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power management 1 SC220 20mhz, 650ma, x-emi ? -enabled synchronous step-down regulator features patented x-emi tm inductor technology enables trace inductors in pc board material excellent emi performance e ciency up to 90% 19 a quiescent current under very light-load wide input voltage range 2.7v to 5.5v adjustable output voltage down to 1.0v output dc current up to 650ma high light-load e ciency via automatic psave mode ultra-fast transient response <1s temperature range -40 to +85c shutdown current 0.1 a (typical) requires tiny 220nh inductor requires only 1f of output capacitance external switching frequency synchronization protection features including over-current protection output short-circuit protection thermal shutdown protection o ered in soic 8 lead package lead-free, halogen-free, and rohs/weee compliant applications hdtv, set top boxes, gaming consoles pol applications white goods automotive (emi sensitive console applications) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? description the SC220 is a 20mhz x-emi? (1) -enabled step-down regu- lator optimized for powering low voltage rails from 2.7 to 5.5v input voltage. x-emi? inductor technology enables inductors to be drawn directly on the pc board. this tech- nology meets or exceeds the emi performance of chip inductors and eliminates the need for discrete inductors. the SC220 uses a unique constant frequency, self-oscil- lating control loop architecture to provide excellent transient performance. under light load condition, the device operates in power save mode (psave) and main- tains a typical quiescent current of 19a. at moderate to heavy loads, this part operates in pwm mode with a con- stant switching frequency of 20mhz. this high switching frequency o ers the advantages of using small and low cost external components like a 1f external capacitor and a small 220nh inductor (including x-emi tm pcb trace inductors). the device provides adjustable output voltages down to 1.0v and an output current up to 650ma. an en pin can be used to synchronize to an external source and includes de-glitching to reduce noise sensitivity. the SC220 is available in soic 8 lead package. note 1: purchase of SC220 includes royalty-free rights to use x-emi tm inductor technology with no additional cost. typical application circuit january 25, 2012 SC220 agnd sw vout v in l, 220nh c out 1 f en enable fb avin pvin c in 1 f r 1 r 2 pgnd v out =1.8v up to 650ma 2.7~5.5v
2 SC220 pin con guration marking information ordering information device package SC220strt (1)(2) soic 8 lead SC220evb evaluation board notes: (1) available in tape and reel only. a reel contains 2,500 devices. (2) device is lead-free, halogen-free, and rohs/weee compliant. nnnnn = part number yyww = date code xxxxx = semtech lot number pgnd agnd avin fb en sw vout pvin 1 2 3 4 8 7 6 5 soic 8 lead, ja = 38 c/w
3 SC220 exceeding the above speci cations may result in permanent damage to the devic e or device malfunction. operation outside of the parameters speci ed in the electrical characteristics section is not recommended. notes: (1) all voltage values in this section are with respect to pgnd pin voltage. (2) tested according to jedec standard jesd22-a114-b. (3) calculated from package in still air, mounted to 3 x 4.5 (in), 4 layer fr4 pcb with thermal vias under the exposed pad per jesd51 standards. absolute maximum ratings (1) avin, pvin (v) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.0 vout, fb, en, sw (v) . . . . . . . . . . . . . . . . . . . . .-0.3 to (v in +0.3) agnd (v) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-0.3 to +0.3 esd protection level (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3kv recommended operating conditions input voltage range (v) . . . . . . . . . . . . . . . . . . . . . +2.7 to +5.5 output dc current (ma). . . . . . . . . . . . . . . . . . . . . up to 650 operating temperature range (c) . . . . . . . . . . -40 to +85 thermal information thermal resistance, junction to ambient (3) (c/w).... 38 junction temperature range (c) . . . . . . . . . . -40 to +150 storage temperature range (c) . . . . . . . . . . . . -65 to +150 peak ir re ow temperature (10s to 30s) (c) . . . . . . . . . 260 unless otherwise speci ed: avin = pvin = en = 3.6v, c in = c out = 1.0f, l = 220nh. t a = 25c for typical values, -40c < t a = t j < 85c for minimum and maximum values. parameter symbol condition min typ max units power supply input voltage v in 2.7 5.5 v input quiescent current i vin_q no load, no switching 19 40 a shutdown current i vin_sd en = 0v 1.0 a power switch pmos on resistance 400 m nmos on resistance 360 m oscillator switching frequency f osc pwm mode 16 20 24 mhz regulation output voltage tolerance (1) v out_tol -4.0 4.0 % current limit i limit 850 1300 ma soft-start (1) t ss en pin low to high 40 s feedback voltage v fb 2.7v vin 5.5v 0.97 1.00 1.03 v electrical characteristics
