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RT9511 1 ds9511-01 april 2011 www.richtek.com fully integrated battery charger with two step-down converters general description the RT9511 is a fully integrated low cost solution with a single-cell li-ion battery charger and two high efficiency step-down dc/dc converters ideal for portable applications. the battery charger is capable of being powered up fro m ac ad apter and usb (universal serial bus) port inputs which can automatically detect and select th e ac ada pter and the usb port as the power source for the charger. the battery charger enters sleep mode when both supplies are removed. the battery charger optimizes the charging task by using a control algorithm including preconditioning mode, fast charge mode and constant voltage mode. the charging task is terminated as the charge current drops below the preset threshold. the usb charge current can be selected from preset ratings100ma and 500ma, while the ac adapter charge current can be programmed up to 1a with an external resister. the internal thermal feedback circuitry regulates the die temperature to optimize the charge rate for all ambient temperatures. the battery charger features 18v and 7v maximum rating voltages for ac adapter and usb port inputs respectively. the other features are external programmed safety timer, under voltage protection, over voltage protection for ac adapter supply, battery temperature monitoring and charge status indicator. the high-efficiency step-down dc /dc converter is capable of delivering 1a output current over a wide input voltage range from 2.5v to 5.5v, the step-down dc/dc converter is ideally suited for portable electronic devices that are powered from 1-cell li-ion battery or from other power sources such as cellular phones, pdas and hand-held devices. two operating modes are available including : pwm/low-dropout autoswitch and shut-down modes. the internal synchronous rectifier with low r ds(on) dramatically reduces conduction loss at pwm mode. no external schottky diode is required in practical application. the RT9511 is available in a wqfn -24l 4x4 package. features z z z z z battery charger ` ` ` ` ` automatic input supplies selection ` ` ` ` ` 18v maximum rating for ac adapter ` ` ` ` ` integrated selectable 100ma and 500ma usb charge current ` ` ` ` ` internal integrated power fets ` ` ` ` ` charge status indicator ` ` ` ` ` external capacitor programmable safety timer ` ` ` ` ` under voltage protection ` ` ` ` ` over voltage protection ` ` ` ` ` automatic recharge feature ` ` ` ` ` battery temperature monitoring ` ` ` ` ` thermal feedback optimizing charge rate ` ` ` ` ` power path controller z z z z z step-down dc/dc converter ` ` ` ` ` adjustable output from 0.6v to vin ` ` ` ` ` 1a output current ` ` ` ` ` 95% efficiency ` ` ` ` ` no schottky diode required ` ` ` ` ` 1.5mhz fixed-frequency pwm operation z z z z z small 24-lead wqfn package z z z z z rohs compliant and halogen free applications z mp3/mp4 player z gps z digital photo frame z hand held device marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area.
RT9511 2 ds9511-01 april 2011 www.richtek.com typical application circuit pin configurations (top view) wqfn-24l 4x4 gnd en1 vdd1 lx1 gnd fb2 i s e t u g n d e n 2 v d d 2 i s e t a l x 2 batt ts timer nc s y s f b 1 a c i n u s b gnd 1 2 3 4 5 6 7 8 9 10 12 11 18 17 16 15 14 13 21 2019 24 22 23 25 en bat_on a c _ o n c h g _ s ordering information note : richtek products are : } rohs compliant and compatible with the current require- ments of ipc/jedec j-std-020. } suitable for use in snpb or pb-free soldering processes. RT9511 23 22 batt timer sys 16 17 18 11 acin iseta ts 15 19 20 usb + battery pack c t 0.1 f chip enable 1, 5, 7, 25 (exposed pad) gnd 14 en ac_on chg_s bat_on 1 f 1 f system 12 isetu 21 10 f lx1 fb1 2.2 h v out1 l1 24 4 c out1 r1 r2 c1 i r2 10 f lx2 fb2 2.2 h v out2 l2 6 10 c out2 r3 r4 c2 i r4 vdd1 en1 2.5v to 5.5v v in 3 2 4.7 f c in1 vdd2 en2 2.5v to 5.5v v in 9 8 4.7 f c in2 v acin v usb r seta RT9511 package type qw : wqfn-24l 4x4 (w-type) lead plating system g : green (halogen free and pb free)
RT9511 3 ds9511-01 april 2011 www.richtek.com functional pin description pin no. pin name pin function 1, 5, 7, 17 (exposed pad) gnd the exposed pad must be soldered to a large pcb and connected to gnd for maximum power dissipation. 2 en1 chip enable input pin of buck converter 1. (active high) 3 vdd1 power input pin of buck converter 1. 4 lx1 switching output pin of buck converter 1. 6 fb2 feedback voltage input pin of buck converter 2. 8 en2 chip enable input pin of buck converter 2. (active high) 9 vdd2 power input pin of buck converter 2. 10 lx2 switching output pin of buck converter 2. 11 iseta adaptor supply charge current set point. 12 isetu usb supply charge current set input. 13 nc no internal connection. 14 en charge enable input pin of charger. (active low) 15 timer safe charge timer setting. 16 ts temperature sense input. 17 batt battery charge current output. 18 bat_on power path controller output. this pin is used to turn on an external p-mosfet. 19 sys system voltage detector input pin. 20 usb usb supply voltage input pin. 21 ac_on p-mosfet switch control output (open drain). 22 acin adaptor supply voltage input pin. 23 chg_s charge status indicator output. (open drain) 24 fb1 feedback voltage input pin of buck converter 1.
