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pwm step-up dc/dc converter rh5rh 1a/ 2b/ 3b series application manual no.ea-023-0006
pwm step-up dc/dc converter 1 rh5rh 1a/ 2b/ 3b series outline the rh5rh 1a/ 2b/ 3b series are pwm step-up dc/dc converter ics by cmos process. the rh5rh 1a ic consists of an oscillator, a pwm control circuit, a driver transistor (lx switch), a refer- ence voltage unit, an error amplifier, a phase compensation circuit, resistors for voltage detection, a soft-start cir- cuit, and an lx switch protection circuit. a low ripple, high efficiency step-up dc/dc converter can be constructed of this rh5rh 1a ic with only three external components, that is, an inductor, a diode and a capacitor. these rh5rh 1a/ 2b/ 3b ics can achieve ultra-low supply current (no load) Ctyp. 15a Cby a new- ly developed pwm control circuit, equivalent to the low supply current of a vfm (chopper) step-up dc/dc con- verter. furthermore, these ics can hold down the supply current to typ. 2a by stopping the operation of the oscil- lator when the input voltage > (the output voltage set value + the dropout voltage by the diode and the inductor). these rh5rh 1a/ 2b/ 3b series ics are recommendable to the user who desires a low ripple pwm dc/dc converter, but cannot adopt a conventional pwm dc/dc converter because of its too large supply current. the rh5rh 2b/ 3b series ics use the same chip as that employed in the rh5rh 1a ic and are pro- vided with a drive pin (ext) for an external transistor. because of the use of the drive pin (ext), an external transistor with a low saturation voltage can be used so that a large current can be caused to flow through the inductor and accordingly a large output current can be obtained. therefore, these rh5rh 2b/ 3b series ics are recommendable to the user who need a current as large as several tens ma to several hundreds ma. the rh5rh 3b ic also includes an internal chip enable circuit so that it is possible to set the standby sup- ply current at max. 0.5a. these rh5rh 1a/ 2b/ 3b ics are suitable for use with battery-powered instruments with low noise and low supply current. ? small number of external components .......... only an inductor, a diode and a capacitor (rh5rh 1a) ? low supply current ........................................... typ. 15a (rh5rh301a) ? low ripple and low noise ? low start-up voltage (when the output current is 1ma) .................. max. 0.9v ? high output voltage accuracy .......................... 2.5% ? high efficiency ................................................... typ. 85% ? low temperature-drift coefficient of output voltage ...................... typ. 50 ppm/?c ? soft-start ............................................................. min. 500s ? small packages ................................................... sot-89 (rh5rh 1a, rh5rh 2b), sot-89-5 (rh5rh 3b) features applications ? power source for battery-powered equipment. ? power source for cameras, camcorders, vcrs, pdas, electronic data banks,and hand-held communication equipment. ? power source for instruments which require low noise and low supply current, such as hand-held audio equip- ment. ? power source for appliances which require higher cell voltage than that of batteries used in the appliances.
2 rh5rh C ? part number -- - ab c selection guide in rh5rh series, the output voltage, the driver, and the taping type for the ics can be selected at the user's request. the selection can be made by designating the part number as shown below : for example, the product with output voltage 5.0v, the external driver (the oscillator frequency 100khz) and taping type t1, is designated by part number rh5rh502b-t1. code description setting output voltage (v out ): a stepwise setting with a step of 0.1v in the range of 2.7v to 7.5v is possible. designation of driver: 1a: internal lx tr. driver (oscillator frequency 50khz) b 2b: external tr. driver (oscillator frequency 100khz) 3b: internal tr./external tr. (selectively available) (oscillator frequency 100khz, with chip enable function) designation of taping type : c ex. sot-89 : t1, t2 sot-89-5 : t1, t2 (refer to taping specifications) t1 is prescribed as a standard. rh5rh block diagram lx vss ext lxsw ce error amp. out v lx limiter buffer pwm control osc chip enable slow start phase comp. vref + error amp. (error amplifier) has a dc gain of 80db, and phase comp. (phase compensation circuit) provides the frequency characteristics including the 1st pole (fp=0.25hz) and the zero point (fz=2.5khz). furthermore, another zero point (fz=1.0khz) is also obtained by the resistors and a capacitor connected to the out pin. (note) lx pin ............ only for rh5rh 1a and rh5rh 3b ext pin ......... only for rh5rh 2b and rh5rh 3b ce pin ........... only for rh5rh 3b } } }
