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RT9953 1 ds9953-02 april 2011 www.richtek.com 4+1 ch power management ic 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. features z z z z z one synchronous step-up/step-down selectable converter z z z z z support 2aa or li-ion battery applications z z z z z internal soft-start control z z z z z 4 chs with internal compensation z z z z z power switches integrated z z z z z up to 95% efficiency z z z z z 100% (max) duty cycle for step-down converter z z z z z adjustable output voltage z z z z z fixed 1mhz switching frequency z z z z z ldo works with low-esr ceramic capacitors z z z z z fast line/load transient response z z z z z high psrr linear regulator z z z z z rohs compliant and halogen free general description the RT9953 is a complete power supply solution for digital still cameras and other handheld devices. the RT9953 is a multi-ch power management ic including one synchronous step-up dc/dc converter, one selectable synchronous step-up/step-down dc/dc converter, two synchronous step-down dc/dc converters, and one low dropout linear regulator. the RT9953 is designed to fulfill the applications for dsc as follows : ch1 is a synchronous step-up output for motor or dsc system i/o power ch2 is a selectable synchronous step-up/step-down output for motor or dsc system i/o power ch3 and ch4 are synchronous step-down outputs for dsp core and memory power supply ch5 is a 500ma, low dropout, low noise linear regulator with soft-start function. the RT9953 is designed to support li+ and 2aa battery applications. the selectable step-up/step-down converter can be set by sel pin. for the synchronous step-up and step down converters, the efficiency can be up to 95%. the RT9953 provides over current protection, thermal shutdown protection, over voltage and under voltage protection to achieve complete protection. the RT9953 is available in the wqfn-24l 4x4 package. applications z cmos digital still camera z cmos dv z portable devices pin configurations (top view) wqfn-24l 4x4 lx1 pvdd1 en3 fb4 ss pvdd4 lx2 pvdd2 fb3 en2 pvdd3 lx3 lx4 en5 vout5 pvdd5 fb5 fb2 sel en1 gnd fb1 en4 vddm 1 2 3 4 5 6 7 21 20 19 18 17 16 15 8910 12 14 13 24 22 23 11 gnd 25 marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area. RT9953 package type qw : wqfn-24l 4x4 (w-type) lead plating system g : green (halogen free and pb free)
RT9953 2 ds9953-02 april 2011 www.richtek.com for 2aa typical application circuit RT9953 pvdd5 3.6v 11 1 f c13 c15 r9 r10 47k 22.1k 10pf c14 1 f vout5 9 fb5 10 lx1 v bat v out_ch1 3.6v 1 c3 r1 r2 l1 2.2 h 10 f 470k 133k 4.7pf c1 c2 10 f x 2 pvdd1 2 fb1 22 lx2 v bat v out_ch2 5v 18 r3 r4 l2 2.2 h 10 f 470k 88.7k c4 c5 10 f x 2 pvdd2 17 fb2 21 pvdd3 3.6v 13 10 f c7 v out_ch3 2.5v c9 r5 r6 768k 360k 22pf c8 10 f lx3 12 fb3 15 l3 4.7 h pvdd4 3.6v 6 10 f c10 v out_ch4 1.8v c12 r7 r8 470k 374k 33pf c11 10 f lx4 7 fb4 4 l4 4.7 h sel 19 v bat en1 24 en2 14 en3 3 en4 20 en5 8 chip enable vddm 16 3.6v c16 1 f ss 5 c17 0.47nf gnd 23, 25 (exposed pad) v out_ch5 2.5v
