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mp28119 ultra-small 1.7mhz, 600ma, low-voltage synchronous step-down converter mp28119 rev.0.9 www.monolithicpower.com 1 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. the future of analog ic technology description the mp28119 is a 1.7mhz constant frequency, current mode, ultra-small pwm step-down converter. the device integrates a main switch and a synchronous rectifier for high efficiency and eliminates the need for an external schottky diode. it is ideal for powering portable equipment that runs from a single cell lithium- ion (li+) battery. the mp28119 can supply 600ma of load current from a 2.5v to 6v input voltage. the mp28119 offers fixed 1.0v and 1.2v output option and adjustable output option. the mp28119 can run at 100% duty cycle for low dropout applications, and includes an output discharge function to control the discharging of the output capacitor. the mp28119 is available in an ultra-small 2x2 qfn package. features ? high efficiency: up to 89% ? 1.7mhz constant switching frequency ? 600ma available load current ? 2.5v to 6v input voltage range ? 100% duty cycle in dropout ? current mode control ? short circuit protection ? thermal fault protection ? output discharge function ? <0.1a shutdown current ? 1.0v and 1.2v fixed out-put versions ? ultra-small 2x2 qfn package applications ? cellular and smart phones ? microprocessors and 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. typical application MP28119EG-1.0 sw 1 5 6,8 4 7 out en gnd in output off on 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
mp28119 ? ultra-small 1.7mhz, 600ma low-vo ltage synchronous step-down converter mp28119 rev.0.9 www.monolithicpower.com 2 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. ordering information part number v out package temperature top marking MP28119EG-1.0 1.0v 2x2 qfn8 -20c to +85c 9k MP28119EG-1.2* 1.2v contact factory for availability MP28119EG* adj contact factory for availability * contact factory for availability. ** MP28119EG-1.0 is fixed to 1v output, and MP28119EG-1.2 is fixed to 1.2v output. for rohs compliant packaging, add suffix - lf (e.g. MP28119EG-lf); for tape and reel, add suffix -z (e.g. MP28119EG-lf-z). package reference top view sw nc nc en 1 2 3 4 gnd in gnd fb 8 7 6 5 exposed pad on backside connect to gnd top view sw nc nc en 1 2 3 4 gnd in gnd out 8 7 6 5 exposed pad on backside connect to gnd external fb qfn8 (2mm x 2mm) fixed output qfn8 (2mm x 2mm) absolute maxi mum ratings (1) v in to gnd .................................. ?0.3v to +6.5v v sw to gnd ........................... ?0.3v to v in +0.3v v fb , v en to gnd .......................... ?0.3v to +6.5v junction temperature ............................ +150 c continuous power dissipation (t a = +25c) (2) ............................................................. 1.6w lead temperature ................................. +260 c storage temperature ............. ?65 c to +150 c recommended operating conditions (3) supply voltage v in ............................. 2.5v to 6v output voltage v out ........................... 0.6v to 6v operating temperature............. ?20 c to +85 c thermal resistance (4) ja jc 2x2 qfn8 ................................ 80 ...... 16 ... c/w notes: 1) exceeding these ratings may damage the device. 2) the maximum allowable power dissipation is a function of the maximum junction temperature. t j (max) the junction-to- ambient thermal resistance ja and the ambient temperature t a . the maximum allowable power dissipation at any ambient temperature is calculated using: p d (max)=(t j (max)-t a )/ ja . exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. internal thermal shutdown circuitry protects the device from permanent damage. 3) the device is not guaranteed to function outside of its operating conditions. 4) measured on jesd51-7 4-layer board.