3 ? sot-89-5 pin configuration ? sot-89 pin description pin no. 1b 2b 3b 115 222 34 3 3 1 12 3 (mark side) 12 3 (mark side) 5 4 rh5rh symbol description v ss ground pin out step-up output pin, power supply (for device itself) lx switching pin (nch open drain) ext external tr. drive pin (cmos output) ce chip enable pin (active low)
absolute maximum ratings are threshold limit values that must not be exceeded even for an instant under any conditions. moreover, such values for any two items must not be reached simultaneously. operation above these absolute maximum ratings may cause degradation or permanent damage to the device. these are stress ratings only and do not necessarily imply functional operation below these limits. 4 rh5rh absolute maximum ratings symbol item v out output pin voltage v lx lx pin voltage v ext ext pin voltage v ce ce pin voltage i lx lx pin output current i ext ext pin current p d power dissipation topt operating temperature range tstg storage temperature range tsolder lead temperature(soldering) rating unit note +12 v +12 v note1 C 0.3 to v out +0.3 v note2 C 0.3 to v out +0.3 v note3 250 ma note1 50 ma note2 500 mw C 30 to +80 ?c C 55 to +125 ?c 260?c,10s (note 1) applicable to rh5rh 1a and rh5rh 3b. (note 2) applicable to rh5rh 2b and rh5rh 3b. (note 3) applicable to rh5rh 3b. vss=0v absolute maximum ratings
5 electrical characteristics ? rh5rh301a symbol item v out output voltage v in input voltage vstart start-up voltage vhold hold-on voltage i dd 1 supply current 1 i dd 2 supply current 2 i lx lx switching current i lx leak lx leakage current fosc oscillator frequency maxdty oscillator maximum duty cycle h efficiency t start soft-start time v lx lim v lx voltage limit conditions min. typ. max. unit note 2.925 3.000 3.075 v 8v i out =1ma,v in : 0 ? 2v 0.8 0.9 v i out =1ma,v in : 2 ? 0v 0.7 v to be measured at out pin (excluding switching current) 15 25 a to be measured at out pin (excluding switching current) 2 5 a v in =3.5v v lx =0.4v 60 ma v lx =6v,v in =3.5v 0.5 a 40 50 60 khz on (v lx l ) side 70 80 90 % 70 85 % time required for the rising 0.5 2.0 ms note1 of v out up to 3v. lx switch on 0.65 0.8 1.0 v note2 v out =3.0v rh5rh unless otherwise provided, v in =1.8v, v ss =0v, i out =10ma, topt=25?c, and use external circuit of typical application (fig. 1). (note 1) soft-start circuit is operated in the following sequence : (1) v in is applied. (2) the voltage (vref) of the reference voltage unit is maintained at 0v for about 200s after the application of v in . (3) the output of error amp. is raised to h level during the maintenance of the voltage (vref) of the reference voltage unit . (4) after the rise of vref, the output of internal error amp. is gradually decreased to an appropriate value by the function o f internal phase compensation circuit, and the output voltage is gradually increased in accordance with the gradual decrease of the output of in ternal error amp. (note 2) i lx is gradually increased after lx switch is turned on. in accordance with the increase of i lx , v lx is also increased. when v lx reaches v lx lim , lx switch is turned off by an lx switch protection circuit.
6 rh5rh ? rh5rh501a v out =5.0v unless otherwise provided, v in =3v, vss=0v, i out =10ma, topt=25?c, and use external circuit of typical application (fig. 1). (note 1) soft-start circuit is operated in the following sequence : (1) v in is applied. (2) the voltage (vref) of the reference voltage unit is maintained at 0v for about 200s after the application of v in . (3) the output of error amp. is raised to h level during the maintenance of the voltage (vref) of the reference voltage unit . (4) after the rise of vref, the output of internal error amp. is gradually decreased to an appropriate value by the function o f internal phase compensation circuit, and the output voltage is gradually increased in accordance with the gradual decrease of the output of in ternal error amp. (note 2) i lx is gradually increased after lx switch is turned on. in accordance with the increase of i lx , v lx is also increased. when v lx reaches v lx lim , lx switch is turned off by an lx switch protection circuit. symbol item v out output voltage v in input voltage vstart start-up voltage vhold hold-on voltage i dd 1 supply current 1 i dd 2 supply current 2 i lx lx switching current i lx leak lx leakage current fosc oscillator frequency maxdty oscillator maximum duty cycle h efficiency t start soft-start time v lx lim v lx voltage limit conditions min. typ. max. unit note 4.875 5.000 5.125 v 8v iout=1ma,vin:0 ? 