MP2012 low voltage, 2.7-6v input,1.5a, 1.2mhz synchronous step -down converter MP2012 rev. 1.01 www.monolithicpower.com 1 9/22/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. the future of analog ic technology description the MP2012 is a fully integrated, internally compensated 1.2mhz fixed frequency pwm step-down converter. it is ideal for powering portable equipment that runs from a single cell lithium-ion (li+) battery, with an input range from 2.7v to 6v. the MP2012 can provide up to 1.5a of load current with output voltage as low as 0.8v. it can also operate at 100% duty cycle for low dropout applications. with peak current mode control and internal compensation, the MP2012 is stable with ceramic capacitors and small inductors. fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. MP2012 is available in a small qfn6 (3x3mm) package. features ? 2.7-6v input operation range ? output adjustable from 0.8v to vin ? 1 a max shutdown current. ? up to 95% efficiency ? 100% duty cycle for low dropout applications ? 1.2mhz fixed switching frequency ? stable with low esr output ceramic capacitors ? thermal shutdown ? cycle-by-cycle over current protection ? short circuit protection ? available in qfn6 (3x3mm) applications ? dvd+/-rw drives ? smart phones ? pdas ? digital cameras ? portable instruments for mps green status, please visit mps website under quality assurance. ?mps? and ?the future of analog ic technology? are trademarks of monolithic power systems, inc. typical application MP2012 pvin vin gnd en sw fb 1 2 3 6 4 5 c1 v in 2.7v to 6v en l1 r1 r2 rt c2 v out 1.8v/1.5a efficiency vs. load current load current(a) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 0 0.3 0.6 0.9 1.2 1.5 vin=5v vin=3v
MP2012 ? 1.5a synchronous step-down converter MP2012 rev. 1.01 www.monolithicpower.com 2 9/22/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. ordering information part number* package top marking free air temperature (t a ) MP2012dq qfn6(3x3mm) 9e ?40 c to +85 c * for tape & reel, add suffix ?z (e.g. MP2012dq?z). for rohs compliant packaging, add suffix ?lf (e.g. MP2012dq?lf?z) package reference top view exposed pad connected to gnd fb gnd sw 1 2 3 en vin pvin 6 5 4 absolute maxi mum ratings (1) pvin, vin to gnd......................?0.3v to + 6.5v sw to gnd .......................... ?0.3v to v in + 0.3v en, fb to gnd ...........................?0.3v to +6.5v operating temperature............. ?40c to +85c continuous power dissipation (t a = +25c) (2) ??????????????????....2.5w junction temperature ...............................150c lead temperature ....................................260c storage temperature ............. ?65c to +150c recommended operating conditions (3) supply voltage v in .............................2.7v to 6v operating junct. temp (t j )..... ?40c to +125c thermal resistance (4) ja jc qfn6 (3x3mm) .......................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.
MP2012 ? 1.5a synchronous step-down converter MP2012 rev. 1.01 www.monolithicpower.com 3 9/22/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 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 = 0.9v 600 750 a shutdown current v en_ = 0v, v in = 6v 0.01 1 a thermal shutdown trip threshol d hysteresis = 20c 150 c en trip threshold -40c t a +85c 0.3 1.0 1.5 v en input current v en = 0v 0.1 1.0 a en input current v en = 6v 6 a in undervoltage lockout thres hold rising edge 2.15 2.40 2.65 v in undervoltage lockout hysteresis 160 mv regulated fb voltage t a = +25c -40c t a +85c 0.784 0.776 0.800 0.800 0.816 0.824 v fb input bias current v fb = 0.8v -50 -2 +50 na sw pfet on resistance i sw = 100ma 0.18 0.25 0.28 ? sw nfet on resistance i sw = -100ma 0.14 0.2 0.24 ? sw leakage current v en =0v; v in =6v v sw_ =0v -1 0.1 1 a sw leakage current v en =0v; v in =6v v sw_ =6v -5 1.5 5 a sw pfet peak current limit duty cycle=100% duty cycle=50% (6) 2.1 3.0 3.5 a switching frequency 1.0 1.2 1.4 mhz notes: 5) production test at +25c. specificat ions over the temperature range are gua ranteed by design and characterization. pin functions pin # name description 1 fb feedback input. a n external resistor divider from the output to gnd, tapped to the fb pin sets the output voltage. 2 gnd, exposed pad ground pin. connect exposed pad to ground plane for proper thermal performance. 3 sw switch node to the inductor. 4 pvin input supply pin for power fet. 5 vin input supply pin for controller. put small decoupling ceramic near this pin. 6 en enable input, ?high? enables MP2012. en is pulled to gnd with 1meg internal resistor.
