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rt9185 ds9185-02 july 2003 www.richtek.com 1 triple, ultra-fast cmos ldo regulator general description the rt9185 series are an efficient, precise triple- channel cmos ldo regulator specifically designed for mother-board applicatio n. the device is intended to powering the standby voltage in which 3.3v_pci, 2.5v_clock and 1.8v_ich 2 or 1.5v_ich4 core voltage of the pc based computer system. moreover, it is also optimized for cd/dvd-rom, cd/rw, xdsl router or ia equipments applications. the regulator outputs are ca pable of sourcing 1.5a, 0.8a and 0.3a of output current respectively. the rt9185 also works with low-esr ceramic capacitors, reducing the amount of board space necessary for power applications. the other features include faster transient response, low dropout voltage, high output accuracy, current limiting and thermal shutdown protections. the rt9185 regulators are available in fused sop-8, 5-lead to-252 and 5-lead to-263 packages. ordering information rt9185 features fixed output voltages: 3.35v at 1.5a, 2.55v at 0.8a and 1.5v or 1.8v at 0.3a low quiescent current (typically 0.4ma) operating voltage ranges: 3.5v~5.5v ultra-fast transient response tight load and line regulation current limiting protection thermal shutdown protection only low-esr ceramic capacitors required for stability custom voltage available applications mother-board power supply cd/dvd-rom, cd/rw xdsl router ia equipments cable modems pin configurations part number pin configurations rt9185 cs (plastic sop-8) rt9185 cl5 (plastic to-252-5) top view 1. vout1 2. vdd 3. gnd (tab) 4. vout2 5. vout3 rt9185 cm5 (plastic to-263-5) top view 1. vout1 2. vdd 3. gnd (tab) 4. vout2 5. vout3 123 45 package type s : sop-8 l5 : to-252-5 m5 : to-263-5 vout3 a : 1.8v b : 1.5v operating temperature range c: commercial standard other voltage versions please contact richtek for detail. gnd gnd gnd gnd 1 2 3 4 8 7 6 5 vout1 vdd vout2 vout3 gnd gnd gnd gnd 1 2 3 4 8 7 6 5 vout1 vdd vout2 vout3 12 3 4 5
rt9185 www.richtek.com ds9185-02 july 2003 2 typical application circuit pin description pin name pin function vout1 channel 1 output voltage vdd supply input gnd common ground vout2 channel 2 output voltage vout3 channel 3 output voltage function block diagram therm al sensor ref erence error amp + _ + _ + _ + _ + _ + _ vdd vout1 vout2 vout3 gnd current limiting error amp error amp current limiting current limiting vdd vdd therm al sensor ref erence error amp + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ vdd vout1 vout2 vout3 gnd current limiting error amp error amp current limiting current limiting vdd vdd gnd v out1 (3.35v / 1.5a) c2 4.7 f v dd (5vsb) c1 2.2 f v out3 (1.5v or 1.8v / 0.3a) v out2 (2.55v / 0.8a) c4 1 f c3 4.7 f vout1 vout2 rt9185 vout3 vdd gnd v out1 (3.35v / 1.5a) c2 4.7 f v dd (5vsb) c1 2.2 f v out3 (1.5v or 1.8v / 0.3a) v out2 (2.55v / 0.8a) c4 1 f c3 4.7 f vout1 vout2 rt9185 vout3 vdd
rt9185 ds9185-02 july 2003 www.richtek.com 3 absolute maximum ratings (note 1) supply input voltage 7v package thermal resistance sop-8 , jc 20c/w to-252-5 , jc 10c/w to-263-5, jc 5.5c/w lead temperature (soldering, 10 sec.) 260 c junction temperature 150 c storage temperature range ? 65 c to 150 c esd susceptibility (note 2) hbm 2kv mm 200v recommended operating conditions (note 3) supply input voltage 3.5v to 5.5v junction temperature range ? 40 c to 125 c electrical characteristics (v dd = 5v, c in = 1 f, t a = 25 c, for each ldo unless otherwise specified) parameter symbol test conditions min typ max units v out1 i out = 1ma 3.315 3.35 3.415 v out2 i out = 1ma 2.525 2.55 2.60 RT9185A 1.782 1.8 1.836 output voltage accuracy v out3 rt9185b i out = 1ma 1.485 1.5 1.530 v i lim1 r load = 1 ? 1.5 1.9 -- i lim2 r load = 1 ? 0.8 1.3 -- current limiting i lim3 r load = 1 ? 0.3 0.5 -- a quiescent current (triple ldos) (note 5) i dd i out = 0ma -- 0.4 0.8 ma ? v drop1 i out = 1.0a -- 600 1085 mv dropout voltage ? v drop2 i out = 0.8a -- 700 -- mv line regulation (triple ldos) ? v line i out = 1ma, v dd = 4v to 6v -- 2 10 mv ? v load1 v out1 , 1ma < i out < 1.0a -- 30 55 ? v load2 v out2 , 1ma < i out < 0.8a -- 30 55 load regulation (note 4) ? v load3 v out3 , 1ma < i out < 0.3a -- 20 45 mv temperature coefficient t c -- 30 -- ppm thermal shutdown t sd 125 165 -- c
