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features applications description n n n n n output current: up to 3a output voltage: 0.6v to v input voltage: 2.7 to 5.5v efficiency up to 95% 42 a (typ) no load quiescent current shutdown current: <1 a 100% duty cycle operation 1.5mhz switching frequency internal soft start no external compensation required current limit protection thermal shutdown psop-8 package 5v or 3.3v point of load conversion telecom/networking equipment set top boxes storage equipment video cards ddr power supply t h e pa m 2 3 2 0 i s a 3 a s t e p - d o w n d c - d c converter. at heavy load, the con stant-frequency pwm control performs excellent stability and transient response. no external compensation components are required the pam2320 supports a range of input voltages from 2.7v to 5.5v, allowing the use of a single l i + /l i - p o l y m e r c e l l , m u l ti p l e a l k a l i n e /n i m h cell,and other standard power sources. the output voltage is adjustable from 0.6v to the input voltage. the pam2320 employs internal power switch and synchronous rectifier to minimize external part count and realize high efficiency. during shutdown, the input is disconnected from the output and the shutdown current is less than 1 a. other key features include over-temperature and short circuit protection, and under-voltage lockout to prevent deep battery discharge. the pam2320 delivers 3a maximum output current while consuming only 42 a of no-load quiescent current. ultra-low rds(on) integrated mosfets and 100% duty cycle operation make the pam2320 an ideal choice for high output voltage, high current applications which requ ire a low dropout threshold. the pam2320 is available in psop8 package. in n n n n n n n n n n n n n n . typical application 1 www.poweranalog.com 05/2011 rev1.0 , power analog microelectronics inc pam2320 3a low noise step-down dc-dc converter 1 0 . 6 1 2 o r v r ? ? = ? + ? ? ? ? ( 5 ) f b g n d ( 4 ) ( 3 ) s w e n ( 7 ) v i n ( 2 ) n c ( 1 , 6 , 8 ) p a m 2 3 1 0 0 c i n 2 2 u f c f w 1 0 0 p c o 2 2 u f v i n 0 l r 1 r 2 0 0 v o pam2320 40uf 30uf
block diagram 2 pin configuration & marking information , power analog microelectronics inc www.poweranalog.com pam2320 3a low noise step-down dc-dc converter 05/2011 rev1.0 top view psop-8 p2320:pam2320 a: adjustable output y: year w: week x: internal code nc vin sw gnd nc en nc fb (exposed pad) en r1 r2 fb + - iamp + - ircmp sw gnd synchronous rectifier nch ( ) main switch pch ( ) vin comp vin shutdown osc rs latch 0.6vref freq shift - + ea s q r q switching logic and blanking circuit slope comp 1.5m osc anti shoot thru - -
3 , power analog microelectronics inc www.poweranalog.com pam2320 3a low noise step-down dc-dc converter 05/2011 rev1.0 absolute maximum ratings these are stress ratings only and functional operation is not implied. exposure to absolute maximum ratings for prolonged time periods may affect device reliability. all voltages are with respect to ground. input voltage v ......................................6v en pin voltage....................................- i n sw pin voltage......................-0.3v to (v +0.3v) fb pin voltage.........................-0.3v to (v +0.3v) 0.3v to 6v maximum junction temperature..................150c storage temperature range...........-65c to 150c soldering temperature.......................300c, 5sec in in recommended operating conditions supply voltage..................................2.7v to 5.5v c c c c junction temperature range..........