ev28119eg-00a low-voltage 600ma synchronous buck step-down converter ev28119eg-00a rev. 1.0 www.monolithicpower.com 1 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. the future of analog ic technology description the ev28119 evaluation board is designed for low dropout step down converter applications. it implements the mp28119 1.7mhz fixed frequency, current-mode, pwm step-down converter. the device integrates a main switch and a synchronous rectifier for high efficiency without an external schottky diode. it is ideal for powering portable equipment that runs from a single cell lithium-ion (li+) battery. it can supply 600ma of load current from a 2.5v to 6v input voltage. the output voltage can be regulated as low as 0.6v. in 100% duty cycle dropout operation, it works with minimum input voltage as low as output voltage. it can output voltage as low as 1v from 6v input due to its very small minimum on-time. furthermore, with the output discharge function, even at no load, the output voltage falls quickly when disabled. electrical specifications parameter symbol value units input voltage range v in 2.5 ? 6.0 v output voltage v out 1 v load max i out 600 ma features ? high efficiency: up to 89% ? 600ma available load current ? 2.5v to 6v input voltage range ? output voltage as low as 0.6v ? short circuit protection ? thermal fault protection ? programmable enable control ? output discharge applications ? cellular and smart phones ? microprocessors/dsp core supplies ? pdas ? mp3 players ? digital still and video cameras ? portable instruments ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. ev28119eg-00a evaluation board dimensions (2.5?x x 2.5?y x 0.5?z) board number mps ic number ev28119eg-00a MP28119EG efficiency vs. load current v out =1v, l=2.2uh efficiency (%) load current(ma) 0 10 20 30 40 50 60 70 80 90 100 10 100 1000 vin=5v vin=3.3v
ev28119eg-00a ? 600ma synchronous buck step-down converter ev28119eg-00a rev. 1.0 www.monolithicpower.com 2 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. evaluation board schematic gnd vin vout en gnd u1 6,8 4 7 5 1 out sw mp28119 en in ev28119eg-00a bill of materials qty ref value description package manufacturer manufacturer p/n 1 c1 4.7uf ceramic cap., 10v, x5r sm0805 tdk c2012x5r1a475k 1 c2 10uf ceramic cap., 6.3v, x5r sm0805 kyocera cm21x5r106k06at 3 c3,c4, c5 do not stuff 1 l1 2.2uh 1.63a smd toko d52lc-#a914byw-2r2m 1 r1 300k ? film res., 1% sm0603 yageo rc0603fr-07300kl 1 r2 450k ? film res., 1% sm0603 yageo rc0603fr-07450kl 1 r3 100k ? film res., 1% sm0603 yageo rc0603fr-07100kl 1 u1 dc-dc converter qfn8 mps MP28119EG
ev28119eg-00a ? 600ma synchronous buck step-down converter ev28119eg-00a rev. 1.0 www.monolithicpower.com 3 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. printed circuit board layout figure 1?top silk layer figure 2?top layer figure 3?bottom layer
ev28119eg-00a ? 600ma synchronous buck step-down converter notice: the information in this document is subject to change wi thout notice. please contact m ps for current specifications. users should warrant and guarantee that third party intellectual property rights ar e not infringed upon when integrating mps products into any application. mps will not assume any legal responsibility for any said applications. ev28119eg-00a rev. 1.0 www.monolithicpower.com 4 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. quick start guide (MP28119EG, adjustable output) the board layout accommodates most commonly used inductors and output capacitors. 1. attach the positive and negative ends of the load to the vout and gnd pins, respectively. 2. attach the input voltage (2.5v v in 6v) and input ground to the vin and gnd pins, respectively. 3. to enable the mp28119 apply a voltage, 1.5v v en 6v, to the en pin. to disable the mp28119 apply a voltage, v en < 0.3v, to the en pin. a 100k ? resistor can be set in r3 to connect the en pin to the in pin, so the part will operate without applying any external voltage to the en pin. 4. the output voltage v out can be changed by varying r2. calculate the new value by formula: 1 v v 1 r 2 r fb out ? ? ? ? ? ? ? ? ? = where v fb = 0.6v and r1 = 300k ? . example: for v out = 1.0v: ? ? k 450 1 v 6 . 0 v 0 . 1 k 300 2 r = ? ? ? ? ? ? ? = therefore, use a 450k ? standard 1% value. quick start guide ( MP28119EG-1.0, MP28119EG- 1.2, fixed output) for modifying the ev28119eg-00a to accommodate a fixed output voltage version of the mp28119: 1. verify that a fixed output version of the mp28119 chip is on the evaluation board. refer to mp28119 datasheet for fixed voltage package codes. 2. remove both r1 and r2. 3. short r1 while leaving r2 open. 4. attach the positive and negative ends of the load to the vout and gnd pins, respectively. 5. attach the input voltage (2.5v v in 6v) and input ground to the vin and gnd pins, respectively. 6. to enable the mp28119 apply a voltage, 1.5v v en 6v, to the en pin. to disable the mp28119 apply a voltage, v en < 0.3v, to the en pin. a 100k ? resistor can be set in r3 to connect the en pin to the in pin, so the part will operate without applying any external voltage to the en pin.
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