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www.ams.com/dc-dc_step-up/AS1341 revision 1.09 1 - 18 a s1 3 4 1 6 50 m a , u lt r a lo w ri p p le s te p do w n d c/ dc co n v e r te r 1 general description the AS1341 is a high-efficiency step-down converter with adjustable output voltages from 1.25v to v in using supply voltages of up to 20v. an integrated current-limited 0.4 w mosfet delivers load currents up to 600ma. the AS1341 also includes a 100% duty cycle ldo mode with a low dropout of only 250mv for high efficiency if input voltages is in the range of the output voltage. the AS1341 has a low quiescent current (12a) to im prove light- load efficiency and minimize battery use, and draws only 0.8a in shutdown mode. high switching frequencies (up to 200khz) allow the use of small surface-mount inductors and output capacitors. the device is available in a tdfn-8 3x3mm pin packa ge. figure 1. AS1341 - typical application 2 key features output voltages: fixed 5v or adjustable input voltage range: 4.5v to 20v output current: up to 600ma 1.25v lowest output voltage efficiency: up to 96% quiescent supply current: 12a power-ok output internal 0.4 w p-channel mosfet shutdown current: 0.8a 100% maximum duty cycle for low dropout current-limited architecture thermal shutdown tdfn-8 3x3mm package 3 applications the device is ideal for notebook computers, distrib uted power systems, keep-alive supplies, and any other battery -operated, portable device. v in 4.5v to 20v 5 in 1 fb c in v out = 5v AS1341 2 gnd 8 out d1 c out + indicates high-power trace 3 pok r pull 7 shdnn 6 ilimit 4 lx l1
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 2 - 18 AS1341 datasheet - p i n a s s i g n m e n t s 4 pin assignments figure 2. pin assignments (top view) 4.1 pin descriptions table 1. pin descriptions pin number pin name description 1 fb feedback input . for the fixed 5v output connect this pin to gnd. for adjustable output, connect to a resistive divider between v out and gnd to set the output voltage between 1.25v an d v in . 2 gnd ground 3 pok power ok . active-low open-drain reset output. note: connect pin pok to gnd when the power-ok feature is not used. 4 lx inductor connection . connect this pin to an external inductor. 5 in 4.5v to 20v input supply voltage 6 ilimit peak current control input . connect this pin to in or gnd to set peak current limit (see setting current limit on page 11) . 7 shdnn shutdown input . a low on this pin puts the AS1341 into shutdown m ode. supply current is reduced to 0.8a and lx goes high-impedance. 8 out regulated output voltage high-impedance sense input . for the fixed 5v output connect this pin to v out . for adjustable output connect this pin to gnd. 9 nc exposed pad. this pad is not connected internally. connect to g nd or do not connect. 5 in 3 pok 2 gnd 1 fb 8 out AS1341 4 lx 7 shdnn 6 ilimit 9
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 3 - 18 AS1341 datasheet - a b s o l u t e m a x i m u m r a t i n g s 5 absolute maximum ratings stresses beyond those listed in table 2 may cause permanent damage to the device. these ar e stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in electrical characteristics on page 4 is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. table 2. absolute maximum ratings parameter min max units comments electrical parameters in to gnd -0.3 +23 v lx to gnd -2 v in + 0.3 v fb to gnd -0.3 +5 v ilimit, shdnn, out, pok to gnd -0.3 v in + 0.3 v peak input current 2 a temperature ranges and storage conditions thermal resistance q ja 36.3 oc/w on pcb storage temperature range -55 +150 oc junction temperature +150 oc package body temperature +260 oc the reflow peak soldering temperature (body temperature) specified is in accordance with ipc/ jedec j-std-020 moisture/reflow sensitivity classification for non-hermetic solid state surface mount devices. the lead finish for pb-free leaded packages is matt e tin (100% sn). humidity non-condensing 5 85 % moisture sensitive level 1 represents a max. floor life time of unlimited
