CM3708A 3a l ow -n oise pwm s tep -d own r egulator general description features the CM3708A is a low-noise, pulse-width-modulated (pwm), dc-dc step-down converter. it powers logic and transmitters in small wireless systems such as cellular phones, communicating pdas, and handy-terminals. the device features an internal synchronous rectifier for high efficiency; it requires no external schottky diode. excellent noise characteristics and fixed-freque ncy operation provide easy post-filtering. the CM3708A is ideally suited for li-lon battery applications. it is also useful for +3v or +5v fixed input applications. the device operates in one of four modes. forced pwm mode operates at a fixed frequ ency regardless of the load. shutdown mode places the device in standby, reducing quiescent supply current to under 0.1 a. the CM3708A can deliver over 3.0a. the output voltage can be adjusted from vref to vin. the input range is from 2.0v to 5.5v. other features of the CM3708A include high efficiency, low dropout voltage. it is available in a space-saving 16-pin sop & tssop package. ? patent filed #6,452,366 ? 600khz switching and synchronization ? dynamic output-voltage adjustment from vref to vin ? 3a guaranteed output current ? 95% efficiency ? no schottky diode required ? 16-pin psop/ptssop power packages ? 6a low noise current limit protection ? external soft start ? rail to rail output buck converter applications ? cellular phone ? cordless phone ? pdas and handy-terminals ? agp chipset supplies ? cpu i/o supplies ? notebook chipset supplies ? battery operated devices pin configuration psop-16 (ps16) / ptssop-16 (pt16) top view 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 vin1 pvin1 lx1 pgnd1 agnd sd vref agsen vin2 pvin2 lx2 pgnd2 agnd vfb nc agnd 2007/02/13 rev1.3 champion microelectronic corporation page 1
CM3708A 3a l ow -n oise pwm s tep -d own r egulator pin description operating rating pin no. symbol description min. typ. max. unit 1,16 vin1, vin2 voltage supply fo r internal circuits 2 2.5 5.5 v 2,15 pvin1, pvin2 voltage supply for output power transistors 2 2.5 5.5 v 3,14 lx1, lx2 inductor connection to the drains of the internal power mosfets 5 v 4,13 pgnd1, pgnd2 ground for output power transistors 5,9,12 agnd ground for internal reference voltage divider 8 agsen ground for remote sensing 6 sd shutdown active high. cmos input level 0.75 x vin vin + 0.3v v 7 vref v out set voltage 0 vin v 10 nc no connection 11 vfb feedback node for the v out 5 v block diagram pwm controller oscillator ramp generator error amp thermal protection mos vref agnd 12 agnd agnd 7 9 5 vfb 11 pgnd1 4 pgnd2 13 lx2 14 lx1 3 pvin2 15 pvin1 2 sd 6 vin2 16 vin1 1 nc 10 agsen 8 2007/02/13 rev1.3 champion microelectronic corporation page 2
CM3708A 3a l ow -n oise pwm s tep -d own r egulator ordering information part number temperature range package CM3708Ait -40 to 85 16-pin ptssop (pt16) CM3708Agit* -40 to 85 16-pin ptssop (pt16) CM3708Ais -40 to 85 16-pin psop (ps16) CM3708Agis* -40 to 85 16-pin psop (ps16) *note: g : suffix for pb free product absolute maximum ratings junction temperature ...???????? ????150c absolute maximum ratings are those values beyond which the device could be permanently damaged. storage temperature ??................??. -65c to 125c pvin/vin ????.............. .............. ..........?.......-0.3v to 6.0v lead tem perature (soldering, 5 sec)??????.. 260c voltage on any other pin ???... gnd ? 0.3v to vin + 0.3v thermal dissipation ?( jc )?.. ???????.. .50c/w output current, source or sink ??......????........?...3.0a operating conditions temperature range ............................. -40c to 85c p vin operating range .........................2.0v to 5.5v electrical characteristics (unless otherwise stated, these specifications apply t a =25 c ; vin=+3.3v and pvin=+3.3v) maximum ratings are stress ratings only and functional device operation is not implied. (note 1) CM3708A symbol parameter test conditions min. typ. max. unit switching regulator v ref adjustable output voltage 0 vin v fsw switching frequency CM3708A 480 660 khz i out(rms) maximum output rms current CM3708A 3.0 a i out(peak) maximum output peak current CM3708A 6.0 a i limit current limit CM3708A 6 a mosfets rds (on) drain to source on-state resistance pvin=5v 150 180 m supply i vin quiescent current vfb = 1.4v lc unconnected 200 a i pvin quiescent current vfb = 1.4v lc unconnected 500 a note 1: limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions note 2: vin, pvin = 3.3v 10% note 3: it?s not 100% test 2007/02/13 rev1.3 champion microelectronic corporation page 3
