, 10mA DC power supply 2) DVM1 should read +2.5V for the no-load case. Set the load to 250mA and observe the output at TP4 +14V, 1A DC power supply with DVM1. The amplified output is added to +2.5V. Electronic load or equivalent resistor load Set the load to -250mA by swapping the cables Two digital voltmeters (DVM1, DVM2) connected to P1 and P2. The output voltage is sub- tracted from +2.5V by the same amount. Procedure The MAX9918 EV kit is fully assembled and tested. Detailed Description of Hardware Follow the steps below to verify board operation: The MAX9918 EV kit provides a proven layout for the 1) Verify that the jumpers are in their default position, MAX9918 current-sense amplifier. The MAX9918 mea- as shown in Table 1. sures the load current and provides an analog output voltage. The full-scale V on the MAX9918 is SENSE 2) Connect the positive terminal of the +5V supply to 50mV, allowing for 1A max load with a 50m current- VCC and the negative terminal to GND. sense resistor. Higher load currents can be accommo- 3) Connect the positive terminal of the +14V supply to dated by adding a current-sense resistor in parallel with P1. Connect P2 into the positive terminal of an elec- R3. Exposed copper is available for adding another tronic load. Connect the negative terminal of the elec- current-sense resistor and vias are also available for a tronic load to the GND terminal on the +14V supply. through-hole resistor. RS+ (TP4) and RS- (TP5) are 4) Connect the positive terminal of DVM1 to OUT Kelvin connected. (TP1) and the negative terminal to the GND pad. Measuring the Load Current 5) Connect the positive terminal of DVM2 to RS+ (TP4) The MAX9918 EV kit comes with a MAX9918ASA+ and the negative terminal to RS- (TP5). installed, which sets the gain externally through resis- 6) Turn on the +5V supply first and then the +14V sup- tors R1 and R2. The current-sense resistor is 50m. ply. The output voltage is dependent on the sense current, current-sense resistor, and gain (eq. 1). For the 7) Set the electronic load to 250mA and turn the elec- MAX9918 EV kit, the current-sense resistor is 50m tronic load on. Observe the output at TP4 with and the gain is 89.7, which is set through resistors R1 DVM1. The output voltage should be approximately and R2 (Table 2). 90 times the voltage read on DVM2. Repeat for load currents of 500mA and 750mA. V=IR A (eq. 1) OUT SENSE SENSE V Table 1. Jumper Table (JU1, JU2) where R is 50m and A is 89.7 for the MAX9918 SENSE V EV kit by default. SHUNT JUMPER DESCRIPTION POSITION Bidirectional Operation The MAX9918 EV kit can be configured for bidirectional 1-2 Connects SHDN to VCC (shutdown) operation by removing the shunt on JU2 and applying JU1 Connects SHDN to GND 2-3* VCC/2 on REFIN (TP3). That sets the bias voltage to (normal operation) VCC/2 for a no-current condition. Current in the positive REFIN is unconnected and can be direction in reference to RS+ and RS- increases the out- Open connected externally to VCC/2 for put voltage from VCC/2 and current in the negative direc- bidirectional operation JU2 tion decreases the output voltage from VCC/2 (eq. 2). Connects REFIN to GND used for Closed* VCC unidirectional operation V=IR A + (eq. 2) () OUT SENSE SENSE V 2 *Default position. 2 Evaluates: MAX9918/MAX9919/MAX9920