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 4 - 18 AS1341 datasheet - e l e c t r i c a l c h a r a c t e r i s t i c s 6 electrical characteristics v in = +12v, shdnn = v in , typical values are at t amb = +25oc (unless otherwise specified). specificatio ns based on circuit shown in figure 1 on page 1 . note: all limits are guaranteed. the parameters with min and max values are guaranteed with production tests or sqc (statistical quality control) methods. table 3. electrical characteristics symbol parameter conditions min typ max units t amb operating temperature range -45 85 c v in input voltage range 4.5 20 v v out output voltage (preset output) fb = gnd 4.85 5.00 5. 15 v output voltage (adjustable) 1.25 v in v dropout dropout voltage i out = 600ma, ilimit = v in 250 mv line regulation v in = 6v to 20v, 200 w load 0.1 %/v load regulation ilimit = v in , i out = 0 to 500ma 1 % v fb feedback set voltage (adjustable output) 1.212 1.25 1.288 v i in input supply current no load 12 18 a i indrop input supply current in dropout no load 45 60 a input shutdown current shdnn = gnd 0.8 3 a v uvlo input undervoltage lockout threshold v in rising 3.6 4.0 4.4 v v in falling 3.5 3.9 4.3 out bias current v out = 5.5v 2 3.5 5 a i fb fb bias current v fb = 1.3v -25 +25 na fb threshold low 50 100 150 mv thermal shutdown 10oc hysteresis 145 oc dc-dc switches t offmin lx switch minimum off-time 0.2 0.4 0.6 s t onmax lx switch maximum on-time v fb = 1.3v 8 10 12 s r lx lx switch on-resistance v in = 6v 0.4 w v in = 4.5v 0.5 i lxpeak lx current limit ilimit = gnd, l = 39h 500 700 900 ma ilimit = in, l = 10h 1000 1400 1800 lx zero-crossing threshold -75 +75 mv zero-crossing timeout lx does not rise above the th reshold 30 s lx switch leakage current v in = 20v, lx = gnd, t amb = +25oc 0.1 a v in = 20v, lx = gnd 1 control inputs digital input level shdnn, ilimit = gnd 0.8 v shdnn, ilimit = in 2.4 digital input leakage current v shdnn , v ilimit = 0 to 20v, v in = 20v -100 +100 na power-ok power-ok threshold falling edge, relative to v out 90 92.5 95 % pok output voltage low i pok = 1ma 0.4 v pok output leakage current v in , v pok = 16v, t amb = 25c 0.1 a v in , v pok = 16v 1
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 5 - 18 AS1341 datasheet - ty p i c a l o p e r a t i n g c h a r a c t e r i s t i c s 7 typical operating characteristics v out = 5v, t amb = +25oc (unless otherwise specified). figure 3. efficiency vs. i out figure 4. efficiency vs. i out 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 100 1000 output current (ma) efficiency (%) . v in = 20v v in = 12v v in = 6v ilimit = high 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 100 1000 output current (ma) efficiency (%) . v in = 20v v in = 12v v in = 6v ilimit = low figure 5. efficiency vs. i out ; v out = 3.3v figure 6. efficiency vs. i out ; v out = 3.3v 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 100 1000 output current (ma) efficiency (%) . v in = 20v v in = 12v v in = 4.5v ilimit = high 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 100 1000 output current (ma) efficiency (%) . v in = 20v v in = 12v v in = 4.5v ilimit = low figure 7. efficiency vs. i out ; v in = 12v figure 8. efficiency vs. i out ; v in = 12v 65 70 75 80 85 90 95 0.1 1 10 100 1000 output current (ma) efficiency (%) . 22uh 10uh 4.1uh ilimit = high 65 70 75 80 85 90 95 0.1 1 10 100 1000 output current (ma) efficiency (%) . 10uh 39uh 22uh ilimit = low