RT9511 4 ds9511-01 april 2011 www.richtek.com function block diagram pre-charge phase fast charge phase constant voltage phase & standby phase re-charge phase programmed charge current 4.1v recharge threshold 2.8v precharge threshold 1/10 programmed charge current charge complete battery voltage charging current figure 1 . charging i-v curve charge input selection acin/usb acin iseta batt acin p-mosfet sense mosfet loop controller temperature sense temperature fault ts v ref thermal sense v fb drv ovp + - 2.5v ovp comparator sys timer timer usb current setting usb usb p-mosfet sense mosfet gnd isetu chg_s en bat_on ac_on logic en1 fb1 vdd1 lx1 + - control logic & v ref en2 fb2 vdd2 lx2 + - control logic & v ref
RT9511 5 ds9511-01 april 2011 www.richtek.com start-up precharge phase fast charge phase standby/fault recharge phase RT9511 flow chart d i s a b l e u v p s l e e p s t a r t - u p acin/usb power up v /ce > 1.4v ? no no v acin < 4.3v and v usb < 3.9v? disable mode pfet off i batt = 0 yes uvp mode pfet off i batt = 0 yes v acin < v batt and v usb < v batt ? sleep mode pfet off i batt = 0 yes v batt > 2.8v? no i batt = 0.1 charge current /chg_s strong pull down no ?t charge up? 1ms delay & start timer v batt > 2.8v? no i batt = charge current /chg_s strong pull down yes yes yes no v ts > 2.5v or v ts < 0.5v? time fault i batt < 0.1 i chg ? yes t charge up? no no yes standby pfet off i batt = 0 yes temp fault yes /chg_s high impedance v batt > 4.1 v? yes v batt > 4.1 v? no rechar ge yes no ovp mode no RT9511 flow chart
RT9511 6 ds9511-01 april 2011 www.richtek.com absolute maximum ratings (note 1) l supply input voltage, acin-------------------------------------------------------------------------------------------- - 0.3v to 18v l supply input voltage, usb-------------------------------------------------------------------------------------------- - 0.3v to 7v l supply input voltage, en1, en2, fb1, fb2----------------------------------------------------------------------- - 0.3v to 6v l vdd1, vdd2--------------------------------------------------------------------------------------------------------------6.5v l power dissipation, p d @ t a = 25 c wqfn-24l 4x4-----------------------------------------------------------------------------------------------------------1.923w l package thermal resistance (note 2) wqfn-24l 4x4, q ja -----------------------------------------------------------------------------------------------------52 c/w wqfn-24l 4x4, q jc -----------------------------------------------------------------------------------------------------7 c/w l lead temperature (soldering, 10 sec.)------------------------------------------------------------------------------260 c l junction temperature---------------------------------------------------------------------------------------------------150 c l storage temperature range------------------------------------------------------------------------------------------- - 65 c to 150 c l esd susceptibility (note 3) hbm (human body mode)---------------------------------------------------------------------------------------------2kv mm (machine mode)----------------------------------------------------------------------------------------------------200v electrical characteristics (v acin = v usb = 5v, t a = 25 c, unless otherwise specification) to be continued recommended operating conditions (note 4) l supply input voltage range, acin-----------------------------------------------------------------------------------4.5v to 12v l supply input voltage range, usb-----------------------------------------------------------------------------------4.1v to 6v l supply input voltage range, vdd1, vdd2-------------------------------------------------------------------------2.5v to 5.5v l junction temperature range------------------------------------------------------------------------------------------ - 25 c to 125 c l ambient temperature range------------------------------------------------------------------------------------------ - 25 c to 85 c parameter symbol test conditions min typ max unit supply input acin uvp threshold voltage v uv_acin rising 4.1 4.3 4.5 v usb uvp threshold voltage v uv_usb v batt = 3v, rising 3.7 3.9 4.1 v acin/usb uvp hysteresis v uv_hys v batt = 3v 40 100 140 mv acin/usb standby current i stby v batt = 4.5v -- 300 500 m a acin/usb shutdown current i shdn v en = high -- 50 100 m a batt sleep leakage current i sleep v acin = 4v, v usb = 4v, v batt = 4.5v -- 5 15 m a voltage regulation batt regulation voltage v reg i batt = 60ma 4.158 4.2 4.242 v acin mosfet dropout v batt = 4v, i chg = 1a 400 500 620 mv usb mosfet dropout v batt = 4v, i set_usb = high 500 650 800 mv current regulation iseta set voltage (fast charge phase) v iseta_fchg v batt = 3.5v 2.43 2.48 2.53 v