2v 0.8 0.9 v iout=1ma,vin:2 ? 0v 0.7 v to be measured at out pin (excluding switching current) 30 45 a to be measured at out pin (excluding switching current) 2 5 a v in =5.5v v lx =0.4v 80 ma v lx =6v,v in =5.5v 0.5 a 40 50 60 khz on (v lx l ) side 70 80 90 % 70 85 % time required for the rising 0.5 2.0 ms note1 of v out up to 5v. lx switch on 0.65 0.8 1.0 v note2
7 rh5rh ? rh5rh302b symbol item v out output voltage v in input voltage vstart oscillator start-up voltage i dd 1 supply current 1 i dd 2 supply current 2 i exth ext h output current i extl ext l output current fosc oscillator frequency maxdty oscillator maximum duty cycle t start soft-start time conditions min. typ. max. unit note 2.925 3.000 3.075 v 8v ext no load,v out :0 ? 2v 0.7 0.8 v ext no load,v out =2.88v 30 50 a ext no load,v out =3.5v 2 5 a v ext =v out C0.4v C1.5 ma v ext =0.4v 1.5 ma 80 100 120 khz v ext h side 70 80 90 % time required for the rising 0.5 2.0 ms note1 of v out up to 3v v out =3.0v unless otherwise provided, v in =1.8v, vss=0v, i out =10ma, topt=25?c, and use external circuit of typical application (fig. 2). ? rh5rh502b v out =5.0v unless otherwise provided, v in =3v, vss=0v, i out =10ma, topt=25?c and use external circuit of typical application (fig. 2). (note 1) refer to page 5 (note 1) symbol item v out output voltage v in input voltage vstart oscillator start-up voltage i dd 1 supply current 1 i dd 2 supply current 2 i exth ext h output current i extl ext l output current fosc oscillator frequency maxdty oscillator maximum duty cycle t start soft-start time conditions min. typ. max. unit note 4.875 5.000 5.125 v 8v ext no load,v out :0 ? 2v 0.7 0.8 v ext no load,v out =4.8v 60 90 a ext no load,v out =5.5v 2 5 a v ext =v out C0.4v C2 ma v ext =0.4v 2 ma 80 100 120 khz v ext h side 70 80 90 % time required for the rising 0.5 2.0 ms note1 of v out up to 5v
8 ? rh5rh303b symbol item v out output voltage v in input voltage vstart start-up voltage vhold hold-on voltage h efficiency i dd 1 supply current 1 i dd 2 supply current 2 i lx lx switching current i lx leak lx leakage current i exth ext h output current i extl ext l output current v ceh 1 ce h level 1 v cel 1 ce l level 1 v ceh 2 ce h level 2 v cel 2 ce l level 2 i ceh ce h input current i cel ce l input current fosc oscillator frequency maxdty oscillator maximum duty cycle t start soft-start time v lx lim v lx voltage limit conditions min. typ. max. unit note 2.925 3.000 3.075 v 8v i out =1ma,v in : 0 ? 2v 0.8 0.9 v i out =1ma,v in : 2 ? 0v 0.7 v 70 85 % to be measured at out pin 30 50 a to be measured at out pin 25a v in =3.5v v lx =0.4v 60 ma v lx =6v,v in =3.5v 0.5 a v ext =v out C0.4v C1.5 ma v ext =0.4v 1.5 ma v out 3 1.5v v out C0.4 v v out 3 1.5v 0.4 v 0.8v v out <1.5v v out C0.1 v 0.8v v out <1.5v 0.1 v ce=3v 0.5 a ce=0v C0.5 a 80 100 120 khz on (v lx l )side 70 80 90 % time required for the rising 0.5 2.0 ms note1 of v out up to 3v. lx switch on 0.65 0.8 1.0 v note2 v out =3.0v unless otherwise provided, v in =1.8v, v ss =0v, i out =10ma, topt=25?c, and use external circuit of typical application (fig. 3). (note 1) soft-start circuit is operated in the following sequence : (1) v in is applied. (2) the voltage (vref) of the reference voltage unit is maintained at 0v for about 200s after the application of v in . (3) the output of error amp. is raised to h level during the maintenance of the voltage (vref) of the reference voltage unit . (4) after the rise of vref, the output of internal error amp. is gradually decreased to an appropriate value by the function o f internal phase com pensation circuit, and the output voltage is gradually increased in accordance with the gradual decrease of the output of inter nal error amp. (note 2) i lx is gradually increased after lx switch is turned on. in accordance with the increase of i lx , v lx is also increased. when v lx reaches v lx lim, lx switch is turned off by an lx switch protection circuit. rh5rh
