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1/12 july 2001 n high speed : t pd = 22 ns (typ.) at v cc = 6v n low power dissipation: stand by state : i cc =4 m a (max.) at t a =25c active state : i cc =700 m a (typ.) at v cc = 6v n high noise immunity: v nih = v nil = 28 % v cc (min.) n symmetrical output impedance: |i oh | = i ol = 4ma (min) n balanced propagation delays: t plh @ t phl n wide operating voltage range: v cc (opr) = 2v to 6v n wide output pulse width range : t wout = 120 ns ~ 60 s over at v cc = 4.5 v n pin and function compatible with 74 series 423a description the m74hc423a is an high speed cmos monostable multivibrator fabricated with silicon gate c 2 mos technology. there are two trigger inputs, a input (negative edge) and b input (positive edge). these inputs are valid for slow rising/falling signals, (tr = tf = 1 sec). after triggering the output maintains the monostable state for the time period determined by the external resistor rx and capacitor cx. the pulse width constant is k @ 1 . taking clr low breaks this monostable state. if the next trigger pulse occurs during the monostable period it makes the monostable period longer. limit for values of cx and rx : cx : no limit rx : v cc < 3.0v 5k w to 1m w v cc > 3.0v 1k w to 1m w all inputs are equipped with protection circuits against static discharge and transient excess voltage. m74hc423a dual retriggerable monostable multivibrator pin connection and iec logic symbols order codes package tube t & r dip m74hc423ab1r sop m74hc423am1r m74hc423arm13tr tssop M74HC423ATTR tssop dip sop
m74hc423a 2/12 input and output equivalent circuit pin description truth table x : dont care system diagram this logic diagram has not be used to estimate propagation delays pin no symbol name and function 1,9 1a , 2a trigger inputs (negative edge triggered) 2, 10 1b, 2b trigger inputs (positive edge triggered) 3, 11 1 clr 2 clr direct reset (active low) 4, 12 1q , 2q outputs (active low) 7 2r x /c x external resistor capacitor connection 13, 5 1q, 2q outputs (active high) 14, 6 1c x 2c x external capacitor connection 15 1r x /c x external resistor capacitor connection 8 gnd ground (0v) 16 vcc positive supply voltage inputs outputs note a bclr qq h h output enable x l h l h inhibit h x h l h inhibit l h output enable x x l l h inhibit
m74hc423a 3/12 timing chart block diagram 1) cx, rx, dx are external components. (2) dx is a clamping diode. the external capacitor is charged to vcc in the stand-by-state, i.e. no trigger. when the supply voltage is turned off cx is di scharged mainly trough an internal parasitic diode(see figures). if cx is sufficiently large and vcc decreases rapidly, there will be some poss ibility of damaging the i.c. with a surge current or latch-up. if the voltage supply filter capacitor is large enough and vcc decrease slowly, the surge current is automatically limited and damage to the i.c. is avoided. the maximum forward current of the parasitic diode is approximately 20 ma. in cases where cx is large the time taken for the supply voltage to fall to 0.4 vcc can be calculated as follows : t f > (vcc - 0.7) x cx/20ma in cases where t f is too short an external clamping diode is required to protect the i.c. from the surge current.
m74hc423a 4/12 functional description stand-by state the external capacitor,cx, is fully charged to vcc in the stand-by state. hence, before triggering, transistor qp and qn (connected to the rx/cx node) are both turned-off. the two comparators that control the timing and the two reference voltage sources stop operating. the total supply current is therefore only leakage current. trigger operation triggering occurs when : 1 st) a is "low" and b has a falling edge; 2 nd) b is "high" and a has a rising edge; 3 rd) a is "low" and b is high and c1 has a rising edge; after the multivibrator has been retriggered comparator c1 and c2 start operating and qn is turned on. cx then discharges through qn. the voltage at the node r/c external falls. when it reaches v refl the output of comparator c1 becomes low. this in turn reset the flip-flop and qn is turned off. at this point c1 stops functioning but c2 continues to operate. the voltage at r/c external begins to rise with a time constant set by the external components rx, cx. triggering the multivibrator causes q to go high after internal delay due to the flip-flop and the gate. q remains high until the voltage at r/c external rises again to v refh . at this point c2 output goes low and o goes low. c2 stop operating. that means that after triggering when the voltage r/c external returns to v refh the multivibrator has returned to its monostable state. in the case where rx cx are large enough and the discharge time of the capacitor and the delay time in the i.c. can be ignored, the width of the output pulse tw (out) is as follows : tw(out) = cx rx re - triggered operation when a second trigger pulse follows the first its effect will depend on the state of the multivibrator. if the capacitor cx is being charged the voltage level of r/c external falls to v refl again and q remains high i.e. the retrigger pulse arrives in a time shorter than the period rx cx seconds, the capacitor charging time constant. if the second trigger pulse is very close to the initial trigger pulse it is ineffective ; i.e. the second trigger must arrive in the capacitor discharge cycle to be ineffective; hence the minimum time for a second trigger to be effective depends on vcc and cx reset operation cl is normally high. if cl is low, the trigger is not effective because q output goes low and trigger control flip-flop is reset. also transistor op is turned on and cx is charged quickly to vcc. this means if cl input goes low the ic becomes waiting state both in operating and non operating state. 