Evaluates: MAX668/MAX669 19-4778 Rev 0a 8/98 MAX668 Evaluation Kit General Description Features The MAX668 evaluation kit (EV kit) combines a con- +3V to V Input Range (as shipped) OUT stant-frequency, pulse-width-modulation (PWM) step- +12V or Adjustable Output Voltage up controller with an external N-channel MOSFET and Output Current Up to 1A Schottky diode to provide a regulated output voltage. The EV kit accepts a +3V to V input and converts it OUT N-Channel External MOSFET to a +12V output for currents up to 1A, with greater than 4A IC Shutdown Current 90% conversion efficiency. The EV kit operates at 500kHz, allowing the use of small external components. 500kHz Switching Frequency The MAX668 EV kit is a fully assembled and tested sur- Surface-Mount Components face-mount circuit board. This EV kit can also be con- Fully Assembled and Tested figured for the application circuits listed in the EV Kit Application Circuit Capabilities table. For input voltages below 3V and down to 1.8V, replace the MAX668 with a Component List MAX669. The MAX669 must always operate in boot- strapped mode (JU2 shunt across pins 1 and 2). DESIGNATION QTY DESCRIPTION 68F, 20V, low-ESR tantalum cap C1 1 Sprague 593D686X0020E2W or AVX TPSE686M020R0150 Ordering Information 120F, 20V, low-ESR tantalum cap C5 1 Sprague 594D127X0020R2T PART TEMP. RANGE IC PACKAGE C2 1 0.1F ceramic capacitor MAX668EVKIT 0C to +70C 10 MAX C3 1 0.22F ceramic capacitor Note: To evaluate the MAX669, request a MAX669EUB free C4, C8 2 1F ceramic capacitors sample with the MAX668EVKIT. C7 1 220pF ceramic capacitor C6 0 Not installed 3A Schottky diode EV Kit Application Circuit D1 1 Hitachi HRF302A or Motorola MBRS340T3 Capabilities 4.7H power inductor V V I IN(MIN) OUT OUT Sumida CDRH104-4R7 (shielded), L1 1 (V) (V) (A) Coiltronics UP2B-4R7, or Coilcraft DO3316P-472 1.8 12 0.4 N-channel MOSFET 1.8 24 0.1 N1 1 Fairchild FDS6680 or 2.5 12 0.65 International Rectifier IRF7801 3 5 3 0.020, 1%, 1/2W resistor 3 12 1 R1 1 Dale WSL-2010-R020F or 3 36 0.02 IRC LR2010-01-R020F 12 24 0.5 R2 1 218k, 1% resistor Note: Design information for these applications is included. R3 1 24.9k, 1% resistor The shaded row shows EV kit configuration as shipped. R4 1 100k, 1% resistor U1 1 MAX668EUB JU1, JU2 2 3-pin headers JU3 1 2-pin header None 2 Shunts (JU1, JU2) None 1 MAX668/MAX669 PC board None 1 MAX668/MAX669 data sheet Maxim Integrated Products 1 For free samples & the latest literature: MAX668 Evaluation Kit If the minimum input voltage is below +3.0V, use the Component Suppliers MAX669 with V bootstrapped from V (Table 1). In CC OUT SUPPLIER PHONE FAX bootstrapped mode, if V is always less than +5.5V, OUT then LDO may be shorted to V to eliminate the AVX 803-946-0690 803-626-3123 CC dropout voltage of the LDO regulator. This increases the CoilCraft 708-639-6400 708-639-1469 gate drive to the MOSFET, which lowers the MOSFET Coiltronics 561-241-7876 561-241-9339 on-resistance but increases the MAX668 supply current Dale-Vishay 402-564-3131 402-563-6418 due to gate-charge loss. Fairchild 408-721-2181 408-721-1635 If V is greater than +3.0V, the MAX668s V can be IN CC Hitachi 888-777-0384 650-244-7947 powered from V . This will decrease quiescent power IN dissipation, especially when V is large. If V is OUT IN International 310-322-3331 310-322-3332 always less than +5.5V, LDO may be shorted to V to Rectifier CC eliminate the dropout voltage of the LDO regulator. If IRC 512-992-7900 512-992-3377 V is in the range of +3V to +4.5V, then the user may IN Motorola 602-303-5454 602-994-6430 still want to bootstrap from V to increase gate drive OUT Siliconix 408-988-8000 408-970-3950 to the MOSFET at the expense of power dissipation. If V is always greater than +4.5V, the V input should Sprague 603-224-1961 603-224-1430 IN CC always be tied to V , since bootstrapping from V IN OUT Sumida 708-956-0666 708-956-0702 will not increase the gate drive from LDO, but quiescent Vishay/Vitramon 203-268-6261 203-452-5670 power dissipation will rise. Jumpers JU2 and JU3 con- Note: Please indicate that you are using the MAX668 when con- trol the V and LDO inputs (see MAX668/MAX669 CC tacting these component suppliers. data sheet). Jumper Selection Quick Start The 3-pin header JU1 selects shutdown mode. Table 1 lists the selectable jumper options. The 3-pin header The MAX668 EV kit is fully assembled and tested. Follow JU2 selects bootstrapped mode. Table 2 lists the these steps to verify board operation. Do not turn on selectable jumper options. For V less than 5.5V, use CC the power supply until all connections are completed. the 2-pin header JU3 to short LDO to V . This elimi- CC 1) Place the shunt on JU1 across pins 1 and 2. Verify nates the internal linear regulator (LDO) dropout volt- that the shunt is across JU2 pins 2 and 3 (V is CC age. For the MAX668, this allows operation with input tied to V ) and JU3 is open (LDO is open). IN voltages down to 2.7V. Table 3 lists the selectable 2) Connect a +5V supply to the V pad. Connect jumper options. IN ground to the GND pad. Other Output Voltages 3) Connect a voltmeter to the V pad. OUT The MAX668 EV kit can also be used to evaluate other 4) Turn on the power supply and verify that the output output voltages. Refer to the Output Voltage Selection voltage is 12V. section in the MAX668 data sheet for instructions on selecting the feedback resistors R2 and R3. For output Detailed Description voltages greater than 15V, replace C5 (20V) with a The MAX668 EV kit provides a regulated +12V output capacitor that has a higher voltage rating. voltage from an input source as low as +3V. It drives In addition to the standard EV kit configuration of 3V IN loads up to 1A with greater than 90% conversion effi- to 12V at 1A, the EV Kit Application Circuit OUT ciency. This EV kit is shipped configured in the non- Capabilities table listed several common Input/Output bootstrapped mode (V is tied to V ). However, there CC IN combinations. Table 4 lists the components recom- are several methods of connecting V and LDO CC mended for these alternative circuits. depending on the specific design including input and output voltage range, quiescent power dissipation, MOSFET selection, and load. 2 Evaluates: MAX668/MAX669