RT9511 7 ds9511-01 april 2011 www.richtek.com parameter symbol test conditions min typ max unit full charge setting range i chg_ac 50 -- 1000 ma ac charge current accuracy i chg_ac v batt = 3.8v, r iset = 1.5k w -- 500 -- ma precharge batt pre-charge threshold v prech 2.7 2.8 2.9 v batt pre-charge threshold hysteresis d v prech 60 100 140 mv pre-charge current i pchg v batt = 2v 8 10 12 % recharge threshold batt re-charge falling threshold hysteresis d v rech_l 50 95 140 mv charge termination detection termination current ratio (note 5) i term v batt = 4.2v -- 10 -- % logic input/output chg_s pull down voltage v chg_s i chg_s = 5ma -- 213 -- mv logic-high v ih 1.5 -- -- v en threshold voltage logic-low v il -- -- 0.4 v en pin input current i en -- -- 1.5 m a high voltage v isetu_high 1.5 -- -- v isetu threshold low voltage v isetu_low -- -- 0.4 v isetu pin input current i isetu -- -- 1.5 m a usb charge current & timing soft-start time t ss v iseta from 0v to 2.5v -- 100 -- m s usb charge current i chg_usb v acin = 3.5v, v usb = 5v, v batt =3.5v, i setu = 5v 400 450 500 ma usb charge current i chg_usb v acin = 3.5v, v usb = 5v, v batt = 3.5v, i setu = 0v 60 80 100 ma timer time pin source current i time v timer = 2v -- 1 -- m a pre-charge fault time t pchg_f c timer = 0.1 m f, f clk = 7hz 1720 2460 3200 s charge fault time t fchg_f c timer = 0.1 m f, f clk = 7hz 13790 19700 25610 s battery temperature sense ts pin source current i ts v ts = 1.5v 96 102 108 m a high voltage v ts_high 0.485 0.5 0.515 v ts pin threshold low voltage v ts_low 2.45 2.5 2.55 v protection thermal regulation -- 125 -- c ovp set voltage internal default -- 6.5 -- v power path controller bat_on pull low as sys falling, v batt = 4v , sys-bat - 150 -- - 20 mv to be continued
RT9511 8 ds9511-01 april 2011 www.richtek.com parameter symbol test conditions min typ max unit bat_on pull high as sys raising, v batt = 4v, sys-bat - 50 -- 0 mv bat_on pull low switch resistance v bat = 4v -- 10 -- w bat_on pull high switch resistance v acin = 5v -- 30 -- w parameter symbol test conditions min typ max unit input voltage range v dd1, 2 2.5 -- 5.5 v quiescent current i qx i outx = 0ma, v fb1, 2 = v ref + 5% -- 50 70 m a shutdown current i shdnx enx = gnd -- 0.1 1 m a reference voltage v ref 0.588 0.6 0.612 v adjustable output range v out1, 2 (note 5) v ref -- v dd1, 2 - 0.2v v adjustable output voltage accuracy d v out v dd1, 2 = v out1, 2 + d v to 5.5v (note 6) 0a < i out < 1a - 3 -- 3 % fb1, 2 input current i fb1, 2 v fb1, 2 = v dd1, 2 - 50 -- 50 na v dd1, 2 = 3.6v -- 0.28 -- p-mosfet r on r ds(on)_p i out1, 2 = 200ma v dd1, 2 = 2.5v -- 0.38 -- w v dd1, 2 = 3.6v -- 0.25 -- n-mosfet r on r ds(on)_n i out1, 2 = 200ma v dd1, 2 = 2.5v -- 0.35 -- w p-channel current limit i lim_p v dd1, 2 = 2.5v to 5.5 v 1.4 1.5 -- a en1, 2 high-level input voltage v en1, 2_h v dd1, 2 = 2.5v to 5.5v 1.5 -- -- v en1, 2 low-level input voltage v en1, 2_l v dd1, 2 = 2.5v to 5.5v -- -- 0.4 v under voltage lock out threshold uvlo -- 1.8 -- v hysteresis -- 0.1 -- v oscillator frequency f osc v dd1, 2 = 3.6v, i out1, 2 = 100ma 1.2 1.5 1.8 mhz thermal shutdown temperature t sd -- 160 -- c maximum duty cycle 100 -- -- % lx1, 2 current source v dd1, 2 = 3.6v, v lx1,2 = 0v or v lx1, 2 = 3.6v 1 -- 100 m a (v dd1, 2 = 3.6v, v out1, 2 = 2.5v, l = 2.2 m h, c in1, 2 = 4.7 m f, c out1, 2 = 10 m f, i max = 1a, t a = 25 c, unless otherwise specification) step-down converter
RT9511 9 ds9511-01 april 2011 www.richtek.com note 1. stresses listed as the above absolute maximum ratings may cause permanent damage to the device. these are for stress ratings. functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. note 2. q ja is measured in the natural convection at t a = 25 c on a high effective four layers thermal conductivity test board of jedec 51-7 thermal measurement standard. the case point of q jc is on the expose pad for the wqfn package. note 3. devices are esd sensitive. handling precaution is recommended. note 4. the device is not guaranteed to function outside its operating conditions. note 5. guarantee by design. note 6. d v = i out x p rds(on)
RT9511 10 ds9511-01 april 2011 www.richtek.com typical operating characteristics charge current vs. r seta 0 200 400 600 800 1000 1200 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 r seta (k ) charge current (ma) v batt = 3.8v, acin = 5v (k w ) enable threshold voltage vs. input voltage 0.0 0.4 0.8 1.2 1.6 2.0 4.5 4.8 5.1 5.4 5.7 6 6.3 6.6 input voltage (v) enable threshold voltage (v) v batt = 3.8v, i charger = 500ma rising falling iseta voltage vs. acin voltage 2.40 2.42 2.44 2.46 2.48 2.50 2.52 2.54 4.5 4.8 5.1 5.4 5.7 6 6.3 6.6 acin voltage (v) iseta voltage (v) v batt = 3.8v, i charger = 500ma battery charger iseta voltage vs. temperature 2.40 2.42 2.44 2.46 2.48 2.50 2.52 2.54 -25-15 -5 5 15 25 35 45 55 65 75 85 temperature ( c) iseta voltage (v) v batt = 3.8v, acin = 5v, i charger = 500ma ts current vs. temperature 95 96 97 98 99 100 101 102 103 104 105 -25-15 -5 5 15 25 35 45 55 65 75 85 temperature ( c) ts current ( a) v batt = 3.8v, acin = 5v, i charger = 500ma ts current vs. input voltage 95 96 97 98 99 100 101 102 103 104 105 4.5 4.8 5.1 5.4 5.7 6 6.3 6.6 input voltage (v) ts current ( a) v batt = 3.8v, i charger = 500ma
RT9511 11 ds9511-01 april 2011 www.richtek.com isetu threshold voltage vs. usb voltage 0.0 0.4 0.8 1.2 1.6 2.0 4.5 4.8 5.1 5.4 5.7 6 6.3 6.6 usb voltage (v) isetu threshold voltage (v) v batt = 3.8v rising falling regulation voltage vs. temperature 4.14 4.16 4.18 4.20 4.22 4.24 4.26 -25-15-5 5 1525354555657585 temperature (c) regulation voltage (v ) acin = 5v, i charger = 500ma acin power on time (1ms/div) en (5v/div) v sys (5v/div) v acin (5v/div) i in (1a/div) v batt = 3.7v, i sys = 500ma, i charger = 500ma acin power off time (500 s/div) v batt (5v/div) v sys (5v/div) v acin (5v/div) i in (1a/div) i sys = 500ma, i charger = 500ma usb power off time (500 s/div) v batt (5v/div) v sys (5v/div) v usb (5v/div) i in (1a/div) i sys = 500ma, i charger = 500ma usb power on time (1ms/div) en (5v/div) v sys (5v/div) v usb (5v/div) i usb (1a/div) v batt = 3.7v, i sys = 500ma, i charger = 500ma
