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AS1321 130ma step-up dc-dc converter www.austriamicrosystems.com revision 1.02 1 - 13 datasheet 1 general description the AS1321 is a high-efficiency step-up dc-dc con- verter designed to generate a fixed output voltage of +5.0v. the AS1321 achieves an efficiency of up to 96%. the minimum input voltage is +1.5v, the output voltage is fixed at +5.0v, and output current is up to 130ma (@ 2v v batt ). in order to save power the AS1321 features a shutdown mode, where it draws less than 1a. in shutdown mode the battery is connected dire ctly to the output enabling the supply of real-time-clocks. the AS1321 provides a power-on reset output that goes high-impedance when the output reaches 90% of its reg- ulation point. the shdnn trip threshold of the AS1321 can be used as an input voltage detector that disables the device when the battery voltage falls to a predetermined level. an internal synchronous rectifier is included, which is parallel with the external schottky diode. the AS1321 is available in a 6-pin sot23 package. figure 1. AS1321 - typical application diagram 2 key features fixed output voltage: +5.0v output current: up to 130ma (@ 2v v batt ) internal synchronous rectifier shutdown mode supply current: less than 1a efficiency: up to 96% minimum input voltage: +1.5v accurate shutdown low-bat tery cutoff threshold battery input connected to pin out in shutdown mode for backup power 6-pin sot23 package 3 applications the AS1321 is ideal for low-power applications where ultra-small size is critical as in medical diagnostic equip- ment, hand-held instruments, pagers, digital cameras, remote wireless transmitters, cordless phones, and pc cards. the device is also perfect as a local +5.0v supply or as a battery backup. AS1321 +1.5v to +5.0v battery +5.0v output c out 22f c in 22f l1 10h resetn output r 1 100k on off 4 lx 3 gnd 2 batt 6 resetn 1 shdnn 5 out
www.austriamicrosystems.com revision 1.02 2 - 13 AS1321 datasheet - pinout 4 pinout pin assignments figure 2. pin assignments (top view) pin descriptions table 1. pin descriptions name pin number description shdnn 1 active-low logic shutdown input 0 = the AS1321 is off and the current into batt is 1a (typ). 1 = the AS1321 is on. batt 2 battery voltage input gnd 3 ground lx 4 external inductor connection out 5 output voltage resetn 6 active-low reset output AS1321 1 batt 2 3 6 5 4 gnd shdnn out lx resetn
www.austriamicrosystems.com revision 1.02 3 - 13 AS1321 datasheet - absolute maximum ratings 5 absolute maximum ratings stresses beyond those listed in table 2 may cause permanent damage to the device. these are stress ratings only, and functional operation of the de vice at these or any other cond itions beyond those indicated in section 6 electrical characteristics on page 4 is not implied. exposure to absolute maxi mum rating conditions for extended periods may affect device reliability. table 2. absolute maximum ratings parameter min max units comments all pins to gnd -0.3 7 v lx current 1 a latch-up -100 100 ma jedec 78 package power dissipation (t amb = +70oc) 500 mw ( ja = 9.1mw/oc above +70oc) operating temperature range -40 +85 oc electrostatic discharge -500 +500 v hbm mil-std. 883e 3015.7 methods humidity (non-condensing) 5 85 % storage temperature range -55 125 oc junction temperature 150 oc package body temperature 260 oc the reflow peak soldering temperature (body temperature) specified is in compliance with ipc/jedec j-std-020d ?moisture/ reflow sensitivity classification for non-hermetic solid state surface mount devices? .
