mp2128 2.5v-6v input, 3mhz, 1a synchronous step -down converter mp2128 rev. 0.9 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 mp2128 is a 3mhz constant frequency, current mode, pwm step-down converter with integrated main switch and synchronous rectifier that is ideal for powering portable equipment that runs from a single li-ion or li- polymer battery. the mp2128 can supply up to 1a load current from a 2.5v to 6v input voltage. the output voltage can be as low as 0.6v. additional features include <1a shutdown current, internal soft-start, cycle-by-cycle over current protection, short circuit protection, and thermal shutdown. the mp2128 is available in low profile (1.5mm) 5-pin sot23 and 8-pin, qfn8 2mm2mm packages. features ? high efficiency: up to 95% ? 3mhz constant switching frequency ? 1a available load current ? 2.5v to 6v input voltage range ? output voltage as low as 0.6v ? current mode control ? cycle-by-cycle over current protection ? short circuit protection ? thermal shutdown ? <1a shutdown current ? internal soft-start ? space saving 5-pin sot23 package and ? 8-pin, qfn8 2mm2mm package applications ? cellular phones ? microprocessors and dsp core supplies ? pdas and smart phones ? mp3 and portable media 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 off on en in vin sw sw nc fb pgnd agnd u1 vout 1.8v 1a 2.5v--6v 3 8 7 6 5 1 4 2 r1 200k 1% r2 100k 1% mp2128dg
mp2128 ? 3mhz, 1a synchrono us step-down converter mp2128 rev. 0.9 www.monolithicpower.com 2 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. ordering information part number* package top marking temperature MP2128DT sot23 2h ?40 c to +85 c part number** package top marking temperature mp2128dg qfn8(2mmx2mm) 2h ?40 c to +85 c * for tape & reel, add suffix ?z (eg. MP2128DT?z). for rohs compliant packaging, add suffix ?lf (eg. MP2128DT?lf?z) ** for tape & reel, add suffix ?z (eg. mp2128dg?z). for rohs compliant packaging, add suffix ?lf (eg. mp2128dg?lf?z) package reference marking top view en gnd sw 1 2 3 5 4 fb in top view fb agnd pgnd in en nc sw sw 18 27 3 4 6 5 sot23 qfn8 absolute maxi mum ratings (1) in to gnd .................................. ? 0.3v to +6.5v sw to gnd .......................... ? 0.3v to v in + 0.3v fb, en to gnd ............................. ? 0.3v to +6.5v continuous power dissipation. (t a = +25c) (2) sot23 ..................................................... 0.57w qfn8 (2mmx2mm) .................................... 2.5w junction temperature ...............................150c lead temperature ....................................260c storage temperature............... ? 65c to +150c recommended operating conditions (3) supply voltage v in .............................2.5v to 6v output voltage v out ...........................0.6v to 6v operating temperature.............. ? 40c to +85c thermal resistance (4) ja jc sot23 ................................... 220 .... 110.. c/w qfn8 (2mmx2mm) ................. 50 ...... 12... 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 continuous power dissipation at any ambient temperature is calculated by p d (max) = (t j (max)-t a )/ ja . exceeding the maximum allowable powe r 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 pcb.
mp2128 ? 3mhz, 1a synchrono us step-down converter mp2128 rev. 0.9 www.monolithicpower.com 3 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. electrical characteristics (5) v in = v en = 3.6v, t a = +25 c, unless otherwise noted. parameters condition min typ max units supply current v en = v in , v fb = 0.65v 350 a shutdown current v en = 0v, v in = 6v 0.01 1 a in under voltage lockout threshold rising edge 1.8 2.1 2.3 v in under voltage lockout hysteresis 250 mv t a = +25c 0.582 0.594 0.606 v regulated fb voltage ?40c t a +85c 0.576 0.594 0.612 v fb input bias current v fb = 0.65v -50 50 na pfet current limit duty=100% 1.5 a pfet on-resistance i sw = 100ma 200 m ? nfet on-resistance i sw = ?100ma 150 m ? sw leakage current v en = 0v; v in = 6v v sw = 0v or 6v ?1 1 a en high threshold ?40c t a +85c 1.6 v en low threshold ?40c t a +85c 0.4 v internal soft-start time 100 s oscillator frequency 2.4 2.8 3.2 mhz thermal shutdown threshold hysteresis=20c 150 c note: 5) production test at +25c. specific ations over the temperature range ar e guaranteed by design and characterization.