RT9511 12 ds9511-01 april 2011 www.richtek.com output voltage vs. temperature 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 -50 -25 0 25 50 75 100 125 temperature (c) output voltage (v) output voltage vs. output current 1.200 1.202 1.204 1.206 1.208 1.210 1.212 1.214 1.216 1.218 1.220 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 output current (a) output voltage (v) v in = 3.6v v in = 5v efficiency vs. output current 0 10 20 30 40 50 60 70 80 90 100 0.001 0.01 0.1 1 output current (a) efficiency (%) v out = 1.2v, c out = 10 f, l = 2.2h v in = 3.6v v in = 5v v in = 3.6v, i out = 0a en threshold v s. input voltage 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 2.52.83.13.43.7 4 4.34.64.95.25.5 input voltage (v) en voltage (v) v out = 1.2v, i out = 0a rising falling step-down converter uvlo threshold vs. temperature 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 -50 -25 0 25 50 75 100 125 temperature (c) input voltage (v) v out = 1.2v, i out = 0a rising falling en threshold vs. temperature 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 -40 -15 10 35 60 85 110 135 temperature (c) en voltage (v) v in = 3.6v, v out = 1.2v, i out = 0a rising falling
RT9511 13 ds9511-01 april 2011 www.richtek.com output ripple voltage time (500ns/div) v in = 5v, v out = 1.2v, i out = 1a v out (10mv/div) v lx (5v/div) output ripple voltage time (500ns/div) v in = 3.6v, v out = 1.2v, i out = 1a v out (10mv/div) v lx (5v/div) current limit vs. input voltage 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.5 2.8 3.1 3.4 3.7 4 4.3 4.6 4.9 5.2 5.5 input voltage (v) output current (a) v out = 1.2v frequency vs. input voltage 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 2.5 2.8 3.1 3.4 3.7 4 4.3 4.6 4.9 5.2 5.5 input voltage (v) frequency (mhz) v in = 3.6v, v out = 1.2v, i out = 300ma frequency vs. temperature 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 -40 -15 10 35 60 85 110 135 temperature (c) frequency (mhz) 1 v in = 3.6v, v out = 1.2v, i out = 300ma current limit vs. temperature 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 -40 -15 10 35 60 85 110 135 temperature (c) output current (a ) v in = 5v v in = 3.6v v in = 3.3v v out = 1.2v
RT9511 14 ds9511-01 april 2011 www.richtek.com load transient response time (50 s/div) v in = 3.6v, v out = 1.2v i out = 50ma to 0.5a v out (50mv/div) i out (500ma/div) load transient response time (50 s/div) v in = 3.6v, v out = 1.2v i out = 50ma to 1a v out (50mv/div) i out (500ma/div) power off from en time (100 s/div) v in = 3.6v, v out = 1.2v, i out = 1a v out (1v/div) v en (2v/div) i in (500ma/div) power on from vin time (250 s/div) v en = 3.6v, v out = 1.2v, i out = 1a v out (1v/div) v in (2v/div) i in (500ma/div) power on from en time (100 s/div) v in = 3.6v, v out = 1.2v, i out = 1a v out (1v/div) v en (2v/div) i in (500ma/div) power on from en time (100 s/div) v in = 3.6v, v out = 1.2v, i out = 10ma v out (1v/div) v en (2v/div) i in (500ma/div)
RT9511 15 ds9511-01 april 2011 www.richtek.com load transient response time (50 s/div) v in = 5v, v out = 1.2v i out = 50ma to 0.5a v out (50mv/div) i out (500ma/div) load transient response time (50 s/div) v in = 5v, v out = 1.2v i out = 50ma to 1a v out (50mv/div) i out (500ma/div)
RT9511 16 ds9511-01 april 2011 www.richtek.com application information the RT9511 is a fully integrated low cost single-cell li-ion battery charger and two high-efficiency step-down dc-dc converters ideal for portable applications. battery charger automatically power source selection the RT9511 can be adopted for two input power source, acin and usb inputs. it will automatically select the input source and operate in different mode as below. acin mode : when the adapter input voltage (v acin ) is higher than the uvp voltage level (4.3v), the RT9511 will enter acin mode. in the acin mode, acin p-mosfet is turned on and usb p-mosfet is turned off. when acin voltage is between the uvp and ovp threshold levels, the switch q1 will be turned on and q2 will be turned off. so, the system load is powered directly from the adapter through the transistor q1, and the battery is charged by the RT9511. once the acin voltage is higher than the ovp or is lower than the uvp threshold, the RT9511 stops charging, and then q1 will be turned off and q2 will be turned on to supply the system by battery. usb mode : when acin voltage is lower than uvp voltage level and usb input voltage is higher than uvp voltage level (3.9v), the RT9511 will operate in the usb mode. in the usb mode, acin p-mosfet and q1 are turned off and usb p-mosfet and q2 are turned on. the system load is powered directly from the usb/battery through the switch q2. note that in this mode, the battery will be discharged once the system current is higher than the battery charge current. sleep mode : the RT9511 will enter sleep mode when both acin and usb input voltage are removed. this feature provides low leakage current from the battery during the absence of input supply. figure 2. input power source operation mode. acin mode usb mode v acin < uvp v usb > uvp sleep mode v acin < uvp v usb < uvp v acin > uvp power-path management the RT9511 powers the system and independently charging the battery while the input is acin. this feature reduces the charge time, allows for proper charge termination, and allows the system to run with an absent or defective battery pack. case 1 : input is acin in this case, the system load is powered directly from the ac adapter through the transistor q1. for the RT9511, q1 and q2 act as a switch as long as the RT9511 is ready. once the acin voltage is ready (>uvp and RT9511 internal mosfet and q1 starts regulating the output voltage supply system (q2 is turn off). once the acin voltage is over operation voltage (ovp), the RT9511 stops charging the battery, q1 turns off and q2 starts to supply power for system. figure 3. acin input case 2 : input is usb in this case, the system load is powered directly from the battery through the switch q2 (q1 is turn off). note that in this case, the system current over battery charge current will lead to battery discharge. figure 4. usb input RT9511 batt sys acin usb battery ac_on bat_on usb system + q1 q2 v acin i charger i sys RT9511 batt sys acin usb battery ac_on bat_on usb system + q1 q2 v acin i charger i sys
RT9511 17 ds9511-01 april 2011 www.richtek.com c in over voltage protection the acin input voltage is monitored by an internal ovp comparator. the comparator has an accurate reference of 2.5v from the band-gap reference. the ovp threshold is set by the internal resistive. the protection threshold is set to 6.5v, but acin input voltage over 18v still leads the RT9511 to damage. when the input voltage exceeds the threshold, the comparator outputs a logic signal to turn off the power p-mosfet to prevent the high input voltage from damaging the electronics in the handheld system. when the input over voltage condition is removed (acin < 6v), the comparator re-enables the output by running through the soft-start. battery temperature monitoring the RT9511 continuously monitors battery temperature by measuring the voltage between the ts and gnd pins. the RT9511 has an internal current source to provide the bias for the most common 10k w negative-temperature coefficient thermal resistor (ntc) (see figure 5). the RT9511 compares the voltage on the ts pin against the internal vts_high and vts_low thresholds to determine if charging is allowed. when the temperature outside the vts_high and vts_low thresholds is detected, the device will immediately stop the charge. the RT9511 stops charging and keep monitoring the battery temperature when the temperature sense input voltage is back to the threshold between vts_high and vts_low, the charger will be resumed. charge is resumed when the temperature returns to the normal range. however, the user may modify thresholds by the negative-temperature coefficient thermal resistor or adding two external resistors. (see figure 6.) the capacitor should be placed close to ts (pin 9) and connected to the ground plane. the capacitance value (0.1 m f to 10 m f) should be selected according to the quality of pcb layout. it is recommended to use a 10 m f if the layout is poor to prevent noise. figure 5. temperature sensing configuration figure 6. temperature sensing circuit tstsntc tsts v = ir turn off when v2.5v or v0.5v 3 t2t1ntc tsts t1t2ntc tsts r(r + r) v = i r + r + r turn off when v2.5v or v0.5v 3 fast-charge current setting case 1: acin mode the RT9511 offers iseta pin to determine the acin charge rate from 100ma to 1.2a. the charge current can be calculated as following equation. set charge_acset seta v i = k r the parameter k set = 300 ; v set = 2.5v. r seta is the resistor connected between the iseta and gnd. + r t2 battery a ts temperature sense i ts v batt ntc r t1 0.1 f to 10 f + 0.1 f to 10 f battery a ts temperature sense i ts v batt ntc
RT9511 18 ds9511-01 april 2011 www.richtek.com figure 7. acin mode charge current setting 0 200 400 600 800 1000 1200 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 r seta (k) charge current (ma) r seta (k w ) case 2 : usb mode when charging from a usb port, the isetu pin can be used to determine the charge current of 100ma or 500ma. a low-level signal of the isetu pin sets the charge current at 100ma and a high level signal sets the charge current at 500ma. pre- charge current setting during a charge cycle if the battery voltage is below the v prech threshold, the RT9511 applies a pre-charge mode to the battery. this feature revives deeply discharged cells and protects battery life. the RT9511 internally determines the pre-charge rate as 10% of the fast-charge current. battery voltage regulation the RT9511 monitors the battery voltage through the batt pin. once the battery voltage level closes to the v reg threshold, the RT9511 voltage enters constant phase and the charging current begins to taper down. when battery voltage is over the v reg threshold, the RT9511 will stop charge and keep to monitor the battery voltage. however, when the battery voltage decreases 100mv below the v reg , it will be recharged to keep the battery voltage. charge status outputs the open-drain chg_s output indicates various charger operations as shown in the following table. these status pin can be used to drive leds or communicate to the host processor. note that on indicates the open-drain transistor is turned on and led is bright. charge state chg_s charge on acin charge done off charge on usb charge done off temperature regulation and thermal protection in order to maximize the charge rate, the RT9511 features a junction temperature regulation loop. if the power dissipation of the ic results in a junction temperature greater than the thermal regulation threshold (125 c), the RT9511 throttles back on the charge current in