MAX1678EVKIT Analog Devices

Evaluates: MAX1678 19-1381 Rev 0 7/98 MAX1678 Evaluation Kit General Description Features The MAX1678 evaluation kit (EV kit) provides a regulated 0.87V to V Input Range OUT 3.3V output while operating on input voltages as low as Synchronous RectifiedNo External Diode 0.7V with guaranteed start-up at 0.87V. The input source Required can be a 1 or 2-cell battery or a DC supply. Efficiency is typically 90% with output loads up to 100mA. 3.3V Output Voltage (or Adjustable) The kit uses surface-mount components and is fully 100mA Output assembled and tested for quick evaluation. Jumpers are provided for selecting an adjustable output voltage 90% Efficiency and for shutdown control. 2A Shutdown Current Small Surface-Mount Components Inductor Damping Switch Suppresses EMI Component List DESIGNATION QTY DESCRIPTION 10F, 10V ceramic capacitor Ordering Information C1, C2 2 Taiyo Yuden LMK325BJ106MN, TDK C3225X5R1A106M PART TEMP. RANGE IC PACKAGE MAX1678EVKIT 47H, 240mA power inductor 0C to +70C 8 MAX Coilcraft DS1608C-473 L1 1 Sumida CD43-470 Murata LQH4N470K Quick Start J1 1 3-pin jumper The MAX1678 EV kit is shipped fully assembled and J2 1 2-pin jumper tested. Follow these steps to verify board operation. Do R1, R4 2 1M, 1% resistors not turn on the power supply until all connections R2, R3 2 Open are completed. R5 1 100k , 5% resistor 1) Verify that the shunts are positioned on the jumpers U1 1 MAX1678EUA as listed in Table 2 for a 3.3V output. None 2 Shunts 2) Connect a +0.87V to +3.3V supply voltage to the None 1 MAX1678 EV kit PC board VIN pad. Connect ground to the GND pad. Note: once started, the input voltage may drop as low as None 1 MAX1678 data sheet 0.7V if the output current is less than 10mA. 3) Connect a voltmeter and the load (if any) to the VOUT pad. 4) Turn on the power and verify that the output voltage is +3.3V. Component Suppliers SUPPLIER PHONE FAX Coilcraft 847-639-6400 847-639-1469 Coiltronics 561-241-7876 561-241-9339 Murata 814-237-1431 814-238-0490 Sumida 847-956-0666 847-956-0702 Taiyo Yuden 408-573-4150 408-573-4159 TDK 847-390-4373 847-390-4428 Maxim Integrated Products 1 For free samples & the latest literature: MAX1678 Evaluation Kit Component Selection Detailed Description The final circuit performance is determined by the quality Jumper Selections of the components surrounding the MAX1678. The input Two jumpers on the PC board allow selection of several and output capacitors must have low equivalent-series- configurations. Table 1 lists the jumper functions. Table resistance (ESR) to handle the high peak currents found 2 lists the jumper positions when setting the board for in switching regulators. Low ESR is especially critical in 3.3V operation. low-voltage circuits to reduce the output ripple. Ceramic capacitors are supplied on the MAX1678 EV kit because of their small size and low ESR in the value range need- ed for the circuit. Table 1. Jumper Functions JUMPER SHUNT POSITION PIN CONNECTION MAX1678 OPERATION J1 1 & 2 SHDN connected to BATT The MAX1678 is enabled. J1 2 & 3 The MAX1678 is disabled. SHDN connected to GND SHDN must be driven by a signal connected to the J1 Open SHDN not controlled by the board SHDN pad. J2 Shorted FB pin connected to GND VOUT is preset to 3.3V. A resistor must be installed in R3 to set the output volt- J2 Open FB pin connected to the resistor-divider age. See the MAX1678 data sheet for more information. Table 2. Jumper Positions for Normal 3.3V Operation JUMPER SHUNT POSITION PIN CONNECTION MAX1678 OPERATION J1 1 & 2 The MAX1678 is enabled. SHDN pin connected to BATT J2 Shorted FB pin connected to GND VOUT is preset to 3.3V. L1 47H 1 7 BATT BATT LX C1 10F 1 J1 2 4 8 SHDN SHDN OUT OUT 3 U1 C2 10F R1 R3 1M OPEN MAX1678 1% R5 100k 2 5 PFI FB GND R4 R2 J2 1M OPEN 1% 6 3 GND GND PFO PFO Figure 1. MAX1678 EV Kit Schematic 2 Evaluates: MAX1678