9 ? rh5rh503b v out =5.0v rh5rh unless otherwise provided, v in =3v, v ss =0v, i out =10ma, topt=25?c, and use external circuit of typical application (fig. 3). (note 1) soft-start circuit is operated in the following sequence : (1) v in is applied. (2) the voltage (vref) of the reference voltage unit is maintained at 0v for about 200s after the application of v in . (3) the output of error amp. is raised to h level during the maintenance of the voltage (vref) of the reference voltage unit . (4) after the rise of vref, the output of internal error amp. is gradually decreased to an appropriate value by the function o f internal phase com pensation circuit, and the output voltage is gradually increased in accordance with the gradual decrease of the output of inter nal error amp. (note 2) i lx is gradually increased after lx switch is turned on. in accordance with the increase of i lx , v lx is also increased. when v lx reaches v lx lim, lx switch is turned off by an lx switch protection circuit. symbol item v out output voltage v in input voltage vstart start-up voltage vhold hold-on voltage h efficiency i dd 1 supply current 1 i dd 2 supply current 2 i lx lx switching current i lx leak lx leakage current i exth ext h output current i extl ext l output current v ceh 1 ce h level 1 v cel 1 ce l level 1 v ceh 2 ce h level 2 v cel 2 ce l level 2 i ceh ce h input current i cel ce l input current fosc oscillator frequency maxdty oscillator maximum duty cycle t start soft-start time v lx lim v lx voltage limit conditions min. typ. max. unit note 4.875 5.000 5.125 v 8v i out =1ma,v in : 0 ? 2v 0.8 0.9 v i out =1ma,v in : 2 ? 0v 0.7 v 70 85 % to be measured at out pin 60 90 a to be measured at out pin 25a v in =5.5v v lx =0.4v 80 ma v lx =6v,v in =5.5v 0.5 a v ext =v out C0.4v C2.0 ma v ext =0.4v 2.0 ma v out 3 1.5v v out C0.4 v v out 3 1.5v 0.4 v 0.8v v out <1.5v v out C0.1 v 0.8v v out <1.5v 0.1 v ce=5v 0.5 a ce=0v C0.5 a 80 100 120 khz on (v lx l )side 70 80 90 % time required for the rising 0.5 2.0 ms note1 of v out up to 5v. lx switch on 0.65 0.8 1.0 v note2
10 operation of step-up dc/dc converter step-up dc/dc converter charges energy in the inductor when lx transistor (lxtr) is on, and discharges the energy with the addition of the energy from input power source thereto, so that a higher output voltage than the input voltage is obtained. the operation will be explained with reference to the following diagrams : < current through l > < basic circuits > rh5rh i2 l sd i out v out cl lx tr i1 v in il ilmin ilmax topen t ton toff t=1/fosc step 1 : lxtr is turned on and current il (= i1 ) flows, so that energy is charged in l. at this moment, il(=i1 ) is increased from ilmin (= 0) to reach ilmax in proportion to the on-time period (ton) of lxtr. step 2 : when lxtr is turned off, schottky diode (sd) is turned on in order that l maintains il at ilmax, so that current il (= i2) is released. step 3 : il (=i2) is gradually decreased, and in the case of discontinuous mode, il reaches ilmin (=0) after a time period of topen, so that sd is turned off. however, in the case of a continuous mode which will be mentioned later,the time period (toff) runs out before il reaches ilmin (=0), so that lxtr is turned on in the next cycle, and sd is turned off. in this case, ilmin does not reach zero, and il (=i1) increases from ilmin (> 0). in the case of pwm control system, the output voltage is maintained constant by controlling the on-time peri- od (ton), with the oscillator frequency (fosc) being maintained constant. ? discontinuous conduction mode and continuous conduction mode in the above two diagrams, the maximum value (ilmax) and the minimum value (ilmin) of the current which flows through the inductor are the same as those when lxtr is on and also when lxtr is off. the difference between ilmax and ilmin, which is represented by ? i, is : ? i=ilmaxCilmin=v in ton/l=(v out Cv in ) topen/l ......................................... equation 1 wherein t=1/fosc=ton+toff duty (%)=ton/t 100=ton fosc 100 topen toff in equation 1, v in ton/l and (v out Cv in ) topen/l are respectively show the change in the current at on, and the change in the current at off.