order to maintain a junction temperature around the thermal regulation threshold (125 c). the RT9511 monitors the junction temperature, t j , of the die and disconnects the battery from the input if t j exceeds 125 c. this operation continues until junction temperature falls below thermal regulation threshold (125 c) by the hysteresis level. this feature prevents the maximum power dissipation from exceeding typical design conditions. external timer as a safety mechanism, the RT9511 has a user- programmable timer that monitors the pre-charge and fast charge time. this timer (charge safety timer) is started at the beginning of the pre-charge and fast charge period. the safety charge timeout value is set by the value of an external capacitor connected to the tmr pin (c tmr ), if pin tmr is short to gnd, the charge safety timer is disabled. as c tmr = 0.1 m f, t prech is ~2460 secs and t fault is 8 x t prech . t prech = c tmr x 2460/0.1 m as timer fault, re-plug-in power or pull high and re-pull low en can release the fault condition. as a safety mechanism, the RT9511 has a user- programmable timer that monitors the pre-charge and fast charge time. this timer (charge safe timer) is started at the beginning of the pre-charge and fast-charge period. the safety charge timeout value is set by an external capacitor (ct) connected between timer pin and gnd. the timeout fault condition can be released by resetting the input power or the en pin. if the timer is shorted to gnd, the charge safety timer will be disabled.
RT9511 19 ds9511-01 april 2011 www.richtek.com selecting the input and output capacitors in most applications, the most important is the high frequency decoupling capacitor on the input of the RT9511. a 1 m f ceramic capacitor, placed in close proximity to input pin and gnd pin is recommended. in some applications depending on the power supply characteristics and cable length, it may be necessary to add an additional 10 m f ceramic capacitor to the input. the RT9511 requires a small output capacitor for loop stability. a 1 m f ceramic capacitor placed between the batt pin and gnd is typically sufficient. step-down dc-dc converters inductor selection for a given input and output voltage, the inductor value and operating frequency determine the ripple current. the ripple current d i l increases with higher v in and decreases with higher inductance. outout l in vv i = 1 flv d- ???? having a lower ripple current reduces the esr losses in the output capacitors and the output voltage ripple. highest efficiency operation is achieved at low frequency with small ripple current. this, however, requires a large inductor. a reasonable starting point for selecting the ripple current is d i l = 0.4(i max ). the largest ripple current occurs at the highest v in . to guarantee that the ripple current stays below a specified maximum, the inductor value should be chosen according to the following equation : outout l(max)in(max) vv l = 1 fiv - d ???? inductor core selection once the value for l is known, the type of inductor must be selected. high efficiency converters generally cannot afford the core loss found in low cost powdered iron cores, forcing the use of more expensive ferrite or mollypermalloy cores. actual core loss is independent of core size for a fixed inductor value but it is very dependent on the inductance selected. as the inductance increases, core losses decrease. unfortunately, increased inductance requires more turns of wire and therefore copper losses will increase. ferrite designs have very low core losses and are preferred at high switching frequencies, so design goals can concentrate on copper loss and preventing saturation. ferrite core material saturates hard , which means that inductance collapses abruptly when the peak design current is exceeded. this results in an abrupt increase in inductor ripple current and consequent output voltage ripple. do not allow the core to saturate! different core materials and shapes will change the size/ current and price/current relationship of an inductor. toroid or shielded pot cores in ferrite or permalloy materials are small and don't radiate energy but generally cost more than powdered iron core inductors with similar characteristics. the choice of which style inductor to use mainly depends on the price vs. size requirements and any radiated field/emi requirements. c in and c out selection the input capacitance, c in , is needed to filter the trapezoidal current at the source of the top mosfet. to prevent large ripple voltage, a low esr input capacitor sized for the maximum rms current should be used. rms current is given by : out in rmsout(max) inout v v i = i1 vv - this formula has a maximum at v in = 2v out , where i rms = i out /2. this simple worst-case condition is commonly used for design because even significant deviations do not offer much relief. choose a capacitor rated at a higher temperature than required. several capacitors may also be paralleled to meet size or height requirements in the design. the selection of c out is determined by the effective series resistance (esr) that is required to minimize voltage ripple and load step transients, as well as the amount of bulk capacitance that is necessary to ensure that the control loop is stable. loop stability can be checked by viewing the load transient response as described in a later section. the output ripple, d v out , is determined by : outl out 1 viesr+ 8fc dd ??