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 6 - 18 AS1341 datasheet - ty p i c a l o p e r a t i n g c h a r a c t e r i s t i c s figure 9. efficiency vs. input voltage figure 10. output voltage vs. input voltage 70 75 80 85 90 95 100 5 8 11 14 17 20 input voltage (v) efficiency (%) . vout=3.3v, iout=500ma vout=5v, iout=500ma vout=3.3v, iout=250ma vout=5v, iout=250ma 4.85 4.9 4.95 5 5.05 5.1 5.15 5 8 11 14 17 20 input voltage (v) v out (v) . iout = 1ma iout = 100ma iout = 300ma iout = 500ma iout = 600ma figure 11. output voltage vs. input voltage; v out = 3.3v figure 12. peak switch current vs. input voltage; v out = 3.3v 3.2 3.25 3.3 3.35 3.4 4 6 8 10 12 14 16 18 20 input voltage (v) v out (v) . iout = 1ma iout = 100ma iout = 300ma iout = 500ma 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 5 8 11 14 17 20 input voltage (v) peak switch current (a) . ilimit = high l=10h ilimit = high l=39h ilimit = low l=10h ilimit = low l=39h figure 13. switching frequency vs. output current; v in = 12v, v out = 5v, l = 10h figure 14. switching frequency vs. output current; v in = 12v, v out = 3.3v, l = 10h 0 50 100 150 200 250 0 100 200 300 400 500 600 output current (ma) switching frequency (khz) . ilimit = high ilimit = low 0 50 100 150 200 250 0 100 200 300 400 500 600 output current (ma) switching frequency (khz) . ilimit = high ilimit = low
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 7 - 18 AS1341 datasheet - ty p i c a l o p e r a t i n g c h a r a c t e r i s t i c s figure 15. load regulation, v out vs. i out ; v in = 12v, v out = 5v figure 16. load regulation, v out vs. i out ; v in = 12v, v out = 3.3v 4.85 4.9 4.95 5 5.05 5.1 5.15 0 100 200 300 400 500 600 output current (ma) output voltage (v) . ilimit = high ilimit = low ilimit = high ilimit = low 3.2 3.25 3.3 3.35 3.4 0 100 200 300 400 500 600 output current (ma) output voltage (v) . ilimit = high ilimit = low figure 17. line transient response; i out = 500ma figure 18. load transient response 200s/div vin vout ilx 10v 15v 1a/div 100mv/div 10s/div vlx ilx vout iload 50mv/div 10ma 500ma 1a/div 10v/div figure 19. lx waveform; v in = 20v, i out = 500ma figure 20. startup waveform; r load = 100 w 2s/div 50mv/div vlx il vout 10v/div 1a/div 100s/div 1a/div ilx vshdnn vout 5v/div 0v 5v
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 8 - 18 AS1341 datasheet - d e t a i l e d d e s c r i p t i o n 8 detailed description the AS1341 step-down converter was specifically des igned for battery-powered portable devices, includi ng laptop computers, pdas, and mp3/ dvd/cd players. the advanced current-limited contro l scheme provides high-efficiency over a wide range of output loads. the highly-efficient operation (up to 100% duty cycle) allows extremely low dropout voltage, increasing the usable supply v oltage range. in no-load conditions the AS1341 draws only 12a; in shutdown mode it draws o nly 0.8a to further reduce power consumption and e xtend battery life. the AS1341 features an integrated 20v switching mos fet, internal current sensing, and a high switching frequency, for minimal pcb space and external component requirements. figure 21. AS1341 - block diagram - 5v fixed outpu t voltage 8.1 current-limit control the AS1341 uses a proprietary current-limiting cont rol scheme with operation up to 100% duty cycle. th e dc-dc converter pulses as needed to maintain regulation, resulting in a variable switch ing frequency that increases with the load. this el iminates the high-supply currents associated with conventional constant-frequency pulse-width-mo dulation (pwm) controllers that unnecessarily switc h the mosfet. when the output voltage is too low, the error compa rator sets a flip-flop, which turns on the internal p-channel mosfet and begins a switching cycle. the inductor current ramps up linearly, stor ing energy in a magnetic field while charging the o utput capacitor and servicing the load (see figure 19 on page 7) . the mosfet turns off when the peak current limit is reached, or when the maximum on-time of 10s is ex ceeded and the output voltage is in regulation. if the output is out of regulation and the peak current is never reached, the mosfet remai ns on, allowing a duty cycle up to 100%. this feature ensures the lowest possible dropout vo ltage. once the mosfet turns off, the flip-flop resets, th e inductor current is pulled through d1 (see figure 21) , and the current through the inductor ramps back down, transferring the stored energy to the output capacitor and load. the mosfet remains o ff until the 0.4s minimum off-time expires, and the output voltage goes out of regulat ion. AS1341 4 lx 8 out 5 in 1 fb 6 ilimit current limit control 2 gnd + C maximum on- time delay q r s minimum off-time delay + C + C 100mv v set 1.25v + C + C + C + C l1 c in c out + d1 r pull 3 pok 7 shdnn
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 9 - 18 AS1341 datasheet - d e t a i l e d d e s c r i p t i o n 8.2 dropout voltage a buck converters minimum input-to-output voltage differential (dropout voltage) determines the lowes t usable supply voltage. in battery- powered systems, this limits the useful end-of-life battery voltage. to maximize battery life, the as1 341 operates with duty cycles up to 100%, which minimizes the dropout voltage and eliminates switching losses while in dropout. when the supply voltage approaches the output voltage, the p-channel mosfet remains on continuously to sup ply the load. note: dropout voltage is defined as the difference betwee n the input and output voltages when the input is l ow enough for the output to drop out of regulation. for a step-down converter with 100% duty cycle, dro pout is related to the mosfet drain-to-source on-re sistance (r dson ) and inductor series resistance (r inductor ), and thus it is proportional to the load current: v dropout = i out x (r dson + r inductor ) (eq 1) 8.3 shutdown a logic low on pin shdnn shuts down the AS1341; a l ogic high on shdnn powers on the device. in shutdown mode the supply current drops to 0.8a to maximize battery life, and the internal p-channe l mosfet turns off to isolate the output from the input. the output capacitance and load cur rent determine the output voltage decay rate. note: pin shdnn should not be left floating. if the shutd own feature is not used, connect shdnn to in. 8.4 power-ok output the AS1341 provides a power ok output (pok) that go es high-impedance when the output reaches 92.5% of its regulation point. pok goes low when the output is below 92.5% of the regulation po int and the AS1341 is turned on (in 3 4.5v and shdnn 3 2.4v). a 12k w to 1m w pullup resistor between pin pok and pin in or pin out or a nother voltage ( in) can provide a microprocessor logic control sig nal. note: connect pin pok to gnd when the power-ok feature is not used. 8.5 thermal-overload protection integrated thermal-overload protection limits total power dissipation in the AS1341. during continuous thermal-overload conditions, when the AS1341 junction temperature exceeds t j = +145oc, the internal thermal sensor turns off th e pass transistor, allowing the AS1341 to cool down . when the AS1341 junction temperature cools by 10oc, the thermal sensor turns the pass transistor on ag ain resulting in a pulsed output.
