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si-8005q description the si-8005q is a step-down switching regulator ic, designed as an output voltage regulator at the secondary stage of switch mode power supplies. the current-mode control system permits small ceramic capacitors to be used as output capacitors. together with the compact hsop8 package, this allows reduction of regulator circuitry area on the pcb by approximately 50% in comparison with conventional topologies. designed to save power, losses in the si-8005q are reduced by controlling the maximum on-resistance of a built-in output mosfet to as low as 165 m . furthermore, die miniaturization has been accomplished through a proprietary bcd process. the si-8005q supplies an output current of 3.5 a and an output voltage that is variable from 0.5 to 24 v, which is easily set to a voltage compatible with the diverse reduced power supply voltages required by signal processing ics. accepting a wide input voltage range, from 4.75 to 28 v, the si-8005q can be driven directly by a 24 v power supply. applications include power supplies for signal processing ics for memories and microcomputers used in plasma display panel (pdp) tvs, liquid crystal display (lcd) tvs, computer hard drives, and dvd recorders. features and benefits ? current-mode control system employed ? excellent line regulation (60 mv maximum) ? 165 m maximum on-resistance of built-in mosfet ? output current 3.5 a ? wide range of input voltages (4.75 to 28 v), supports 24 v direct drive ? output voltage 0.5 to 24 v, compatible with various ic power supply voltages, through low v ref of 0.5 v. ? high efficiency, 94% maximum at v in = 8 v, v o = 5 v, and i o = 0.5 a ? operating frequency 500 khz, supports downsizing of smoothing choke coil ? soft start and output on/off functions built-in ? built-in protection: ? drooping overcurrent protection ? overtemperature protection ? undervoltage lockout (uvlo) step-down switching regulator with current-mode control functional block diagram not to scale package: hsop8 surface mount with exposed thermal pad drive tsd p. r eg current sense amp osc boot reg pwm logic bs sw fb comp en amp in v in v o 0.5v c4 l1 di c3 7 6 5 3 1 2 gnd 4 r2 r3 r1 c1 c2 8 ss ocp on/ off vref ovp 0.5v 5v_ldo 5v_ldo c5 uvlo 27469.058, rev. 1
step-down switching regulator with current-mode control si-8005q 2 all performance characteristics given are typical values for circuit or system baseline design only and are at the nominal operating voltage and an ambient temperature, t a , of 25c, unless oth er wise stated. recommended operating conditions* characteristic symbol remarks min. typ. max. units dc input voltage range v in v in (min) is the greater of either 4.75 v or v o +1 v; except if v o + 0.5 v in v o +1 v, then v in (min) is set such that i o 2 a see remarks ?28v dc output current range i o using the circuit defined in the typical application diagram and within p d limits 0 ? 3.5 a operating junction temperature range t jop ?30 ? 125 c operating temperature range t op operation within p d limits ?30 ? 85 c *recommended operating range indicates conditions which are required for maintaining normal circuit functions shown in the elec trical characteristics table. selection guide part number packing SI8005Q-TL 1000 pieces per reel absolute maximum ratings characteristic symbol remarks rating unit dc input voltage v in 30 v dc input voltage v en 6v allowable power dissipation p d limited by internal thermal shutdown, mounted on a 30 mm 30 mm glass epoxy pcb with 25 mm 25 mm exposed copper area, t j (max) = 125c 1.35 w junction temperature t j internal thermal shutdown activates at approximately 140c ?30 to 150 c storage temperature t stg ?40 to 150 c thermal resistance (junction to ambient) r ja mounted on a 30 mm 30 mm glass epoxy pcb with 25 mm 25 mm exposed copper area 74 c/w thermal resistance (junction to case) r jc 40 c/w 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 ?25 0 25 50 ambient temperature, t a (c) power dissipation, p d (w) 75 100 125 results calculated as: p d v o i o 100 h x = ? ? ? ? ? ? ? ? ? 