www.austriamicrosystems.com revision 1.02 4 - 13 AS1321 datasheet - electrical characteristics 6 electrical characteristics t amb = -40 to +85oc, v batt = +2v, v out = +5.0, v shdnn = +1.5v (unless otherwise specified). typ values @ t amb = +25oc. table 3. electrical characteristics parameter symbol conditions min typ max unit battery input range v batt 1.5 5.0 v startup battery input voltage 1 1. guaranteed by design. v su r load = 100 , t amb = +25oc 1.22 1.5 v r load = 100 , t amb = -40 to +85oc 1.24 output voltage 2 2. voltage which triggers next loading cycle. rip ple and rms value depend on external components. v out t amb = +25oc 4.950 5.000 5.050 v t amb = -40 to +85oc 4.875 5.125 n-channel on-resistance r nch i lx = 100ma, t amb = +25oc 0.3 1.2 i lx = 100ma, t amb = -40 to +85oc 1.5 p-channel on-resistance r pch i lx = 100ma, t amb = +25oc 0.4 1.3 i lx = 100ma, t amb = -40 to +85oc 1.6 n-channel switch current limit 1 i max t amb = +25oc 550 700 850 ma t amb = -40 to +85oc 450 950 switch maximum on-time t on t amb = +25oc 5 7 9 s t amb = -40 to +85oc 4 10 synchronous rectifier zero-crossing current t amb = +25oc 8 30 60 ma t amb = -40 to +85oc 0 65 quiescent curr ent into out 3 3. the quiescent current is measured while the dc-dc converter is not switching. v out = +5.5v, t amb = +25oc 35 55 a v out = +5.5v, t amb = -40 to +85oc 60 shutdown current into out v shdnn = 0v, t amb = +25oc 0.01 1 a v shdnn = 0v, t amb = -40 to +85oc 2 quiescent current into batt 3 v out = +5.5v, t amb = +25oc 0.01 1 a v out = +5.5v, t amb = -40 to +85oc 2 shutdown current into batt v shdnn = 0v, t amb = +25oc 0.01 1 a v shdnn = 0v, t amb = -40 to +85oc 2 shdnn logic low 1 v batt = +1.5 to +5.0v 0.3 v shdnn threshold rising edge, t amb = +25oc 1.185 1.228 1.271 v rising edge, t amb = -40 to +85oc 1.170 1.286 shdnn threshold hysteresis 0.02 v resetn threshold falling edge, t amb = +25oc 4.288 4.500 4.712 v falling edge, t amb = -40 to +85oc 4.242 4.758 resetn voltage low i resetn = 1ma, v out = +2.5v, t amb = +25oc 0.15 v i resetn = 1ma, v out = +2.5v, t amb = -40 to +85oc 0.2 resetn leakage current v resetn = +5.5v, t amb = +25oc 0.1 100 na v resetn = +5.5v, t amb = +85oc 1 lx leakage current t amb = +25oc 0.1 1000 na t amb = +85oc 10 maximum load current i load v batt = +2v 130 ma efficiency v batt = +3v, i load = 100ma 91 %
www.austriamicrosystems.com revision 1.02 5 - 13 AS1321 datasheet - typical operating characteristics 7 typical operating characteristics v batt = 2.0v, v out = 5.0v, t amb = +25c (unless otherwise specified). figure 3. efficiency vs. load current figure 4. efficiency vs. input voltage 75 80 85 90 95 100 1 10 100 1000 load current (ma) efficiency (%) v batt = 3v v batt = 2.5v v batt = 2v v batt = 1.5v v batt = 3.5v v batt = 4.5v 50 60 70 80 90 100 12345 battery voltage (v) efficiency (%) iout = 1ma iout = 10 ma iout = 10 0ma figure 5. v out vs. v batt ; on, 39 figure 6. v out vs. v batt ; on, 470 0 1 2 3 4 5 6 012345 battery voltage (v) output voltage (v) 0 1 2 3 4 5 6 012345 battery voltage (v) output voltage (v) figure 7. v out vs. v batt ; shutdown, 130ma load figure 8. v out vs. v batt ; shutdown, no load 0 1 2 3 4 5 6 1.5 2 2.5 3 3.5 4 4.5 5 battery voltage (v) output voltage (v) 0 1 2 3 4 5 6 012345 battery voltage (v) output voltage (v)
www.austriamicrosystems.com revision 1.02 6 - 13 AS1321 datasheet - typical operating characteristics figure 9. maximum ou tput current vs. v batt figure 10. startup voltage vs. load resistance 0 50 100 150 200 250 300 350 400 1.5 2 2.5 3 3.5 4 4.5 5 battery voltage (v) maximum output current (ma) 0 1 2 3 4 5 10 100 1000 10000 load resistance (ohm) supply voltage (v ) figure 11. input current vs. input voltage figure 12. waveforms; r load = 100 , v batt = 3v 0 50 100 150 200 250 300 350 400 12345 battery voltage (v) input current (a) iout = 4a iout = 34 a 10s/div v out v lx 50mv/div 500ma/div i l 2v/div figure 13. line transient figure 14. load transient 100s/div v in 100mv/div 1v/div v out 500s/div v out i out 100mv/div 130ma 2ma
www.austriamicrosystems.com revision 1.02 7 - 13 AS1321 datasheet - typical operating characteristics figure 15. on / off response; r load = 100 figure 16. shutdown response; r load = 100 2ms/div v out v in 1v/div 1v/div 500s/div v out v shdnn 1v/div 2v/div
