ams3120 2a fast transient linear regulator 02/11/2010 www.advanced-monolithic.com phone (925) 443-0722 1 fax (925) 443-0723 general description the ams3120 is a high performance linear regulator with very low dropout voltage and excellent transient response. it is designed to operate with wide input voltage range of 1.5 ? 7volts making it ideal for two step conversion while maintaining high efficiency for many power sensitive applications. the device is capable of supplying 2a of output current with a typical dropout voltage of 550mv at 2a. the product is available in either fixed or adjustable output voltage. the linear regulator has been optimized for noise sensitive applications. the device includes an enable pin for electrical on/off of the regulator. forcing the enable pin to logic low shuts down the ldo and reduces the supply current to less than 1a. the product includes complete shor t-circuit and thermal protection. the co mbination of these two internal protection circuits gives the device a comprehensive safety system to safe guard against extreme adverse operating conditions. the ams3120 is available in a thermally enhanced soic-8 edp package, and it is rated for -40c to +125c temperature range. features ? v in range: 1.5 ? 7v ? fixed and adjustable output voltage as low as 0.6v ? 2a maximum output current ? 550mv typical dropout voltage at 2a ? low self noise ? optional power good (pg) output ? enable (en) pin for ldo on/off ? 125a typical supply current ? psrr >40db at 10khz ? stable with electrolytic, tantalum or ceramic capacitors ? current limit protection ? over-temperature shutdown ? -40 to +125c temperature range ? thermally enhanced soic-8 exposed paddle package ? rohs & weee compliant applications ? set-top box ? dvd, blue-ray dvd writers ? lcd tvs and lcd monitors ? infotainment ? wireless & rf: applications ? laptops & notebook typical application ams3120 v out =1.8v v in = 3.3v v in gnd en adj * c in =10 f c out = 22 f v out * * optional power good, fixed and adjustable v out are available pg *
ams3120 2a fast transient linear regulator 02/11/2010 www.advanced-monolithic.com phone (925) 443-0722 2 fax (925) 443-0723 pin description (so-8ep package) pin # symbol description 1 nc no connection 2 en enable pin. it controls the electrical on/o ff of the device. when connected to logic low, the device shuts off and consumes 1 a of current. a logic high will resume normal operation. 3 v in input supply voltage. it powers the internal control circuitry and the internal power switch. bypass v in with at ceramic capacitor from this pin to ground. 4 nc no connection pg power good pin. it is an open collector, acti ve high output that indicates the status of the output voltage. when output voltage (v out ) exceeds the pg trip threshold, the pg pin goes in to a high impedance st ate. when the device is out of regulation or shutdown, the pg pin is pulled low. a 10k ? to 1m ? resistor should be connected from pg to v out . 5 nc no connection 6 v out output voltage 7 adj provides feedback to error amplifier from the resistive divider that sets the output voltage. nc no connection 8,9 gnd ground pin configuration so-8ep (top view)
ams3120 2a fast transient linear regulator 02/11/2010 www.advanced-monolithic.com phone (925) 443-0722 3 fax (925) 443-0723 absolute maximum ratings (1) maximum input supply voltage?????..........?.? -0.3v to 15v enable voltage (en)?????....????...?..?? -0.3v to 15v power good (pg).?????..?..???????.? -0.3v to 15v adjustable voltage (adj).?...????????....?? -0.3v to 3v storage temperature range?????................. -65 ? c to 150 ? c lead temperature???????..????.?????..? 260 ? c junction temperature???...??????..????..?? 125 ? c recommended operating conditions (2) input voltage????????????...?.????.. 1.5v to 7v ambient operating temperature??????.?? -40 ? c to 125 ? c thermal information 8l soic ep ja (3) ??????????....???.?.?...45 ? c/w electrical characteristics unless otherwise noted: v in =3.3v; v out =1.8v; c in =10 f; c out =22f; -40 ? c t a =t j 85 ? c; t j(max) = 125 c; typical values are t a = 25 c parameter symbol conditions min. typ. max. units output voltage accuracy v out -3 3 % adjustable voltage v adj adjustable v out only 0.588 0.6 0.612 v adjustable pin bias current i adj_bias adjustable v out only 10 100 na maximum output current i out_max 2 a load regulation i out = 0 ? 2a 0.1 % line regulation v in =3.0 ? 