1 ? v f i o v o v in ? ? ? ? ? ? ? ? 1 ? where: v o is the output voltage, v in is the input voltage (0.4 v for these results), i o is the output current (0.3 a for these results), x is the efficiency (%), which varies with v in and i o (derived from the efficiency curves in the characteristic performance section), and v f is the diode forward voltage for d1, determination of the value for d1 should be made based on testing with the actual application (sanken diode sjpb-d4 was used for these results). maximum allowable package power dissipation allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
step-down switching regulator with current-mode control si-8005q 3 electrical characteristics 1 , valid at t a =25c, unless otherwise noted characteristics symbol conditions min typ max units reference voltage v ref v in = 12 v, i o = 1.0 a 0.485 0.500 0.515 v output voltage temperature coefficient ? v ref / ? tv in = 12 v, i o = 1.0 a, t a = ?40c to 85c ? 0.05 ? mv/c efficiency 2 v in = 12 v, v o = 5 v, i o = 1 a ? 90 ? % operating frequency f o v in = 16 v, v o = 5 v, i o = 1 a 450 500 550 khz line regulation v line v in = 8 to 28 v, v o = 5 v, i o = 1 a ? 10 60 mv load regulation v load v in = 12 v, v o = 5 v, i o = 0.1 to 3.5 a ? 10 60 mv overcurrent protection threshold i s v in = 12 v, v o = 5 v 3.6 ? 6.0 a quiescent current 1 i in v in = 12 v, v o = 5 v, i o = 0 a, v en = open ? 18 ? ma quiescent current 2 i in(off) v in = 12 v, v o = 5 v, i o = 0 a,v en = 0 v ? ? 20 a ss terminal leakage current 3 i ssl v ssl = 0 v, v in = 16 v ? 5 ? a en terminal high level voltage v ceh v in = 12 v 2.8 ? ? v en terminal low level voltage v cel v in = 12 v ? ? 2.0 v en terminal leakage current i ceh v en = 0 v ? 1 ? a error amplifier voltage gain a ea ? 1000 ? v/ v error amplifier transconductance g ea ? 800 ? a/v current sense to comp transimpedance 1/g cs ? 0.35 ? v/a maximum duty cycle (on) dc max ?92? % minimum on-time t min ? 100 ? ns 1 using circuit shown in measurement circuit diagram. 2 efficiency is calculated as: (%) = ([ v o i o ] / [ v in i in ]) 100. 3 ss terminal enables soft start when a an external capacitor is connected to it. because a pull-up resistor is provided inside t he ic, no external voltage can be applied to this terminal. si-8005q ii n bs sw ss gnd comp fb en c1 c3 di c4 l1 c2 r1 r2 i i in v i in v o i o v ss v en v fb i en i ss rl 1 2 3 4 5 6 7 8 r3 component rating c1 22 f / 50 v c2 47 f / 25 v c3 220 pf / 10 v c4 10 nf / 25 v di spb-g56s l1 10 h r1 46 k r2 5.1 k r3 62 k measurement circuit diagram allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
step-down switching regulator with current-mode control si-8005q 4 performance characteristics at t a = 25c 100 90 80 70 60 50 40 012345 (%) efficiency versus output current v o = 1.2 v 4.75 v 6 v 5 v i o (a) 100 90 80 70 60 50 40 012345 (%) efficiency versus output current v o = 3.3 v i o (a) 8 v 12 v v in v in 8 v 16 v 12 v 24 v 28 v 100 90 80 70 60 50 40 012345 (%) efficiency versus output current v o = 5 v i o (a) 100 90 80 70 60 50 40 012345 (%) efficiency versus output current v o = 12 v i o (a) v in v in 16 v 20 v 28 v 8 v 16 v 12 v 20 v 28 v allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