www.austriamicrosystems.com revision 1.02 8 - 13 AS1321 datasheet - detailed description 8 detailed description the AS1321 is a high-efficiency, compact step-up converte r with 35a quiescent supply current which ensures the highest efficiency over a wide load range. with a minimum of +1.5v input voltage, the device is well suited for applica- tions with one- or two-cells, such as lithium i on (li+), nickel-metal-hydride (nimh), or alkaline. figure 17. AS1321 - block diagram the input battery is connected to the device through an inductor and an inte rnal p-fet when pin shdnn is low. in this state, the step-up converter is off and the voltage drop across the p-fet body diode is eliminated, and the input bat- tery can be used as a battery-backup or real-time-clock supply. the built-in synchronous rectifier si gnificantly improves efficiency. control circuitry the AS1321 integrated current-limited key circuitry provi des low quiescent current and extremely-high efficiency over a wide v out range without the need for an oscillator. inductor current is limited by the 7s switch maximum on-time or by the 0.7a n-channel current limit. at each cycle, the inductor current must ramp down to zero after the on-time before the next cycle may start. when t he error comparator senses that the ou tput has fallen be low the regulation threshold, anot her cycle begins. shutdown when pin shdnn is low the AS1321 is switched off and no cu rrent is drawn from batter y; when pin shdnn is high the device is switched on. if shdnn is driven from a logic-leve l output, the logic high-level (on) should be referenced to v out to avoid intermittently switching the device on. note: if pin shdnn is not used, it should be connected directly to pin out. in shutdown the battery input is connected to the output th rough the inductor and the internal synchronous rectifier p- fet. this allows the input battery to provide backup power fo r devices such as an idle microcontroller, memory, or real- time-clock, without the usual diode forward drop. in this way a separate backup battery is not needed. in cases where there is residual voltage during shutdown , some small amount of energy will be transferred from pin out to pin batt immediately after shutdown, resulting in a momentary spike of the voltage at pin batt. the ratio of c in and c out partly determine the size and duration of this spike, as does the current-sink ability of the input device. v ref zero crossing detector AS1321 driver and control logic startup circuitry 10h +1.5 to +5.0v battery current limiter +1.228v c in 22f + ? + ? +1.1v +5.0v output c out 22f 4 lx 2 batt 6 resetn 1 shdnn 5 out gnd 3
www.austriamicrosystems.com revision 1.02 9 - 13 AS1321 datasheet - detailed description low-battery cutoff the AS1321 shdnn trip threshold (1.228v) can be used as an input voltage detector that disables the device when the battery input voltage falls to a pre-set level. an exter nal resistor-divider network can be used to set the battery- detection voltage (see figure 18) . figure 18. low-battery cutoff application diagram for the resistor-divider network shown in figure 18 , calculate the value for r 1 by: r 1 = r 2 x ((v off /v shdnn ) - 1) (eq 1) where: v off is the battery voltage at which the AS1321 shuts down. v shdnn = 1.228v the value of r 2 should be between 100k and 1m to minimize battery drain. note: input ripple can cause false shutdowns, therefore to minimize the effect of ripple, a low-value capacitor from shdnn to gnd should be used to filter out input noise. the value of the capa citor should be su ch that the r/c time constant is > 2ms. power-on reset the AS1321 provides a power-on reset ou tput (resetn) that goes high-impedance wh en the output reaches 90% of its regulation point. resetn goes low when the output is below 90% of the regula tion point. a 100k to 1m pullup resistor between pin resetn a nd pin out can provide a micropr ocessor logic co ntrol signal. note: connect pin resetn to gnd when the pow er-on reset feature is not used. +1.5 to +5.0v battery +5.0v output c out 22f c in 22f l1 10h power-on reset r 3 100k 10nf r 1 220k r 2 1m AS1321 4 lx 3 gnd 2 batt 6 resetn 1 shdnn 5 out
www.austriamicrosystems.co m revision 1.02 10 - 13 AS1321 datasheet - application information 9 application information inductor selection the control circuitry of the AS1321 permits a wide range of indu ctor values to be selected ? from 4.7 to 47h; 10h is ideal for most applications. the intended application should dictate the value of l. the trade-off between required pcb surface area and desired output ripple are the determining factors: smaller values fo r l require less pcb space, larger values of l reduce output ripple. if the value of l is large enough to prevent i max from being reached before t on expires, the AS1321 output power will be reduced. for maximum output current calculate the value for l as: (v batt(max) (1s))/0.7a < l < (v batt(min) (7s))/0.7a (eq 2) i out(max) = (0.7a/2)(v batt(min) - (0.7a/2)(r nch + r ind ))/v out (eq 3) where: r ind is the inductor series resistance. r nch is the r ds(on) of the n-channel mosfet (0.3 typ). note: coils should be able to handle 500ma rms and have a i sat 1a and should have a r ind 100m . capacitor selection c out selection choose