RT9953 3 ds9953-02 april 2011 www.richtek.com for li-ion RT9953 pvdd5 v bat 11 1 f c13 c15 r9 r10 47k 22.1k 10pf c14 1 f vout5 9 fb5 10 lx1 v bat v out_ch1 5v 1 c3 r1 r2 l1 2.2 h 10 f 470k 88.7k 4.7pf c1 c2 10 f x 2 pvdd1 2 fb1 22 lx2 v bat or 5v v out_ch2 3.3v 18 r3 r4 l2 2.2 h 10 f 470k 150k c4 c5 10 f pvdd2 17 fb2 21 pvdd3 v bat 13 10 f c7 v out_ch3 2.5v c9 r5 r6 768k 360k 22pf c8 10 f lx3 12 fb3 15 l3 4.7 h pvdd4 v bat 6 10 f c10 v out_ch4 1.8v c12 r7 r8 470k 374k 33pf c11 10 f lx4 7 fb4 4 l4 4.7 h sel 19 en1 24 en2 14 en3 3 en4 20 en5 8 chip enable vddm 16 5v c16 1 f ss 5 c17 0.47nf c6 10pf gnd 23, 25 (exposed pad) v out_ch5 2.5v
RT9953 4 ds9953-02 april 2011 www.richtek.com channel ch3 formula v out_ch3 = (1+r5/r6) x 0.8 v out_ch3 (v) 3.3 2.5 1.8 1.5 1.3 1.2 1.0 l3 ( m h) 4.7 4.7 4.7 4.7 4.7 4.7 4.7 r5 (k w ) 86.6 768 470 330 237 187 23.2 r6 (k w ) 27.4 360 374 374 374 374 93.1 c9 (pf) 22 22 33 47 68 82 47 c8 ( m f) 10 10 10 10 10 10 10 channel ch4 application v out_ch4 = (1+r7/r8) x 0.8 v out_ch4 (v) 3.3 2.5 1.8 1.5 1.3 1.2 1.0 l4 ( m h) 4.7 4.7 4.7 4.7 4.7 4.7 4.7 r7 (k w ) 86.6 768 470 330 237 187 23.2 r8 (k w ) 27.4 360 374 374 374 374 93.1 c12 (pf) 22 22 33 47 68 82 47 c11 ( m f) 10 10 10 10 10 10 10 channel ch5 formula v out_ch5 = (1+r9/r10) x 0.8 v out_ch5 (v) 2.5 r9 (k w ) 47 r10 (k w ) 22.1 c15 (pf) 10 c14 ( m f) 1 table 1. recommended components for the typical application circuit
RT9953 5 ds9953-02 april 2011 www.richtek.com functional pin description pin no. pin name pin function 1 lx1 switch node of ch1. high impedance in shutdown mode. 2 pvdd1 power input of ch1. 3 en3 enable control input of ch3. 4 fb4 feedback input of ch4. high impedance in shutdown mode. 5 ss soft-start control input. 6 pvdd4 power input of ch4. 7 lx4 switch node of ch7. high impedance in shutdown mode. 8 en5 enable control input of ch5. 9 vout5 output voltage of ch5. 10 fb5 feedback input of ch5. high impedance in shutdown mode. 11 pvdd5 power input of ch5. 12 lx3 switch node of ch3. high impedance in shutdown mode. 13 pvdd3 power input of ch3. 14 en2 enable control input of ch2. 15 fb3 feedback input of ch3. high impedance in shutdown mode. 16 vddm analog power input. 17 pvdd2 power input of ch2. 18 lx2 switch node of ch2. high impedance in shutdown mode. 19 sel selection input for ch2 step-up or step-down operation mode. logic state can not be changed during operation. 20 en4 enable control input of ch4. 21 fb2 feedback input of ch2. high impedance in shutdown mode. 22 fb1 feedback input of ch1. high impedance in shutdown mode. 23, 25 (exposed pad) gnd ground pin. the exposed pad must be soldered to a large pcb and connected to gnd for maximum thermal dissipation. 24 en1 enable control input of ch1.
