f f e e a a t t u u r r e e s s output up to 24v internal mosfet with high switch current up to 3a 20 a quiescent (switch-off) supply current 90% efficiency up to 450khz switching frequency sot-23-6l package a a p p p p l l i i c c a a t t i i o o n n s s pda dsc lcd panel rf-tags mp3 portable instrument wireless equipment d d e e s s c c r r i i p p t t i i o o n n the AMS1302 is a compact, high efficiency, and low voltage step-up dc/dc converter including an error amplifier, ramp generator, comparator, switch pass element and driver in which providing a stable and high efficient operation over a wide range of load currents. it operates in stable waveforms without external compensation. the high switching rate minimized the size of external components. besides, the low quiescent current together with high efficiency maintains long battery lifetime. the output voltage is set with two external resistors. the output voltage is set with two external resistors. AMS1302 advanced monolithic systems http://www.ams-semitech.com 1
t t y y p p i i c c a a l l a a p p p p l l i i c c a a t t i i o o n n s s figure 1 (1.8v stat-up input voltage) AMS1302 advanced monolithic systems http://www.ams-semitech.com 2
a a b b s s o o l l u u t t e e m m a a x x i i m m u u m m r r a a t t i i n n g g s s ( ( n n o o t t e e 1 1 ) ) supply voltage?????????????????????????? .? 0.3v to 6v sw pin switch voltage?????????????????????????? 0.3v to 28v other i/o pin voltages??????????????????????? 0.3v to 6v sw pin switch current ??????????????????????? ...??????..3a operating junction temperature???????????????????? .?????..125c storage temperature range ??????????????????. 65c ~ +150c note 1: absolute maximum ratings are threshold limit value s that must not be exceeded even for an instant und er any conditions. moreover, such values for any two items must not be reached simultaneously. operation abov e these absolute maximum ratings may cause degradation or p ermanent damage to the device. these are stress rat ings only and do not necessarily imply functional operation b elow these limits. p p i i n n a a s s s s i i g g n n m m e e n n t t sot-23-6l pin number sot-23-6l pin name function 1 gnd ground 2 sw switch output 3 soe source of the mosfet 4 fb feedback 5 vdd output 6 en on/off control(high enable) 1 2 3 6 5 4 AMS1302 advanced monolithic systems http://www.ams-semitech.com 3
e e l l e e c c t t r r i i c c a a l l c c h h a a r r a a c c t t e e r r i i s s t t i i c c s s (v in = 1.5v, vdd set to 3.3v, load current = 0a, ta = 25 c, unless otherwise specified) parameter test conditions min typ max units start-up voltage il = 1ma 1.00 v operating vdd range vdd pin voltage 2 5.5 v switch-off current i (v in ) v in = 5v 20 AMS1302 advanced monolithic systems http://www.ams-semitech.com 4
t t y y p p i i c c a a l l p p e e r r f f o o r r m m a a n n c c e e c c h h a a r r a a c c t t e e r r i i s s t t i i c c s s ta=25 AMS1302 advanced monolithic systems http://www.ams-semitech.com 5
p p i i n n i i n n f f o o r r m m a a t t i i o o n n gnd (pin 1): signal and power ground. provide a short direct pcb p ath between gnd and the (?) side of the output capacitor(s). sw (pin 2): switch pin. connect inductor between sw and v in . keep these pcb trace lengths as short and wide as possible to reduce emi and voltage overshoot . soe (pin 3): source of the mosfet. connect resistor to gnd fb (pin 4): feedback input to the g m error amplifier. connect resistor divider tap to this pin. the output voltage can be adjusted from 3.3v to 20v by: v out = 1.212v ? [1 + (r1/r2)] vdd (pin 5): input positive power pin. en (pin 6): en control input. forcing this pin above 1v enables th e part. forcing this pin below 0.6v shuts down the device. in shutdown, all functions are disa bled, drawing <1 m a supply current. do not leave en floating. f f u u n n c c t t i i o o n n a a l l d d i i a a g g r r a a m m AMS1302 advanced monolithic systems http://www.ams-semitech.com 6
a a p p p p l l i i c c a a t t i i o o n n i i n n f f o o r r m m a a t t i i o o n n output voltage setting referring to typical application circuits, the output voltage of the switching regulator (v out ) can be set with equation (1). feedback loop design referring to the typical application circuits. the select ion of r1 and r2 based on the trade-off between quiescent current consumption and interference immunity is stated below: follow equation (1) higher r reduces the quiescent current (path current = 1.212v/r2), however resistors beyond 5mw are not recommended. lower r gives better noise immunity, and is less sensitiv e to interference, layout parasitics, fb node leakage, and improper probing to fb pin. for applications without standby or suspend modes, lower values of r1 and r2 are preferred. for applications concerning the current consumption in standby or suspend modes, the higher values of r1 and r2 are needed. such high impedance feedback loop is sensitive to any interference, which requires careful pcb layout and avoid any interference, especial ly to fb pin. to improve the system stability, a proper value capacitor between fb pin and gnd pin is suggested. an empirical suggestion is around 22pf. pcb layout guide pcb layout shall follow these guidelines for better sy stem stability: a full gnd plane without gap break. vdd to gnd noise bypass - short and wide connection for the 20-100uf capacitor between pin 5 and pin 1. vin to gnd noise bypass - add a 10uf capacitor close to l1 inductor, when v in is not an idea voltage source. minimized fb node copper area and keep far away fro m noise sources. AMS1302 advanced monolithic systems http://www.ams-semitech.com 7
p p a a c c k k a a g g i i n n g g i i n n f f o o r r m m a a t t i i o o n n sot-23-6l package outline dimension dimensions in millimeters dimensions in inches symbol min max min max a 1.050 1.250 0.041 0.049 a1 0.000 0.100 0.000 0.004 a2 1.050 1.150 0.041 0.045 b 0.300 0.500 0.012 0.020 c 0.100 0.200 0.004 0.008 d 2.820 3.020 0.111 0.119 e 1.500 1.700 0.059 0.067 e1 2.650 2.950 0.104 0.116 e 0.950(bsc) 0.037(bsc) e1 1.800 2.000 0.071 0.079 l 0.300 0.600 0.012 0.024 0 8 0 8 subject changes without notice. AMS1302 advanced monolithic systems http://www.ams-semitech.com 8
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