CM3708A 3a l ow -n oise pwm s tep -d own r egulator functional description the CM3708A step-down, pulse-width-modulated (pwm), dc-dc converter has an adjustabl e output range from vref to the input voltage (vin). an internal synchronous rectifier improves efficiency and eliminates an external schottky diode. fixed-frequency operation enables easy post-filtering, thereby providing excellent noise characteristics. as a result, the CM3708A is an ideal choice fo r many small wireless systems. vref the reference voltage could be ranged from 0v to vin. ouputs the output voltage pins (lx1, lx 2) are tied to the rf power amp, via an external inductor. output voltage is determined by the vref inputs so it can be from 0v to vin. internal power switches: CM3708A has been integrated 2 power mosfets whose rds (on) is around 100m ohm each. low noise current limit: CM3708A?s current limit is a low noise current limit. it increase the system loop noise immunity while it is doing the current limit protection for the system. t he current limit is around 6a for the normal 3a operation. inputs the input voltage reference pin, vref determine the output voltages (lx1, lx2). if a specific voltage is forced at the vref pin, the output voltage follows the voltage at the vref pin. other supply voltages several inputs are provided for the supply voltages: pvin and vin. the pvin provide the power supply to the power mosfets. vin provides the voltage supply to the logic section and internal error amplifiers. feedback the vfb pin is an input that can be used for closed loop compensation. this input is derived from the voltage output. agnd pin is a contact node of internal resistor divider for remote sense. application circuit pvin vin pvin pvin r1 5r1 r3 1k 2 1 vref vin r2 200k 2 1 c6 100uf/6.3v c2 104 j2 dc-input 1 2 u1 CM3708A 2 1 3 13 14 15 16 4 5 6 7 8 9 10 11 12 pvin1 vin1 lx1 pgnd2 lx2 pvin2 vin2 pgnd1 agnd sd vref agsen agnd nc vfb agnd c9 104 c1 220uf/6.3v c8 104 c12 102 c7 104 l1 3.3uh c11 104 j1 vout 1 2 c3 10uf/6.3v c10 100uf/6.3v c4 104 c5 470uf/6.3v 2007/02/13 rev1.3 champion microelectronic corporation page 4
CM3708A 3a l ow -n oise pwm s tep -d own r egulator package dimension 16-pin ptssop (pt16) 16-pin psop (ps16) 2007/02/13 rev1.3 champion microelectronic corporation page 5
CM3708A 3a l ow -n oise pwm s tep -d own r egulator important notice champion microelectronic corporation (c mc) reserves the right to make changes to its products or to discontinue any integrated circuit product or serv ice without notice, and advises its cust omers to obtain the latest version of relevant information to verify, before placing orders , that the information being relied on is current. a few applications using integrated circuit products may in volve potential risks of death, personal injury, or severe property or environmental damage. cmc integrated circui t products are not designed, intended, authorized, or warranted to be suitable for use in life-s upport applications, devices or systems or other critic al applications. use of cmc products in such applications is un derstood to be fully at the risk of the customer. in order to minimize risks associated with the customer?s applications, the cu stomer should provide adequate design and operating safeguards. hsinchu headquarter sales & marketing 5f, no. 11, park avenue ii, science-based industrial park, hsinchu city, taiwan 300 7f-6, no.32, sec. 1, chenggong rd., nangang district, taipei city 115, taiwan t e l : +886-3-567 9979 t e l : +886-2-2788 0558 f a x : +886-3-567 9909 f a x : +886-2-2788 2985 http://www.champion-micro.com 2007/02/13 rev1.3 champion microelectronic corporation page 6
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