RT9953 6 ds9953-02 april 2011 www.richtek.com function block diagram ch1 c-mode step-up + - 0.8v ref vddm fb1 lx1 pvdd1 enable mode sequence en1 en3 en4 sel en2 en5 ch5 ldo + - 0.8v ref fb5 pvdd5 ss vout5 vddm ch2 c-mode step-up or step-down + - 0.8v ref lx2 pvdd2 fb2 ch3 c-mode step-down + - 0.8v ref fb3 pvdd3 lx3 lx4 fb4 ch4 c-mode step-down + - 0.8v ref pvdd4 gnd
RT9953 7 ds9953-02 april 2011 www.richtek.com electrical characteristics (v ddm = 3.3v, t a = 25 c, unless otherwise specified) absolute maximum ratings (note 1) l supply voltage, vddm, pvdd5--------------------------------------------------------------------------------------0.3v to 7v l power switch : lx1, lx2, lx3, lx4------------------------------------------------------------------------------------------------------- - 0.3v to 6.5v l the other pins----------------------------------------------------------------------------------------------------------- - 0.3v to 6.5v l power dissipation, p d @ t a = 25 c wqfn 24l 4x4-----------------------------------------------------------------------------------------------------------1.852w l package thermal resistance (note 2) wqfn 24l 4x4, q ja -----------------------------------------------------------------------------------------------------54 c/w wqfn 24l 4x4, q jc -----------------------------------------------------------------------------------------------------7 c/w l junction temperature---------------------------------------------------------------------------------------------------150 c l lead temperature (soldering, 10 sec.)------------------------------------------------------------------------------260 c l storage temperature range------------------------------------------------------------------------------------------- - 65 c to 150 c l esd susceptibility (note 3) hbm (human body mode)---------------------------------------------------------------------------------------------2kv mm (machine mode)----------------------------------------------------------------------------------------------------200v recommended operating conditions (note 4) l junction temperature range------------------------------------------------------------------------------------------ - 40 c to 125 c l ambient temperature range------------------------------------------------------------------------------------------ - 40 c to 85 c parameter symbol test conditions min typ max unit supply voltage vddm operating voltage v ddm 2.7 -- 5.5 v vddm startup voltage v st 1.5 -- -- v vddm over voltage protection 5.7 6 6.25 v pvdd5 operating voltage v pvdd5 2.5 -- 5.5 v supply current shutdown supply current into vddm i off all en = 0 -- -- 0.1 m a ch1 (syn step-up) : supply current into vddm i q1 non switching, en1 = 3.3v -- -- 800 m a ch2 (syn step-up or syn step-down) : supply current into vddm i q2 non switching, en2 = 3.3v -- -- 800 m a ch3 (syn step-down) : supply current into vddm i q3 non switching, en3 = 3.3v -- -- 800 m a ch4 (syn step-down) : supply current into vddm i q4 non switching, en4 = 3.3v -- -- 800 m a ch5 (ldo) : supply current into pvdd5 i q5 en5 = 3.3v, i out = 0ma -- 90 130 m a to be continued
RT9953 8 ds9953-02 april 2011 www.richtek.com parameter symbol test conditions min typ max unit oscillator ch1,2,3,4 operating frequency f osc 900 1000 1100 khz ch1 maximum duty cycle (step-up) v fb1 = 0.7v 80 83 86 % ch2 maximum duty cycle (step-up) v fb2 = 0.7v 80 83 86 % ch2 maximum duty cycle (step-down) v fb2 = 0.7v -- -- 100 % ch3 maximum duty cycle (step-down) v fb3 = 0.7v -- -- 100 % ch4 maximum duty cycle (step-down) v fb4 = 0.7v -- -- 100 % feedback regulation voltage feedback regulation voltage @ fb1, fb2, fb3, fb4, fb5 0.788 0.8 0.812 v total accuracy (including load regulation and line