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description the GM431 is a three terminal adjustable shunt regulator with thermal stability guaranteed over temperature. output voltage can be adjusted to any value between 2.5v (v ) ref and 36v by using two external resistors. the GM431 has a typical dynamic output impedance of 0.2 w . active output circuitry provides a very unique turn on characteristic, mak- ing the GM431 an excellent replacement for zener diodes in many applications such as onboard regulation and ad- justable power supplies. the GM431 is an ideal voltage ref- erence for 3.0 to 3.3v switching power supplies. the GM431 shunt regulator is available with 3 voltage tol- erances 0.5%, 1.0% and 2.0% over t = 0c to + 70c, a and four package options (sot-23, to-92, sot -89 and sop-8). whatever your application is, the GM431 offers the optimum combination of performance, reliability, and economy. logic symbol application switching power supplies linear regulators adjustable supplies battery-operated computers computer disk drives instrumentation block diagram (positive logic) cathode reference anode + _ v ref cathode reference anode features sink current capability 1 ma to 100ma low dynamic output impedance, 0.2 w typ. low output noise 0.5%, 1% or 2% reference voltage tolerance temperature range 0c to+ 70 c available in sot -23, to-92, sot-89 and sop- 8 packages alternate for tl431, tl431, lm431 & as431 g m 4 3 1 v 0 . 1 1 www.gammamicro.com 1 a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
sot - 89 to- 92 sop- 8 ref cathode 1 anode 2 3 1 2 3 4 8 7 6 5 anode ref anode nc cathode anode nc anode GM431g ayww xxx = marking code g** = grade a = assembly location y = y ear ww, w= weekly gm 431g ayww 12 3 1. ref 2. anode 3. cathode GM431g ayww marking information & pin configura tions (top view) device code grade package shipping sot-23 sop-8 sop-8 sot-89 sot-23 to-92 to-92 sot-89 sot-23 to-92 to-92 sot-89 aaa aab aac 3,000 / t ape &reel units 100 / tube units 2,500 / t ape & reel units 1,000 / t ape & reel units GM431ast23r GM431bst23r GM431cst23r GM431as8t GM431as8r GM431bs8t GM431bs8r GM431cs8t GM431cs8r GM431ast89r GM431bst89r GM431cst89r ordering number precision 0.5% to-92 to-92 a a 1,000 units/ esd bag 2,000 units/ ammo pack(t ape) GM431at92b GM431bt92b GM431ct92b GM431at92rl GM431bt92rl GM431ct92rl 0.5% 0.5% 0.5% 0.5% 0.5% 1% 2% 1% 1% 1% 1% 1% 2% 2% 2% 2% 2% 3,000 / t ape &reel units 2,500 / t ape & reel units 1,000 / t ape & reel units 3,000 / t ape &reel units 2,500 / t ape & reel units 1,000 / t ape & reel units b b c c a a a b b b c c c 2,000 units/ ammo pack(t ape) 2,000 units/ ammo pack(t ape) g m 4 3 1 2 sop-8 sop-8 sop-8 sop-8 sot-23 xxxyw anode cathode 2 3 ref 1 100 / tube units 100 / tube units ordering information 1,000 units/ esd bag 1,000 units/ esd bag * for detail ordering number identification, please see last page. **grade a: indicates precision of 0.5%, b : indicates precision of 1%, c: indicates precision of 2% a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
g m 4 3 1 3 equivalent schema tic * all component values are nominal. pin numbers shown are for the d package. cathode ref anode 2.4k w 7.2k w 3.28k w 20pf 800 w 1k w 4k w 800 w 800 w 20pf 150 w 10k w a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