7.0v; i out =100ma 0.2 % supply current i sup v in =3.3v, io=0a 0.2 0.5 ma shutdown current i shdn v in =3.3v, v en =0v <1 3 a current limit i lim 2.5 a dropout voltage v do i out =0.1a; v out =90% of v out(nom) 85 mv i out =0.5a; v out =90% of v out(nom) 180 i out =1a; v out =90% of v out(nom) 275 i out =2a; v out =90% of v out(nom) 550 psrr v out / v in f=10khz io=20ma 40 db output noise voltage e n bw = 100hz ?100 khz c out = 10f i out = 500ma 125 v(rms) enable threshold low v en(l) 1.2 v enable threshold high v en(h) 1.3 v input enable low current i en(l) v en = 0v 0 10 na input enable high current i en(h) v en = 1.5v 150 300 na power good low threshold v pg % of v out pg on 89 % power good high threshold v pg % of v out pg off 97 % power good output low voltage v pgl ipg_sink = 500 a, fault condition 200 300 mv power good leakage current i pg pg off, v pg = 12v 0.01 a thermal shutdown t sd 145 c thermal shutdown hysteresis t sd_hys 15 c notes: 1. stresses above those listed in absolute maximu m ratings may cause permanent damage to the device. 2. measured on approximately 1? square of 1 oz. copper. 3. the total power dissipation for so-8 ed p package is recommended to 2.5w rated at 25 ? c ambient temperature. the thermal resistance junction to case is 45 ? c/w. total power dissipation for the switching regulator and the ldo should be taken in consideration when calculating the outp ut current capability of each regulator
t y out p ut volta g e ( v ) out p ut volta g e error ( % ) out p ut volta g e chan g e ( % ) 02/11/201 0 y pical perf o 1.792 1.794 1.796 1.798 1.800 1.802 1.804 1.806 1.808 -50 pg() o u -0.2 -0.1 0.0 0.1 0.2 3 pg() -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.0 pgg() 0 o rmance c -25 0 ambient t u tput voltag e (fixed volta 4 input line regu l 0.1 output load c haracteri s 25 50 7 5 t emperatur e e temperatu r ge option) v 5 voltage (v) l ation v out = 1.0 current (a) regulation www.a d s tics (t a = 2 5 100 12 5 e (oc) r e variation v o = 1.8v 67 2.5 v 10. 0 d vanced-mon o 4 2 5c unless o 5 0 adjustable voltage (v) voltage (v) voltage (v) 2a fa s o lithic.com o therwise s p 0.595 0.597 0.599 0.601 0.603 0.605 -50 - 2 ad v ari 0.0 0.2 0.4 0.6 0.8 1.0 -50 - dr o 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0 dro a s t transie n p ecified) 2 50 2 5 a mbient t e d just (adj) v ation (adju s 25 0 2 5 a mbient t e o pout volta g 0.5 output pout voltag e a ms 3 n t linear r phone (925 ) fax (925 ) 5 50 75 e mperature ( v oltage tem p s table voltag 5 50 75 e mperature ( g e vs. temp e 1 ? a 2a 11 current (a) e vs. output v o 3 120 egulator ) 443-0722 ) 443-0723 100 125 ( oc) p erature e option) 100 125 ( c) e rature .5 2 current o ut = 2.5v
ams3120 2a fast transient linear regulator 02/11/2010 www.advanced-monolithic.com phone (925) 443-0722 5 fax (925) 443-0723 typical performance characteristics (t a = 25c unless otherwise specified) 0.0 0.5 1.0 1.5 01234567 shutdown current (a) input voltage (v) shutdown current vs. input voltage 125c \ 50c ? & ? 25c 0 10 20 30 40 50 60 70 0.0 0.4 0.8 1.2 1.6 2.0 ground current (ma) output current (a) i gnd vs. output current v o =1.8v, v in =2.5v 100 sec/div enable start-up 550ma , v out =1.8 v, v in =3.3 v , c in =c out =22 f enable 1v/div v out 1v /div 10 sec/div load transient 100ma to 1.5 a , v out =1.8 v, v in =3.3 v , c in =c out =22 f i sw out 500ma / div v out 50mvac / div
ams3120 2a fast transient linear regulator 02/11/2010 www.advanced-monolithic.com phone (925) 443-0722 6 fax (925) 443-0723 functional block diagram figure 1: block diagram of ams 3120 with power good and adjustable voltage option figure 2: block diagram of ams 3120 with power good and fixed voltage option figure 3: block diagram of ams 3120 with fixed voltage option only
ams3120 2a fast transient linear regulator 02/11/2010 www.advanced-monolithic.com phone (925) 443-0722 7 fax (925) 443-0723 device summary the ams3120 is a high voltage low drop out linear regulator with a current capability of up to 2a. the ldo has an input voltage range of 1.5v to 7v with an output voltage as low as 0.6v and is stable with a wide range of ceramic, tantalum, and electrolytic output capacitors. shutdown/enable the enable (on/off) input threshold voltage is 1.2v. when disabled the ldo quiescent current decreases to a typical value of <1a. fault protection short circuit and over-temperature shutdown disable the converter and ldo in the event of an overload condition. overtemp shutdown disables the device when the junction temperature exceeds 145 oc. the output