regulation) - 3 -- 3 % power switch p-mosfet, pvdd1 = 3.3v -- 200 250 ch1 on resistance of mosfet r ds(on) n-mosfet, pvdd1 = 3.3v -- 150 200 m w ch1 current limitation (step-up) -- 3 -- a p-mosfet, pvdd2 = 3.3v -- 200 250 ch2 on resistance of mosfet r ds(on) n-mosfet, pvdd2 = 3.3v -- 150 200 m w ch2 current limitation (step-down) -- 1.8 -- a ch2 current limitation (step-up) -- 3 -- a p-mosfet, pvdd3 = 3.3v -- 350 400 ch3 on resistance of mosfet r ds(on) n-mosfet, pvdd3 = 3.3v -- 300 400 m w ch3 current limitation (step-down) -- 1.5 -- a p-mosfet, pvdd4 = 3.3v -- 350 400 ch4 on resistance of mosfet r ds(on) n-mosfet, pvdd4 = 3.3v -- 300 400 m w ch4 current limitation (step-down) -- 1.5 -- a 2.2v Q pvdd5 Q 2.7v, i out = 400ma -- 160 320 ch5 dropout voltage (ldo) v drop 2.7v Q pvdd5 Q 5.5v, i out = 500ma -- 250 400 mv protection over voltage protection of ch1, ch2 step-up, pvdd1 and pvdd2 5.7 6 6.25 v over voltage protection hysteresis of ch1, ch2 step-up, pvdd1 and pvdd2 -- 0.5 -- v under voltage protection (ch1 to ch5) fb threshold 0.36 0.4 0.44 v 2.2v Q pvdd5 Q 2.7v 0.4 0.7 1.05 ch5 current limit i lim 2.7v Q pvdd5 Q 5.5v 0.5 0.8 1.05 a protection fault delay -- 100 -- ms to be continued
RT9953 9 ds9953-02 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. parameter symbol test conditions min typ max unit control logic high 1.3 -- 5.5 v en1 to en5, sel input threshold logic low -- -- 0.4 v en1 to en5, sel sink current -- 2 6 m a ch5 ldo regulation line regulation v line v pvdd5 = (v out5 + 1v) to 5.5v i out = 1ma -- -- 0.3 % load regulation v load 1ma < i out < 300ma -- -- 0.6 % f = 100hz -- - 60 -- power supply rejection rate f = 10khz psrr c out = 1uf, i out = 100ma -- - 30 -- db thermal protection thermal shutdown t sd 125 160 -- c thermal shutdown hysteresis t sd -- 20 -- c
RT9953 10 ds9953-02 april 2011 www.richtek.com ch1 step-up efficiency vs. output current 0 10 20 30 40 50 60 70 80 90 100 10 100 1000 output current (ma) efficiency (%) typical operating characteristics ch1 step-up efficiency vs. output current 0 10 20 30 40 50 60 70 80 90 100 10 100 1000 output current (ma) efficiency (%) v ddm = 5v, v out_ch1 = 5v, l1 = 2.2 m h, c2 = 10 m fx2 v bat = 4.5v v bat = 4.2v v bat = 3.9v v bat = 3.6v v bat = 3.3v v bat = 3v ch2 step-down efficiency vs. output current 0 10 20 30 40 50 60 70 80 90 100 10 100 1000 output current (ma) efficiency (%) v ddm = 5v, v out_ch2 = 1.2v, l2 = 4.7 m h, c5 = 10 m f v bat = 1.8v v bat = 3v v bat = 3.3v v bat = 3.6v v bat = 4.2v v bat = 4.5v ch2 step-up efficiency vs. output current 0 10 20 30 40 50 60 70 80 90 100 10 100 1000 output current (ma) efficiency (%) v ddm = 3v, v out_ch2 = 3.3v, l2 = 2.2 m h, c5 = 10 m fx2 v bat = 3v v bat = 2.7v v bat = 2.5v v bat = 2.2v v bat = 2v v bat = 1.8v ch3 step-down efficiency vs. output current 0 10 20 30 40 50 60 70 80 90 100 10 100 1000 output current (ma) efficiency (%) v ddm = 5v, v out_ch3 = 1.8v, l3 = 4.7 m h, c8 = 10 m f v bat = 2.7v v bat = 3.3v v bat = 3.6v v bat = 3.9v v bat = 4.2v v bat = 4.5v ch3 step-down efficiency vs. output current 0 10 20 30 40 50 60 70 80 90 100 10 100 1000 output current (ma) efficiency (%) v ddm = 5v, v out_ch3 = 1.2v, l3 = 4.7 m h, c8 = 10 m f v bat = 1.8v v bat = 2.5v v bat = 3v v bat = 3.3v v bat = 3.6v v bat = 4.5v v ddm = 3v, v out_ch1 = 5v, l1 = 2.2 m h, c2 = 10 m fx2 v bat = 3.4v v bat = 3v v bat = 2.7v v bat = 2.5v v bat = 2.2v v bat = 1.8v