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 10 - 18 AS1341 datasheet - a p p l i c a t i o n i n f o r m a t i o n 9 application information 9.1 adjusting output voltage the AS1341 feedback input features dual-mode operat ion. connect fb to gnd for the 5.0v preset output v oltage (see figure 21 on page 8) . adjust the output voltage by connecting a voltage-d ivider from the output to gnd (see figure 22) . figure 22. adjustable output voltage circuit select a value for r 2 between 10k and 1m w . calculate r 1 as: (eq 2) where: v fb = 1.25v. v out may range from 1.25v to v in . 9.2 negative output voltage v in may range from 4.5v to (20v-v out ). therefore the maximum negative output voltage is -15v. figure 23. adjustable negative output voltage circ uit v in 4.5v to 20v 5 in 7 shdnn 8 out c in 1.25v to v in 2 gnd 6 ilimit 1 fb d1 c out + r 2 r 1 indicates high-power trace AS1341 3 pok r pull 4 lx l1 r 1 r 2 v out v fb ------------- 1C ? ? ? ? = v in 4.5v to (20v-v out) 5 in 7 shdnn 4 lx 8 out c in v out = -1.25v to -15v 2 gnd 6 ilimit 1 fb d1 l1 r 2 r 1 indicates high-power trace AS1341 3 pok c out +
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 11 - 18 AS1341 datasheet - a p p l i c a t i o n i n f o r m a t i o n 9.3 setting current limit the AS1341 adjustable peak current limit is set by connecting ilimit as shown in table 4 . the current limit chosen should reflect the maximum load current. the maximum output current is half o f the peak current limit. choosing a lower current limit allows using an inductor with a lower current rating, however, it requires a higher indu ctance (see inductor selection) and does not allow for reduced inductor package size. 9.4 inductor selection the AS1341 operates with a wide range of inductance values. for most applications, values between 10h and 47h work best with the controllers high switching frequency. larger induc tor values will reduce the switching frequency and thereby improve efficiency and emi. note: the four key factors in inductor selection are indu ctance value, saturation rating, series resistance, and size. the trade-off for improved efficiency is a higher o utput ripple and slower transient response. on the other hand, low-value inductors respond faster to transients, improve output ripple, offer smaller physical size, and minimize cost. if the in ductor value is too small, the peak inductor current exceeds the current limit due to current-se nse comparator propagation delay, potentially excee ding the inductors current rating. calculate the minimum inductance value as follows: l min = ((v inmax - v output ) x t onmin /i lxpeak (eq 3) where: t onmin = 1s the inductor saturation current rating must be grea ter than the peak switch current limit, plus the ov ershoot due to the 250ns current-sense comparator propagation delay. saturation occurs whe n the magnetic flux density of the inductor reaches the maximum level the core can support and the inductance starts to fall. choose an induct or with a saturation rating greater than ipeak in t he following equation: i peak = (i lxpeak + (v in - v output ) x 250ns)/l (eq 4) inductor series resistance affects both efficiency and dropout voltage (see dropout voltage on page 9) . high series resistance limits the maximum current available at lower input voltages, and increases the dropout voltage. for optimum perf ormance, select an inductor with the lowest possible dc resistance that fits in the allo tted dimensions. table 4. setting peak current limit current limit ilimit connected to 700ma gnd 1400ma in table 5. recommended inductors part number l dcr current rating manufacturer mss6132-103ml 10h 85m w 1.4a coilcraft www.coilcraft.com lps4018-472ml 4.7h 125m w 1.8a mss6132-393ml 39h 345m w 0.8a lps4018-223ml 22h 360m w 0.7a cdrh6d28np-150 15h 62m w 1.4a sumida www.sumida.com cdrh5d18np-4r1 4.1h 57m w 1.95a cdrh6d28np-470 47h 176m w 0.8a cdrh5d18np-220 22h 215m w 0.8a lqh66sn-100m03 10h 36m w 1.6a murata www.murata.com lqh55dn-150m03 15h 150m w 1.4a lqh66sn-470m03 47h 170m w 0.8a lqh55dn-470m03 47h 400m w 0.8a
