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MP2161 2a, 6v, 1.5mhz, 17 a i q , cot synchronous step down switcher in 8-pin tsot23 MP2161 rev. 1.03 www.monolihicpower.com 1 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. the future of analog ic technology description the MP2161 is a monolithic step-down switch mode converter with built-in internal power mosfets. it achieves 2a continuous output current from a 2.5v to 6v input voltage with excellent load and line regulation. the output voltage can be regulated as low as 0.6v. the constant-on-time control scheme provides fast transient response and eases loop stabilization. fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. the MP2161 is available in the small tsot23-8 package and requires a minimum number of readily available standard external components. the MP2161 is ideal for a wide range of applications including high performance dsps, fpgas, pdas, and portable instruments. features ? very low i q : 17 a ? default 1.5mhz switching frequency ? en and power good for power sequencing ? wide 2.5v to 6v operating input range output adjustable from 0.6v ? up to 2a output current ? 100% duty cycle in dropout ? 100m ? and 60m ? internal power mosfet switches ? cycle-by-cycle over current protection ? short circuit protect with hiccup mode ? stable with low esr output ceramic capacitors ? available in a tsot23-8 package applications ? wireless/networking cards ? portable instruments ? battery powered devices ? low voltage i/o system power all mps parts are lead-free and adhere to the rohs directive. for mps green status, please visit mps website under products, quality assurance page. ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 2 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. ordering information part number* package top marking MP2161gj tsot23-8 aeb * for tape & reel, add suffix ?z (e.g. MP2161gj?z); package reference pg vin sw pgnd en fb agnd out 1 2 3 4 8 7 6 5 top view tsot23-8 absolute maxi mum ratings (1) supply voltage v in ...................................... 6.5v v sw ...................................................................... -0.3v (-1.5v for <10ns) to 6.5v (7v for <10ns) all other pins ................................-0.3v to 6.5 v junction temperature ...............................150 c lead temperature ....................................260 c continuous power dissipation (t a = +25c) (2) ???.?.. ............................................... 1.25w storage temperature............... -65 c to +150 c recommended operating conditions (3) supply voltage v in .............................2.5v to 6v operating junction temp. (t j ). -40c to +125c thermal resistance (4) ja jc tsot23-8.............................. 100 ..... 55... 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.
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 3 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. electrical characteristics (5) v in = 5v, t a = +25 c, unless otherwise noted. parameter symbol condition min typ max units 2.5v v in 6v -3% 0.600 +3% feedback voltage v fb t a =-40 o c to +85 o c (6) -3.5% +3.5% v/% feedback current i fb v fb = 0.6v 10 50 na pfet switch on resistance r dson_p 100 m ? nfet switch on resistance r dson_n 60 m ? switch leakage v en = 0v, v in = 6v v sw = 0v and 6v 0 1 a pfet current limit 2.7 3.2 4.0 a v in =5v, v out =1.2v 185 on time t on v in =3.6v, v out =1.2v 245 ns v out =1.2v -20% 1500 +20% khz/% switching frequency f s t a =-40 o c to +85 o c (6) -25% 1500 +25% khz/% minimum off time t min-off 60 ns soft-start time t ss-on 1.5 ms power good upper trip threshold pg h fb voltage respect to the regulation +10 % power good lower trip threshold pg l -10 % power good delay pg d 50 s power good sink current capability v pg-l sink 1ma 0.4 v power good logic high voltage v pg-h v in =5v, v fb =0.6v 4.9 v power good internal pull up resistor r pg 550 k ? under voltage lockout threshold rising 2.15 2.3 2.45 v under voltage lockout threshold hysteresis 260 mv en input logic low voltage 0.4 v en input logic high voltage 1.2 v v en =2v 1.5 a en input current v en =0v 0 a supply current (shutdown) v en =0v, v in =3v 20 100 na supply current (quiescent) v en =2v, v fb =0.63v, v in =5v 17 20 a thermal shutdown (5) 150 c thermal hysteresis (5) 30 c notes: 5) guaranteed by design. 6) guaranteed by characterization test.