step-down switching regulator with current-mode control si-8005q 5 performance characteristics at t a = 25c 6 5 4 3 2 1 0 0246810 v o (v) v o (v) overcurrent protection load = cr 0 a 1 a 2 a 3 a v in (v) 6 5 4 3 2 1 0 01234 6 5 v o (v) overcurrent protection i o (a) i o v in 8 v 15 v 12 v 20 v 24 v 28 v 5.05 5.04 5.03 5.02 5.01 5.00 4.99 4.98 4.97 4.96 4.95 012345 load regulation i o (a) 25 20 15 10 5 0 0 10203040 0 10203040 quiescent current versus input voltage i o = 0 a v in (v) v in (v) v in 8 v 15 v 12 v 20 v 28 v i o(q) ( a) i o(q) (ma) 10 9 8 7 6 5 4 3 2 1 0 quiescent current versus input voltage v en = 0 v overvoltage protection v in = 12 v i o = 0 a f o (khz) 550 540 530 520 510 500 490 480 470 460 450 550 540 530 520 510 500 490 480 470 460 450 012345 operating frequency versus output current i o (a) 0 10203040 f o (khz) operating frequency versus input voltage v in (v) v in 8 v 15 v 12 v 20 v 28 v 24 v 6 5 4 3 2 1 0 120 130 140 160 150 t j (c) v o (v) otp on otp off allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
step-down switching regulator with current-mode control si-8005q 6 component selection for general applications si- 8005q i in b s sw ss gnd comp fb r3 r2 r1 c4 c1 c2 5 v c5 c3 c6 open l1 en di v i in v o 1 2 3 4 5 6 7 8 gnd gnd v fb i adj component rating manufacturer c1 (2 ea) 10 f / 50 v murata, p/n grm55db31h106ka87 c2 (2 ea) 22 f / 16 v murata, p/n grm32er71a226ke20 c3 220 pf murata, p/n grm18 series c4, c5 10 nf murata, p/n grm18 series di sanken, p/n spb-g56s or sjpb-l4 l1 10 h r1 46 k r2 5.1 k r3 62 k all external components should be mounted as closely as possible to the si-8005q. the ground of all components should be connected at one point. the exposed copper area on the pcb that is connected to the heat sink on the reverse side of package is ground. enlarging the pcb copper area enhances thermal dissipation from the package. recommended pcb layout recommended solder pad layout typical application diagram diode di a schottky-barrier diode must be used for di. if other diode types, such as fast recovery diodes, are used, the ic may be destroyed because of reverse voltages applied by the recovery voltage or turn-on voltage. choke coil l1 if the winding resistance of the choke coil is too high, ic efficiency may go down to the extent that the resistance is beyond the rating. because the overcurrent protection threshold current is approximately 4 a, attention must be paid to the heat- ing of the choke coil by magnetic saturation due to overload or short-circulated load. capacitors c1, c2, and c5 because large ripple currents for smps flow across c1 and c2, capacitors with high frequency and low impedance must be used. especially when the impedance of c2 is high, the switching waveform may not be normal at low temperatures. c5 is used to enable soft start. if the soft start function is not used, leave the ss terminal open. resistors r1 and r2 r1 and r2 set the output voltage, v o . select the resistor values to set i adj to 0.1 ma. r 1 and r 2 are calculated by the following expression: ?? ?? ?? ?? ? ? ? ? ? ? ? ? ? ? ? ? k i v r v i v v r adj fb o adj fb o 5 10 1 . 0 5 . 0 2 10 1 . 0 5 . 0 1 3 3 P phase compensation components c3, c6, and r3 the stability and response of the loop is controlled through the comp pin. the comp pin is the output of the internal transconductance 4.30 1.35 0.54 1.27 2.80 3.00 unit: mm c2 r1 r2 l1 fb gnd vout vsw d1 vin c4 c1 c6 c5 u1 comp c3 r3 en ss figure 1. typical application circuit for general use application information allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
step-down switching regulator with current-mode control si-8005q 7 amplifier. the combination of a series-connected capacitor and resistor sets the combination of a pole and zero frequency point that decide the characteristics of the control system. the dc gain of the voltage feedback loop is calculated by the following equa- tion: vout v a gcs fb ea ? ? ? ? rl adc , (1) where v fb is the feedback voltage (0.5 v), a ea is the error amplifier voltage gain, g cs is the current sense transconductance, and rl is the load resistor value. the system has two important poles. one is set by the phase compensation capacitor (c3) and the output resistor of the error amplifier. the other is set by the output capacitor and load resis- tor. these poles are calculated by the following equations: ea ea a c g fp ? ? ? 3 2 1 rl c fp ? ? ? 2 2 1 2 r c fz ? ? ? resr c fesr ? ? ? 2 2 1 r c fp ? ? ? fb v vout gcs gea fs c vfb vout gcs gea fc c r ? ? ? ? ? ? ? ? ? ? ? 1 . 0 2 2 2 2 3 fc r c ? ? ? 3 2 4 3 fs resr c ? ? ? r resr c c ? ? allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