RT9953 11 ds9953-02 april 2011 www.richtek.com ch4 step-down efficiency vs. output current 0 10 20 30 40 50 60 70 80 90 100 10 100 1000 output current (ma) efficiency (%) v ddm = 5v, v out_ch4 = 3.3v, l4 = 4.7 m h, c11 = 10 m f v bat = 3.4v v bat = 3.6v v bat = 3.9v v bat = 4.2v v bat = 4.5v ch4 step-down efficiency vs. output current 0 10 20 30 40 50 60 70 80 90 100 10 100 1000 output current (ma) efficiency (%) v ddm = 3v, v out_ch4 = 1.2v, l4 = 4.7 m h, c11 = 10 m f v bat = 1.8v v bat = 2.5v v bat = 3v v bat = 3.3v v bat = 3.6v v bat = 4.5v ch1 step-up output voltage vs. output current 4.950 4.955 4.960 4.965 4.970 4.975 4.980 4.985 4.990 4.995 5.000 0 100 200 300 400 500 600 output current (ma) output voltage (v) v ddm = 5v v bat = 3v v bat = 4.5v ch2 step-down output voltage vs. output current 1.190 1.193 1.195 1.198 1.200 1.203 1.205 1.208 1.210 0 200 400 600 800 1000 output current (ma) output voltage (v) v bat = 3v v bat = 4.5v v ddm = 5v ch2 step-up output voltage vs. output current 3.15 3.20 3.25 3.30 3.35 3.40 3.45 0 100 200 300 400 500 600 output current (ma) output voltage (v) v bat = 1.8v v bat = 3v v ddm = 3v ch3 step-down output voltage vs. output current 1.78 1.79 1.80 1.81 1.82 1.83 1.84 1.85 0 100 200 300 400 500 600 output current (ma) output voltage (v) v bat = 4.5v v bat = 3v v bat = 2.7v v ddm = 5v
RT9953 12 ds9953-02 april 2011 www.richtek.com ch4 step-down output voltage vs. output current 3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 0 100 200 300 400 500 600 output current (ma) output voltage (v) v bat = 4.5v v bat = 5v v ddm = 5v ch3 output voltage ripple time (500ns/div) lx3 (2v/div) v out_ch3_ac (5mv/div) v ddm = 5v, v bat = 3.7v, v out_ch3 = 1.8v, i out = 300ma, l3 = 4.7 h, c8 = 10 f ch4 output voltage ripple time (500ns/div) lx4 (2v/div) v out_ch4_ac (5mv/div) v ddm = 5v, v bat = 4.2v, v out_ch4 = 3.3v, i out = 300ma, l4 = 4.7 h, c11 = 10 f ch2 step-up output voltage ripple time (500ns/div) lx2 (2v/div) v out_ch2_ac (10mv/div) v ddm = 3v, v bat = 1.8v, v out_ch2 = 3.3v, i out = 300ma, l2 = 2.2 h, c5 = 10 fx2 ch2 step-down output voltage ripple time (500ns/div) lx2 (2v/div) v out_ch2_ac (5mv/div) v ddm = 5v, v bat = 3.7v, v out_ch2 = 1.2v, i out = 300ma, l2 = 2.2 h, c5 = 10 f ch1 output voltage ripple time (500ns/div) lx1 (2v/div) v out_ch1_ac (10mv/div) v ddm = 5v, v bat = 3.7v, v out_ch1 = 5v, i out = 300ma, l1 = 2.2 h, c2 = 10 fx2
RT9953 13 ds9953-02 april 2011 www.richtek.com ch1 load transient response time (1ms/div) i load (200ma/div) v out_ch1_ac (100mv/div) v ddm = 5v, v bat = 3v, v out_ch1 = 5v, i out = 100ma to 400ma, l1 = 2.2 h, c2 = 10 fx2 ch2 step-down load transient response time (1ms/div) i load (200ma/div) v out_ch2_ac (50mv/div) v ddm = 5v, v bat = 3.7v, v out_ch2 = 1.2v, i out = 100ma to 400ma, l2 = 2.2 h, c5 = 10 f ch2 step-up load transient response time (1ms/div) i load (200ma/div) v out_ch2_ac (100mv/div) v ddm = 3v, v bat = 1.8v, v out_ch2 = 3.3v, i out = 100ma to 400ma, l2 = 2.2 h, c5 = 10 fx2 ch3 load transient response time (1ms/div) i load (200ma/div) v out_ch3_ac (50mv/div) v ddm = 5v, v bat = 3.7v, v out_ch3 = 1.8v, i out = 50ma to 300ma, l3 = 4.7 h, c8 = 10 f ch4 load transient response time (1ms/div) i load (200ma/div) v out_ch4_ac (50mv/div) v ddm = 5v, v bat = 3.7v, v out_ch4 = 3.3v, i out = 50ma to 300ma, l4 = 4.7 h, c11 = 10 f frequency vs. temperature 850 870 890 910 930 950 970 990 1010 1030 1050 -40-30-20-100 102030405060708090 temperature (c) frequency (khz ) v ddm = 3v, v bat = 3v
RT9953 14 ds9953-02 april 2011 www.richtek.com ch5 ldo load transient response time (1ms/div) i load (200ma/div) v out_ch5_ac (10mv/div) v ddm = 5v, v bat = 3.7v, v out_ch5 = 2.5v, i out = 1ma to 300ma, c14 = 1 f ch5 ldo dropout voltage vs. output current 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0 100 200 300 400 500 output current (ma) dropout voltage (v) ? 