-40 to 125 ambient temperature range...........-40 to 85 thermal information p a r a m e t e r s y m b o l p a c k a g e m a x i m u m u n i t t h e r m a l r e s i s t a n c e ( j u n c t i o n t o a m b i e n t ) j a p s o p - 8 9 0 c / w t h e r m a l r e s i s t a n c e ( j u n c t i o n t o c a s e ) j c p s o p - 8 1 1 c / w i n t e r n a l p o w e r d i s s i p a t i o n ( @ t a = 2 5 c ) p d p s o p - 8 1 1 0 0 m w n a m e p i n n u m b e r f u n c t i o n n c 1 n o c o n n e c t e d v i n 2 b i a s s u p p l y . c h i p m a i n p o w e r s u p p l y p i n s w 3 t h e d r a i n s o f t h e i n t e r n a l m a i n a n d s y n c h r o n o u s p o w e r m o s f e t . g n d 4 g n d f b 5 f e e d b a c k v o l t a g e t o i n t e r n a l e r r o r a m p l i f i e r , t h e t h r e s h o l d v o l t a g e i s 0 . 6 v . n c 6 n o c o n n e c t e d e n 7 e n a b l e c o n t r o l i n p u t . f o r c e t h i s p i n v o l t a g e a b o v e 1 . 5 v , e n a b l e s t h e c h i p , a n d b e l o w 0 . 3 v s h u t s d o w n t h e d e v i c e . n c 8 n o c o n n e c t e d pin description
electrical characteristic t =25 , unless otherwise noted. a c vin=3.6v, vo=1.8v, cin=33uf,co=22uf, l=2.2uh, 4 , power analog microelectronics inc www.poweranalog.com p a r a m e t e r s y m b o l t e s t c o n d i t i o n s m i n t y p m a x u n i t s i n p u t v o l t a g e r a n g e v i n 2 . 7 5 . 5 v o u t p u t v o l t a g e r a n g e v o 0 . 6 v i n v v i n r i s i n g 2 . 4 2 . 5 v h y s t e r e s i s 2 4 0 m v u v l o t h r e s h o l d v u v l o v i n f a l l i n g 1 . 8 v r e g u l a t e d o u t p u t v o l t a g e a c c u a r y v o i o = 0 t o 3 a - 3 + 3 % r e g u l a t e d f e e d b a c k v o l t a g e v f b 0 . 5 9 1 0 . 6 0 . 6 0 9 v f b l e a k a g e c u r r e n t i f b v o = 1 v 0 . 2 a o u t p u t v o l t a g e l i n e r e g u l a t i o n l n r v i n = 2 . 5 v t o 5 v 0 . 2 % / v o u t p u t v o l t a g e l o a d r e g u l a t i o n l d r i o = 0 a t o 3 a 0 . 5 % / a q u i e s c e n t c u r r e n t i q n o l o a d 4 2 9 0 a s h u t d o w n c u r r e n t i s d v e n = 0 v 1 a c u r r e n t l i m i t i l i m 4 a o s c i l l a t o r f r e q u e n c y f o s c 1 . 2 1 . 5 1 . 8 m h z h i g h s i d e 8 5 m d r a i n - s o u r c e o n - s t a t e r e s i s t a n c e r d s ( o n ) l o w s i d e 6 0 m h i g h e f f i c i e n c y 9 5 % a n a l o g s o f t s t a r t t i m e t s f r o m e n a b l e t o o u t p u t r e g u l a t i o n 0 . 5 m s e n t h r e s h o l d h i g h v e h 1 . 5 v e n t h r e s h o l d l o w v e l 0 . 3 v e n l e a k a g e c u r r e n t i e n v i n = v e n = 0 v - 1 . 0 1 . 0 a o v e r t e m p e r a t u r e p r o t e c t i o n o t p 1 5 0 c o t p h y s t e r e s i s o t h 3 0 c pam2320 3a low noise step-down dc-dc converter 05/2011 rev1.0
5 , power analog microelectronics inc www.poweranalog.com pam2320 3a low noise step-down dc-dc converter efficiency vs output current ( ) vo=1.8v efficiency vs output current (vo=3.3v) efficiency vs output current (vo=1.2v) efficienvy vs input voltage (vo=1.2v) efficienvy vs input voltage (vo=1.8v) efficienvy vs input voltage (vo=3.3v) typical performance characteristics c t =25 , c =33uf,co=22 f unless otherwise noted. a in 05/2011 rev1.0 0 % 1 0 % 2 0 % 3 0 % 4 0 % 5 0 % 6 0 % 7 0 % 8 0 % 9 0 % 1 0 0 % 1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 o u t p u t c u r r e n t ( m a ) 3 . 3 v 4 . 2 v 5 v 0 % 1 0 % 2 0 % 3 0 % 4 0 % 5 0 % 6 0 % 7 0 % 8 0 % 9 0 % 1 0 0 % 1 1 0 % 1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 o u t p u t c u r r e n t ( m a ) 4 . 