11 rh5rh when the output current (i out ) is relatively small, topen0). the former mode is referred to as the discontinuous mode and the latter mode is referred to as the continuous mode. in the continuous mode, when equation 1 is solved for ton and the solution is tonc, tonc =t (1Cv in /v out ) ................................................................................................ equation 2 when ton the above explanation is directed to the calculation in an ideal case where there is no energy loss caused by the resistance in the external components and lxsw. in an actual case, the maximum output current will be 50 to 80% of the above calculated maximum output current. in particular, care must be taken because v in is decreased in an amount corresponding to the voltage drop caused by lxsw when il is large or v in is low. furthermore, it is required that with respect to v out , vf of the diode (about 0.3v in the case of a schottky type diode) be taken into consideration. 12 rh5rh therefore it is necessary that the setting of the input/output conditions and the selection of peripheral compo- nents should be made with ilmax taken into consideration. ? output current in continuous conduction mode when the operation enters into the continuous conduction mode by increasing the i out , ilmin becomes equal to iconst (> 0), and this current always flows through the inductor. therefore, v in iconst is added to p in in equation 5. thus, p in =v in iconst+(p on +p off )/t=v out i out =p out when the above equation is solved for i out , i out =v in 2 tonc 2 /(2 l t (v out Cv in ))+v in iconst/v out ............................................ equation 8 the peak current which flows through l lxtr sd is ilmax=v in ton/l+iconst ................................................................................................... equation 9 from equations 6 and 9, the larger the value of l, the smaller the load current at which the operation enters into the continuous mode, and the smaller the difference between ilmax and ilmin, and the smaller the value of ilmax. therefore, when the load current is the same, the larger the value of l, the easier the selection of peripheral components with a small allowable current becomes, and the smaller the ripple of the peripheral components can be made. in this case, however, it must be noted from equation 6 that i out becomes small when the allowable cur- rent of the inductor is small or when v in is so small that the operation cannot enter into the continuous mode. hints
13 rh5rh typical characteristics 1) output voltage vs. output current rh5rh301a l=120? v in =1.0v 1.5v 2.0v 020 40 60 3.1 3.0 2.9 2.8 2.7 2.6 2.5 output current i out (ma) output voltage v out (v) l= 270? 1.5v 3.1 3.0 2.9 2.8 2.7 2.6 2.5 output current i out (ma) output voltage v out (v) 0 10 20 30 40 50 60 v in =1.0v 2.0v rh5rh501a l=120? v in = 1.0v output current i out (ma) output voltage v out (v) 3.0v 4.0v 0 50 100 150 4.0 4.2 4.4 4.6 4.8 5.0 5.2 2.0v rh5rh302b l=28? output current i out (ma) output voltage v out (v) 2.5v 2.0v 1.5v 0 200 400 600 2.8 2.9 3.0 3.1 v in =0.9v rh5rh301a rh5rh501a l=270? v in =1.0v output current i out (ma) output voltage v out (v) 2.0v 3.0v 4.0v 0 50 100 150 4.0 4.2 4.4 4.6 4.8 5.0 5.2 rh5rh502b l=28? v in =1.5v output current i out (ma) output voltage v out (v) 2.0v 3.0v 4.0v 0 500 1000 4.4 4.6 4.8 5.0 5.2
14 rh5rh 2) efficiency vs. output current rh5rh301a l=120? v in =1.0v 1.5v 2.0v 010 20 30 90 80 70 60 50 40 output current i out (ma) efficiency h (%) l=270? 1.5v 2.0v 010 20 30 40 90 100 80 70 60 50 40 output current i out (ma) efficiency h (%) v in =1.0v rh5rh501a l=120? v in =1.0v 3.0v 4.0v 050 100 150 90 100 80 70 60 50 40 output current i out (ma) efficiency h (%) 2.0v rh5rh302b l = 28? v in =0.9v 2.0v 2.5v 0 200 400 600 80 100 60 40 20 0 output current i out (ma) efficiency h (%) 1.5v rh5rh301a rh5rh501a l=270? v in = 1.0v 3.0v 4.0v 2.0v 050 100 150 90 100 80 70 60 50 40 output current i out (ma) efficiency h (%) rh5rh502b l=28? v in =1.5v 3.0v 4.0v 2.0v 0 500 1000 80 100 60 40 20 0 output current i out (ma) efficiency h (%)