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 4 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. typical performanc e characteristics v in = 5v, v out = 1.2v, l = 1.0h, t a = +25oc, unless otherwise noted. quiescent current vs. input voltage shutdown current vs. input voltage load regulation line regulation case temp rise v in =3v, v out =1.2v case temp rise v in =5v, v out =3.3v efficiency 0 10 20 30 40 2 2.5 3 3.5 4 4.5 5 5.5 6 input voltage (v) 0 0.0005 0.001 0.0015 0.002 0.0025 0.003 2 2.5 3 3.5 4 4.5 5 5.5 6 input voltage (v) -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 0 0.5 1 1.5 2 2.5 load current (a) v in =5v v in =6v -1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 0.40 0.60 0.80 1.00 23456 input voltage (v) load=1a load=2a load=0a 0 5 10 15 20 25 30 35 40 45 50 0 0.5 1 1.5 2 2.5 output current (a) 0 5 10 15 20 25 30 35 40 45 50 0 0.5 1 1.5 2 2.5 output current (a) 50 55 60 65 70 75 80 85 90 95 100 1 10 100 1000 10000 load current(ma) v in =3.3v v in =5v v in =6v i out (a) efficiency 5/3.3v in to 1.8v out efficiency 5v in to 3.3v out i out (a) 50 60 70 80 90 100 0 0.5 1 1.5 2 2.5 v in =5v v in =3.3v 50 60 70 80 90 100 0 0.5 1 1.5 2 2.5
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 5 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. typical performanc e characteristics (continued) v in = 5v, v out = 1.2v, l = 1.0h, t a = +25oc, unless otherwise noted.
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 6 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. typical performanc e characteristics (continued) v in = 5v, v out = 1.2v, l = 1.0h, t a = +25oc, unless otherwise noted
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 7 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. pin functions pin # name description 1 pg power good indicator. the output of this pin is an open drain with internal pull up resistor to in. pgood is pulled up to in when the fb voltage is within 10% of the regulation level, if fb voltage is out of t hat regulation range, it is low. 2 vin supply voltage. the MP2161 operates from a +2.5v to +6v unregulated input. c1 is needed to prevent large voltage spikes from appearing at the input. 3 sw switch output 4 pgnd power ground 5 out input sense pin for output voltage 6 agnd analogy ground for internal control circuit 7 fb feedback pin. an external resistor divider fr om the output to gnd, tapped to the fb pin, sets the output voltage. 8 en on/off control
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 8 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. block diagram main switch (pch) synchronous rectifier (nch) constant on- time pulse pw m bias & voltage reference 0.6 v en fb sw comp + - vin + + - fbcomp en driver pdrv ndrv soft star t gnd out pw m comp + - comp + - 0. 66 v 0. 54 v pg hi-z fb for fixed output in e.a. + - + ramp gener ator comp + - vout rst sw lo -iq lo-iq lo-iq lo-iq lo-iq v th figure 1: MP2161 block diagram
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 9 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. operation MP2161 uses constant on-time control with input voltage feed forward to stabilize the switching frequency over full input range. at light load, MP2161 employs a proprietary control of low side switch and inductor current to eliminate ringing on switching node and improve efficiency. constant on-time control compare to fixed frequency pwm control, constant on-time control offers the advantage of simpler control loop and faster transient response. by using input voltage feed forward, MP2161 maintains a nearly constant switching frequency across input and output voltage range. the on- time of the switching pulse can be estimated as: out on in v t0.667s v =? to prevent inductor current run away during load transient, MP2161 fixes the minimum off time to be 60ns. however, this mini mum off time limit will not affect operation of MP2161 in steady state in any way. light load operation in light load condition, MP2161 uses a proprietary control scheme to save power and improve efficiency. the MP2161 will turn off the low side switch when inductor current starts to reverse. then MP2161 works in discontinuous conduction mode (dcm) operation. enable when input voltage is greater than the under- voltage lockout threshold (uvlo), typically 2.3v, MP2161 can be enabled by pulling en pin to higher than 1.2v. leaving en pin float or pull down to ground will disable MP2161. there is an internal 1meg ohm resistor from en pin to ground. soft start MP2161 has built-in soft start that ramps up the output voltage in a controlled slew rate, avoiding overshoot at startup. the soft start time is about 1.5ms typical. power good indictor MP2161 has an open drain with 550k ? pull-up resistor pin for power good indicator pgood. when fb pin is within +/-10% of regulation voltage, i.e. 0.6v, pgood pin is pulled up to in by the internal resistor. if fb pin voltage is out of the +/-10% window, pgood pin is pulled down to ground by an internal mos fet. the mos fet has a maximum r dson of less than 100 ohm. current limit MP2161 has a typical 3.2a current limit for the high side switch. when the high side switch hits current limit, MP2161 will touch the hiccup threshold until the current lower down. this will prevent inductor current from continuing to build up which will result in damage of the components. short circuit and recovery MP2161 enters short circuit protection mode also when the current limit is hit, and tries to recover from short circuit with hiccup mode. in short circuit protection, MP2161 will disable output power stage, discharge soft-start cap and then automatically try to soft-start again. if the short circuit condition still holds after soft- start ends, MP2161 repeats this operation cycle till short circuit disappears and output rises back to regulation level.
