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1 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 general description the l432 is a three-terminal adjustable shunt regulator utilizing an a ccurate 1.24v band gap reference. the output vo ltage can be set to any value between 1.24v (v ref ) to 18v with two external resistors as shown in the typical application circuit. the device exhibit a wide operating current range of 0.2 to 100 ma with a typical dynamic impedance of 0.25 . active output circuitry provides a very sharp turn-on characteristic, making the l432 excellent re- placements for low-voltage zener diodes in many applications, including on-board regulat- ion and adjustable power supplies. when used with an opto- coupler, the l432 is ideal voltage reference in isolated feedback circuits for 3.3v switching-mode power supplies. the l432 shunt regulator is available in two voltage tolerances (0.5% & 1.0%) and three package options (to-92, sot-23-3 and so-8). features z internal amplifier with 100 ma capability z programmable output voltage to 18v z 0.25 typical output impedance z pin to pin compatible with tlv431a, ts431, sc431l & as432 z trimmed bandgap design 0.5% & 1.0% with three package options z low output noise applications z linear regulator controller z precision voltage reference z switching power supplies z battery operating equipment z instrumentation z pcs, computer disk drives symbol & block diagram anode (a) cathod reference - + cathode (k) anode (a) reference (r) 1.24 vref functional block diagram symbol (r) (k)
2 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 absolute maximum ratings parameter value cathode-anode reverse breakdown voltage - v ka 20v anode-cathode forward current - i ak 1 a operating cathode current - i ka 100 ma reference input current - i ref 1 ma storage temperature range - t stg -65 to +150 c junction temperature - t j 150 c lead temperature (soldering, 10 seconds) - t l 300 c continuous power at 25 c - p d to-92 soic-8 sot-23 700 mw 650 mw 200 mw recommended conditions typical thermal resistances parameter rating package ja jc typ. de-rating cathode voltage (v ka ) v ref to 18v to-92 160 c/w 80 c/w 6.3 mw/c cathode current (i k ) 10 ma soic-8 175 c/w 45 c/w 5.7 mw/c sot-23 575 c/w 150 c/w 1.7 mw/c electrical specifications (ambient temperature must be derated base on power dissipation and package thermal characterist ics. the conditions are: v ka = v ref and i k = 10 ma unless otherwise stated) parameter test conditions min typ max units test circuit t a = 25 c, l432 (0.5%) 1.234 1.240 1.246 output voltage - v ref t a = 25 c, l432 (1%) 1.228 1.240 1.252 v 1 line regulation - ? v ref v ka = v ref to 15v 28 50 mv 2 load regulation - ? v ref i k = 1 to 100 ma 3.9 6 mv 1 temperature deviation - ? v ref 0 < t j < 105 c 5 12 mv 1 reference input current - i ref 2.3 6 a 1 reference input current temperature coefficient - ? i ref 0 < t j < 105 c 0.14 0.6 a 1 minimum cathode current for regulation - i k(min) 0.2 1 ma 1 off state leakage - i k(min) v ref = 0v, v ka = 15v 40 500 na 3 dynamic impedance v ka = v ref , f Q 1khz i k = 0.1 ma to 100 ma 0.25 0.4 1
3 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 test circuits in v v ka k i ref i v ref r1 r2 - test circuit 2 - > (v ka v ref ) ref i ) v ka v = - test circuit 1 - ka v ref (v in - test circuit 3 - ka vv in k (off) i (off state current) i k applications information ? stability selection of load capacitance when using l432 as a shunt regulator when the l432 is used as a shunt regulator, two options for selection of cl are recommended for optimal stability: 1. no load capacitance across the device, decouple at the load. 2. large capacitance across the device, optional decoupling at the load. the reason for this is that l432 exhibits instability with capacitances in the range of 1nf to 1uf (approx.) at light cathode currents (up to 3ma typical). the device is less stable the lower the cathode voltage has been set for. therefore while the device will be perfectly stable operating at a cathode current of 10ma with a 0.1uf capacitor across it, it will oscillate transiently during start-up as the cathode current passes through the instability region. selecting a very low (or preferably, no)capacitance, or alter- natively a high capacitance (such as 10uf) will avoid this issue altogether. since the user will probably wis h to have local decoupling at the load anyway, the most cost effective method is to use no capacitance at all directly across the device. pcb trace/via resistance and inductance prevent the local load de- coupling from causing the oscillation during the transient start-up phase. note : if the l432 is located right at the load, so the load decoupling capacitor is directly across it, then this capacitor will have to be Q 100pf or R 1uf.
4 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 stability boundary condition for shunt regulation vs. cathode current and load capacitance small-signal gain and phase shift vs. frequency vs. cathode voltage cathode current cl 1 2 r2 r1 r test circuit for stability l432 2 3 1 iz cathode current vs. cathode voltage 15k 232 gnd 1 2 10uf out 1 2 iz 8.25k test circuit for small signal gain and phas e l432 2 3 1
5 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 vs. frequency reference impedance reference voltage vs. junction temperature ratio of delta reference voltage to delta cathode voltage vz = 16v to vref v r e f / v z ( - m v / v ) vs. junction temperature vs. junction temperature reference input current
6 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 pin configurations vs. junction temperature r z ( ) reference impedance vs. junction temperature off-state cathode current
7 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 device selection guide device L432NA l432m3a l432va l432m5a package to-92 sot-23-3 soic-8 sot-23-5 marking L432NA 2m3a l432v 2m5a tolerance 0.5% 0.5% 0.5% 0.5% application circuit + 10uf + cout + cin p01n02lm or p3055l l431 or l432 r1 r2 1k 5v or 12v vin vout g d s a k r niko niko vout = (1 + ) vref r2 r1
8 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 to-92 mechanical data mm mm dimension min. typ. max. dimension min. typ. max. a 4.445 5.207 h 2.413 2.540 2.667 b 4.318 5.334 i 0.356 0.533 c 12.7 15.5 j d 0.356 0.533 k e 1.143 1.27 1.397 l f 3.175 4.191 m g 0.762 1.270 n
9 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 sot-23 (m3) mechanical data mm mm dimension min. typ. max. dimension min. typ. max. a 0.95 h 0.10 0.15 0.25 b 2.60 2.80 3.00 i 0.37 c 1.40 1.60 1.80 j d 2.70 2.90 3.10 k e 1.00 1.10 1.30 l f 0.00 0.10 m g 0.35 0.4 0.5 n
10 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 soic-8 (d) mechanical data mm mm dimension min. typ. max. dimension min. typ. max. a 4.8 5.0 h 0.4 1.27 b 3.8 4.0 i 0.18 0.25 c 5.8 6.2 j 0.22 d 0.35 0.48 k 0 8 e 1.27 l f 1.65 m g 0.1 0.25 n
11 1.24v low-voltage adjustable precision shunt regulator niko-sem l432 nov-21-2001 sot-23 (m5) mechanical data mm mm dimension min. typ. max. dimension min. typ. max. a 1.0 1.10 1.30 e 1.90(typ) a1 0.00 0.10 h 2.60 2.80 3.00 a2 0.70 0.80 0.90 l 0.37 b 0.35 0.40 0.50 c 0.10 0.15 0.25 d 2.70 2.90 3.10 e 1.40 1.60 1.80

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