rt9185 www.richtek.com ds9185-02 july 2003 4 note 1. stresses beyond those listed under ?absolute maximum ratings? may cause permanent damage to the device. these are stress ratings only, and functi onal operation of the devic e 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 affect device reliability. note 2. devices are esd sensitive. handling precaution re commended. the human body model is a 100pf capacitor discharged through a 1.5k ? resistor into each pin. note 3. the device is not guaranteed to func tion outside its operating conditions. note 4. regulation is measured at constant j unction temperature by using a 20ms current pulse. devices are tested for load regulation in the load range from 1ma to 1.5a , 0.8a and 0.3a for each ldo respectively. note 5. quiescent, or ground current, is the difference be tween input and output currents. it is defined by i q = i in ? i out under no load condition (i out = 0ma). the total current drawn from the suppl y is the sum of the load current plus the ground pin current.
rt9185 ds9185-02 july 2003 www.richtek.com 5 typical operating characteristics i load1 (a) short thermal shutdown 3 2.5 2 1.5 1 0.5 0 time 25ms/div v dd = 5v c 1 = 2.2 f t a = 25c v dd = 5v v out1 v out2 v out3 current limit vs. temperature 0 0.5 1 1.5 2 2.5 -35 -15 5 25 45 65 85 105 125 temperature ( c) current limit (a) -40 (c) psrr -80 -70 -60 -50 -40 -30 -20 -10 10 100 1000 10000 100000 1000 0 fre q uenc y ( hz ) psrr (db) 10 100 1k 10k 100k 1m v out1 v out2 v out3 v dd = 5v c 1 =2.2 f, c 2 = 4.7 f c 3 =4.7 f, c 4 = 1 f i o1 , i o2 , i o3 = 10ma t a =25 c v dd = 5v dropout valtage vs. temperature 0.2 0.4 0.6 0.8 1 -35 -15 5 25 45 65 85 105 125 temperature ( c) dropout valtage (v) v out1 = 3.3v v out2 = 2.5v -40 (c) v out1 = 3.3v v out2 = 2.5v v out3 = 1.8v/1.5v temperature stability 1.4 1.8 2.2 2.6 3 3.4 3.8 4.2 -35 -15 5 25 45 65 85 105 125 temperature ( c) output voltage (v) -40 quiescent current 200 300 400 500 600 -35 -15 5 25 45 65 85 105 125 temperature iq ( a) -40
rt9185 www.richtek.com ds9185-02 july 2003 6 v dd =5v v out3 =1.5v t a =25 c c 1 =2.2 f load current (ma) output voltage deviation (mv) 400 200 0 100 50 -50 0 time 500 load transient response load transient response time 500 c c 1 = 2.2 f load current (a) output voltage deviation (mv) 1 0 100 50 -50 0 v dd = 5v v out2 = 2.5v t a = 25 c c 1 = 2.2 f load current (a) output voltage deviation (mv) 1 0 100 50 -50 0 time 500 load transient response v dd = 4.5v to 5.5v v out1 = 3.3v t a = 25 c c 1 = 2.2 f i out1 = 500ma input voltage deviation (v) output voltage deviation (mv) 5.5 4.5 10 5 -5 0 time 100 line transient response v dd = 4.5v to 5.5v v out2 = 2.5v t a = 25 c c 1 = 2.2 f c 3 = 4.7 f i out1 = 400ma output voltage deviation (mv) 5.5 4.5 20 10 -10 0 time 100 line transient response input voltage deviation (v) v dd = 4.5v to 5.5v v out1 = 1.5v t a = 25 c c 1 = 2.2 f i out1 = 150ma input voltage deviation (v) output voltage deviation (mv) 5.5 4.5 20 10 -10 0 time 100 line transient response
rt9185 ds9185-02 july 2003 www.richtek.com 7 power dissipation vs. copper area 0 100 200 300 400 500 11.5 22.53 power dissipation (w) copper area t j = 125c ( mm 2 ) t a = 65c t a = 50c t a = 25c sop-8 power dissipation vs. copper area 0 100 200 300 400 500 22.5 33.544.55 power dissipation (w) copper area (mm 2 ) t a = 65c t a = 50c t a = 25c t j = 125c to-252 ( mm 2 ) t a = 65c t a = 25c t j = 125c to-263-5 power dissipation vs. copper area 100 150 200 250 300 2.5 3.5 4.5 5.5 6.5 7.5 8.5 power dissipation (w) copper area t a = 50c