RT9511 20 ds9511-01 april 2011 www.richtek.com the output ripple is highest at maximum input voltage since d i l increases with input voltage. multiple capacitors placed in parallel may be needed to meet the esr and rms current handling requirements. dry tantalum, special polymer, aluminum electrolytic and ceramic capacitors are all available in surface mount packages. special polymer capacitors offer very low esr but have lower capacitance density than other types. tantalum capacitors have the highest capacitance density but it is important to only use types that have been surge tested for use in switching power supplies. aluminum electrolytic capacitors have significantly higher esr but can be used in cost-sensitive applications provided that consideration is given to ripple current ratings and long term reliability. ceramic capacitors have excellent low esr characteristics but can have a high voltage coefficient and audible piezoelectric effects. the high q of ceramic capacitors with trace inductance can also lead to significant ringing. using ceramic input and output capacitors 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. however, care must be taken when these capacitors are used at the input and output. when a ceramic capacitor is used at the input and the power is supplied by a wall adapter through long wires, a load step at the output can induce ringing at the input, v in . at best, this ringing can couple to the output and be mistaken as loop instability. at worst, a sudden inrush of current through the long wires can potentially cause a voltage spike at v in large enough to damage the part. output voltage programming the resistive divider allows the fb pin to sense a fraction of the output voltage as shown in figure 8. figure 8. setting the output voltage RT9511 gnd fb r1 r2 v out for adjustable voltage mode, the output voltage is set by an external resistive divider according to the following equation : ) r2 r1 (1 v v ref out + = where v ref is the internal reference voltage (0.6v typ.) efficiency considerations the efficiency of a switching regulator is equal to the output power divided by the input power times 100%. it is often useful to analyze individual losses to determine what is limiting the efficiency and which change would produce the most improvement. efficiency can be expressed as : efficiency = 100% - (l1+ l2+ l3+ ...) where l1, l2, etc. are the individual losses as a percentage of input power. although all dissipative elements in the circuit produce losses, two main sources usually account for most of the losses: v in quiescent current and i 2 r losses. the v in quiescent current loss dominates the efficiency loss at very low load currents whereas the i 2 r loss dominates the efficiency loss at medium to high load currents. in a typical efficiency plot, the efficiency curve at very low load currents can be misleading since the actual power lost is of no consequence. 1. the v in quiescent current appears due to two factors including : the dc bias current as given in the electrical characteristics and the internal main switch and synchronous switch gate charge currents. the gate charge current results from switching the gate capacitance of the internal power mosfet switches. each time the gate is switched from high to low to high again, a packet of charge d q moves from v in to ground. the resulting d q/ d t is the current out of v in that is typically larger than the dc bias current. in continuous mode, i gatechg = f (qt + qb) where q t and q b are the gate charges of the internal top and bottom switches. both the dc bias and gate charge losses are proportional to v in and thus their effects will be more pronounced at higher supply voltages. 2. i 2 r losses are calculated from the resistances of the internal switches, r sw and external inductor r l . in continuous
RT9511 21 ds9511-01 april 2011 www.richtek.com figure 9. derating curves for RT9511 packages 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0 25 50 75 100 125 ambient temperature ( c) maximum power dissipation (w) wqfn-24l 4x4 four layers pcb layout consideration the RT9511 is a fully integrated solution for portable applications including a single-cell li- ion battery charger and two ideal high-efficiency step-down dc-dc converters ideal. careful pcb layout is necessary. for best performance of the RT9511, the following guidelines should be strictly followed. } input capacitors should be placed close to the ic and connected to ground plane. } the gnd and exposed pad should be connected to a strong ground plane for heat sinking and noise protection. } the connection of r seta should be isolated from other noisy traces. the short wire is recommended to prevent noise coupling. mode, the average output current flowing through inductor l is chopped between the main switch and the synchronous switch. thus, the series resistance looking into the lx pin is a function of both top and bottom mosfet r ds(on) and the duty cycle (dc) as follows : r sw = r ds(on)top x dc + r ds(on)bot x (1-dc) the r ds(on) for both the top and bottom mosfets can be obtained from the typical performance characteristics curves. thus, to obtain i 2 r losses, simply add r sw to r l and multiply the result by the square of the