g m 4 3 1 4 these are stress ratings only. functional operation of the device at these or any conditions beyond the "recommended operating conditions" is not implied. exposure to absolute maximum rated conditions may affect device reliability. notes: 1. voltage values are with respect to the anode except as noted. 2. maximum power dissipation is a function of t , q and t . maximum allowable power dissipation at any allowable ambient temperature is j(max) ja a p = (t - t )/ q . d j(max) a ja 3. package thermal impedance is calculated per jesd 51. recommended opera ting conditions p ara met er sym bol v alue uni t 37 v cont inuou s cat hode curr ent r ange i k -100 to 15 0 ma refe rence inpu t curr ent r ange i ref -50 a t o 10m a ma powe r diss ipatio n at t = 25 c a sot -23 sop -8 to- 92 sot -89 oper ating amb ient t empe ratur e ran ge t a 0 to + 70 c lead temp eratu re (so lderin g) 10 seco nds t lead 260 p d 0.23 0.60 0.78 0.80 w q ja 336 132 163 132 c/w c (1) cath ode v oltag e pack age t herm al im peda nce (2, 3) sot -23 to- 92 sop -8 sot -89 v ka p ara met er sym bol mini mum max imum unit cath ode v oltag e v ka v ref 36 v cath ode c urren t i k 1.0 100 ma absolute maximum ratings (over free-air temperature range except as noted) a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
g m 4 3 1 5 electrical characteristics (t = 25c unless otherwise noted) a GM431a (0.5%) p ara met er con ditio n min typ max unit refe rence vo ltage v ref (1) v = v , i = 10 ma, t = 25 c ka ref k a 2.487 2.50 0 2.512 v (1) v =v ,i =10 m a,t = 0 to 70c ka ref k a v temp devi ation ref v dev (1) v = v , i = 10 ma , t = ful l rang e ka ref k a 4 17 mv ratio of ch ange in v ref to ch ange in v ka i = 10 ma k -1.0 -0.4 mv /v refe rence inpu t curr ent i ref (2) i = 10m a, r 1 = 1 0k w , r2 = k 0.7 4.0 m a devi ation of re feren ce input curr ent o ver fu ll temp eratu re ra nge i ref(de v) (2) i = 10 ma, r1 = 10k w , r2 = k t = fu ll ran ge a 0.4 1.2 m a mini mum ope rating curr ent i k(min ) (1) v= v ka ref 1.0 ma off- state cath ode curre nt i k(off ) (3) v = 36v , v = 0v ka ref 0.1 1 (3) v = 16 v , v = 0v ka ref dyna mic i mped ance | z | ka (1) f 1kh z,v =v , i =1ma to 10 0ma ka ref k 0.2 0.50 w d v ref d v ka m a gm4 31b (1.0 %) notes: (1) see test circuit 1 on page 5. (2) see test circuit 2 on page 5. (3) see test circuit 3 on page 5. d v = 10v to v ka ref d v = 36v to 10v ka -2.7 -2.0 0.4 p ara met er con ditio n min typ max unit refe rence vo ltage v ref (1) v = v , i = 10 ma, t = 25 c ka ref k a 2.475 2.50 0 2.525 v (1) v =v ,i =10 m a,t = 0 to 70c ka ref k a v temp devi ation ref v dev (1) v = v , i = 10 ma , t = ful l rang e ka ref k a 4 17 mv ratio of ch ange in v ref to ch ange in v ka i = 10 ma k -1.0 -0.4 mv /v refe rence inpu t curr ent i ref (2) i = 10m a, r 1 = 1 0k w , r2 = k 0.7 4.0 m a i ref(de v) (2) i = 10 ma, r1 = 10k w , r2 = k t = fu ll ran ge a 0.4 1.2 m a mini mum ope rating curr ent i k(min ) (1) v= v ka ref 1.0 ma off- state cath ode curre nt i k(off ) (3) v = 36v , v = 0v ka ref 0.1 1 (3) v = 16 v , v = 0v ka ref dyna mic i mped ance | z | ka (1) f 1kh z,v =v , i =1ma to 10 0ma ka ref k 0.2 0.50 w d v ref d v ka m a d v = 10v to v ka ref d v = 36v to 10v ka -2.7 -2.0 0.4 devi ation of re feren ce input curr ent o ver fu ll temp eratu re ra nge a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
g m 4 3 1 6 electrical characteristics (t = 25c unless otherwise noted) a GM431c (2.0%) notes: (1) see test circuit 1. (2) see test circuit 2. (3) see test circuit 3. test circuits v in v ka l k test circuit 1 v = v ka ref l ref r2 v in v ka r1 v ref l ref test circuit 2 v > v ka ref l (off) k v in v ka test circuit 3 off-state p ara met er con ditio n min typ max unit refe rence vo ltage v ref (1) v = v , i = 10 ma, t = 25 c ka ref k a 2.45 2.50 0 2.55 v (1) v =v ,i =10 m a,t = 0 to 70c ka ref k a v temp devi ation ref v dev (1) v = v , i = 10 ma , t = ful l rang e ka ref k a 4 17 mv ratio of ch ange in v ref to ch ange in v ka i = 10 ma k -1.0 -0.4 mv /v refe rence inpu t curr ent i ref (2) i = 10m a, r 1 = 1 