adjustable precision zener shunt regulator issue 3 C march 1998 zr431 device description the zr431 is a three terminal adjustable shunt regulator offering excellent temperature stability and output current handling capability up to 100ma. the output voltage may be set to any chosen voltage between 2.5 and 20 volts by selection of two external divider resistors. the devices can be used as a replacement for zener diodes in many applications requiring an improvement in zener performance. features surface mount so8, sot89, sot223 and sot23 packages to92 package 2% and 1 % tolerance max. temperature coefficient 55 ppm/c temperature compensated for operation over the full temperature range programmable output voltage 50 m a to 100ma current sink capability low output noise applications shunt regulator series regulator voltage monitor over voltage/ under voltage protection switch mode power supplies v z g nd v ref schematic diagram 4-189
zr431 absolute maximum rating cathode voltage (v z ) 20v cathode current 150ma operating temperature -40 to 85c storage temperature -55 to 125c recommended operating conditions min max cathode voltage vref 20v cathode current 50 m a 100ma power dissipation (t amb =25c,t jmax =150c) sot23 330mw to92 780mw sot223 2w so8 780mw sot89 1.5w electrical characteristics test conditions (unless otherwise stated):t amb =25c parameter symbol value units conditions min typ max reference voltage 2% 1% v ref 2.45 2.475 2.50 2.50 2.55 2.525 vi l =10ma (fig1), v z =v ref deviation of reference input voltage over temperature v dev 8.0 17 mv i l =10ma, v z =v ref t a =full range (fig1) ratio of the change in reference voltage to the change in cathode voltage d v ref d v z -1.85 -2.7 mv/v v z from v ref to 10v i z =10ma (fig2) -1.0 -2.0 mv/v v z from 10v to 20v i z =10ma (fig2) reference input current i ref 0.12 1.0 m a r1=10k, r2=o/c, l l =10ma (fig2) deviation of reference input current over temperature d i ref 0.04 0.2 m a r1=10k, r2=o/c, i l =10ma t a =full range (fig2) minimum cathode current for regulation i zmin 35 50 m a v z =v ref (fig1) off-state current i zoff 0.1 m a v z =20v, v ref =0v (fig3) dynamic output impedance r z 0.75 w v z =v ref (fig1), f=0hz deviation of reference input voltage, v dev, is defined as the maximum variation of the reference input voltage over the full temperature range. the average temperature coefficient of the reference input voltage, v ref is defined as: v ref ( ppm c )= v dev x 1000000 v ref ( t 1 - t 2 ) the dynamic output impedance, rz, is defined as: r z = d v z d i z when the device is programmed with two external resistors, r1 and r2, (fig 2) , the dynamic output impedance of the overall circuit, r, is defined as: r = r z ( 1 + r 1 r 2 ) vmax vmin t1 t2 vdev = vmax - vmin temperature 4-190
zr431 typical characteristics cathode current v temperature dynamic impedance v frequency frequency (hz) 100 10 1.0 0.1 100 1k 10k 100k 1m dynamic impedance ( w ) temperature (c) minimum cathode current( m a) 24 -40 0 20 40 60 -20 80 26 28 30 32 34 36 38 v ref =v z reference current v temperature temperature (c) reference voltage (v) 100 -40 0 20 40 60 -20 80 110 120 130 140 150 160 2.490 2.492 2.494 2.496 2.498 2.500 2.502 2.504 2.506 reference current (na) -40 0 20 40 60 -20 80 reference voltage v temperature temperature (c) i z =10ma v ref =v z i z =10ma change in vr ef v cathode voltage cathode voltage (v) 0 -25 change in reference output voltage (mv) 5101520 -20 -15 -10 -5 0 i z =10ma v ref =v z 10ma 1ma power dissipation derating ambient temperature (c) 50 100 75 power dissipation (w) 0 1.0 25 2.0 85 sot 223 so8/to92 sot23 sot 89 4-191
zr431 typical charact eristics gain v frequency frequency (hz) load capacitance (f) stability boundary conditions time ( m s) pulse response i z 15k v z test circuit for open loop voltage gain 8k25 9 m f 230 + - i z = 10ma, t a = 25c test circuit for stability boundary conditions input 150 10k v ref < v z < 20, i z = 10ma, t a = 25c v z i z input monitor v z test circuit for pulse response 220 50 pulse generator t a = 25c 60 40 20 0 100 1k 10k 100k 1m open loop voltage gain (db) voltage swing (v) 2.0 0 0 0.4 0.6 0.8 1.0 0.2 1.0 0 5.0 3.0 repetitive pulse single pulse v z input stable stable 0 10p 20 40 60 80 100 100p 1000p 0.01 m 0.1 m 1 m cathode current (ma) 4-192
application circuits zr431 r2 vout = 1 + r1 r2 vref series regulator v+ vout r1 30 0.01f vref vout = 1 + r1 r2 vref vout = vref + vreg min output control of a three terminal fixed regulator r2 r1 v + vout vref zsr*** in out common r2 r1 v+ vout vout = vref 1 + r1 r2 vref higher current shunt regulator v+ output input v = 2.5v th v 2v on v = v+ off single supply comparator with temperature compensated threshold r2a r1a v+ vref r2b r1b vref 1 + r1b r2b vref over voltage / under voltage protection circuit low limit = high limit = 1 + r1a r2a vref r2 r1 vout = vref 1 + r1 r2 vref shunt regulator v+ vout output 4-193
i l input fig 1 C test circuit for v z =v ref dc test circuits fig 2 C test circuit for v z >v ref input v i z zoff fig 3 C test circuit for off state current zr431 4-194
zr431 to92 package suffix C c bottom view connection diagrams so8 package suffix C n8 top view sot223 package suffix C g top view C pin 4 floating or connected to pin 2 sot23 package suffix C f top view sot89 package suffix C z top view C pin 4 floating or connected to pin 2 part number package tol. % part mark zr431c01 to92 1.0 zr43101 zr431c to92 2.0 zr431 zr431g01 sot223 1.0 zr43101 zr431g sot223 2.0 zr431 zr431f01 sot23 1.0 43b zr431f sot23 2.0 43a zr431z01 sot89 1.0 43d zr431z sot89 2.0 43c zr431n801 so8 1.0 zr43101 zr431n8 so8 2.0 zr431 ordering information 4-195
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