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1/12 december 2004 high speed: t pd = 5.5 ns (typ.) at v cc = 5v low power dissipation: i cc = 4 a (max.) at t a =25c compatible with ttl outputs: v ih = 2v (min.), v il = 0.8v (max) power down protection on inputs & outputs symmetrical output impedance: |i oh | = i ol = 8 ma (min) balanced propagation delays: t plh ? t phl operating voltage range: v cc (opr) = 4.5v to 5.5v pin and function compatible with 74 series 238 improved latch-up immunity description the 74vhct238a is an advanced high-speed cmos 3 to 8 line decoder fabricated with sub-micron silicon gate and double-layer metal wiring c 2 mos technology. when the device is enabled, 3 binary select inputs (a, b, and c) determine which one of the outputs will go high. if enable input g1 is held low or either g2a or g2b is held high, decoding function is inhibited and all the 8 outputs go to low. the three enable inputs are provided to ease cascade connection and application of address decoders for memory systems. power down protection is provided on all inputs and outputs and 0 to 7v can be accepted on inputs with no regard to the supply voltage. this device can be used to interface 5v to 3v since all inputs are equipped with ttl threshold. all inputs and outputs are equipped with protection circuits against static discharge, giving them 2kv esd immunity and transient excess voltage. 74vhct238a 3 to 8 line decoder figure 1: pin connection and iec logic symbols table 1: order codes package t & r sop 74vhct238amtr tssop 74vhct238attr tssop sop rev. 3
74vhct238a 2/12 figure 2: input equivalent circuit table 2: pin description table 3: truth table x : don?t care figure 3: logic diagram this logic diagram has not be used to estimate propagation delays pin n symbol name and function 1, 2, 3 a, b, c address inputs 4, 5 g2a , g2b enable inputs 6 g1 enable input 15, 14, 13, 12, 11, 10, 9, 7 y0 to y7 outputs 8 gnd ground (0v) 16 v cc positive supply voltage inputs outputs enable select g2b g2a g1 c b a y0 y1 y2 y3 y4 y5 y6 y7 xxlxxxllllllll xhxxxx llllllll hxxxxx llllllll llhlllhlllllll llhllhlhllllll llhlhlllhlllll llhlhhlllhllll llhhllllllhlll llhhlhlllllhll llhhhlllllllhl l lhhhh lllllllh
74vhct238a 3/12 table 4: absolute maximum ratings absolute maximum ratings are those values beyond which damage to the device may occur. functional operation under these conditi ons is not implied 1) v cc = 0v 2) high or low state table 5: recommended operating conditions 1) v cc = 0v 2) high or low state 3) v in from 0.8v to 2v symbol parameter value unit v cc supply voltage -0.5 to +7.0 v v i dc input voltage -0.5 to +7.0 v v o dc output voltage (see note 1) -0.5 to +7.0 v v o dc output voltage (see note 2) -0.5 to v cc + 0.5 v i ik dc input diode current - 20 ma i ok dc output diode current 20 ma i o dc output current 25 ma i cc or i gnd dc v cc or ground current 50 ma t stg storage temperature -65 to +150 c t l lead temperature (10 sec) 300 c symbol parameter value unit v cc supply voltage 4.5 to 5.5 v v i input voltage 0 to 5.5 v v o output voltage (see note 1) 0 to 5.5 v v o output voltage (see note 2) 0 to v cc v t op operating temperature -55 to 125 c dt/dv input rise and fall time (see note 3) (v cc = 5.0 0.5v) 0 to 20 ns/v