0k w , r2 = k 0.7 4.0 m a i ref(de v) (2) i = 10 ma, r1 = 10k w , r2 = k t = fu ll ran ge a 0.4 1.2 m a mini mum ope rating curr ent i k(min ) (1) v= v ka ref 1.0 ma off- state cath ode curre nt i k(off ) (3) v = 36v , v = 0v ka ref 0.1 1 (3) v = 16 v , v = 0v ka ref dyna mic i mped ance | z | ka (1) f 1kh z,v =v , i =1ma to 10 0ma ka ref k 0.2 0.50 w d v ref d v ka m a d v = 10v to v ka ref d v = 36v to 10v ka -2.7 -2.0 0.4 devi ation of re feren ce input curr ent o ver fu ll temp eratu re ra nge v ref v ref a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
g m 4 3 1 7 typical applica tions GM431a, GM431b figure 3. output control for a three terminal fixed regulator r1 r2 gm 7805 in out common v = v + 5.0v out(min) ref v =( + ) out 1 r1 r2 v ref v in v out series pass regulator figure 4. v in v out r1 r2 figure 1. shunt regulator v in r1 r2 v =( + ) out 1 r1 r2 v ref v out figure 2. high current shunt regulator r1 r2 v =( + ) out 1 r1 r2 v ref v in v out constant current source figure 5. r cl v in i= out v ref r cl i out v out figure 6. constant current sink v in i = sink v ref r s i sink r s figure 7. triac crowbar r1 r2 v in v out v =( + ) out(trip) 1 r1 r2 v ref figure 8. scr crowbar r2 r1 v =( + ) out(trip) 1 v ref r1 r2 v in v out v =( + ) out 1 r1 r2 v ref v = v + v 2.0v out(min) ref be a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
g m 4 3 1 8 typical performance characteristics cathode voltage (v) -1 -0.5 0 0.5 1 1.5 2 2.5 3 1000 800 600 400 200 0 -200 -400 c a t h o d e c u r r e n t ( m a ) figure 9. cathode current vs. cathode voltage -2 -1 0 1 2 3 200 150 100 50 0 -50 -100 -150 cathode voltage (v) c a t h o d e c u r r e n t ( m a ) figure 10. cathode current vs. cathode voltage 0 20 40 60 80 0.6 0.5 0.4 0.3 0.2 0.1 0 t , ambient tempera ture (c) a i , r e f e r e n c e i n p u t c u r r e n t ( m a ) r e f figure 11. reference input current versus ambient temperature 0 100k 200k 300k 400k 500k 600k 2.5 2 1.5 1 0.5 0 frequency (hz) i m p e d a n c e ( w ) figure 12. dynamic impedance frequency 0 20 40 60 80 2.5 2.498 2.496 2.494 2.492 2.49 2.488 2.486 t , ambient tempera ture (c) a v , r e f e r e n c e i n p u t v o l t a g e ( v ) r e f figure 13. reference input voltage versus ambient temperature 10 100 1k 10k 100k 1m 60 50 40 30 20 10 0 -10 figure 14. open-loop voltage gain vs. frequency a , o p e n l o o p v o l t a g e g a i n ( d b ) v o l f, frequency (hz) i =10ma ka t =25c a 0 36 72 108 144 180 p h a s e s h i f t a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
g m 4 3 1 9 design guide for ac-dcsmps (switching mode power supply) use of shunt regulator in t ransformer secondary side control this example is applicable to both forward transformers and flyback transformers. a shunt regulator is used on the secondary side as an error amplifier, and feedback to the primary side is provided via a photocoupler. dc characteristic determination: in figure 16, r 1 and r are protection resistor for the light emitting 2 diode in the photocoupler, and r is a bypass 2 resistor to feed i minimum, and these are k determined as shown below. the photocoupler specification should be obtained separately from the manufacturer. using the parameters in figure 16, the following formulas are obtained: v is the GM431 operating voltage, and is set at k around 3v, taking into account a margin for fl uctuation. r is the current shunt resistance for the 2 light emitting diode, in which a bias current i of b around 1/5 i flows. f next, the output voltage can be determined by r 3 and r , and the following formula is obtained: 4 the absolute values of r and r are determined by 34 the GM431 reference input current i and the ac ref characteristics described in the next section. the i ref value is around 0.7a t yp. determination of external costants for the shunt regulator r1 = , r 2 = v - v - v of k i + i fb v f i b v = x v , v =2 .5 v typ o ref erf r3 +r4 r4 gm384x gm38c4x transformer phototransistor photocoupler light emitting diode v f r 1 r 2 r 3 r 4 r 5 c 1 v k i f i b ref gnd v o (+) (-) output vref figure 16. typical shunt regulator/ error amplifier GM431 sbd a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