2 v 5 v 5 . 5 v 0 % 1 0 % 2 0 % 3 0 % 4 0 % 5 0 % 6 0 % 7 0 % 8 0 % 9 0 % 1 0 0 % 2 2 . 5 3 3 . 5 4 4 . 5 5 5 . 5 6 i n p u t v o l t a g e ( v ) 0 . 1 a 1 a 3 a 0 % 1 0 % 2 0 % 3 0 % 4 0 % 5 0 % 6 0 % 7 0 % 8 0 % 9 0 % 1 0 0 % 2 2 . 5 3 3 . 5 4 4 . 5 5 5 . 5 6 i n p u t v o l t a g e ( v ) 0 . 1 a 1 a 3 a 0 % 1 0 % 2 0 % 3 0 % 4 0 % 5 0 % 6 0 % 7 0 % 8 0 % 9 0 % 1 0 0 % 3 3 . 5 4 4 . 5 5 5 . 5 6 i n p u t v o l t a g e ( v ) 0 . 1 a 1 a 3 a 0 % 1 0 % 2 0 % 3 0 % 4 0 % 5 0 % 6 0 % 7 0 % 8 0 % 9 0 % 1 0 0 % 1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 o u t p u t c u r r e n t ( m a ) 3 . 3 v 4 . 2 v 5 v
6 , power analog microelectronics inc www.poweranalog.com pam2320 3a low noise step-down dc-dc converter output voltage vo=1.8v vs output current ( ) output voltage vs output current (vo=1.2v) load regulation (vo=1.2v) load regulation (vo=1.8v) load regulation (vo=3.3v) typical performance characteristics c t =25 , c =33uf,co=22 f unless otherwise noted. a in 05/2011 rev1.0 output voltage vo=3.3v vs output current ( ) 1 . 1 6 1 . 1 6 5 1 . 1 7 1 . 1 7 5 1 . 1 8 1 . 1 8 5 1 . 1 9 1 . 1 9 5 1 . 2 0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 o u t p u t c u r r e n t ( m a ) 3 . 3 v 4 . 2 v 5 v - 2 . 0 % - 1 . 8 % - 1 . 6 % - 1 . 4 % - 1 . 1 % - 0 . 9 % - 0 . 7 % - 0 . 5 % - 0 . 3 % - 0 . 1 % 0 . 1 % 1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 o u t p u t c u r r e n t ( m a ) 3 . 3 v 4 . 2 v 5 v 1 . 7 6 1 . 7 7 1 . 7 8 1 . 7 9 1 . 8 1 . 8 1 1 . 8 2 0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 o u t p u t c u r r e n t ( m a ) 3 . 3 v 4 . 2 v 5 v - 2 . 0 % - 1 . 8 % - 1 . 6 % - 1 . 4 % - 1 . 2 % - 1 . 0 % - 0 . 8 % - 0 . 6 % - 0 . 4 % - 0 . 2 % 0 . 0 % 1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 o u t p u t c u r r e n t ( m a ) 3 . 3 v 4 . 2 v 5 v 3 . 2 6 3 . 2 6 5 3 . 2 7 3 . 2 7 5 3 . 2 8 3 . 2 8 5 3 . 2 9 0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 o u t p u t c u r r e n t ( m a ) 4 . 2 v 5 v 5 . 5 v - 1 . 0 % - 0 . 8 % - 0 . 6 % - 0 . 4 % - 0 . 2 % 0 . 1 % 1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 o u t p u t c u r r e n t ( m a ) 4 . 2 v 5 v 5 . 5 v
pam2320 3a low noise step-down dc-dc converter www.poweranalog.com , power analog microelectronics inc 7 rdson vs input voltage 1 . 5 0 1 . 5 2 1 . 5 4 1 . 5 6 1 . 5 8 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 t e m p e r a t u r e ( quiescent current vs input voltage typical performance characteristics c t =25 , c =33uf,co=22 f unless otherwise noted. a in 05/2011 rev1.0 oscillator frequency vs temperature oscillator frequency vs input voltage vin =3.6v 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 2 2 . 5 3 3 . 5 4 4 . 5 5 5 . 5 6 i n p u t v o l t a g e ( v ) p - 0 . 1 a n - 0 . 1 a 3 0 3 2 3 4 3 6 3 8 4 0 4 2 4 4 2 2 . 5 3 3 . 5 4 4 . 5 5 5 . 5 6 i n p u t v o l t a g e ( v ) v o 1 . 2 v v o 1 . 8 v v o 3 . 3 v 0 . 5 8 4 0 . 5 8 6 0 . 5 8 8 0 . 5 9 0 0 . 5 9 2 0 . 5 9 4 0 . 5 9 6 0 . 5 9 8 0 . 6 0 0 0 . 6 0 2 2 3 4 5 6 i n p u t v o l t a g e i = 1 0 0 m a i = 6 0 0 m a i = 8 0 0 m a reference voltage vs input voltage reference voltage vs temperature 1 . 3 0 1 . 3 2 1 . 3 4 1 . 3 6 1 . 3 8 1 . 4 0 1 . 4 2 1 . 4 4 1 . 4 6 1 . 4 8 1 . 5 0 2 . 5 3 3 . 5 4 4 . 5 5 5 . 5 i n p u t v o l t a g e ( v ) 0 . 5 8 0 . 5 8 2 0 . 5 8 4 0 . 5 8 6 0 . 5 8 8 0 . 5 9 0 . 5 9 2 0 . 5 9 4 0 . 5 9 6 0 . 5 9 8 0 . 6 2 5 5 0 7 5 1 0 0 1 2 5 1 5 0 t e m p e r a t u r e io=3a