40 c v ddm = 5v, c14 = 1 f 25 c 90 c ch5 ldo psrr -80 -70 -60 -50 -40 -30 -20 -10 0 10 100 1000 10000 100000 1000000 frequency (hz) psrr (db) v bat = 5v v bat = 3.7v v ddm = 5v, c14 = 1 f, i out = 100ma ch5 ldo output voltage vs. output current 2.45 2.46 2.47 2.48 2.49 2.50 2.51 2.52 2.53 2.54 2.55 0 100 200 300 400 500 600 output current (ma) output voltage (v) v bat = 3v v bat = 4.5v v ddm = 5v ch5 ldo output voltage vs. temperature 2.45 2.46 2.47 2.48 2.49 2.50 2.51 2.52 2.53 2.54 2.55 -40-30-20-100 102030405060708090 temperature (c) output voltage (v) v ddm = 5v, c14 = 1 f, i out = 300ma v bat = 4.5v v bat = 3v ch5 ldo i pvdd5 quiescent current vs. temperature 30 40 50 60 70 80 90 100 110 120 130 -40-30-20-10 0 102030405060708090 temperature (c) quiescent current ( a ) v ddm = 3.3v, v bat = 3.3v, c14 = 1 f, i out = 0ma
RT9953 15 ds9953-02 april 2011 www.richtek.com application information the RT9953 includes the following four dc/dc converters and one ldo to build a multiple-output power-supply system. ch1 : synchronous step-up dc/dc converter the ch1 is a synchronous step-up converter for motor or dsc system i/o power. the converter operates at fixed frequency and pwm current mode. the ch1 converter integrated internal mosfets, compensation network and synchronous rectifier for up to 95% efficiency. the output voltage can be set by the following equation : v out_ch1 = (1+r1/r2) x v fb1 where v fb1 is 0.8v typically. ch2 : synchronous step-up or step-down selectable dc/dc converter the ch2 is a synchronous step-up/step-down selectable converter for motor or dsc system i/o power. mode setting the ch2 of RT9953 features flexible step-up or step-down topology setting for either 1 x li-ion or 2 x aa application by sel pin. please refer to electrical characteristics for level of logic-high or logic-low. when the ch2 operates as a step-up converter, the sel must be set at logic-high. if the ch2 operates at step-down mode, the sel must be set at logic-low. in addition, please note that the logic state can not be changed during operation. table 2. ch2 mode setting sel ch2 operating mode logic -high step-up logic -low step-down step-up : the converter operates at fixed frequency pwm mode, continuous current mode (ccm), and discontinuous current mode (dcm) with internal mosfets, compensation network and synchronous rectifier for up to 95% efficiency. step-down : the converter operates at fixed frequency pwm mode and continuous current mode (ccm) with internal mosfets, compensation network and synchronous rectifier for up to 95% efficiency. the ch2 step-down converter can be operating at 100% maximum duty cycle to extend the input operating voltage range. while the input voltage is close to the output voltage, the converter enters low dropout mode. the output voltage can be set by the following equation : v out_ch2 = (1+r3/r4) x v fb2 where v fb2 is 0.8v typically. ch3 and ch4 : synchronous step-down dc/dc converter the converter operates at fixed frequency pwm mode, ccm and integrated internal mosfets and compensation network. the ch3 and ch4 step-down converter can be operating at 100% maximum duty cycle to extend battery operating voltage range. when the input voltage is close to the output voltage, the converter could enter low dropout mode with low output ripple. the output voltage can be set by the following equation : v out_ch3 = (1+r5/r6) x v fb3 v out_ch4 = (1+r7/r8) x v fb4 where v fb3 and v fb4 is 0.8v typically. ch5 : 500ma low dropout, low noise linear regulator like any low-dropout regulator, this ch requires input and output decoupling capacitors. the ch5 linear regulator can support 500ma output current when pvdd5 > 2.7v. the typical current limit is 0.8a. if the output is shorted to ground, the under voltage protection function will be triggered to shutdown the ic to prevent the part from damaging. the output voltage can be set by the following equation : v out_ch5 = (1+r9/r10) x v fb5 where v fb5 is 0.8v typically.
