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1/11 july 2001 n high speed : t pd = 25 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 =200 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 4538 description the m74hc4538 is an high speed cmos monostable multivibrator fabricated with silicon gate c 2 mos technology. each multivibrator features both a negative a, and a positive b, edge triggered input, either of which can be used as an inhibit input. also included is a clear input that when taken low resets the one shot. the monostable multivibrator are retriggerable. that is, they may be triggered repeatedly while their outputs are generating a pulse and the pulse will be extended. pulse width stability over a wide range of temperature and supply is achieved using linear cmos techniques. the output pulse equation is simply : pw = 0.7 (r)(c) where pw is in seconds, r in omhs and c is in farads. all inputs are equipped with protection circuits against static discharge and transient excess voltage. m74hc4538 dual retriggerable monostable multivibrator pin connection and iec logic symbols order codes package tube t & r dip m74hc4538b1r sop m74hc4538m1r m74hc4538rm13tr tssop M74HC4538TTR tssop dip sop
m74hc4538 2/11 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, 15 1t1, 2t1 external capacitor con- nections 2, 14 1t2, 2t2 external resistor/ capacitor connections 3, 13 1cd , 2cd direct reset inputs (active low) 4, 12 1a, 2a trigger inputs (low to high, edge-triggered) 5, 11 1b , 2b trigger inputs (high to low, edge triggered) 6, 10 q1, q2 pulse outputs 7, 9 q 1, q 2 complementary pulse outputs 8 gnd ground (0v) 16 vcc positive supply voltage inputs outputs note ab cd 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
m74hc4538 3/11 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.
m74hc4538 4/11 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; 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 rx/cx 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 g 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 : t w(out) = 0.72 cx rx re - triggered operation when a second triggere 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 rx/cx 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, trr (min.) depends on vcc and cx reset operation cd is normally high. if cd 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 cd 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
m74hc4538 5/11 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 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 (cd only) 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 input leakage current 6.0 v i = v cc or gnd rext/cext 0.1 1 1 m a i cc quiescent supply current 6.0 v i = v cc or gnd 44080 m a i cc quiescent supply current 2.0 v i = v cc or gnd pin 2 or 14 v in = v cc /2 40 120 160 200 m a 4.5 0.2 0.3 0.4 0.6 ma 6.0 0.3 0.6 0.8 1.0 ma
m74hc4538 6/11 ac electrical characteristics (c l = 50 pf, input t r = t f = 6ns) 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 95 110 ns 4.5 8151922 6.0 7131619 t plh t phl propagation delay time (a, b - q, q ) 2.0 120 250 315 375 ns 4.5 30 50 63 75 6.0 25 43 54 64 t plh t phl propagation delay time (cd - q, q ) 2.0 100 195 245 295 ns 4.5 25 39 49 59 6.0 20 33 42 50 t wout output pulse width 2.0 cx=0 rx = 5k w 540 1200 1500 1800 ns 4.5 rx = 1k w 180 250 320 375 6.0 rx= 1k w 150 200 260 320 2.0 cx = 0.01 m f rx = 10k w 70 83 96 70 96 70 96 m s 4.5 69 77 85 69 85 69 85 6.0 69 77 85 69 85 69 85 2.0 cx = 0.1 m f rx = 10k w 0.67 0.75 0.83 0.67 0.83 0.67 0.9 ms 4.5 0.67 0.73 0.77 0.67 0.77 0.67 0.8 6.0 0.67 0.73 0.77 0.67 0.77 0.67 0.8 d t wout output pulse width error between circuits in same package 1 % t w(h) t w(l) minimum pulse width (a,b ) 2.0 30 75 95 110 ns 4.5 8151922 6.0 7131619 t w(l) minimum pulse width (cd ) 2.0 30 75 95 110 ns 4.5 8151922 6.0 7131619 t rem minimum clear removal time 2.0 0151520 ns 4.5 0 5 5 7 6.0 0 5 5 t rr minimum retrigger time 2.0 cx = 0.1 m f rx = 1k w 380 ns 4.5 92 6.0 72 2.0 cx = 0.01 m f rx = 1k w 6 m s 4.5 1.4 6.0 1.2
m74hc4538 7/11 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 : %) test circuit c l = 50pf or equivalent (includes jig and probe capacitance) r t = z out of pulse generator (typically 50 w ) 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 70 pf
m74hc4538 8/11 switching characteristics test waveform (f=1mhz; 50% duty cycle)
m74hc4538 9/11 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
m74hc4538 10/11 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
m74hc4538 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 11/11

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