8 , power analog microelectronics inc www.poweranalog.com application information pam2320 3a low noise step-down dc-dc converter the basic pam2320 application circuit is shown in page 1. external component selection is determined by the load requirement, selecting l first and then cin and cout. for most applications, the value of the inductor will fall in the range of 1h to 3.3h. its value is chosen based on the desired ripple current and efficiency. large value inductors lower ripple current and small value inductors result in higher ripple currents. higher v or vout also increases the ripple current as shown in equation 3a reasonable starting point for setting ripple current is i = 1.2a (40% of 3a). (1) the dc current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. thus, a 4.2a rated inductor should be enough for most applications (3a + 1.2a). for better efficiency, choose a low dc-resis tance inductor. in continuous mode, the source current of the top m osfet is a square wave of duty cycle vout/vin. to prevent large voltage transients, a low esr input capacitor sized for the maximum rms current must be used. the maximum rms capacitor current is given by: this formula has a maximum at v =2vout, w h e r e i = i / 2 . t h i s s i m p l e w o r s t - c a s e condition is com monly used for design because even significant deviations do not offer much relief. note that the capacitor manufacturer's ripple current ratings are often based on 2000 hours of life. this makes it advis able to further derate the capacitor, or choose a capacitor rated at a higher temperature than required. consult the manufac turer if there is any question. the selection of cout is driven by the required effective series resistance (esr). typically, once the esr requirement for cout has been met, the rms current rating generally far exceeds the i (p-p) requirement. the output ripple vout is determined by: where f = operating frequency, c =output capacitance and i = ripple current in the inductor. for a fixed output voltage, the output ripple is highest at maximum input voltage since i increases with input voltage. higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. their high ripple current, high voltage rating and low esr make them ideal for switching regulator applications. using ceramic capacitors can achieve very low output ripple and small circuit size. when choosing the input and output ceramic capacitors, choose the x5r or x7r dielectric formul ations. these dielectrics have the best temperature and voltage charac teristics of all the ceramics for a given value and size. inductor selection c and c selection using ceramic input and output capacitors in l in r m s o u t ripple out l l in out thermal consideration thermal protection limits power dissipation in the pam2320. when the junction temperature exceeds 150c, the otp (over temperature protection) starts the thermal shutdown and turns the pass transistor off. the pass transistor r e s u m e s o p e r a t i o n a f t e r t h e j u n c t i o n temperature drops below 120c. f o r c o n t i n u o u s o p e r a t i o n , t h e j u n c t i o n temperature should be maintained below 125c. the power dissipation is defined as: i is the step-down converter quiescent current. the term tsw is used to estimate the f ull load step-down converter switching losses. q ( ) 1 2 o u t i n o u t i n r m s o m a x i n v v v c r e q u i r e d i i v - ? ? ? ? @ ( ) ( ) ? ? d ? ? ? ? o u t o u t l i n 1 v i = v 1 - f l v ( ) ( ) o d s o n h i n o d s o n l 2 d o s w s o q i n i n v r + v - v r p = i + t f i + i v v v o 1 . 2 v 1 . 5 v 1 . 8 v 2 . 5 v 3 . 3 v l 1 h 1 . 5 h 2 . 2 h 2 . 2 h 3 . 3 h v o u t i l ( e s r + 1 / 8 f c o u t ) 05/2011 rev1.0