average output current. other losses including c in and c out esr dissipative losses and inductor core losses generally account for less than 2% of the total loss. checking transient response the regulator loop response can be checked by looking at the load transient response. switching regulators take several cycles to respond to a step in load current. when a load step occurs, v out immediately shifts by an amount equal to d i load (esr), where esr is the effective series resistance of c out . d i load also begins to charge or discharge c out generating a feedback error signal used by the regulator to return v out to its steady-state value. during this recovery time, v out can be monitored for overshoot or ringing that would indicate a stability problem. thermal considerations for continuous operation, do not exceed absolute maximum operation junction temperature. the maximum power dissipation depends on the thermal resistance of ic package, pcb layout, the rate of surroundings airflow and temperature difference between junction to ambient. the maximum power dissipation can be calculated by following formula : p d(max) = ( t j(max) - t a ) / q ja where t j(max) is the maximum operation junction temperature 125 c, t a is the ambient temperature and the q ja is the junction to ambient thermal resistance. for recommended operating conditions specification of the RT9511, the maximum junction temperature is 125 c. the junction to ambient thermal resistance q ja is layout dependent. for wqfn-24l 4x4 packages, the thermal resistance q ja is 52 c/w on the standard jedec 51-7 four layers thermal test board. the maximum power dissipation at t a = 25 c can be calculated by following formula : p d(max) = (125 c - 25 c) / (52 c/w) = 1.923w for wqfn-24l 4x4 packages the maximum power dissipation depends on operating ambient temperature for fixed t j(max) and thermal resistance q ja . for RT9511 packages, the figure 9 of derating curves allows designers to see the effect of rising ambient temperature on the maximum power dissipation allowed.
RT9511 22 ds9511-01 april 2011 www.richtek.com gnd gnd en1 vdd1 lx1 gnd fb2 i s e t u g n d e n 2 v d d 2 i s e t a l x 2 batt ts timer nc s y s f b 1 a c i n u s b 1 2 3 4 5 6 7 8 9 10 12 11 18 17 16 15 14 13 21 20 19 24 22 23 25 en bat_on a c _ o n c h g _ s battery sys v out1 v out2 r seta gnd the capacitors should be placed close to the ic pin and connected to ground plane. the gnd should be connected to a strong ground plane for heat sinking and noise protection. the connection of r seta should be isolated from other noisy traces. the short wire is recommended to prevent emi and noise coupling figure 10. pcb layout guide } output capacitors should be placed close to the ic and connected to ground plane to reduce noise coupling. } keep the main current traces as possible as short and wide. } lx node of step-down dc-dc converter is with high frequency voltage swing. it should be kept at a small area. } place the feedback components as close as possible to the ic and keep away from the noisy devices.
RT9511 23 ds9511-01 april 2011 www.richtek.com table 1. recommended inductors table 2. recommended capacitors for c in and c out supplier inductance ( m h) current rating (ma) dcr (m w ) dimensions (mm) series taiyo yuden 2.2 1480 60 3.00 x 3.00 x 1.50 nr 3015 gotrend 2.2 1500 58 3.85 x 3.85 x 1.80 gtsd32 sumida 2.2 1500 75 4.50 x 3.20 x 1.55 cdrh2d14 sumida 4.7 1000 135 4.50 x 3.20 x 1.55 cdrh2d14 taiyo yuden 4.7 1020 120 3.00 x 3.00 x 1.50 nr 3015 gotrend 4.7 1100 146 3.85 x 3.85 x 1.80 gtsd32 supplier capacitance ( m f) package part number tdk 4.7 603 c1608jb0j475m murata 4.7 603 grm188r60j475ke19 taiyo yuden 4.7 603 jmk107bj475ra taiyo yuden 10 603 jmk107bj106ma tdk 10 805 c2012jb0j106m murata 10 805 grm219r60j106me19 murata 10 805 grm219r60j106ke19 taiyo yuden 10 805 jmk212bj106rd
RT9511 24 ds9511-01 april 2011 www.richtek.com richtek technology corporation headquarter 5f, no. 20, taiyuen street, chupei city hsinchu, taiwan, r.o.c. tel: (8863)5526789 fax: (8863)5526611 richtek technology corporation taipei office (marketing) 5f, no. 95, minchiuan road, hsintien city taipei county, taiwan, r.o.c. tel: (8862)86672399 fax: (8862)86672377 email: marketing@richtek.com information that is provided by richtek technology corporation is believed to be accurate and reliable. richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. no third party intellectual property infringement of the applications should be guaranteed by users when integrating richtek products into any application. no legal responsibility for any said applications is assumed by richtek. outline dimension a a1 a3 d e d2 e2 l b e 1 see detail a dimensions in millimeters dimensions in inches symbol min max min max a 0.700 0.800 0.028 0.031 a1 0.000 0.050 0.000 0.002 a3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 d 3.950 4.050 0.156 0.159 d2 2.300 2.750 0.091 0.108 e 3.950 4.050 0.156 0.159 e2 2.300 2.750 0.091 0.108 e 0.500 0.020 l 0.350 0.450 0.014 0.018 w-type 24l qfn 4x4 package note : the configuration of the pin #1 identifier is optional, but must be located within the zone indicated. detail a pin #1 id and tie bar mark options 1 1 2 2

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