step-down switching regulator with current-mode control si-8005q 8 using the si-8005q as an led driver si-8005q also can be configured as a high-efficiency constant current led driver. figure 2 is a typical circuit diagram for this application. led current is set by the formula below: i led = v ref / r 2 . note that led current runs through the ic. therefore, choose a proper power rating for r3, based on actual power dissipa- tion and derating based on application ambient temperature. the power dissipation for the resistor is calculated as: p d = i led v ref . pwm dimming by pulsing en input at 100 to 300 hz, led brightness can be dimmed. figure 3 shows led current versus the duty cycle of the en pin. the test was performed with four leds in series. the waveforms in figure 4 show how it works. the en pin peak voltage should be in the range 3 to 5 v, si-8005q i in b s sw ss gnd comp fb r3 r5 r2 c4 c1 c2 c3 l1 en di v i in v o 1 2 3 4 5 6 7 8 gnd gnd v fb leds figure 2. typical application circuit for driving leds figure 3. total led driving current for 4 leds in series figure 4. pwm dimming timing example component rating description c1 (2 ea) 10 f / 50 v input capacitor c2 (2 ea) 22 f / 16 v output capacitor c4 10 nf / 50 v bootstrap capacitor di 5 a / 60 v schottky barrier diode l1 10 h choke coil r2 0.5 / 1 w current sensing resistor r5 1.5 m / 0.5 w trim resistor for improved response time leds in series 345 c3 560 pf 470 pf 360 pf phase compensation capacitor r3 46.4 k 69.8 k 100 k phase compensation resistor 1200 1000 800 600 400 200 0 02040 duty cycle (%) 150 ma 350 ma 500 ma 1000 ma i led (ma) 60 80 100 ic switching i led v sw v en allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
step-down switching regulator with current-mode control si-8005q 9 package outline drawing leadframe plating pb-free. device composition complies with the rohs directive. 5.20 0.15 1.50 0.08 0.08 0.05 0.05 0.40 0.695 typ tracking number in dimple 4.40 6.20 2.90 2.70 1.27 0.40 2 1 8 dimensions in millimeters branding codes (exact appearance at manufacturer discretion): 1st line, type: 8005q 2nd line, lot: sk ymdd where: y is the last digit of the year of manufacture m is the month ( 1 to 9, o, n, d ) dd is the date 3rd line, control : nnnn branding area allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
step-down switching regulator with current-mode control si-8005q 10 packing specification empty tape trailer ic occupied tape leade r cover tape empty tape 160mm 1,000pcs (1,000 pockets) more than 160mm more than 400mm 4 2 8 direction of reel 1.55 5.6 7 2 5.5 ( 4.75 ) 12 180 60 13 0.3 15.4 0.1 13 0.2 b 3 r22 vo i d 10 vo i d vo i d vo i d 60 60 13 3 r 22 5 5 2 30 3 60 60 10 10.5 center extension 4 11.9 vo i d vo i d vo i d vo i d units mm allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
step-down switching regulator with current-mode control si-8005q 11 in general, the junction temperature level of surface mount pack- age ics is dependent upon the area and material of the pc board and its copper area. therefore, please design the pcb to allow sufficient margin for heat dissipation. parallel operation parallel operation of multiple products to increase the current is not allowed. thermal shutdown the si-8000q series has a thermal protec- tion circuit. this circuit keeps the ic from the damage by over- load. but this circuit cannot guarantee the long-term reliability against the continuous overload conditions. esd susceptibility take precautions against damage by static electricity. cautions the products described herein are manufactured in ja pan by sanken electric co., ltd. for sale by allegro microsystems, inc. sanken and