mp28119 ? ultra-small 1.7mhz, 600ma low-vo ltage synchronous step-down converter mp28119 rev.0.9 www.monolithicpower.com 3 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. electrical characteristics (5) (continued) v in = v en = 3.6v, t a = +25 c, unless otherwise noted. parameter symbol condition min typ max units supply current v en = v in , v fb = 0.51v 400 600 a shutdown current v en = 0v, v in = 6v 0.01 1 a in under voltage lockout threshold uvlo rising edge 2.15 2.3 2.45 v in under voltage lockout hysteresis 80 mv discharge mosfet on resistance 100 regulated fb voltage v fb t a = +25c, MP28119EG 0.588 0.600 0.612 v ?20c t a +85c 0.582 0.600 0.618 fb input bias current v fb = 0.65v, MP28119EG ?50 0.5 +50 na regulated output voltage MP28119EG-1.0 i out = 50ma;?20c t a +85c 0.970 1.000 1.030 v MP28119EG-1.2 i out = 50ma;?20c t a +85c 1.164 1.200 1.236 pfet on resistance r ds(on)1 i sw = 100ma 0.42 ? nfet on resistance r ds(on)2 i sw = ?100ma 0.28 ? sw leakage current v en = 0v,v in = 6v, v sw = 0v or 6v ?1 +1 a pfet current limit duty cycle = 100%, current pulse width < 1ms 1 1.7 2.4 a oscillator frequency f ocs 1.7 mhz minimum on time t on 100 ns thermal shutdown trip threshold 145 c en turn-ontrip threshold ?20c t a +85c 1.5 v en turn-off trip threshold ?20c t a +85c 0.3 v en input current v en = 0v to 6v ?1 +1 a notes: 5) 100% production test at +25c. typical and temperature s pecifications are guaranteed by design and characterization.
mp28119 ? ultra-small 1.7mhz, 600ma low-vo ltage synchronous step-down converter mp28119 rev.0.9 www.monolithicpower.com 4 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. pin functions pin # name description 1 sw power switch output. inductor connection to drains of the internal pfet and nfet switches. 2, 3 nc no connection 4 en regulator enable control input. drive en above 1.5v to turn on the mp28119. drive en below 0.3v to turn it off (shutdown current < 0.1a). 5 fb feedback input (MP28119EG). connect fb to the center point of the external resistor divider. the feedback threshold voltage is 0.6v. out output voltage sense input (MP28119EG-1.0 and MP28119EG-1.2). an internal resistor divider is connected to this pin to set the proper output voltage. 6, 8 gnd, exposed pad ground. connect exposed pad to gnd plane for optimal thermal performance. 7 in supply input. bypass to gnd with a 2.2f or greater ceramic capacitor.
mp28119 ? ultra-small 1.7mhz, 600ma low-vo ltage synchronous step-down converter mp28119 rev.0.9 www.monolithicpower.com 5 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics v in =5v, v out =1v, l1=2.2uh, c1=4.7uf, c2=10uf, t a =25 o c, tested on MP28119EG-1.0, unless otherwise noted. supply voltage(v) oscillator frequency vs. supply voltage i out =300ma 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2 2.5 3 3.5 4 4.5 5 5.5 6 oscillator frequency(mhz) output voltage vs. load current v in =5v load current(ma) output voltage(v) 0.996 0.9965 0.997 0.9975 0.998 0.9985 0.999 0 100 200 300 400 500 600 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 output voltage vs. supply voltage i out =300ma output voltage(v) supply voltage(v) 0.997 0.9972 0.9974 0.9976 0.9978 0.998 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 pfet current limit vs. temperature 1 1.2 1.4 1.6 1.8 2 2.2 2.4 -50 -30 -10 10 30 50 70 90 110130 temperature ( c) pfet current limit(a)
mp28119 ? ultra-small 1.7mhz, 600ma low-vo ltage synchronous step-down converter mp28119 rev.0.9 www.monolithicpower.com 6 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics (continued) v in =5v, v out =1v, l1=2.2uh, c1=4.7uf, c2=10uf, t a =25 o c, tested on MP28119EG-1.0, unless otherwise noted. enable off v in = 5v, v out = 1v, i out = 0ma enable off v in = 2.5v, v out = 1v, i out = 0ma enable on v in =5v, v out =1v, i out =600ma load transient v in =5v, i out =0ma->600ma step v out =1v heavy load operation v in =5v, v out =1v, i out =600ma v sw 5v/div v out 10mv/div v sw 5v/div v out 10mv/div v out 20mv/div light load operation v in =5v, v out =1v, i out =0a 200ns/div 1ms/div 1ms/div 200ns/div enable on v in =2.5v, v out =1v, i out =600ma v out 1v/div v en 5v/div v sw 5v/div v out 1v/div v en 5v/div v sw 5v/div v out 1v/div v en 5v/div v sw 5v/div v out 1v/div v en 5v/div v sw 5v/div 10 10 short circuit protection v in =5v, i out =0ma v sw 5v/div v out 1v/div v out 1v/div v sw 5v/div short circuit recovery v in =5v, i out =0ma