g m 4 3 1 10 this refers to the determination of the gain frequency characteristic of the shunt regulator as an error amplifier. t aking the configuration in figure 16, the error amplifier characteristic is as shown in figure 17. ac characteristic determination: figure 17. GM431 error amplification characteristic g1 g2 when r = 0 5 g a i n g ( d b ) f1 f ac f2 when r = 0 5 in figure 17, the following formulas are obtained: gain g = g 50 db to 60 db (determined by shunt regulator) 10 g = 2 corner frequencies f = 1/(2 p c g r) 11 0 3 f = 1/(2 p c r) 2 1 5 g is the shunt regulator open-loop gain; this is given by the reciprocal of the reference voltage fluctuation 0 d vref/ d v , and is approximately 50 db. ka r 5 r 3 practical example consider the example of a photocoupler, with an internal light emitting diode v = 1.05 v and i = 2.5 ma, f f power supply output voltage v = 5 v, and bias resistance r current of approximately 1/5 i at 0.5 ma. if 22 f the shunt regulator v = 3 v, the following values are found. k next, assume that r = r = 10 k w . this gives a 5 v output. if r = 3.3 k w and c = 0.022 f , the 34 5 1 following values are found. g = 3.3 k w / 10 k w = 0.33 times (?10 db) 2 f = 1 / (2 x p x 0.022 f x 316 x 10 k w ) = 2.3 (hz) 1 f = 1 / (2 x p x 0.022 f x 3.3 k w ) = 2.2 (khz) 2 r = =316 w 1 5v - 1.05v - 3v 2.5ma + 0.5ma r = =2.1 k w 2 1.05v 0.5ma f frequency f (hz) osc * : pwm switching frequency f osc a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
g m 4 3 1 11 sot-23 p ackage outline dimensions 2.90 0.1 sot-89 package outline dimensions pad layout 45 1 . 5 1.5 0.7 3 2 1 4.50 0.05 units: mm 1.650 ref 1.400 ref 4.20 0.05 1.00 0.07 2.5 0.05 0.46 0.025 3.00 0.025 1.50 1.50 1.50 0.05 0.38 0.01 6 r 0.13~3x no draft~2 r 0.1 max 6~2x 6~2x r 0.13~2x r 0.13~2x unit: mm r 0.13~4x 0.4 0.1 1.5 0.05 0.95 0.038 2.8 0.1 1.9 0.05 unit: mm 0.65 0.05 1.10 0.1 5 0.13 0~0.1 0.8 0.05 a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator 0.079 2.0 0.031 0.8 inches mm ( ) 0.035 0.9 0.037 0.95 0.037 0.95 pad layout power management
g m 4 3 1 12 to-92 p ackage outline dimensions 4.6 0.1 4.6 0.1 2.3 3 - 0.46 1.45 0.1 14.5 0.5 1.27 1.27 2 2 2 2 3.6 0.15 0.38 0.015 3.6 0.15 1.3 0.1 5 5 unit: mm a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator 0.275 7.0 0.155 4.0 0.060 1.52 0.050 1.270 0.024 0.6 inches mm ( ) pad layout sop-8 p ackage outline dimensions 0.236 0.008 0.050 nom 1.270 nom +0.21 -0.20 5.990 3.91 0.1 +0.003 -0.004 0.154 pin indent 1.600 0.130 0.063 0.005 0.057 nom 1.450 nom 0.175 0.075 0.007 0.003 +0.004 -0.003 0.016 +0.10 -0.08 0.410 +0.0018 -0.0005 0.008 +0.05 -0.01 0.200 +0.013 -0.022 0.028 +0.33 -0.56 0.710 +0.002 -0.004 0.191 +0.05 -0.10 4.850 inches mm ( ) 0 ~ 8 power management
g m 4 3 1 13 ordering number gm 431 a t92 b gamma micro. circuit type voltage t olerance a: 0.5% b: 1.0% c: 2.0% package t92: to-92 st23: sot-23 s8: sop-8 st89: sot-89 shipping b : eds bag rl: ammo pack (tape) r: t ape & reel t : tube a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management
a a m i c r o e l e c t r o n i c s GM431 2.5v adjustable shunt regulator power management g m 4 3 1 14

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