15 rh5rh 3) supply curret (no load) vs. input voltage 4) output current vs.ripple voltage rh5rh301a l=120? 1.0 1.2 1.4 1.6 1.8 2.0 50 60 70 40 30 20 10 0 input voltage v in (v) supply current i in (?) l=270? 1.0 1.2 1.4 1.6 1.8 2.0 50 60 70 40 30 20 10 0 input voltage v in (v) supply current i in (?) rh5rh501a l=120? 12 3 4 200 150 100 50 0 input voltage v in (v) supply current i in (?) rh5rh301a l=120? 1 5 10 20 30 40 50 60 70 80 90 100 50 60 70 80 40 30 20 10 0 output current i out (ma) ripple voltage vr (mv p-p) v in =0.9v 2.0v 3.0v rh5rh301a rh5rh501a l=270? 12 3 4 200 150 100 50 0 input voltage v in (v) supply current i in (?) rh5rh501a l=120? 1 5 10 20 30 40 50 60 70 80 90 100 50 60 70 80 90 100 40 30 20 10 0 output current i out (ma) ripple voltage vr (mv p-p) 4.0v 3.0v 2.0v v in =0.9v
16 5) start-up/hold-on voltage vs. output current (topt=25?c) rh5rh rh5rh301a l=270? 1 10 20 30 40 50 60 70 80 50 60 70 40 30 20 10 0 output current i out (ma) ripple voltage vr (mv p-p) 2.0v 3.0v v in =0.9v l=270? 1 10 90 20 30 40 50 60 70 80 50 60 70 80 40 30 20 10 0 output current i out (ma) ripple voltage vr (mv p-p) 2.0v 3.0v 4.0v v in =0.9v rh5rh302b l=28? 1 50 100 150 200 50 60 70 40 30 20 10 0 output current i out (ma) ripple voltage vr (mv p-p) v in =0.9v 2.0v 3.0v rh5rh301a l=120? 0 10 20 30 1.0 1.2 1.4 0.8 0.6 0.4 0.2 0 output current i out (ma) start-up/hold-on voltage vstart/vhold (v) vstart vhold rh5rh501a rh5rh502b l=28? 1 50 100 150 250 200 100 120 80 60 40 20 0 output current i out (ma) ripple voltage vr (mv p-p) v in =0.9v 2.0v 3.0v 4.0v rh5rh501a l=120? 0 10 20 30 1.0 1.2 1.4 1.6 0.8 0.6 0.4 0.2 0 output current i out (ma) start-up/hold-on voltage vstart/vhold (v) vstart vhold
17 rh5rh 6) output voltage vs.temperature rh5rh302b l=28? 0 20 40 60 80 100 1.0 1.2 1.4 0.8 0.6 0.4 0.2 0 output current i out (ma) start-up/hold-on voltage vstart/vhold (v) vstart vhold l=28? 1.0 1.2 1.4 0.8 0.6 0.4 0.2 0 0 20 40 60 80 100 output current i out (ma) start-up/hold-on voltage vstart/vhold (v) vstart vhold rh5rh301a i out =10ma v in =2v l=120? ?0 ?0 0 20 40 60 80 100 3.1 3.0 3.2 2.9 2.8 2.7 temperature topt(?c) output voltage v out (v) rh5rh302b i out =10ma v in =2v l=28? 3.1 3.2 3.0 2.9 2.8 2.7 ?0 ?0 02040 60 80 100 temperature topt(?c) output voltage v out (v) rh5rh502b rh5rh501a i out =10ma v in =3v l=120? ?0 ?0 0 20406080 100 5.1 5.2 5.0 4.9 4.8 4.7 temperature topt(?c) output voltage v out (v) rh5rh502b i out =10ma v in =3v l=28? ?0 ?0 02040 60 80 100 temperature topt(?c) 5.1 5.2 5.0 4.9 4.8 4.7 output voltage v out (v)
18 rh5rh 9) supply current 1 vs.temperature rh5rh501a 0.8 1.0 1.2 0.6 0.4 0.2 0 ?0 ?0 0 20 40 60 80 temperature topt(?c) start-up voltage vstart(v) ?0 20 0 20 40 60 80 temperature topt(?c) 0.8 1.0 0.6 0.4 0.2 0 hold-on voltage vhold(v) rh5rh501a ?0 ?0 020406080 temperature topt(?c) 80 100 60 40 20 0 supply current 1 i dd1 (?) rh5rh501a ?0 ?0 020406080 temperature topt(?c) 100 125 150 75 50 25 0 lx switching current i lx (ma) rh5rh501a rh5rh501a ?0 ?0 020406080 temperature topt(?c) 4 5 3 2 1 0 supply current 2 i dd2 (?) rh5rh501a ?0 ?0 020 40 60 80 temperature topt(?c) 0.8 1.0 0.6 0.4 0.2 0 lx leakage current i lxleak (?) 7) start-up voltage vs. temperature 8) hold-on voltage vs. temperature 10) supply current 2 vs.temperature 11) lx switching current vs.temperature 12) lx leakage current vs.temperature
19 rh5rh 13) oscillator frequency vs. temperature 14) oscillator duty cycle vs. temperature rh5rh301a i out =10ma v in =2v l=120? oscillator frequency fosc(khz) 50 60 70 80 90 100 40 30 20 10 0 ?0 0 20 40 60 80 100 ?0 temperature topt(?c) i out =10ma v in =3v l=120? ?0 ?0 0 20 40 60 80 100 temperature topt(?c) oscillator frequency fosc(khz) 50 60 70 80 90 100 40 30 20 10 0 rh5rh302b i out =10ma v in =2v l=28? ?0 ?0 020406080 100 temperature topt(?c) oscillator frequency fosc(khz) 60 80 100 120 140 40 20 0 rh5rh301a i out =10ma v in =2v l=120? ?0 ?0 02040 60 80 temperature topt(?c) oscillator duty cycle maxdty(%) 70 80 90 100 60 50 rh5rh501a rh5rh502b i out =10ma v in =3v l=28? ?0 ?0 020406080 100 temperature topt(?c) oscillator frequency fosc(khz) 60 80 100 120 140 40 20 0 rh5rh501a i out =10ma v in =3v l=120? ?0 ?0 020406080 temperature topt(?c) oscillator duty cycle maxdty(%) 70 80 90 100 60 50