RT9953 16 ds9953-02 april 2011 www.richtek.com 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, t a is the ambient temperature and the q ja is the junction to ambient thermal resistance. for recommended operating conditions specification of RT9953, the maximum junction temperature is 125 c. the junction to ambient thermal resistance q ja is layout dependent. for wqfn-24l 4x4 package, the thermal resistance q ja is 54 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) / (54 c/w) = 1.852w for wqfn-24l 4x4 the maximum power dissipation depends on operating ambient temperature for fixed t j(max) and thermal resistance q ja . for RT9953 package, the figure 1 of derating curve allows the designer to see the effect of rising ambient temperature on the maximum power dissipation allowed. figure 1. derating curves for RT9953 package 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) four layers pcb wqfn-24l 4x4 layout considerations for the best performance of the RT9953, the following pcb layout guidelines must be strictly followed : } place the input and output capacitors as close as possible to the input and output pins respectively for good filtering. } keep the main power traces as wide and short as possible. } the switching node area connected to lx and inductor should be minimized for lower emi. } place the feedback components as close as possible to the fb pin and keep these components away from the noisy devices. } connect the gnd and exposed pad to a strong ground plane for maximum thermal dissipation and noise protection. } ch5 pcb trace and component had put different pcb side to avoid lx3 and lx4 switching noise.
RT9953 17 ds9953-02 april 2011 www.richtek.com gnd r5 c9 r6 c16 l3 c8 c7 gnd v out4_ch4 c10 c11 r7 r8 c12 l4 gnd v out1_ch1 gnd c2 c1 l1 r1 r2 c3 v bat gnd v out2_ch2 r4 r3 c6 l2 c4 c5 gnd r9 r10 c15 c13 c14 c17 lx should be connected to inductor by wide and short trace, keep sensitive compontents away from this trace place the feedback components as close as possible to the fb pin and keep away from noisy devices. input/output capacitors must be placed as close as possible to the input/ output pins. connect the exposed pad to a ground plane. v out3_ch3 v o u t 5 _ c h 5 lx1 pvdd1 en3 fb4 ss pvdd4 lx2 pvdd2 fb3 en2 pvdd3 l x 3 l x 4 e n 5 v o u t 5 p v d d 5 f b 5 f b 2 s e l e n 1 g n d f b 1 e n 4 vddm 1 2 3 4 5 6 7 21 20 19 18 17 16 15 8 9 10 12 14 13 24 22 23 11 gnd 25 v bat v b a t v bat v bat figure 2. pcb layout guide
RT9953 18 ds9953-02 april 2011 www.richtek.com table 3. protection items protection type threshold (typical) refer to electrical spec protection methods delay time reset method v ddm over voltage protection v ddm > 6v disable all channels 100ms restart if v ddm < 5.5 v (with hysteresis) current limit n-mosfet current > 3a ic shutdown 100ms v ddm power reset ch1 step-up pvdd1 ovp pvdd1 > 6v ic shutdown no-delay v ddm power reset current limit n-mosfet current > 3a ic shutdown 100ms v ddm power reset ch2 step-up pvdd2 ovp pvdd2 > 6v ic shutdown no-delay v ddm power reset ocp p-mosfet current > 1.5a ic shutdown 100ms v ddm power reset ch2 step-down uvp fb2 < 0.4v ic shutdown 100ms v ddm power reset ocp p-mosfet current > 1.5a ic shutdown 100ms v ddm power reset ch3 step-down uvp fb3 < 0.4v ic shutdown 100ms v ddm power reset ocp p-mosfet current > 1.5a ic shutdown 100ms v ddm power reset ch4 step-down uvp fb4 < 0.4v ic shutdown 100ms v ddm power reset current limit i out (p-mosfet current) > 0.8a current limiting no-delay no reset ch5 ldo uvp fb5 < 0.4v ic shutdown 100ms v ddm power reset thermal thermal shutdown temperature > 160 c all channels stop switching 100ms temperature < 140 c
RT9953 19 ds9953-02 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 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. 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 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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