_______________general description the max761 evaluation kit (ev kit) provides a 12v out- put 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 300? from a 5v input, and drops to 1? 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 0.3in 2 . ____________________component list ____________________________features ? 2v to 12v input range for 12v output ? 85% efficiency for 4ma to 200ma loads ? 1? shutdown supply current ? small external components ? low-battery detector ? current-limited pfm control scheme ? fully assembled and tested ______________ordering information 22?, 16v, low-esr tantalum capacitor sprague 595d226x0016c2b 2 c1, c2 max761 ev kit max761 evaluation kit ________________________________________________________________ maxim integrated products 1 ______________________________ev kit call toll free 1-800-998-8800 for free samples or literature. 19-0241; rev 0; 3/94 part temp. range MAX761EVKIT-so 0? to +70? surface mount pin-package designation qty description u1 1 max761csa c3, c5 2 0.1? ceramic capacitor l1 1 18?, 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) c4 0 capacitor (not supplied) ju3 1 3-pin header none 1 shunt none 1 max761 data sheet supplier phone fax capacitors avx (207) 282-5111 (207) 283-1941 matsuo (714) 969-2491 (714) 960-6492 murata erie (814) 237-1431 (800) 831-9172 (814) 238-0490 sprague (603) 224-1961 (603) 224-1430 inductors coilcraft (708) 639-6400 (708) 639-1469 coiltronics (407) 241-7876 (407) 241-9339 sumida (708) 956-0666 (708) 956-0702 diodes central semiconductor (516) 435-1110 (516) 435-1824 ______________component suppliers nihon (805) 867-2555 (805) 867-2556 motorola (602) 244-3576 (602) 244-4015
max761 ev kit max761 evaluation kit 2 _______________________________________________________________________________________ __________________________________________typical operating characteristics (max761 ev kit, t a = +25?, unless otherwise noted.) 0.1 10 1000 efficiency vs. output current output current (ma) efficiency (%) 1 100 0 10 20 30 40 50 60 70 80 90 100 bootstrapped
v out = 12v v in = 5v v in = 2v v in = 3v 0 0 quiescent current vs. input voltage input voltage (v) quiescent current (ma)
1
2
3
4
5
6 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 bootstrapped
(internal resistors)
v out = 12v 0 maximum output current vs.
input voltage input voltage (v) maximum output current (ma) 50 100 150 200 250 300 350 400 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 bootstrapped 1ms/div shdn response time
12v 5v
4v 0v a b i load = 100ma, v in = 5v
a: v out, 2v/div
b: shdn, 2v/div (0v to 4v) _________________________quick start 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 out- put 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 sec- tion of the max761 data sheet for further details. for an adjustable output in bootstrapped mode, refer to the output voltage adjustment section.
shutdown control the max761 provides a shdn pin to disable the out- put. 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. table 1. jumper ju3 functions low-battery indicator the max761 provides a low-battery comparator that compares the voltage on lbi to the 1.5v reference volt- age. lbo, an open-drain output, goes low when the lbi voltage falls below v ref . 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 val- ues 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 100k pull-up resistor between vin (r5) or vout (r6) if lbo is used. lbo is disabled in shutdown mode. output voltage adjustment to adjust the output voltage, add output voltage divider resistors r1 and r2 to either bootstrapped or non-boot- strapped 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. max761 ev kit max761 evaluation kit _______________________________________________________________________________________ 3 shunt location shdn pin max761 output 1 & 2 connected to gnd max761 enabled v out = 12v 2 & 3 connected to v in shutdown mode v out = v in - 0.3v
4 1 2 5 7 8 3 6 shdn lbo u1 lbi ref lx v+ fb gnd c5
0.1? ju1 r1
open ju2 r2
open c4
open c2
22?
16v v out
12v v+ v in
2v to 12v shdn c1
22?
16v
d1
1n5817 c3
0.1? r3
0 w
(short) r4
open ju3 1 2 3 r5
open r6
open lb0 lb1 l1
18? max761 figure 1. max761 ev kit schematic diagram
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. max761 ev kit max761 evaluation 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?omponent side figure 5. max761 ev kit pc board layout?older side
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