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 (*) 500mw at 65 c; derate to 300mw by 10mw/ c from 65 c to 85 c symbol parameter value unit v cc supply voltage -0.5 to +7 v v i dc input voltage -0.5 to v cc + 0.5 v v o dc output voltage -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 p d power dissipation 500(*) mw t stg storage temperature -65 to +150 c t l lead temperature (10 sec) 300 c
m74hc423a 5/12 recommended operating conditions the maximum allowable values of cx and rx are a function of leakage of capacitor cx, the leakage of device and leakage due to t he board layout and surface resistance. susceptibility to externally induced noise may occur for rx > 1m w dc specifications (1) : per circuit symbol parameter value unit v cc supply voltage 2 to 6 v v i input voltage 0 to v cc v v o output voltage 0 to v cc v t op operating temperature -55 to 125 c t r , t f input rise and fall time v cc = 2.0v 0 to 1000 ns v cc = 4.5v 0 to 500 ns v cc = 6.0v 0 to 400 ns cx external capacitor no limitation pf rx external resistor vcc < 3v 5k to 1m w vcc > 3v 1k to 1m 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 2.0 1.5 1.5 1.5 v 4.5 3.15 3.15 3.15 6.0 4.2 4.2 4.2 v il low level input voltage 2.0 0.5 0.5 0.5 v 4.5 1.35 1.35 1.35 6.0 1.8 1.8 1.8 v oh high level output voltage 2.0 i o =-20 m a 1.9 2.0 1.9 1.9 v 4.5 i o =-20 m a 4.4 4.5 4.4 4.4 6.0 i o =-20 m a 5.9 6.0 5.9 5.9 4.5 i o =-4.0 ma 4.18 4.31 4.13 4.10 6.0 i o =-5.2 ma 5.68 5.8 5.63 5.60 v ol low level output voltage 2.0 i o =20 m a 0.0 0.1 0.1 0.1 v 4.5 i o =20 m a 0.0 0.1 0.1 0.1 6.0 i o =20 m a 0.0 0.1 0.1 0.1 4.5 i o =4.0 ma 0.17 0.26 0.33 0.40 6.0 i o =5.2 ma 0.18 0.26 0.33 0.40 i i input leakage current 6.0 v i = v cc or gnd 0.1 1 1 m a i i r/c terminal off state current 6.0 v i = v cc or gnd 0.1 1 1 m a i cc quiescent supply current 6.0 v i = v cc or gnd 44080 m a i cc active state supply current (1) 2.0 v i = v cc or gnd pin 7 or 15 v in = v cc /2 45 200 260 320 m a 4.5 500 600 780 960 m a 6.0 0.7 1 1.3 1.6 ma
m74hc423a 6/12 ac electrical characteristics (c l = 50 pf, input t r = t f = 6ns) capacitive characteristics 1) c pd is defined as the value of the ics 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 duty/100 + ic/2(per monostable) (i cc : active supply current) (duty : %) 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. t tlh t thl output transition time 2.0 30 75 95 ns 4.5 8 15 19 6.0 7 13 16 t plh t phl propagation delay time (a , b - q, q ) 2.0 102 210 265 ns 4.5 29 42 53 6.0 22 36 45 t plh t phl propagation delay time (clr - q, q ) 2.0 68 160 200 ns 4.5 20 32 40 6.0 16 27 34 t wout output pulse width 2.0 cx = 100 pf rx = 10k w 1.7 m s 4.5 1.4 6.0 1.3 2.0 cx = 0.1 m f rx = 100k w 10 ms 4.5 9.5 6.0 9.5 d t wout output pulse width error between circuits in same package 1% t w(h) t w(l) minimum pulse width 2.0 75 95 ns 4.5 15 19 6.0 13 16 t w(l) minimum pulse width (clr ) 2.0 75 95 ns 4.5 15 19 6.0 13 16 t rr minimum retrigger time 2.0 cx = 100 pf rx = 10k w 325 ns 4.5 108 6.0 78 2.0 cx = 0.1 m f rx = 100k w 5 m s 4.5 1.4 6.0 1.2 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. c in input capacitance 5.0 5101010pf c pd power dissipation capacitance (note 1) 5.0 160 pf
m74hc423a 7/12 test circuit c l = 50pf or equivalent (includes jig and probe capacitance) r t = z out of pulse generator (typically 50 w ) switching characteristics test waveform (f=1mhz; 50% duty cycle)
m74hc423a 8/12 dim. mm. inch min. typ max. min. typ. max. a1 0.51 0.020 b 0.77 1.65 0.030 0.065 b 0.5 0.020 b1 0.25 0.010 d 20 0.787 e 8.5 0.335 e 2.54 0.100 e3 17.78 0.700 f 7.1 0.280 i 5.1 0.201 l 3.3 0.130 z 1.27 0.050 plastic dip-16 (0.25) mechanical data p001c
m74hc423a 9/12 dim. mm. inch min. typ max. min. typ. max. a 1.75 0.068 a1 0.1 0.2 0.003 0.007 a2 1.65 0.064 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 po13h
m74hc423a 10/12 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 0.0089 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 80 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
m74hc423a 11/12
m74hc423a 12/12 information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result f rom its use. no license is granted by implication or otherwise under any patent or patent rights of stmicroelectronics. specificati ons mentioned in this publication are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of stmicroelectronics. ? the st logo is a registered trademark of stmicroelectronics ? 2001 stmicroelectronics - printed in italy - all rights reserved stmicroelectronics group of companies australia - brazil - china - finland - france - germany - hong kong - india - italy - japan - malaysia - malta - morocco singapore - spain - sweden - switzerland - united kingdom ? http://www.st.com

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