19-0241; Rev 0; 3/94 MAX761 Evaluation Kit ____________________Component List DESIGNATION QTY ____________________________Features ♦ 2V to 12V Input Range for 12V Output ♦ 85% Efficiency for 4mA to 200mA Loads ♦ 1µA Shutdown Supply Current ♦ Small External Components ♦ Low-Battery Detector ♦ Current-Limited PFM Control Scheme ♦ Fully Assembled and Tested DESCRIPTION U1 1 MAX761CSA C1, C2 2 22µF, 16V, low-ESR tantalum capacitor Sprague 595D226X0016C2B C3, C5 2 0.1µF ceramic capacitor PART L1 1 18µH, 0.8A inductor (SMT) Sumida CD43-180 D1 1 1N5817 Schottky diode (SMT) Nihon EC10QS02L Motorola MBRS120LT3 R1, R2, R3, R4, R5, R6 0 Resistors (not supplied) Capacitor (not supplied) C4 0 JU3 1 3-pin header None 1 Shunt None 1 MAX761 data sheet ______________Ordering Information MAX761EVKIT-SO TEMP. RANGE PIN-PACKAGE 0°C to +70°C Surface Mount ______________________________EV Kit ______________Component Suppliers SUPPLIER PHONE FAX Capacitors AVX (207) 282-5111 Matsuo (714) 969-2491 (207) 283-1941 (714) 960-6492 Murata Erie (814) 237-1431 (800) 831-9172 (814) 238-0490 Sprague (603) 224-1961 (603) 224-1430 Coilcraft (708) 639-6400 (708) 639-1469 Coiltronics (407) 241-7876 (407) 241-9339 Sumida (708) 956-0666 (708) 956-0702 Central (516) 435-1110 Semiconductor (516) 435-1824 Motorola (602) 244-3576 (602) 244-4015 Nihon (805) 867-2555 (805) 867-2556 Inductors Diodes ________________________________________________________________ Maxim Integrated Products Call toll free 1-800-998-8800 for free samples or literature. 1 MAX761 EV Kit _______________General Description The MAX761 evaluation kit (EV kit) provides a 12V output for programming flash memories and powering other circuitry. From 5V inputs, it provides better than 85% efficiency for 4mA to 200mA loads. Quiescent supply current is only 300µA from a 5V input, and drops to 1µA in logic-controlled shutdown. The MAX761 comes in an 8-pin SO package and uses tiny external components; the entire circuit fits into less than 0.3in2. __________________________________________Typical Operating Characteristics (MAX761 EV kit, TA = +25°C, unless otherwise noted.) EFFICIENCY vs. OUTPUT CURRENT VIN = 3V 70 VIN = 2V 60 1.75 50 40 30 20 BOOTSTRAPPED (INTERNAL RESISTORS) VOUT = 12V 1.50 1.25 1.00 0.75 0.50 0.25 10 0 0.1 1 10 100 0 OUTPUT CURRENT (mA) 300 BOOTSTRAPPED 250 200 150 100 50 2 3 4 5 6 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 INPUT VOLTAGE (V) _________________________Quick Start 12V A 5V 4V B 0V 1ms/div ILOAD = 100mA, VIN = 5V A: VOUT, 2V/div B: SHDN, 2V/div (0V to 4V) 1 INPUT VOLTAGE (V) SHDN RESPONSE TIME 350 0 0 1000 MAXIMUM OUTPUT CURRENT (mA) 80 400 2.00 VIN = 5V BOOTSTRAPPED VOUT = 12V QUIESCENT CURRENT (mA) 90 MAXIMUM OUTPUT CURRENT vs. INPUT VOLTAGE QUIESCENT CURRENT vs. INPUT VOLTAGE 100 EFFICIENCY (%) MAX761 EV Kit MAX761 Evaluation Kit The MAX761 EV kit is fully assembled and tested. Follow these steps to verify board operation. Do not turn on the power supply until all connections are completed. 1) Connect a 5V power supply to the pad marked VIN. Connect ground to the GND pad. 2) Connect a voltmeter and load (if any) to the VOUT pad. 3) For normal operation, place the shunt across pins 1 and 2 on the JU3 jumper. 4) Turn on the power supply and verify that the output voltage is 12V. 5) Instructions for modifying the board for different output voltages are in the Output Voltage Adjustment section. _______________Detailed Description Bootstrapped Mode The MAX761 EV kit is configured for bootstrapped mode. In bootstrapped mode, the MAX761 is powered from the output voltage, which increases efficiency at lower input voltages and requires fewer components. Refer to the Bootstrapped/Non-Bootstrapped Mode section of the MAX761 data sheet for further details. For an adjustable output in bootstrapped mode, refer to the Output Voltage Adjustment section. 2 _______________________________________________________________________________________ MAX761 Evaluation Kit LBI voltage falls below VREF. Resistors R3 and R4 form a voltage divider between the LBI pad and the MAX761 LBI pin. Refer to the Low-Battery Detector section of the MAX761 data sheet for instructions on selecting values for R3 and R4. Note that the printed circuit board trace across R3 shorts the LBI pin to ground when this function is not used. Cut this trace before installing R3. Install a 100kΩ pull-up resistor between VIN (R5) or VOUT (R6) if LBO is used. LBO is disabled in shutdown mode. Table 1. Jumper JU3 Functions SHUNT LOCATION SHDN PIN Output Voltage Adjustment MAX761 OUTPUT 1&2 Connected to GND MAX761 Enabled VOUT = 12V 2&3 Connected to VIN Shutdown Mode VOUT = VIN - 0.3V To adjust the output voltage, add output voltage divider resistors R1 and R2 to either bootstrapped or non-bootstrapped configurations. Refer to the Setting the Output Voltage section of the MAX761 data sheet for instructions on selecting values for R1 and R2. When using output voltage divider resistors, disconnect the MAX761 feedback pin (FB) from ground by cutting the thin PC board trace between the pads of JU1. Some users may want to install a small (100pF to 200pF) capacitor (C4), to increase light-load efficiency. Low-Battery Indicator The MAX761 provides a low-battery comparator that compares the voltage on LBI to the 1.5V reference voltage. LBO, an open-drain output, goes low when the 1 R6 OPEN JU3 2 3 R5 OPEN SHDN 4 VIN 2V to 12V C1 22µF L1 16V 18µH SHDN LX 7 V+ D1 1N5817 VOUT 12V U1 1 LB0 LBO R4 OPEN 8 V+ LBI FB REF GND 5 C3 0.1µF JU2 R2 OPEN 3 2 LB1 R3 0Ω (SHORT) MAX761 6 C5 0.1µF JU1 C4 OPEN C2 22µF 16V R1 OPEN Figure 1. MAX761 EV Kit Schematic Diagram _______________________________________________________________________________________ 3 MAX761 EV Kit Shutdown Control The MAX761 provides a SHDN pin to disable the output. Table 1 lists the options available for the shutdown control jumper, JU3. To use an external control signal, remove the shunt on JU3 completely and connect the external signal to the pad labeled SHDN. SHDN is a TTL/CMOS-logic-level input. MAX761 EV Kit MAX761 Evaluation Kit Figure 2. MAX761 EV Kit Component Placement Guide— Component Side Figure 3. MAX761 EV Kit Component Placement Guide— Solder Side Figure 4. MAX761 EV Kit PC Board Layout—Component Side Figure 5. MAX761 EV Kit PC Board Layout—Solder Side Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 4 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1994 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.