4 SC220 parameter symbol condition min typ max units feedback leakage current i fb 1a enable en input high voltage threshold v enh 1.2 v en input low voltage threshold v enl 0.4 v en input high current i enh v en = v in -1.0 1.0 a en input low current i enl v en = agnd -1.0 1.0 a minimum synchronization frequency f syn_min square wave applied at en pin 3 mhz protection over temp thermal shutdown (1) t ot 150 c thermal shutdown hysteresis (1) t hyst 15 c notes (1) guaranteed by design. not tested in production. electrical characteristics (continued) unless otherwise speci ed: avin = pvin = en = 3.6v, c in = c out = 1.0f, l = 220nh. t a = 25c for typical values, -40c < t a = t j < 85c for minimum and maximum values.
5 SC220 pin descriptions pin # pin name pin function 1 sw switching output node connect to the output lc lter. 2 pvin power input supply voltage (2.7v to 5.5v). 3 vout input for sensing the output of lc lter. 4fb input for regulation of output lc lter using r 1 and r 2 to set the output voltage, v out = v fb x (1+ r 1 /r 2 ). (please refer to the typical application circuit diagram on page 1). 5en enable input when low, circuit draws <1 a. apply a square wave clock at en to synchronize the switching frequency with an external clock. it is recommended that the externally applied clock frequency should not be above 20mhz. 6avin input supply voltage. 7 agnd analog ground. 8 pgnd power gr ound. block diagram sw pgnd en avin pvin fb 6 agnd 8 4 1 7 3 2 5 vout clim compensator control logic zcd + - 1.0v + - frequency control soft-start thermal shutdown ref 1.0v osc 20mhz driver external freq . synchronization comp e rror amp
6 SC220 e ciency vs. v in input voltage (v) i out = 1ma 2.5 3.0 3.5 4.0 4.5 5.0 i out = 50ma i out = 300ma e ciency vs. load current load current (a) e ciency v out = 1.8v v in = 3.7v 0.001 0.01 0.1 1 30 % 40 % 50 % 60 % 70 % 100 % v in = 4.2v 80 % 90 % v in = 2.7v e ciency v out = 1.8v typical characteristics switching frequency vs. v in switching frequency vs. v in input voltage (v) i out = 650ma switching frequency (mhz) 2.5 3.0 3.5 4.0 4.5 5.5 0 5.0 10.0 15.0 20.0 22.5 2.5 7.5 12.5 17.5 v out = 1.8v 5.0 i out = 450ma i out = 300ma i out = 200ma input voltage (v) i out = 650ma switching frequency (mhz) 2.5 3.0 3.5 4.0 4.5 5.5 0 5.0 10.0 15.0 20.0 22.5 2.5 7.5 12.5 17.5 v out = 1.0v 5.0 i out = 450ma i out = 300ma i out = 200ma load regulation output voltage (v) 1.77 1.79 1.80 1.78 nominal v out = 1.8v v in = 3.7v v in = 4.2v v in = 5.0v v in = 2.7v load current (a) 0.001 0.01 0.1 1 0 10 % 20 % e ciency vs. load current (chip inductor vs. x-emi tm inductor) load current (a) e ciency v out = 1.8v v in = 3.7v 0.001 0.01 0.1 1 v in = 4.2v v in = 2.7v 30 % 40 % 50 % 60 % 70 % 100 % 80 % 90 % 0 10 % 20 % dashed lines: e ciency with x-emi tm inductor solid lines: e ciency with chip inductor 30 % 40 % 50 % 60 % 70 % 100 % 80 % 90 % 0 10 % 20 %
7 SC220 load transient response load transient response typical characteristics (continuous) v in = 3.7v, v out = 2.0v, i out = 0ma - 650ma time (1s/div) v out (ac coupled) 100mv/div. i out 200ma/div. v in = 3.7v, v out = 2.0v, i out = 200ma - 500ma time (1s/div) v out (ac coupled) 50mv/div. i out 200ma/div. steady state operation (i out = 50ma) steady state operation (i out = 300ma) time (200ns/div) i out 50ma/div. v in = 3.6v, v out = 1.8v, i out = 50ma i l 200ma/div. v sw 2v/div. time (50ns/div) i out 200ma/div. v in = 3.6v, v out = 1.8v, i out = 300ma i l 200ma/div. v sw 2v/div. output hard short time (500ns/div) v out 1v/div. v in = 5.0v, v out = 1.8v, i out = 650ma i l 500ma/div. i out 500ma/div. input quiescent current vs. temperature temperature (c) quiescent current (a) -40 -20 02040 80 18 18.5 20.0 19.0 19.5 v in = 5.5v, en = high, fb = high 60 100
