Evaluates: MAX1795/MAX1796/MAX1797 19-1966 Rev 0 2/01 MAX1797 Evaluation Kit General Description Features The MAX1797 evaluation kit (EV kit) is a high-efficiency, Output Disconnects from Input During Shutdown step-up DC-DC converter for portable hand-held Operates Down to 0.7V Input Supply Voltage devices. Unlike typical boost circuits, the MAX1797 out- put is completely disconnected from the input in shut- Adjustable Output Voltage (2V to 5.5V, External down. The EV kit accepts a positive input voltage Divider) between 0.7V and V and converts it to a 3.3V out- OUT Up to 500mA Output Current put for currents up to 500mA. The EV kit provides ultra- low quiescent current and high efficiency for maximum No External Schottky Diode Required battery life. Synchronous Rectification for Improved The MAX1797 EV kit is a fully assembled and tested Efficiency surface-mount printed circuit (PC) board. It can also be used to evaluate other output voltages in the 2V to 5.5V Damping Circuit Reduces EMI range. Additional pads on the board accommodate the 1A (typ) Shutdown Current external feedback resistors for setting different output voltages. Low-Battery Detector (LBI/LBO) 8-Pin MAX Package Surface-Mount Construction Fully Assembled and Tested Component Suppliers SUPPLIER PHONE FAX Ordering Information AVX 803-946-0690 803-626-3123 Sprague 603-224-1961 603-224-1430 PART TEMP. RANGE IC PACKAGE Sumida 847-956-0666 847-956-0702 MAX1797EVKIT 0C to +70C8 MAX Note: To evaluate the MAX1795 or MAX1796, request a free Note: Please indicate that you are using the MAX1797 when sample of the MAX1795EUA or MAX1796EUA along with the contacting these component suppliers MAX1797 EV kit. Component List Quick Start The MAX1797 EV kit is a fully assembled and tested DESIGNATION QTY DESCRIPTION surface-mount board. Follow the steps below to verify 47 F, 16V tantalum capacitors board operation. Do not turn on the power supply C1, C2 2 AVX TPSD476M016R0150 or until all connections are completed: Sprague 593D476X0016D 1) Connect a voltmeter and load (if any) to the V OUT pad. C3 1 0.1 F ceramic capacitor (1206) 2) Verify that the shunt is across JU1 pins 2 and 3. 22 H, 1.2A inductor L1 1 Sumida CDRH6D28-220NC 3) Connect a 2V supply to the pads marked VIN and GND. R1, R2, R4, R5 0 Not installed 4) Turn on the power and verify that the output voltage R3 1 1M 1% resistor (1206) is 3.3V. U1 1 MAX1797EUA (8-pin MAX) 5) See the Output Voltage Selection section to modify JU1 1 3-pin header the board for a different output voltage. None 1 Shunt None 1 MAX1797 PC board None 1 MAX1797EVKIT data sheet None 1 MAX1797 data sheet Maxim Integrated Products 1 For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.MAX1797 Evaluation Kit across R5 shorts the LBI pin to VIN when this function is Detailed Description not used. Cut the trace before installing R5. Refer to the Input Source Low-Battery Detection section of the MAX1797 data The input source for the MAX1797 EV kit must be sheet for instructions on selecting values for R4 and R5. greater than 1.0V for guaranteed startup (0.7V for oper- Output Voltage Selection ation once started), and less than the output voltage. A The MAX1797 is initially set for a 3.3V output by connect- typical input voltage range would be the 2.0V to 3.3V ing the FB pin to OUT, or set to 5V by connecting the FB range of a 2-cell NiCd battery. An input voltage greater pin to GND. However, by adding external resistors R1 than the selected output voltage (but less than 6V) will and R2, the output can be adjustable from 2.0V to 5.5V. not damage the circuit however, the MAX1797 output Cut the trace shorting resistor R1, and install output volt- will nearly equal the input voltage when the device is age-divider resistors R1 and R2. The Selecting the not shutdown. In shutdown, the output is high imped- Output Voltage section of the MAX1797 data sheet gives ance, and the ouput voltage will be 0V if a load is pre- instruction for calculating R1 and R2 values. sent. If OUT is driven by another voltage source, such as a backup battery, when the MAX1797 is shut down, the IC presents no load to the backup source. Table 1. Jumper JU1 Functions Once started, the MAX1797 operates from the regulat- (Shutdown Mode) ed output voltage. This means that the input voltage can fall below the 1.0V minimum guaranteed startup SHUNT MAX1797 SHDN PIN voltage. Typically, the regulated output will be main- LOCATION OUTPUT tained even if the input voltage drops to 0.7V. Connected to VIN, Shutdown mode, Shutdown Jumper Selection 1 and 2 SHDN = high V = 0 OUT The MAX1797 EV kit features a shutdown mode that reduces quiescent current to <1A to preserve battery MAX1797 life. In shutdown, the output of the boost converter goes Connected to GND, 2 and 3 enabled, to high impedance and is fully disconnected from the SHDN = low V = 3.3V OUT input. Using the Low-Battery Detector The MAX1797 has an additional comparator useful for monitoring the input sources voltage level. Resistors R4 and R5 are connected as a voltage-divider between the VIN pad and the MAX1797 LBI pin. Note that a PC trace 2 Evaluates: MAX1795/MAX1796/MAX1797