mp2128 ? 3mhz, 1a synchrono us step-down converter mp2128 rev. 0.9 www.monolithicpower.com 4 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. typical performanc e characteristics v in =6v, v out =1.8v, l=1.2h, c2=10f, t a =25c, unless otherwise noted. v en 5v/div. v out 1v/div. v sw 5v/div. i inductor 1a/div. v en 5v/div. v out 1v/div. v sw 5v/div. i inductor 1a/div. v en 5v/div. v out 1v/div. v sw 5v/div. i inductor 1a/div. v out /ac 20mv/div. v sw 5v/div. i inductor 1a/div. v out /ac 20mv/div. v sw 5v/div. i inductor 1a/div. 200ns/div. 200ns/div. 2s/div. load transient load step: 100ma-400ma, v in =4.2v, v out =3.4v efficiency vs. load current efficiency (%) load current ( ma ) steady state operation i out =0a start-up through enable i out =0a start-up through enable i out =1a power-down through enable i out =0a v en 5v/div. v out 1v/div. v sw 5v/div. i inductor 1a/div. 1ms/div. power-down through enable i out =1a steady state operation i out =1a 70 75 80 85 90 95 0 100 200 300 400 500 600 700 800 9001000 4.2v to 3.4v 3.3v to 1.8v 5v to 3.4v v out /ac 100mv/div. i load 200ma/div. i inductor 200ma/div. v out /ac 50mv/div. i inductor 500ma/div.
mp2128 ? 3mhz, 1a synchrono us step-down converter mp2128 rev. 0.9 www.monolithicpower.com 5 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. pin functions sot23 pin # qfn pin # name description 1 8 en regulator enable control input. drive en above 1.6v to turn on the part. drive en below 0.4v to turn it off. 2 2,4 gnd ground. 3 5,6 sw power switch output. inductor connection to drains of the internal pfet and nfet switches. 4 3 in supply input. bypass to gnd with a 4.7 f or bigger value ceramic capacitor. 5 1 fb feedback input. connect fb to the center point of the external resistor divider. the regulated feedback voltage is 0.6v. functional block diagram figure 1? functional block diagram
mp2128 ? 3mhz, 1a synchrono us step-down converter mp2128 rev. 0.9 www.monolithicpower.com 6 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. functional description mp2128 is a 3mhz constant frequency, current mode, pwm step-down converter. the device integrates both a main switch and a synchronous rectifier, which provides high efficiency and eliminates an external schottky diode. it is ideal for powering portable equipment that runs from a single li-lon or li-polymer battery. the mp2128 can achieve 100% duty cycle. the duty cycle d of a step-down converter is defined as: out on osc in v dt f 100% 100% v = where, ton: main switch on time fosc: switching frequency (3mhz) vout: output voltage vin: input voltage peak 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 mp2128 switches at a constant frequency (3mhz) 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 the next cycle starts. dropout operation the mp2128 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 mp2128 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 mp2128 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 inductor current as a function of the duty cycle to prevent sub-harmonic oscillations at duty cycles greater than 50%. conversely the current limit increases as the duty cycle decreases.
mp2128 ? 3mhz, 1a synchrono us step-down converter mp2128 rev. 0.9 www.monolithicpower.com 7 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. package information sot23 0.30 0.50 seating plane 0.95 bsc 0.90 1.30 1.45 max 0.00 0.15 top view front view side view recommended land pattern 2.80 3.00 1.50 1.70 2.60 3.00 1 3 4 5 0.09 0.20 note: 1) all dimensions are in millimeters. 2) package length does not include mold flash, protrusion or gate burr. 3) package width does not include interlead flash or protrusion. 4) lead coplanarity (bottom of leads after forming) shall be 0.10 millimeters max. 5) drawing conforms to jedec mo-178, variation aa. 6) drawing is not to scale. 0.30 0.55 0 o -8 o 0.25 bsc gauge plane 2.60 typ 1.20 typ 0.95 bsc 0.60 typ see detail "a" detail a
mp2128 ? 3mhz, 1a synchrono us 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. mp2128 rev. 0.9 www.monolithicpower.com 8 7/20/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. qfn8 (2mmx2mm) 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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