mp28119 ? ultra-small 1.7mhz, 600ma low-vo ltage synchronous step-down converter mp28119 rev.0.9 www.monolithicpower.com 7 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation the mp28119 is a constant frequency current mode pwm step-down converter. the mp28119 is optimized for low voltage, li-ion battery powered applications where high efficiency and small size are critical. the mp28119 uses an external resistor divider to set the output voltage from 0.6v to 6v. the device integrates both a main switch and synchronous rectifier, which provides high efficiency and eliminates an external schottky diode. the mp28119 can achieve 100% duty cycle. the duty cycle d of a step-down converter is defined as: % 100 v v % 100 f t d in out osc on = where t on is the main switch on time, f osc is the oscillator frequency (1.7mhz), v out is the output voltage and v in is the input voltage. m=1 m=2500 0.4 sws r sws output discharge pgs figure 1?functional block diagram (MP28119EG)
mp28119 ? ultra-small 1.7mhz, 600ma low-vo ltage synchronous step-down converter mp28119 rev.0.9 www.monolithicpower.com 8 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. 0.4 m=2500 sws r sws out output discharge pgs 300k 450k figure 2?functional block diagram (MP28119EG-1.0) current mode pwm control slope compensated current mode pwm control provides stable switching and cycle-by-cycle current limit for superior load and line response and protection of the internal main switch and synchronous rectifier. the mp28119 switches at a constant frequency (1.7mhz) and regulates the output voltage. during each cycle the pwm comparator modulates the power transferred to the load by changing the inductor peak current based on the feedback error voltage. during normal operation, the main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. when the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the next cycle starts. dropout operation the mp28119 allows the main switch to remain on for more than one switching cycle and increases the duty cycle while the input voltage is dropping close to the output voltage. when the duty cycle reaches 100%, the main switch is held on continuously to deliver current to the output up to the pfet current limit. the output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. short circuit protection the mp28119 has short circuit protection. when the output is shorted to ground, the oscillator frequency is reduced to prevent the inductor current from increasing beyond the pfet current limit. the pfet current limit is also reduced to lower the short circuit current. the frequency and current limit will return to the normal values once the short circuit condition is removed and the feedback voltage reaches 0.6v. maximum load current the mp28119 can operate down to 2.5v input voltage, however the maximum load current decreases at lower input due to large ir drop on the main switch and synchronous rectifier. the slope compensation signal reduces the peak
mp28119 ? ultra-small 1.7mhz, 600ma low-vo ltage synchronous step-down converter mp28119 rev.0.9 www.monolithicpower.com 9 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. inductor current as a function of the duty cycle to prevent sub-harmonic oscill ations at duty cycles greater than 50%. conversely the current limit increases as the duty cycle decreases. output discharge function when the device is disabled, the part goes into output discharge mode automatically and its internal discharge mosfet provides a resistive discharge path for the output capacitor. this function is only suitable for discharge output capacitor for the limited time. if the part is used in a pre-bias application, the external power supply providing the pre-bias should supply larger current than the discharge mosfet sinks. application information output voltage setting (MP28119EG) the external resistor divider sets the output voltage (see figure 3). the feedback resistor r1 also sets the feedback loop bandwidth with the internal compensation capacitor (see figure 1). choose r1 around 300k ? for optimal transient response. r2 is then given by: 1 v 6 . 