rt9185 www.richtek.com ds9185-02 july 2003 8 applications information like any low-dropout regulator, the rt9185 requires input and output decoupling capacitors. the device is specifically designed for portable applications requiring minimum board space and smallest components. these capacitors must be correctly selected for good performance (see capacitor characteristics section). please note that linear regulators with a low dropout voltage have high internal loop gains which require care in guarding against oscillation caused by insufficient decoupling capacitance. input capacitor an input capacitance of ? 2.2 f is required between the device input pin and grou nd directly (the amount of the capacitance may be increased without limit). the input capacitor must be located less than 1 cm from the device to assure input stability (see pcb layout section). a lower esr capacitor allows the use of less capacitance, while higher esr type (like aluminum electrolytic) require more capacitance. capacitor types (aluminum, ceramic and tantalum) can be mixed in parallel, but the total equivalent input capacitance/esr must be defined as above to stable operation. there are no requirements for the esr on the input capacitor, but tolerance and temperature coefficient must be considered when selecting the capacitor to ensure the capacitance will be ? 2.2 f over the entire operating temperature range. output capacitor the rt9185 is designed specifically to work with very small ceramic output capacitors. the recommended minimum capacitance (temperature characteristics x7r, x5r, z5u, or y5v) are 2.2 f to 4.7 f range with 10m ? to 50m ? range ceramic capacitors between each ldo output and gnd for transient stability, but it may be increased without limit. higher capacitance values help to improve transient. the output capacitor?s esr is critical because it forms a zero to provide phase lead which is required for loop stability. no load stability the device will remain stable and in regulation with no external load. this is specially important in cmos ram keep-alive applications. input-output (dropout) voltage a regulator?s minimum input-to-output voltage differential (dropout voltage) determines the lowest usable supply voltage. in battery-powered systems, this determines the useful end-of-life battery voltage. because the device uses a pmos, its dropout voltage is a function of drain-to-source on-resistance, r ds(on) , multiplied by the load current: v droupout = v dd ? v out = r ds(on) i out current limit the rt9185 monitors and controls the pmos ? gate voltage, limiting the output cu rrent to 1.9a, 1.3a and 0.5a (typ) respectively. the outputs can be shorted to ground for an indefinite period of time without damaging the part. short-circuit protection the device is short circuit protected and in the event of a peak over-current condition, the short-circuit control loop will rapidly drive the output pmos pass element off. once the power pass element shuts down, the control loop will rapidly cycle the output on and off until the average power dissipation causes the thermal shutdown circuit to respond to servo the on/off cycling to a lower frequency. please refer to the section on thermal information for power dissipation calculations. capacitor characteristics it is important to note that capacitance tolerance and variation with temperature must be taken into consideration when selecting a capacitor so that the minimum required amount of capacitance is provided over the full operating temperature range. in general,
rt9185 ds9185-02 july 2003 www.richtek.com 9 a good tantalum capacitor will show very little capacitance variation with temperature, but a ceramic may not be as good (depending on dielectric type). aluminum electrolytics al so typically have large temperature variation of capacitance value. equally important to consider is a capacitor?s esr change with temperature: th is is not an issue with ceramics, as their esr is extremely low. however, it is very important in tantalum and aluminum electrolytic capacitors. both show increasing esr at colder temperatures, but the increase in aluminum electrolytic capacitors is so severe they may not be feasible for some applications. ceramic: for values of capacitance in the 10 f to 100 f range, ceramics are usually larger and more costly than tantalums but give superior ac performance for by-passing high frequency noise because of very low esr (typically less than 10m ? ). however, some