74vhct238a 4/12 table 6: dc specifications table 7: ac electrical characteristics (input t r = t f = 3ns) (*) voltage range is 5.0v 0.5v table 8: capacitive characteristics 1) c pd is defined as the value of the ic?s internal equivalent capacitance which is calculated from the operating current consumption without load. (refer to test circuit). average operating current can be obtained by the following equation. i cc(opr) = c pd x v cc x f in + i cc symbol parameter test condition value unit v cc (v) t a = 25c -40 to 85c -55 to 125c min. typ. max. min. max. min. max. v ih high level input voltage 4.5 to 5.5 222v v il low level input voltage 4.5 to 5.5 0.8 0.8 0.8 v v oh high level output voltage 4.5 i o =-50 a 4.4 4.5 4.4 4.4 v 4.5 i o =-8 ma 3.94 3.8 3.7 v ol low level output voltage 4.5 i o =50 a 0.0 0.1 0.1 0.1 v 4.5 i o =8 ma 0.36 0.44 0.55 i i input leakage current 0 to 5.5 v i = 5.5v or gnd 0.1 1.0 1.0 a i cc quiescent supply current 5.5 v i = v cc or gnd 44040 a + i cc additional worst case supply current 5.5 one input at 3.4v, other input at v cc or gnd 1.35 1.5 1.5 ma i opd output leakage current 0 v out = 5.5v 0.5 5.0 5.0 a symbol parameter test condition value unit v cc (*) (v) c l (pf) t a = 25c -40 to 85c -55 to 125c min. typ. max. min. max. min. max. t plh t phl propagation delay time a,b,c to y 5.0 15 5.5 8.1 1.0 9.5 1.0 9.5 ns 5.0 50 7.0 10.1 1.0 11.5 1.0 11.5 t plh t phl propagation delay time g1 to y 5.0 15 5.4 8.1 1.0 9.5 1.0 9.5 ns 5.0 50 6.9 10.1 1.0 11.5 1.0 11.5 t plh t phl propagation delay time g2a , g2b to y 5.0 15 5.7 8.1 1.0 9.5 1.0 9.5 ns 5.0 50 7.2 10.1 1.0 11.5 1.0 11.5 symbol parameter test condition value unit t a = 25c -40 to 85c -55 to 125c min. typ. max. min. max. min. max. c in input capacitance 610 10 10pf c pd power dissipation capacitance (note 1) 37 pf
74vhct238a 5/12 figure 4: test circuit c l =15/50pf or equivalent (includes jig and probe capacitance) r t = z out of pulse generator (typically 50 ? ) figure 5: waveform - propagation delays for inverting outputs (f=1mhz; 50% duty cycle)
74vhct238a 6/12 figure 6: waveform - propagation delays for non-inverting outputs (f=1mhz; 50% duty cycle)
74vhct238a 7/12 dim. mm. inch min. typ max. min. typ. max. a 1.75 0.068 a1 0.1 0.25 0.004 0.010 a2 1.64 0.063 b 0.35 0.46 0.013 0.018 b1 0.19 0.25 0.007 0.010 c 0.5 0.019 c1 45 (typ.) d 9.8 10 0.385 0.393 e 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 8.89 0.350 f 3.8 4.0 0.149 0.157 g 4.6 5.3 0.181 0.208 l 0.5 1.27 0.019 0.050 m 0.62 0.024 s8 (max.) so-16 mechanical data 0016020d
74vhct238a 8/12 dim. mm. inch min. typ max. min. typ. max. a 1.2 0.047 a1 0.05 0.15 0.002 0.004 0.006 a2 0.8 1 1.05 0.031 0.039 0.041 b 0.19 0.30 0.007 0.012 c 0.09 0.20 0.004 0.0079 d 4.9 5 5.1 0.193 0.197 0.201 e 6.2 6.4 6.6 0.244 0.252 0.260 e1 4.3 4.4 4.48 0.169 0.173 0.176 e 0.65 bsc 0.0256 bsc k0? 8?0? 8? l 0.45 0.60 0.75 0.018 0.024 0.030 tssop16 mechanical data c e b a2 a e1 d 1 pin 1 identification a1 l k e 0080338d
74vhct238a 9/12 dim. mm. inch min. typ max. min. typ. max. a 330 12.992 c 12.8 13.2 0.504 0.519 d 20.2 0.795 n 60 2.362 t 22.4 0.882 ao 6.45 6.65 0.254 0.262 bo 10.3 10.5 0.406 0.414 ko 2.1 2.3 0.082 0.090 po 3.9 4.1 0.153 0.161 p 7.9 8.1 0.311 0.319 tape & reel so-16 mechanical data
74vhct238a 10/12 dim. mm. inch min. typ max. min. typ. max. a 330 12.992 c 12.8 13.2 0.504 0.519 d 20.2 0.795 n 60 2.362 t 22.4 0.882 ao 6.7 6.9 0.264 0.272 bo 5.3 5.5 0.209 0.217 ko 1.6 1.8 0.063 0.071 po 3.9 4.1 0.153 0.161 p 7.9 8.1 0.311 0.319 tape & reel tssop16 mechanical data
74vhct238a 11/12 table 9: revision history date revision description of changes 16-dec-2004 3 order codes revision - pag. 1.
74vhct238a 12/12 information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsibility for the co nsequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of stmicroelectronics. specifications mentioned in this publicati on are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectronics prod ucts are not authorized for use as critical components in life support devices or systems without express written approval of stmicroelectro nics. the st logo is a registered trademark of stmicroelectronics all other names are the property of their respective owners ? 2004 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com

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