0 v 1 r 2 r out ? = table 1?resistor selection vs. output voltage setting v out r1 r2 1.2v 300k ? (1%) 300k ? (1%) 1.5v 300k ? (1%) 200k ? (1%) 1.8v 300k ? (1%) 150k ? (1%) 2.5v 300k ? (1%) 95.3k ? (1%) for the fixed output versions (MP28119EG-1.0 and MP28119EG-1.2), r1 is shorted and r2 is open. input capacitor selection the input capacitor reduces the surge current drawn from the input and switching noise from the device. the input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passing to the input. ceramic capacitors with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. for most applications, a 4.7f capacitor is sufficient. inductor selection a 1h to 10h inductor with dc current rating at least 25% higher than the maximum load current is recommended for most applications. for best efficiency, the inductor dc resistance shall be <200m ? . for most designs, the inductance value can be derived from the following equation: () osc l in out in out f i v v v v l ? ? = where ? i l is the inductor ripple current. choose inductor ripple current approximately 30% of the maximum load current, 600ma. the maximum inductor peak current is: 2 i i i l load ) max ( l ? + = under light load conditions below 100ma, larger inductance is recommended for improved efficiency. output capacitor selection the output capacitor keeps output voltage ripple small and ensures regulation loop stable. the output capacitor impedance shall be low at the switching frequency. ceramic capacitors with x5r or x7r dielectrics are recommended. the output ripple ? v out is approximately: ( ) ? ? ? ? ? ? ? ? + ? ? 3 c f 8 1 esr l f v v v v v osc osc in out in out out
mp28119 ? ultra-small 1.7mhz, 600ma low-vo ltage synchronous step-down converter mp28119 rev.0.9 www.monolithicpower.com 10 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. pcb layout guide pcb layout is very important to achieve stable operation. it is highly recommended to duplicate evb layout for optimum performance. if change is necessary, please follow these guidelines and take figure 3 for reference. 1) keep the path of switching current short and minimize the loop area formed by input cap, high-side mosfet and low-side mosfet. 2) bypass ceramic capacitors are suggested to be put close to the vin pin. 3) place the external feedback resistors as close to the fb pin as possible. 4) route sw away from sensitive analog areas such as fb. 5) connect in, sw, and especially gnd respectively to a large copper area to cool the chip to improve thermal performance and long- term reliability. mp28119 sw 1 5 6,8 4 7 fb en gnd in output input 2.5v - 6v c2 c1 l1 r1 r2 mp28119 typical application circuit top layer bottom layer figure 3?mp28119 typical application circuit and pcb layout guide
mp28119 ? ultra-small 1.7mhz, 600ma low-vo ltage synchronous step-down converter notice: the information in this document is subject to change wi thout notice. users should warra nt and guarantee that third party intellectual property rights are not infringed upon w hen integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mp28119 rev. 0.9 www.monolithicpower.com 11 4/4/2011 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. package information 2mm x 2mm qfn8 top view 1 8 54 bottom view 1.90 2.10 0.45 0.65 1.90 2.10 1.05 1.25 0.50 bsc 0.18 0.30 pin 1 id marking 0.60 0.50 0.25 recommended land pattern 1.90 note: 1) all dimensions are in millimeters. 2) exposed paddle size does not include mold flash. 3) lead coplanarity shall be 0.10 millimeter max. 4) drawing conforms to jedec mo-229, variation vccd-3. 5) drawing is not to scale. pin 1 id see detail a 0.70 pin 1 id option a r0.20 typ. pin 1 id option b r0.20 typ. detail a 0.25 0.45 pin 1 id index area side view 0.00 0.05 0.80 1.00 0.20 ref 1.20

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