current is internally limited to 2.5a. input capacitor an input bypass capacitor ranging from 1f to 10f is required. the capacitor should be placed as close as possible to the device and not be placed more than 1 inch from the ldo. output capacitor the output capacitor requirements range from the minimum value required to guarantee stability to larger values required to meet the extreme transient response requirements. values range from 10 to 22f x5r ceramic capacitors. due to the extreme voltage coefficient of x5r ceramic capacitors, the voltage rating should be at least double the maximum applied voltage. adjustable version: feedback resistor selection choosing ams 3120 with adjustable output voltage option allows the user to select an output voltage by using an external resistor divider. ams 3120 uses a 0.6v reference voltage at the positive terminal of the error amplifier. to set the output voltage a programming resistor from the adjust pin (adj) to ground must be selected (see pg.1). a 10k ? resistor is a good selection for a programming resistor r2. a higher value may result in an excessively sensitive feedback node while a lower value will draw more current and degrade the light load efficiency. the equation for selecting the voltage specific resistor is: r4= vout vref -1 r3 = 5v 0.6v -1 10k ? =73.2k ? table 1: adjustable feedback resistor values v out (v) r1 (k ? ) (r2=10k ? ) 1.8 20.0 2.5 31.6 3.3 45.3 5.0 73.2 pcb layout the following guidelines should be followed to insure proper layout. 1. v in capacitor. a low esr ceramic bypass capacitor must be placed as close to the ic as possible. 2. adjustable (adj) feedback resistors. the adjustable feedback resistors should be placed as close as possible the ic. minimize the length of the trace from the feedback pin to the resistors. this is a high impedance node susceptible to interference from external rf noise sources. 3. ground. 4. for good thermal performance vias are required to couple the exposed tab of the so-8 package to the pcb ground plane. the via diameter should be 0.3mm to 0.33mm positioned on a 1.2mm grid. power good during operation, fault conditions can occur unexpectedly. such conditions include input voltage dropout (low v in ), overheating, or overloading (excessive output current). if any of these conditions occurs, the pg pin will set an ?error flag?. the pg pin, which is an open- collector output, will go low when v out is less than 95% or the specified output voltage. when the voltage at v out is greater than 95% of the specified output voltage, the pg pin is high. a logic pull-up resistor of 10k ? is recommended at this output. the pin can be left disconnected if unused. output power and thermal limits the ams3120 junction temperature and current capability depends on the internal dissipation and the junction to case thermal resistance of the so8 exposed paddle package. additionally, the paddle and pcb temperature will be elevated due to the total losses of the ldo and of other circuits mounted to the pcb. tjmax=pd jc+tpcb+tamb the internal losses contribute to the junction temperature rise above the paddle and pcb temperature.
ams3120 2a fast transient linear regulator 02/11/2010 www.advanced-monolithic.com phone (925) 443-0722 8 fax (925) 443-0723 figure 4: ams3120 soic-8 adjustable option evaluation board - top side figure 5: ams3120 soic-8 adjustable option evaluation board - bottom side figure 4. ams3120 evaluation board schematic table 2. evaluation board bill of materials component value manufacturer manufacturer part number c1,c2 22f, 10v, x5r, 0805, ceramic taiyo yuden lmk212bj226mg-t c3 5.6nf 0603 20% r2 10k ? , 0.1w, 0603 1% various CRCW060310K0FKEA r1 see table 2 various crcw0603xxkxfkea u1 low drop out linear regulator ams ams3120 vin vout c1 10uf gnd 8 nc 4 vin 3 en 2 nc 1 vout 6 adj 7 nc 5 u1 ams3120-8 r2 10.0k r1 20.0k gnd gnd c3 5.6nf c2 22uf 1 2 enable
ams3120 2a fast transient linear regulator 02/11/2010 www.advanced-monolithic.com phone (925) 443-0722 9 fax (925) 443-0723 ordering information device package ams3120s (1)(2) soic-8 edp ams3120s-pg (1)(2) soic-8 edp ams3120s-xxpg (1)(2) soic-8 edp ams3120s-xx (1)(2) soic-8 edp notes: 1. available in tape and reel only. a reel contains 2,500 devices. 2. available in lead-free package only. de vice is fully weee and rohs compliant 3. need to specify output voltage option ( ) 4. outline drawing and landing pattern package dimensions are inches (millimeters) unless otherwise noted.
|