dielectric types do not have good capacitance characteristics as a function of voltage and temperature. z5u and y5v dielectric ceramics have capacitance that drops severely with applied voltage. a typical z5u or y5v capacitor can lose 60% of its rated capacitance with half of the rated voltage applied to it. the z5u and y5v also exhibit a severe temperature effect, losing more than 50% of nominal capacitance at high and low limits of the temperature range. x7r and x5r dielectric ceramic capacitors are strongly recommended if ceramics are used, as they typically maintain a capacitance range within 20% of nominal over full operating ratings of temperature and voltage. of course, they are typically larger and more costly than z5u/y5u types for a given voltage and capacitance. tantalum: solid tantalum capacitors are recommended for use on the output because their typical esr is very close to the ideal value required for loop compensation. they also work well as input capacitors if selected to meet the esr requirements previously listed. tantalums also have good temperature stability: a good quality tantalum will typically show a capacitance value that varies less than 10~15% across the full temperature range of 125c to ? 40c. esr will vary only about 2x going from the high to low temperature limits. the increasing esr at lower temperatures can cause oscillations when marginal quality capacitors are used (if the esr of the capacitor is near the upper limit of the stability range at room temperature). aluminum: this capacitor type offers the most capacitance for the money. the disadvant ages are that they are larger in physical size, not widely available in surface mount, and have poor ac performance (especially at higher frequencies) due to higher esr and esl. compared by size, the esr of an aluminum electrolytic is higher than either tantalum or ceramic, and it also varies greatly with temperature. a typical aluminum electrolytic can exhibit an esr increase of as much as 50x when going from 25c down to ? 40c. it should also be noted that many aluminum electrolytics only specify impedance at a frequency of 120hz, which indicates they have poor high frequency performance. only aluminum electrolytics that have an impedance specified at a higher frequency (between 20khz and 100khz) should be used for the device. derating must be applied to the manufacturer?s esr specification, since it is typically only valid at room temperature. any applications using aluminum electrolytics should be thoroughly tested at the lowest ambient operating temperature where esr is maximum.
rt9185 www.richtek.com ds9185-02 july 2003 10 thermal considerations the rt9185 is a triple channel cmos regulator designed to provide two output voltage from one package. each output pin the rt9185 can deliver a current of up to 1.5a, 0.8a and 0.3a respectively over the full operating junction temperature range. however, the maximum output current must be derated at higher ambient te mperature to ensure the junction temperature does not exceed 125 c. with all possible conditions, the junction temperature must be within the range specified under operating conditions. each regulator contributes power dissipation to the overall power dissipation of the package. power dissipation can be calculated based on the output current and the voltage drop across each regulator. p d = (v dd ?v out1 ) i out1 + (v dd ? v out2 ) i out2 + (v dd ? v out3 ) i out3 + v in i gnd although the device is rated for 1.5a, 0.8a and 0.3a of output current, the application may limit the amount of output current based on the total power dissipation and the ambient temperature. the final operating junction temperature for any set of conditions can be estimated by the following thermal equation: p d (max) = ( t j (max) ? t a ) / ja where t j (max) is the maximum junction temperature of the die (125 c) and t a is the maximum ambient temperature. j a is the thermal resistance from the junction to the surrounding environment which is combined with j c + ca . where j c is junction to case thermal resistance which for fused sop-8 is 20c/w, to-252-5 is 