pam2320 3a low noise step-down dc-dc converter for the condition where the step-down converter is in dropout at 100% duty cycle, the total device dis sipation reduces to: since r , quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input voltage range. the maximum power dissipation de pend s on th e ther ma l r esi sta nc e of ic package, pcb layout, the rate of surrounding airflow and temperature difference between junction and ambient. the maximum power dissipation can be calc ulated by the following formula: where tj(max) is the maximum allowable junction temperature 125c.t is the ambient temperature and is the thermal resistance from the junction to the ambient. based on the standard jedec for a two layers thermal test board, the thermal resistance of sop-8(ep) 90c/w respec tively. the maximum power dissipation at t = 25c can be calculated by following formula: p =(125c-25c)/90c/w=1.11w(sop-8) the internal reference is 0.6v (typical). the output voltage is ca lculated as below: the output voltage is given by table 1. resistor recommend for output voltage setting as the input voltage approaches the output voltage, the converter turns the p-chan nel transistor continuously on. in this mode the output voltage is equal to the input voltage minus th e voltag e d rop ac ros s the p - c hannel transistor: v = v ?i (r + r ) where r = p-channel switch on resistance, i = o ut pu t c u rr e n t, r = i nd uc t or dc resistance the reference and the circuit remain reset until the vin crosses its uvlo threshold. the pam2320 has an internal soft-start circuit that limits the in-rush current during start-up. this prevents possible voltage drops of the input voltage and eliminates the output voltage overshoot. the soft-start make the output voltage rise up smoothly. the switch peak current is limited cycle-by-cycle to a typical value of 4a. in the event of an output voltage short circuit, the device operates with a frequency of 500khz and minimum duty cycle, therefore the average input current is more smaller than current limit. when the die temperature exceeds 150c, a reset occurs and the reset remains until the temperature decrease to 120c, at which time the circuit can be restarted. ds(on) a ja ja a d out in load dson l dson l o a d l setting the output voltage table 1: 100% duty cycle operation uvlo and soft-start short circuit protection thermal shutdown ? ? ? ? ? ? o r 1 v = 0 . 6 1 + r 2 v o r 1 r 2 1 . 2 v 1 5 0 k 1 5 0 k 1 . 5 v 2 2 5 k 1 5 0 k 1 . 8 v 3 0 0 k 1 5 0 k 2 . 5 v 4 7 5 k 1 5 0 k 3 . 3 v 6 8 0 k 1 5 0 k 2 d o d s o n h q i n p = i r + i v j ( m a x ) a d j a t - t p = 9 , power analog microelectronics inc www.poweranalog.com 05/2011 rev1.0
ordering information 1 0 , power analog microelectronics inc www.poweranalog.com pam2320 3a low noise step-down dc-dc converter 05/2011 rev1.0 p i n c o n f i g u r a t i o n p a c k a g e t y p e n u m b e r o f p i n s o u t p u t v o l t a g e b t y p e 8 p i n s e : p s o p - 8 c : 8 a d j : a d j pam 2320 x x x xxx x output voltage number of pins package type pin configuration shipping package p a r t n u m b e r o u t p u t v o l t a g e p a c k a g e t y p e s h i p p i n g p a c k a g e p a m 2 3 2 0 b e c a d j r a d j p s o p - 8 2 , 5 0 0 u n i t s / t a p e & r e e l
outline dimensions 1 1 , power analog microelectronics inc www.poweranalog.com pam2320 3a low noise step-down dc-dc converter psop-8 05/2011 rev1.0

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