8 SC220 start-up operation disable operation typical characteristics (continuous) v in = 3.7v, v out = 1.8v, i out = 10ma en 5v/div. v out 1v/div. i out 10ma/div. v in 2v/div. v in = 3.7v, v out = 1.8v, i out = 10ma en 5v/div. v out 1v/div. i out 10ma/div. v in 2v/div. time (20s/div) time (100s/div) start-up operation disable operation v in = 3.7v, v out = 1.8v, i out = 650ma en 5v/div. v out 1v/div. i out 500ma/div. v in 2v/div. v in = 3.7v, v out = 1.8v, i out = 650ma en 5v/div. v out 1v/div. i out 500ma/div. v in 2v/div. time (20s/div) time (20s/div)
9 SC220 general description the SC220 is a step-down regulator capable of delivering a lower voltage from an input supply voltage of 2.7v to 5.5v with high e ciency. using a unique control architec- ture, the SC220 is capable of delivering a peak e ciency of 90%, while maintaining e ciency over 80% during light load condition. the converter operates at 20mhz switch- ing frequency with pulse width modulation (pwm) with moderate to heavy output load current of up to 650ma, which is referred as pwm mode. under light-load condi- tion, the converter operates in power save (psave) mode. control scheme the SC220 operates with a self-oscillating control method based on the output voltage ripple. this control loop com- pares the output voltage to an internal 1v reference to regulate the output voltage directly, adjusting the turn-on and turn-off time of the power switches such that the output voltage is held at a precise value. this architecture gives a single-cycle response to transient events. to maintain constant frequency, a phase locked loop (pll) is included to synchronize the switching with an internal clock. this pll adjusts the effective upper and lower thresholds of the comparator, thus maintaining a constant frequency. under transient conditions the voltage control loop determines the required switching pattern to best maintain the output voltage. after a short transient, the pll will bring the switching frequency back to normal. at extreme duty cycles, where the frequency control loop may not be able to maintain frequency lock even under steady-state conditions, frequency may fall, but the output voltage regulation will be maintained by the main voltage control loop. this unique architecture helps to achieve the excellent line and load transient response. operating modes the SC220 operates in two modes over a wide range of load currents. under moderate to heavy load conditions, it operates in pwm mode with the switching frequency held constant. under light-load condition, the converter enters psave mode automatically. with the typical 220nh inductor, the transition between pwm and psave mode typically occurs in the range of 100-200ma, depending on the input and output voltages. under very light load condition, the SC220 maintains high e ciency by shut- ting down all but the most essential circuit blocks, maintaining a typical quiescent current of about 19a. in this mode, some circuitry used to control absolute dc accuracy is turned o . in that case, there may be a small dc shift (tens of millivolts) between normal operation and this no-load state. however, in the case of a load transient, the system will turn on the high-side fet within nanoseconds as a discontinuous pulse is issued. the tran- sition to pwm mode can occur within that nominal on-time, giving superior no load to full load transient response. the transition from pwm mode to psave mode is con- trolled by sensing the minimum value of the ripple current. when it drops below a threshold level for 32 consecutive cycles, the transition to psave mode is initi- ated. once in psave mode, the regulation is maintained by modulating the time between xed current pulses. when a new pulse is required by the loop before the existing pulse has terminated, the loop determines that the load cannot be maintained in psave mode. this prompts an instantaneous switch from psave mode back to pwm mode. enable and start-up the SC220 is enabled by applying a voltage higher than 1.2v on the en pin, and it is disabled when the applied voltaga is pulled below the logic low threshold. the en pin can also be used to set the switching frequency: if a digital clock is fed to en, the SC220 will sense this as a valid enable signal and the external clock will be used rather than the internal 20mhz oscillator. the SC220 has an internal soft start circuit that limits the inrush current during start-up with a stepped current limit. over the course of about 40s, the SC220 is stepped in increments of one quarter of the nominal current limit to full current limit, thereby reducing the worst-case surge current that might otherwise be re ected to the input current. current limit the SC220 integrates a current limit feature to protect itself and the external components under overload con- applications information applications information