10c/w and to-263-5 is 5.5c/w, ca is case to ambient thermal resistance which depend on pcb board area and air flow. pcb layout the rt9185 is a fixed output voltage regulator which the voltage are sensed at the output pin. a long pcb trace to load will cause a voltage drop between load and rt9185. be careful with pcb layout which minimum the output trace length and maximum the trace width. the gnd pin of the rt9185 performs the dual function of providing an electrical connection to ground and channeling heat away. connect the gnd pin to ground using a large pad or ground plane. good board layout practices must be used or instability can be induced because of ground loops and voltage drops. the input and output capacitors must be directly connected to the input, output, and ground pins of the device using traces which have no other currents flowing through them. the best way to do this is to layout c in and c out near the device with short traces to the v dd , v out , and ground pins. the regulator ground pin should be connected to the external circuit ground so that the regulator and its capacitors have a ?single point ground?. it should be noted that stability problems have been seen in applications where ?vias? to an internal ground plane were used at the ground points of the device and the input and output capacitors. this was caused by varying ground potentials at these nodes resulting from current fl owing through the ground plane. using a single point ground technique for the regulator and it?s capacitors fixed the problem. since high current flows through the traces going into v in and coming from v out , kelvin connect the capacitor leads to these pins so there is no voltage drop in series with the input and output capacitors. optimum performance can only be achieved when the device is mounted on a pc board according to the diagram below: rt 9185 vdd vout1 vout3 vout2 gnd gnd plane + + load trace resistance rp drop = i o * r p i o rt 9185 vdd vout1 vout3 vout2 gnd gnd plane + + load trace resistance rp drop = i o * r p i o
rt9185 ds9185-02 july 2003 www.richtek.com 11 sop-8 board layout to-252-5/to-263-5 board layout gnd v out3 gnd gnd v dd v out2 v out1 + + + + + + ++ gnd gnd gnd v dd v out2 v out1 v out3
rt9185 www.richtek.com ds9185-02 july 2003 12 package information dimensions in millimeters dimensions in inches symbol min max min max a 4.801 5.004 0.189 0.197 b 3.810 3.988 0.150 0.157 c 1.346 1.753 0.053 0.069 d 0.330 0.508 0.013 0.020 f 1.194 1.346 0.047 0.053 h 0.178 0.254 0.007 0.010 i 0.102 0.254 0.004 0.010 j 5.791 6.198 0.228 0.244 m 0.406 1.270 0.016 0.050 8?lead sop plastic package a b j f h m c d i
rt9185 ds9185-02 july 2003 www.richtek.com 13 dimensions in millimeters dimensions in inches symbol min max min max a 2.184 2.388 0.086 0.094 b 0.381 0.889 0.015 0.035 b3 4.953 5.461 0.195 0.215 c2 0.457 0.889 0.018 0.035 d 5.334 6.223 0.210 0.245 e 6.350 6.731 0.250 0.265 h 9.000 10.414 0.354 0.410 l 0.508 1.780 0.020 0.070 l2 0.508 ref. 0.020 ref. l3 0.889 2.032 0.035 0.080 p 1.270 ref. 0.050 ref. v 4.572 -- 0.180 -- 5-lead to-252 plastic package e p v h l l2 c2 a l3 d b b3
rt9185 www.richtek.com ds9185-02 july 2003 14 dimensions in millimeters dimensions in inches symbol min max min max d 9.652 10.668 0.380 0.420 b 1.143 1.676 0.045 0.066 e 8.128 9.652 0.320 0.380 a 4.064 4.826 0.160 0.190 c 1.143 1.397 0.045 0.055 u 6.223 ref. 0.245 ref. v 7.620 ref. 0.300 ref. l1 14.605 15.875 0.575 0.625 l2 2.286 2.794 0.090 0.110 b 0.660 0.914 0.026 0.036 b2 0.305 0.584 0.012 0.023 e 1.524 1.829 0.060 0.072 5-lead to-263 plastic surface mount package c b2 a b e v u d e l1 b l2
rt9185 ds9185-02 july 2003 www.richtek.com 15
rt9185 www.richtek.com ds9185-02 july 2003 16 richtek technology corp. headquarter 5f, no. 20, taiyuen street, chupei city hsinchu, taiwan, r.o.c. tel: (8863)5526789 fax: (8863)5526611 richtek technology corp. taipei office (marketing) 8f-1, no. 137, lane 235, paochiao road, hsintien city taipei county, taiwan, r.o.c. tel: (8862)89191466 fax: (8862)89191465 email: marketing@richtek-ic.com.tw

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