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 10 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. application information component selection setting the output voltage the external resistor divider is used to set the output voltage (see typical application on page 1). the feedback resistor r1 can not be too large neither too small considering the trade-off for stability and dynamic. choose r1 to be around 120k ? to 200k ? . r2 is then given by: out r1 r2 v 1 0.6 = ? the feedback circuit is shown as figure 2. r1 r2 vout fb MP2161 figure 2: feedback network table 1 lists the recommended resistors value for common output voltages. table 1?resistor selection for common output voltages v out (v) r1 (k ? ) r2 (k ? ) 1.0 200(1%) 300(1%) 1.2 200(1%) 200(1%) 1.8 200(1%) 100(1%) 2.5 200(1%) 63.2(1%) 3.3 200(1%) 44.2(1%) selecting the inductor a 0.68h to 2.2h inductor is recommended for most applications. for highest efficiency, the inductor dc resistance should be less than 15m ? . for most designs, the inductance value can be derived from the following equation. out in out 1 in l osc v(vv) l vif ? = where i l is the inductor ripple current. choose inductor current to be approximately 30% of the maximum load current. the maximum inductor peak current is: 2 i i i l load ) max ( l + = selecting the input capacitor the input current to the step-down converter is discontinuous, therefore a capacitor is required to supply the ac current to the step-down converter while maintaining the dc input voltage. use low esr capacitors for the best performance. ceramic capacitors with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. for most applications, a 10f capacitor is sufficient. for higher output voltage, 47uf may be needed for more stable system. since the input capacitor absorbs the input switching current it requires an adequate ripple current rating. the rms current in the input capacitor can be estimated by: ? ? ? ? ? ? ? ? ? = in out in out load 1 c v v 1 v v i i the worse case condition occurs at v in = 2v out , where: 2 i i load 1 c = for simplification, choose the input capacitor whose rms current rating greater than half of the maximum load current. the input capacitor can be electrolytic, tantalum or ceramic. when using electrolytic or tantalum capacitors, a small and high quality ceramic capacitor, i.e. 0.1 f, should be placed as close to the ic as possible. when using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. the input voltage ripple caused by capacitance can be estimated by: load out out in in sin iv v v1 fc1v v ?? = ? ?? ??
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 11 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. selecting the output capacitor the output capacitor (c2) is required to maintain the dc output voltage. ceramic capacitors are recommended. low esr capacitors are preferred to keep the output voltage ripple low. the output voltage ripple can be estimated by: out out out esr s1 in s vv 1 v1r fl v 8fc2 ?? ?? = ? + ?? ?? ?? ?? where l 1 is the inductor value and r esr is the equivalent series resistance (esr) value of the output capacitor. using ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. the output voltage ripple is mainly caused by the capacitance. for simplification, the output voltage ripple can be estimated by: out out out 2 in s1 vv v1 v 8f l c2 ?? =? ?? ?? in the case of tantalum or electrolytic capacitors, the esr dominates the impedance at the switching frequency. for simplification, the output ripple can be approximated to: out out out esr in s1 vv v1r fl v ?? =? ?? ?? the characteristics of the output capacitor also affect the stability of the regulation system. pcb layout proper layout of the switching power supplies is very important, and sometimes critical for proper function. for the high-frequency switching converter, poor layout design can result in poor line or load regulation and stability issues. the high current paths (gnd, in and sw) should be placed very close to the device with short, direct and wide traces. the input capacitor needs to be as close as possible to the in and gnd pins. the external feedback resistors should be placed next to the fb pin. keep the switching node sw short and away from the feedback network. en agnd out gnd vin pg r1 c2 r2 c1 8 7 6 5 1 2 3 4 sw figure 3: pcb layout recommendation design example below is a design example following the application guidelines for the specifications: table 2: design example v in 5v v out 1.2v f sw 1500khz the detailed application schematic is shown in figure 4. the typical performance and circuit waveforms have been shown in the typical performance characteristics section. for more device applications, please refer to the related evaluation board datasheets.
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher MP2161 rev. 1.03 www.monolihicpower.com 12 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. typical application circuits figure 4: typical application circuit
MP2161 ? 2a, 6v, 1.5mhz synchronous step-down switcher 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. MP2161 rev. 1.03 www.monolithicpower.com 13 9/6/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. package information tsot23-8 front view 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) jedec reference is mo -193, variation ba . 6) drawing is not to scale . 7) pin 1 is lower left pin when reading top mark from left to right, (see example top mark ) top view recommended land pattern seating plane side view detail ''a'' see detail '' a'' iaaaa pin 1 id see note 7 example top mark

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