10 SC220 dition. when the current owing through the high-side pmos switch exceeds the current limit, the pmos switch is turned o . the high-side switch is then held o for a period su cient to allow inductor current to decay. when the output voltage is close to the nominal regulation point, this will look similar to constant current limiting. as the output voltage falls, the imposed o -time is such that the frequency will drop, thus the inductor will have appro- priate time to reset. this may cause the average current to reduce, giving a mild fold-back characteristic to the current limit, where the average load current drops as the output voltage collapses (although the peak current maintains its nominal value). in a short-circuit condition, the system runs continuously at this reduced frequency. load transient response the SC220 features excellent regulation during line and load transients. this is due to the nature of the proprietary control method and the high di/dt allowed by the use of a small inductor. this allows for best performance while providing the benefit of using a small low cost output capacitor. v out shows only tens of millivolts of ripple voltage d uring a load current step change from less than 1ma to 650ma within hundreds of nanoseconds, using typical a 1f output capacitor. (see the typical perfor- mance curves on page 7). x-emi? inductor technology the SC220 is the industrys rst buck regulator that enables designers to draw their own inductors directly on the pc board. this patented technology is called x-emi? inductor technology and is di erent from conventional pcb trace inductors. conventional pcb trace inductors can be used with high-frequency switchers, but they exhibit signi cant emi issues. x-emi? inductor technology solves these emi problems and can meet or exceed the emi performance of conventional chip inductors. x-emi tm technology works by placing two small air-core inductors adjacent to each other in anti-phase position, where the magnetic elds of each air-core inductor par- tially cancel one another to reduce emi. the net ux from the two inductors, partially cancels the wide leakage paths caused by the wide geometry, but is still able to store the energy of the inductors in series. this approach uses mul- tiple air core inductors implemented using printed circuit traces. because these traces may be located on internal layers of the pcb, inductors can be designed with almost no impact on the available pcb area for components on the surface of the board. (see the e ciency curves using x-emi? inductor technology on page 6). external components the input and output capacitors used for the operation of the SC220 should be multilayer ceramic capacitors, prefer- ably with x7r or x5r dielectric. the SC220 is optimized to operate with typical 1f input and output capacitance. in practice, the self-resonant frequency of surface mount capacitors of this type is well below the 20mhz ripple fre- quency, so e orts to minimize output ripple may best be focused on minimizing the inductance of the output capacitor and the length of the circuit path to ground rather than on increasing the capacitance value of the output capacitor. the inductor should be a high current inductor rated for currents at least up to 1a. typical power inductors may be too lossy at 20mhz unless speci cally designed for high frequency operation. for inductor value of 220nh, it may be preferred to use wire-wound rf chokes, many of which are rated for appropriate currents. some recommended external components value manufacturer part number package l 0.22h coilcraft xfl2005-221me 2x2mm 0.24h coilcraft 0603ls-241xjl 0603 c in 1f murata grm155r61c105ka12 0402 c out 1f murata grm155r61c105ka12 0402 applications information (cont.) figure 1. top view of an evaluation board with x-emi inductor