MP2012 ? 1.5a synchronous step-down converter MP2012 rev. 1.01 www.monolithicpower.com 4 9/22/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics v in = 5v, v out = 1.8v, l=3.3uh, t a = +25oc, unless otherwise noted. load regulation enable supply current vs. input voltage 500 550 600 650 700 750 800 850 2.5 3 3.5 4 4.5 5 5.5 6 v in (v) case temperature risevs. output cur r e nt 0 5 10 15 20 25 30 35 0 0.5 1 1.5 output current (a) duty cycle peak current vs. duty line regulation load regulation load current(a) input voltage (v) line regulation -0.4% -0.3% -0.2% -0.1% 0.0% 0.1% 00.5 11.5 peak current(a) -0.60% -0.40% -0.20% 0.00% 0.20% 0.40% 2 2.5 3 3.5 4 4.5 5 5.5 6 io=0a io=0.75a io=1.5a vin=3v vin=5v efficiency vs. load current load current(a) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 0 0.3 0.6 0.9 1.2 1.5 vin=5v vin=3v 1.5 2 2.5 3 3.5 4 4.5 40% 50% 60% 70% 80% 90% 100%
MP2012 ? 1.5a synchronous step-down converter MP2012 rev. 1.01 www.monolithicpower.com 5 9/22/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics v in = 5v, v out = 1.8v, l=3.3uh, t a = +25oc, unless otherwise noted. input ripple voltage v in 50mv/div short entry full load en start up without load short recovery no load power up without load power up with 1.5a load sw 2v/div v out 2v/div v in 10v/div en 2v/div i inductor 2a/div sw 5v/div v out 1v/div v in 5v/div i inductor 1a/div sw 5v/div v out 1v/div i inductor 1a/div sw 5v/div v out 1v/div v in 10v/div i inductor 2a/div sw 5v/div v out 1v/div v in 5v/div i inductor 1a/div en start up with 1.5a load en 2v/div sw 5v/div v out 1v/div i inductor 1a/div sw 2v/div 400ns/div 400ns/div 400us/div output ripple voltage sw 2v/div v out 20mv/div i inductor 2a/div load transient response i out =0.75a-1.5a step @ 1a/us v out 20mv/div i out 500ma/div
MP2012 ? 1.5a synchronous step-down converter MP2012 rev. 1.01 www.monolithicpower.com 6 9/22/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. function block diagram figure 1 D function block diagram
MP2012 ? 1.5a synchronous step-down converter MP2012 rev. 1.01 www.monolithicpower.com 7 9/22/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation the MP2012 is a fixed frequency 1.2mhz current mode 1.5a step-down converter, optimized for low voltage, li-ion battery powered applications where high efficiency and small size are critical. MP2012 integrates a high side pfet main switch and a low side synchronous rectifier. it always operates in continuous conduction mode, simplifies the control scheme and eliminates the random spectrum noise due to discontinuous conduction mode. the steady state duty cycle d for this mode can be calculated as: % 100 v v % 100 f t d in out osc on = where t on is the main switch on time and f osc is the oscillator frequency (1.2mhz typ.). current mode pwm control slope compensated current mode pwm control provides stable switching and cycle-by-cycle current limiting for superior load and line response as well as protection of the internal main switch and synchronous rectifier. the MP2012 switches at a constant frequency (1.2mhz) and modulates the inductor peak current to regulate the output voltage. specifically, for each cycle the pwm controller forces the inductor peak current to an internal reference level derived from the feedback error voltage. at normal operation, the main switch is turned on at each rise edge of the internal oscillator, and remains on for a certain period of time to ramp up the inductor current. as soon as the inductor current reaches the reference level, the main switch is turned off and immediately the synchronous rectifier will be turned on to provide the inductor current. in forced pwm mode, the synchronous rectifier will stay on until the next oscillator cycle. dropout operation the MP2012 allows the main switch to remain on for more than one switching cycle to increase the duty cycle when 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. in this case, the output voltage becomes the input voltage minus the voltage drop across the main switch and the inductor. maximum load current the MP2012 can operate down to 2.5v input voltage; however the maximum load current decreases at lower input due to a 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. short circuit protection when short circuit or over current condition happens, and fb is lower than about 0.3v, the MP2012 enters fold back mode. 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 approaches 0.8v.