allegro reserve the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be re quired to per mit im- prove ments in the per for mance, reliability, or manufacturability of its prod ucts. therefore, the user is cau tioned to ve rify that the in for ma tion in this publication is current before placing any order. when using the products described herein, the ap pli ca bil i ty and suit abil i ty of such products for the intended purpose s hall be reviewed at the users responsibility. although sanken undertakes to enhance the quality and reliability of its prod ucts, the occurrence of failure and defect of sem i con duc tor products at a certain rate is in ev i ta ble. users of sanken products are requested to take, at their own risk, preventative measures including safety design of the equipme nt or systems against any possible injury, death, fires or damages to society due to device failure or malfunction. sanken products listed in this publication are designed and intended for use as components in general-purpose electronic equip ment or apparatus (home ap pli anc es, office equipment, tele com mu ni ca tion equipment, measuring equipment, etc.). their use in any applicat ion requiring radiation hardness assurance (e.g., aero space equipment) is not supported. when considering the use of sanken products in ap pli ca tions where higher reliability is re quired (transportation equipment and its control systems or equip ment, fire- or burglar-alarm systems, various safety devices, etc.), contact a company sales representative to discuss and obtain written confirmation of your spec i fi ca tions. the use of sanken products without the written consent of sanken in applications where ex treme ly high reliability is required (aerospace equip- ment, nuclear power-control stations, life-support systems, etc.) is strictly prohibited. the information in clud ed herein is believed to be accurate and reliable. ap pli ca tion and operation examples described in this pub li ca tion are given for reference only and sanken and allegro assume no re spon si bil i ty for any in fringe ment of in dus tri al property rights, intellectual property rights, or any other rights of sanken or allegro or any third party that may result from its use. copyright ? 2009 allegro microsystems, inc. allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
step-down switching regulator with current-mode control si-8005q 12 asia-pacific china sanken electric hong kong co., ltd. suite 1026, ocean centre, canton road tsimshatsui, kowloon, hong kong tel: 852-2735-5262, fax: 852-2735-5494 sanken electric (shanghai) co., ltd. room 3202, maxdo centre, xingyi road 8 changning district, shanghai, china tel: 86-21-5208-1177, fax: 86-21-5208-1757 taiwan sanken electric co., ltd. room 1801, 18th floor, 88 jung shiau east road sec. 2, taipei 100, taiwan r.o.c. tel: 886-2-2356-8161, fax: 886-2-2356-8261 japan sanken electric co., ltd. overseas sales headquarters metropolitan plaza building, 1-11-1 nishi-ikebukuro toshima-ku, tokyo 171-0021, japan tel: 81-3-3986-6164, fax: 81-3-3986-8637 korea sanken electric korea co., ltd. mirae asset life building, 6f 168 kongduk-dong, mapo-ku seoul 121-705, korea tel: 82-2-714-3700, fax: 82-2-3272-2145 singapore sanken electric singapore pte. ltd. 150 beach road, #14-03 the gateway west singapore 189720 tel: 65-6291-4755, fax: 65-6297-1744 europe sanken power systems (uk) limited pencoed technology park pencoed, bridgend cf35 5hy, united kingdom tel: 44-1656-869-100, fax: 44-1656-869-162 north america united states allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01606, u.s.a. tel: 1-508-853-5000, fax: 1-508-853-7895 allegro microsystems, inc. 14 hughes street, suite b105 irvine, california 92618, u.s.a. tel: 1-949-460-2003, fax: 1-949-460-7837 worldwide contacts allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com

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