20 rh5rh 15) v lx voltage limit vs. temperature rh5rh302b i out =10ma v in =2v l=28? ?0 ?0 020406080 temperature topt(?c) oscillator duty cycle maxdty(%) 70 80 90 100 60 50 i out =10ma v in =3v l=28? ?0 ?0 020 40 60 80 temperature topt(?c) oscillator duty cycle maxdty(%) 70 80 90 100 60 50 rh5rh501a ?0 ?0 0 20 40 60 80 temperature topt(?c) v lx voltage limit v lxlim (v) 0.4 0.6 0.8 1.0 1.2 0.2 0.0 rh5rh501a ?0 ?0 0 20 40 60 80 temperature topt(?c) ext "h" output current i exth (ma) 4 6 8 10 2 0 rh5rh502b rh5rh501a ?0 ?0 02040 60 80 temperature topt(?c) ext "l" output current i extl (ma) 4 6 8 10 2 0 16) ext h output current vs. temperature 17) ext l output current vs. temperature
21 rh5rh 18) load transient response rh5rh301a i out =1ma-30ma v in =2v l=120? 0 20 40 60 80 time t(ms) 3.0 3.5 4.0 4.5 5.0 2.5 2.0 1.5 1.0 output voltage v out (v) 150 180 210 240 120 90 60 30 0 output current i out (ma) output voltage output voltage output current i out =1ma-30ma v in =3v l=120? 0 20 40 60 80 time t(ms) 5.0 5.5 6.0 6.5 7.0 4.5 4.0 3.5 3.0 output voltage v out (v) 150 180 210 240 120 90 60 30 0 output current i out (ma) output voltage output current rh5rh302b i out =1ma-30ma v in =2v l=28? 020406080 time t(ms) 3.0 3.5 4.0 4.5 5.0 2.5 2.0 1.5 1.0 output voltage v out (v) 150 180 210 240 120 90 60 30 0 output current i out (ma) output voltage output current rh5rh501a rh5rh502b i out =1ma-30ma v in =3v l=28? 0 20 40 60 80 time t(ms) 5.0 5.5 6.0 6.5 7.0 4.5 4.0 3.5 3.0 output voltage v out (v) 150 180 210 240 120 90 60 30 0 output current i out (ma) output voltage output current
22 rh5rh 19) distribution of output voltage 0 5 10 15 20 25 30 35 distribution (%) output voltage v out (v) 5.18~5.20 5.16~5.18 5.14~5.16 5.12~5.14 5.10~5.12 5.08~5.10 5.06~5.08 5.04~5.06 5.02~5.04 5.00~5.02 4.98~5.00 4.96~4.98 4.94~4.96 4.92~4.94 4.90~4.92 4.88~4.90 4.86~4.88 4.84~4.86 4.82~4.84 4.80~4.82 rh5rh501a 20) distribution of oscillator frequency 0 5 10 15 20 25 distribution (%) oscillator frequency fosc (khz) 59~60 58~59 57~58 56~57 55~56 54~55 53~54 52~53 51~52 50~51 49~50 48~49 47~48 46~47 45~46 44~45 43~44 42~43 41~42 40~41 rh5rh501a
23 rh5rh typical applications v in inductor diode lx out vss v out + capacitor components inductor (l) : 120h (sumida electric co., ltd.) diode (d) : ma721 (matsushita electronics corporation, schottky type) capacitor (c l ) : 22f (tantalum type) fig. 1 v in inductor diode out vss v out + capacitor cb rb tr ext components inductor (l) : 28h (troidal core) diode (d) : hrp22 (hitachi, schottky type) capacitor (c l ) : 100f (tantalum type) transistor (tr) : 2sd1628g base resistor (rb) : 300 base capacitor (cb) : 0.01f fig. 2 ? rh5rh 2b ? rh5rh 1a
24 rh5rh v in inductor diode lx out vss v out + capacitor ext ce nc components inductor (l) : 120h (sumida electric co., ltd.) diode (d) : ma721 (matsushita electronics corporation, schottky type) capacitor (c l ) : 22f (tantalum type) fig. 3 v in inductor diode lx out vss v out + capacitor cb rb tr ext ce nc components inductor (l) : 28h (troidal core) diode (d) : hrp22 (hitachi, schottky type) capacitor (c l ) : 100f (tantalum type) transistor (tr) : 2sd1628g base resistor (rb) : 300 base capacitor (cb) : 0.01f fig. 4 ? rh5rh 3b
25 v in inductor diode lx out vss v out + capacitor ext ce nc rh5rh 3b pull-up resistor tr ce rh5rh ? ce pin drive circuit fig. 5