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 12 - 18 AS1341 datasheet - a p p l i c a t i o n i n f o r m a t i o n 9.5 maximum output current the AS1341 output current determines the regulator s switching frequency. when the converter approache s continuous mode, the output voltage falls out of regulation. for the typical ap plication, the maximum output current is approximat ely: i loadmax = 1/2 x i lxpeakmin (eq 5) for low-input voltages, the maximum on-time may be reached and the load current is limited by: i load = (1/2 x (v in - v out ) x 10s)/l (eq 6) 9.6 output capacitor choose the output capacitor to service the maximum load current with acceptable voltage ripple. the ou tput ripple has two components: variations in the charge stored in the output capac itor with each lx pulse, and the voltage drop acros s the capacitors equivalent series resistance (esr) caused by the current into and out of the capacitor: v ripple @ v rippleesr + v ripplec (eq 7) the output voltage ripple as a consequence of the e sr and output capacitance is: v rippleesr = esr x i peak (eq 8) v ripplec = (l x (i peak - i output )2)/(2 x (c out x v output )) x v in /(v in - v output ) (eq 9) where: i peak is the peak inductor current (see inductor selection on page 11) . the worst-case ripple occurs at no-load. equations eq 7 , eq 8 , and eq 9 are suitable for initial capacitor selection, but actual values should be set by testing a prototype or evaluation circuit. as a general rule, a smaller amount of cha rge delivered in each pulse results in less output ripple. since the amount of charge delivered in each oscillator pulse is determined by the induc tor value and input voltage, the voltage ripple inc reases with larger inductance, and as the input voltage decreases. table 6. recommended output capacitor part number c esr rated voltage manufacturer t520v107m010ate018 100f 18m w 10v kemet www.kemet.com a700v826m006ate018 82f 18m w 6.3v t520b107m006ate040 100f 40m w 6v t520a336m006ate070 33f 70m w 6.3v a700v226m006ate028 22f 28m w 6.3v 510x107m020ate040 10f 40m w 20v eefud0j101r 100f 15m w 6.3v panasonic www.panasonic.com eefcd0k330r 33f 18m w 8v 10tpb100ml 100f 55m w 10v sanyo www.edc.sanyo.com 6tpb47m 47f 70m w 6.3v
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 13 - 18 AS1341 datasheet - a p p l i c a t i o n i n f o r m a t i o n 9.7 input capacitor the input filter capacitor reduces peak currents dr awn from the power source and reduces noise and vol tage ripple on the input caused by the circuits switching. the input capacitor must meet the ripple-current requirement (i rms ) imposed by the switching current defined as: i rms = (i load x v output )/v in x ? ((4/3) x (v in - v output ) - 1) (eq 10) for most applications, non-tantalum type (ceramic, aluminum, polymer, or os-con) are preferred due to their robustness to high in-rush currents typical of systems with low-impedance batt ery inputs. alternatively, connect two (or more) sm aller value low-esr capacitors in parallel to reduce cost. choose an input capacitor that exhi bits less than +10oc temperature rise at the rms in put current for optimal circuit life. 9.8 diode selection the current in the d1 (see figure 22 on page 10) changes abruptly from zero to its peak value each time the lx switch turns off. to avoid excessive losses, the diode must have a fast turn-o n time and a low forward voltage. note: ensure that the diode peak current rating exceeds t he peak current limit set by the current limit (see setting current limit on page 11) , and that its breakdown voltage exceeds v in . schottky diodes are recommended. 9.9 stable operation a well-designed system and selection of high-qualit y external components can eliminate excessive noise on pins out, fb, or gnd, which can lead to unstable device operation. instability typi cally manifests itself as grouped switching pulses with large gaps and excessive low-frequency output ripple (motorboating) during no-load or ligh t-load conditions. 9.10 recommended components table 7. recommended input capacitor c tc code rated voltage manufacturer 10f x7r 25v murata www.murata.com taiyo yuden www.t-yuden.com kemet www.kemet.com panasonic www.panasonic.com sanyo www.edc.sanyo.com table 8. recommended components input voltage output voltage ilimit inductor output capacitor 4.5v to 20v 1.25v to 5v high mss6132-103ml lqh66sn-100m03 lqh55dn-150m03 cdrh6d28np-150 t520v107m010ate018 a700v826m006ate018 t520b107m006ate040 eefud0j101r 10tpb100ml 4.5v to 12v cdrh5d18np-4r1 lps4018-472ml 4.5v to 20v 1.25v to 5v low mss6132-393ml cdrh6d28np-470 lqh66sn-470m03 lqh55dn-470m03 eefcd0k330r 6tpb47m t520a336m006ate070 a700v226m006ate028 4.5v to 12v mss6132-103ml lps4018-223ml cdrh5d18np-220 6v to 20v 5v to v in high or low see inductors above 510x107m020ate040