11 SC220 applications information (cont.) pcb layout considerations pcb layout is important in designing a switching regula- tor. a few fundamental layout considerations will help to achieve the specified performance. poor layout can degrade the performance of the switching regulator and may contribute to emi problems, ground bounce, and possibly poor regulation and instability. the following guidelines are recommended when devel- oping a pcb layout: the input capacitor, c in should be placed as close to the pvin and pgnd pins as possible. this capacitor provides a low impedance loop for the pulsed currents present at the buck converters input. use short wide traces to connect this capacitor as close to the ic as possible. this will minimize emi and input voltage ripple by localizing the high frequency current pulses. keep the sw pin traces as short as possible to minimize 1. 2. the pickup of high frequency switching edges to other parts of the circuit. the output capacitor, c out and the inductor should be put as close as possible to the related pins of the ic, and connected as close as possible between the sw and ground pins. route the output voltage feedback/sense path from the output capacitor path, and away from the inductor and sw node to minimize the possible noise and magnetic interference to the output feedback/ sense path. use a ground plane referenced to the pgnd pin, and the ground connection of the input and output capacitors should be put on this plane and close to each other if possible, and as close to the pgnd pin as possible. use several vias to connect to the component side ground to further reduce noise and interference on sensitive circuit nodes. if possible, minimize the resistance from the vout and agnd pins to the load. this will reduce the voltage drop on the ground plane and improve the load regulation. and it will also improve the overall e ciency by reducing the copper losses on the output and ground planes. 3. 4. 5.
12 SC220 outline drawing soic 8 lead see detail detail a a .050 bsc .236 bsc 8 .010 .150 .189 .154 .193 .012 - 8 0.25 1.27 bsc 6.00 bsc 3.90 4.90 - .157 .197 3.80 4.80 .020 0.31 4.00 5.00 0.51 bxn 2x n/2 tips seating aaa c e/2 2x 12 n a d a1 e1 bbb c a-b d ccc c e/2 a2 (.041) .004 .008 - .028 - - - - 0 .016 .007 .049 .004 .053 8 0 0.20 0.10 - 8 0.40 0.17 1.25 0.10 .041 .010 .069 .065 .010 1.35 (1.04) 0.72 - 1.04 0.25 - - - 1.75 1.65 0.25 0.25 - .010 .020 0.50 - c l (l1) 01 0.25 gage plane h h 3. dimensions "e1" and "d" do not include mold flash, protrusions or gate burrs. -b- controlling dimensions are in millimeters (angles in degrees). datum s and to be determined at datum plane notes: 1. 2. -a- -h- side view a b c d e h plane reference jedec std ms-012, variation aa. 4. l1 n 01 bbb aaa ccc a b a2 a1 d e e1 l h e c dim min millimeters nom dimensions inches min max max nom e
13 SC220 land pattern soic 8 lead (.205) (5.20) z g y p (c) 3.00 .118 1.27 .050 0.60 .024 2.20 .087 7.40 .291 x inches dimensions z p y x dim c g millimeters this land pattern is for reference purposes only. consult your manufacturing group to ensure your company's manufacturing guidelines are met. notes: 1. reference ipc-sm-782a, rlp no. 300a. 2.
semtech corporation power management products division 200 flynn road, camarillo, ca 93012 phone: (805) 498-2111 fax: (805) 498-3804 www.semtech.com contact information 14 SC220 ? semtech 2012 all rights reserved. reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. the information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. no liability will be accepted by the publisher for any conse- quence of its use. publication thereof does not convey nor imply any license under patent or other industrial or intellectual property rights. semtech assumes no responsibility or liability whatsoever for any failure or unexpected operation resulting from misuse, neglect improper installation, repair or improper handling or unusual physical or elec- trical stress including, but not limited to, exposure to parameters beyond the speci ed maximum ratings or operation outside the speci ed range. semtech products are not designed, intended, authorized or warranted to be suitable for use in life- support applications, devices or systems or other critical applications. inclusion of semtech products in such applications is understood to be undertaken solely at the customers own risk. should a customer purchase or use semtech products for any such unauthorized application, the customer shall indemnify and hold semtech and its o cers, employees, subsidiaries, a liates, and distributors harmless against all claims, costs damages and attorney fees which could arise. notice: all referenced brands, product names, service names and trademarks are the property of their respective owners.

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