26 v in inductor diode out vss v out + capacitor ext zd:6.8v rh5rh502b tr cb r zd rb starter circuit (note) when the output current is small or the output voltage is unstable,use the rzd for flowing the bias current through th e zener diode zd. fig. 6 v in inductor diode out vss v out + capacitor rh5rh 1a tr pnp lx rb1 rb2 starter circuit (note) when the l x pin voltage is over the rating at the time pnp tr is off,use a rh5rh 2b and drive the pnp tr. by the external npn tr. fig. 7 application circuits ? 12v step-up circuit rh5rh ? step-down circuit
27 v in trance1:1 diode out vss v out + capacitor lx rh5rh 1a starter circuit (note) use a rh5rh 2b,depend on the output current. fig. 8 zd st r st tr v out side v out side v in side v in side starter circuit starter circuit zdst 2.5v /zdst designation of output voltage rst input bias current of zdst and tr. (several k to several hundreds k ) ? step-up/step-down circuit with flyback * the starter circuit is necessary for all above circuits. 1.for step-up circuit. 2.for step-down and step-up/step-down circuit. rh5rh
rh5rh 28 when using these ics, be sure to take care of the following points : ? set external components as close as possible to the ic and minimize the connection between the components and the ic. in particular, when an external component is connected to out pin, make minimum connection with the capacitor. ? make sufficient grounding. a large current flows through vss pin by switching. when the impedance of the vss connection is high, the potential within the ic is varied by the switching current. this may result in unstable operation of the ic. ? use capacitor with a capacity of 10f or more, and with good high frequency characteristics such as tanta- lum capacitor. we recommend the use of a capacitor with a resistance to the voltage being at least three times the output set voltage. this is because there may be the case where a spike-shaped high voltage is gen- erated by the inductor when lx transistor is turned off. ? take the utmost care when choosing a inductor. namely, choose such an inductor that has sufficiently small d.c. resistance and large allowable current, and hardly reaches magnetic saturation. when the inductance value of the inductor is small, there may be the case where i lx exceeds the absolute maximum ratings at the maximum load. use an inductor with an appropriate inductance. ? use a diode of a schottky type with high switching speed, and also take care of the rated current. ? these ics are provided with a soft-start circuit. however, there may be the case where the overshoot of the out put voltage takes place depending upon the peripheral circuits employed and the input/output condi- tions. in particular, when the input voltage is increased slowly, the occurrence of the overshoot of the output voltage becomes conspicuous. therefore in the case where the overshoot becomes a problem, take a counter- measure against this problem, for example, by clamping the output (out pin) by use of a zener diode. ? the transient response characteristics corresponding to the variations in the input and output are set so as to be slightly delayed by an internal phase compensation circuit in order to prevent the oscillation. because of such setting of the transient response characteristics, take care of the occurrence of the overshoot and/or undershoot of the output voltage. ? the internal phase compensation circuit is designed with the avoidance of the problem of the occurrence of the oscillation fully taken into consideration. however, there may be the case the oscillation takes place depending upon the conditions for the attachment of external components. in particular, take the utmost care when an inductor with a large inductance is used. the performance of power source circuits using these ics largely depends upon the peripheral components. take the utmost care in the selection of the peripheral components. in particular, design the peripheral circuits in such a manner that the values such as volt- age, current and power of each component, pcb patterns and the ic do not exceed their respective rated values. application hints

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