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 14 - 18 AS1341 datasheet - a p p l i c a t i o n i n f o r m a t i o n 9.11 pc board layout and grounding high switching frequencies and large peak currents make pc board layout an important part of AS1341-ba sed designs. good pcb layout can avoid switching noise being introduced into the fee dback path, resulting in jitter, instability, or de graded performance. - high-power traces (see figure 22 on page 10) should be as short and wide as possible. - the current loops formed by the external component s (c in , c out , l1, and d1 see figure 22 on page 10 ) should be as short as possible to avoid radiated noise. connect the ground pins of these power components at a common node in a star- ground configuration. - separate noisy traces, such as the lx node, from t he feedback network with grounded copper. - keep the extra copper on the pcb and integrate it into a pseudo-ground plane. - when using external feedback, place the resistors as close to pin fb as possible to minimize noise co upling.
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 15 - 18 AS1341 datasheet - p a c k a g e d r a w i n g s a n d m a r k i n g s 10 package drawings and markings figure 24. tdfn-8 3x3mm marking as 1341 xxxx xxx - encoded datecode
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 16 - 18 AS1341 datasheet - p a c k a g e d r a w i n g s a n d m a r k i n g s figure 25. tdfn-8 3x3mm package
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 17 - 18 AS1341 datasheet - o r d e r i n g i n f o r m a t i o n 11 ordering information the device is available as the standard products sh own in table 9 . note: all products are rohs compliant and ams green. buy our products or get free samples online at icdi rect: http://www.ams.com/icdirect technical support is found at http://www.ams.com/technical-support for further information and requests, please contac t us mailto:sales@ams.com or find your local distributor at http://www.ams.com/distributor table 9. ordering information ordering code marking description delivery form package AS1341-btdt-1k 1341 20v, 600ma, 100% duty cycle, step -down converter tape and reel 1000 pcs tdfn-8 3x3mm AS1341-btdt-6k 1341 20v, 600ma, 100% duty cycle, step -down converter tape and reel 6000 pcs tdfn-8 3x3mm
www.ams.com/dc-dc_step-up/AS1341 revision 1.09 18 - 18 AS1341 datasheet copyrights copyright ? 1997-2010, ams ag, tobelbaderstrasse 30 , 8141 unterpremstaetten, austria-europe. trademark s registered ?. all rights reserved. the material herein may not be reproduced , adapted, merged, translated, stored, or used with out the prior written consent of the copyright owner. all products and companies mentioned are trademarks or registered trademarks of their respective compa nies. disclaimer devices sold by ams ag are covered by the warranty and patent indemnification provisions appearing in its term of sale. ams ag makes no warranty, express, statutory, implied, or by descri ption regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. ams ag reserves t he right to change specifications and prices at any time and without notice. therefore, prior to designing this product into a system, it is nece ssary to check with ams ag for current information. this product is intended for use in normal commercial applications. applications requiring ext ended temperature range, unusual environmental requ irements, or high reliability applications, such as military, medical life-suppor t or life-sustaining equipment are specifically not recommended without additional processing by ams ag for each application. for shipments of le ss than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location . the information furnished here by ams ag is believe d to be correct and accurate. however, ams 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 indi- rect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the tech- nical data herein. no obligation or liability to re cipient or any third party shall arise or flow out of ams ag rendering of technical or other services. contact information headquarters ams ag tobelbaderstrasse 30 a-8141 unterpremstaetten, austria tel: +43 (0) 3136 500 0 fax: +43 (0) 3136 525 01 for sales offices, distributors and representatives , please visit: http://www.ams.com/contact

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