a c out value to achieve the desired output ripple percentage. a 22f ceramic capacitor is a good initial value. the value for c out can be determined by: c out > (l + 2.5h) x v batt(max) 2 / (r% x 4) (eq 4) where: r is the desired output ripple in %. c in selection c in reduces the peak current drawn from t he battery and can be the same value as c out . a larger value for c in can be used to further reduce ripple and improve AS1321 efficiency. external diode an external schottky diode must be connected, in parallel wit h the on-chip synchronous rectif ier, from lx to out. use diodes such as mbr0520l, ep05q03l, or the generic 1n5817 . the diode should be rated for 500ma, since it carries current during startup and after the synchronous rectifier tu rns off. the schottky diode must be connected as close to the ic as possible. ordinary rectifier diodes must not be us ed, since the slow recovery ra te will compromise efficiency. pc board layout and grounding well-designed printed circuit-board layout is important for minimizing ground bounce and noise. place pin gnd lead and the ground leads of c in and c out as close to the device as possible. keep the lead to pin lx as short as possible. to maximize output power and efficiency and minimize output ripple voltage, use a ground plane and solder the gnd pin directly to the ground plane.
www.austriamicrosystems.co m revision 1.02 11 - 13 AS1321 datasheet - package drawings and markings 10 package drawings and markings the AS1321 is available in a 6-pin sot23 package. figure 19. 6-pin sot23 package symbol min max a 0.90 1.45 a1 0.00 0.15 a2 0.90 1.30 b 0.35 0.50 c 0.08 0.20 d 2.80 3.00 e 2.60 3.00 e1 1.50 1.75 l 0.35 0.55 e0.95 ref 0o 10o notes: 1. all dimensions are in millimeters. 2. foot length is measured at the intercept point between datum a and lead surface. 3. package outline exclusive of mold flash and metal burr. 4. pin 1 is the lower left pin when reading the top mark from left to right. 5. pin 1 identifier dot is 0.3mm. min and is located above pin 1. 6. meets jedec mo178 .
www.austriamicrosystems.co m revision 1.02 12 - 13 AS1321 datasheet - ordering information 11 ordering information the AS1321 is available as the standard products shown in table 4 . note: all products are rohs compliant and pb-free. buy our products or get free samples online at icdirect: http://www.austriamicr osystems.com/icdirect for further information and requests, please contact us mailto:sales@austriamicrosystems.com or find your local distributor at http://www.a ustriamicrosystems.com/distributor table 4. ordering information ordering code marking description delivery form package AS1321-t askx 130ma step-up dc-dc converter tape and reel 6-pin sot23
www.austriamicrosystems.co m revision 1.02 13 - 13 AS1321 datasheet copyrights copyright ? 1997-200 9, austriamicrosystems ag, tobelbaderstrasse 30, 8141 unterpremstaet ten, austria-europe. trademarks registered ?. all rights reserved. the mate rial herein may not be reproduced, adapted, merged, translated, stored, or used wit hout the prior written consent of the copyright owner. all products and companies mentioned are trademarks or registered trademarks of their respective companies. disclaimer devices sold by austriamicrosystems ag are covered by t he warranty and patent indemni fication provisions appearing in its term of sale. austriamicrosystems ag makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freed om of the described devices from patent infringement. austriamicrosystems ag reserves the right to change spec ifications and prices at an y time and without notice. therefore, prior to designing this pro duct into a system, it is necessary to check with austriam icrosystems ag for current information. this product is intended for use in normal commercial applications. applications requiring extended temperature range, unus ual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by austriamicrosystems ag for each application. for shipments of less than 100 parts the m anufacturing flow might show deviations from the standard production flow, such as test flow or test location. the information furnished here by austriamicrosystems ag is believed to be correct and accurate. however, austriamicrosystems ag shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. no obligation or liability to reci pient or any third party shall arise or flow out of austriamicrosystems ag rendering of technical or other services. contact information headquarters austriamicrosystems ag tobelbaderstrasse 30 a-8141 unterpremstaetten, austria tel: +43 (0) 3136 500 0 fax: +43 (0) 3136 525 01 for sales offices, distributors a nd representatives, please visit: http://www.austriamicrosystems.com/contact

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