MP2012 ? 1.5a synchronous step-down converter MP2012 rev. 1.01 www.monolithicpower.com 8 9/22/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. application information output voltage setting the external resistor divider sets the output voltage. 1 o u t 2 r v 0 . 8 1 r ?? =+ ?? ?? rt is recommended when output voltage is high, as the figure 2 shows. r1 fb rt r2 v out figure 2 D feedback network table 1 lists the recommended resistor value for common output voltages. table 1?resistor selection vs. output voltage setting v out / v rt / k ? r1 / k ? r2 / k ? l1 / h c2 / f 1.2 300 4.99 10 2.2 22 1.8v 243 4.99 4.02 3.3 22 2.5v 100 121 57.6 3.3 22 3.3v 100 121 39 3.3 22 inductor selection a 1 h to 10 h 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 ? . see table 2 for recommended inductors and manufacturers. 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 inductor ripple current. choose inductor ripple current approximately 30% of the maximum load current, 1.5a. the maximum inductor peak current is: 2 i i i l load ) max ( l + = table 2?suggested inductors manufacturer part number inductance ( h) dimensions lxwxh (mm 3 ) cooper sd25-3r3 3.3 5.2x5.2x2.5 toko d63lcb#a921 cy-3r6m 3.6 6.3x6.2x3 tdk slf7045t- 3r3m2r5-pf 3.3 7x7x4.5 input capacitor c in selection the input capacitor reduces the surge current drawn from the input and switching noise from the device. ceramic capacitors with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. for most applications, a 10 f capacitor is sufficient. output capacitor c out 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. for forced pwm mode operation, the output ripple v out is approximately: ( ) o u t i n o u t o u t e s r i n o s c o s c o u t v v v 1 1 v r v f l 8 f c ?? ?? = +? ?? ?? ? ?? for most applications, a 22 f capacitor is sufficient. thermal dissipation power dissipation shall be considered when operates MP2012 at maximum 1.5a output current. if the junction temperature rises above 150 c, MP2012 will be shut down by internal thermal protection circuitry. the junction-to-ambient thermal resistance of the 6-pin qfn (3mm x 3mm) r ja is 50 c/w. the maximum allowable power dissipation is about 1.6w when MP2012 is operating in a 70 c ambient temperature environment: w 6 . 1 w / c 50 c 70 c 150 pd o o o max = ? =
MP2012 ? 1.5a synchronous step-down converter MP2012 rev. 1.01 www.monolithicpower.com 9 9/22/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. pc board layout pcb layout is very important to achieve stable operation. please follow these guidelines and take figure2 for references. the high current paths (gnd, in and sw) should be placed very close to the device with short, direct and wide traces. input capacitors should be placed as close as possible to the respective in and gnd pins. the external feedback resistors shall be placed next to the fb pins. keep the switching nodes sw short and away from the feedback network. c1 l1 c2 c5 r4 r1 gnd r2 fb gnd pvin sw vin en 4 5 6 1 2 3 r3 r5 c3 c4 gnd vin vout gnd top layer bottom layer figure 3?pcb layout
MP2012 ? 1.5a 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. MP2012 rev. 1.01 www.monolithicpower.com 10 9/22/2011 mps proprietary information. unauthoriz ed photocopy and duplication prohibited. ? 2011 mps. all rights reserved. package information qfn6 (3mmx3mm) side view top view 1 6 4 3 bottom view 2.90 3.10 1.40 1.60 2.90 3.10 2.20 2.40 0.95 bsc 0.35 0.45 0.80 1.00 0.00 0.05 0.20 ref pin 1 id marking 1.50 0.95 0.40 recommended land pattern 2.90 note: 1) all dimensions are in millimeters . 2) exposed paddle size does not include mold flas h . 3) lead coplanarity shall be 0.10 millimeter max. 4) jedec reference is mo-229, variation veea-2. 5) drawing is not to scale . pin 1 id see detail a 2.30 0.80 pin 1 id option a r0.20 typ. pin 1 id option b r0.20 typ. detail a 0.35 0.55 pin 1 id index area
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