philips semiconductors linear products product specification icm7555 general purpose cmos timer 337 august 31, 1994 853-1192 13721 description the icm7555 is a cmos timer providing significantly improved performance over the standard ne/se555 timer , while at the same time being a direct replacement for those devices in most applications. improved parameters include low supply current, wide operating supply voltage range, low threshold, trigger , and reset currents, no crowbarring of the supply current during output transitions, higher frequency performance and no requirement to decouple control voltage for stable operation. the icm7555 is a stable controller capable of producing accurate time delays or frequencies. in the one-shot mode, the pulse width of each circuit is precisely controlled by one external resistor and capacitor . for astable operation as an oscillator , the free-running frequency and the duty cycle are both accurately controlled by two external resistors and one capacitor . unlike the bipolar 555 device, the control volt age terminal need not be decoupled with a capacitor . the trigger and reset inputs are active low. the output inverter can source or sink currents large enough to drive ttl loads or provide minimal offsets to drive cmos loads. features ? exact equivalent in most applications for ne/se555 ? low supply current: 80 m a (typ) ? extremely low trigger , threshold, and reset currents: 20pa (typ) ? high-speed operation: 500khz guaranteed ? wide operating supply voltage range guaranteed 3 to 16v over full automotive temperatures ? normal reset function; no crowbarring of supply during output transition ? can be used with higher-impedance timing elements than the bipolar 555 for longer time constants pin configuration threshold d and n packages discharge v dd control voltage 1 2 3 4 5 6 7 8 gnd trigger output reset ? timing from microseconds through hours ? operates in both astable and monostable modes ? adjustable duty cycle ? high output source/sink driver can drive ttl/cmos ? t ypical temperature stability of 0.005%/ o c at 25 c ? rail-to-rail outputs applications ? precision timing ? pulse generation ? sequential timing ? time delay generation ? pulse width modulation ? pulse position modulation ? missing pulse detector ordering information description temperature range order code dwg # 8-pin plastic dual in-line package (dip) 0 to +70 c icm7555CN 0404b 8-pin plastic small outline (so) package 0 to +70 c icm7555cd 0174c 8-pin plastic dual in-line package (dip) -40 to +85 c icm7555in 0404b 8-pin plastic small outline (so) package -40 to +85 c icm7555id 0174c
philips semiconductors linear products product specification icm7555 general purpose cmos timer august 31, 1994 338 equivalent block diagram note : unused inputs should be connected to appropriate voltage from truth table. v dd 8 r 6 5 2 r 1 r comparator a comparator b flipflop reset 4 output drivers 3 output discharge 7 n 1 + + threshold control voltage trigger truth table threshold voltage trigger voltage reset 1 output discharge switch don't care don't care low low on >2/3(v+) > 1/3(v+) high low on v th < 2/3 v tr > 1/3 high stable stable don't care <1/3(v+) high high off notes: 1. reset will dominate all other inputs: trigger will dominate over threshold. absolute maximum ratings 1 symbol parameter rating units v dd supply voltage +18 v v trig 1 trigger input voltage v cv control voltage > -0.3 to v th threshold input voltage philips semiconductors linear products product specification icm7555 general purpose cmos timer august 31, 1994 339 dc and ac electrical characteristics t a = 25 c unless otherwise specified. symbol parameter test conditions limits units symbol parameter test conditions icm7555 units min typ max v dd supply voltage t min < t a < t max 3 16 v i dd supply current 1 v dd = v min v dd = v max 50 180 200 300 m a m a astable mode timing 2 initial accuracy drift with supply voltage drift with temperature 3 r a , r b = 1k to 100k, c = 0.1 m f 5 v philips semiconductors linear products product specification icm7555 general purpose cmos timer august 31, 1994 340 typical performance characteristics supply current vs supply voltage high output voltage drop vs output source current 225 200 175 150 125 100 75 50 25 0 0 5 10 15 20 supply voltage (v dd ) supply current (i ) ( a) dd m t a = +25 c t a = +125 c t a = 55 c v dd = 18v v dd = 5v v dd = 2v t a = +25 c 100.0 10.0 1.0 0.1 0.1 1.0 10.0 output source current 9ma) v dd v out (v)
philips semiconductors linear products product specification icm7555 general purpose cmos timer august 31, 1994 341 typical performance characteristics (continued) 100.0 10.0 1.0 0.1 0.1 1.0 10.0 discharge voltage (v) discharge current (ma) t a = 25 c v dd = 18v v dd = 5v v dd = 2v v dd = 18v v dd = 5v v dd = 2v t a = +125 c 100.0 10.0 1.0 0.1 0.1 1.0 10.0 output voltage (v) output current (ma) discharge low output voltage vs discharge sink current low output voltage vs output sink current
philips semiconductors linear products product specification icm7555 general purpose cmos timer august 31, 1994 342 typical performance characteristics (continued) 100.0 10.0 1.0 0.1 0.1 1.0 10.0 output voltage (v) output current (ma) t a = 25 c v dd = 18v v dd = 5v v dd = 2v v dd = 18v v dd = 5v v dd = 2v t a = -55 c 100.0 10.0 1.0 0.1 0.1 1.0 10.0 output voltage (v) output current (ma) 0 10 20 30 40 500 400 300 200 100 0 pulse width for trigger (ns) lowest level of trigger pulse (%v dd ) low output voltage vs output sink current low output voltage vs output sink current minimum pulse width for triggering v dd = 18v v dd = 5v v dd = 2v
philips semiconductors linear products product specification icm7555 general purpose cmos timer august 31, 1994 343 typical performance characteristics (continued) 0 10 20 30 40 1.0 750.0 500.0 250.0 0.0 propagation dela y (ns) lowest voltage of trigger pulse (%v dd ) propagation delay vs voltage level of trigger pulse v dd = 5v 0 5 10 15 20 6 4 2 0 2 4 normalized frequency (%) supply voltage (v dd ) normalized frequency stability as a function of supply v oltage (astable mode) 3 normalized frequency (%) 4 2 0 2 4 5.0e1 2.5e1 0.0 25.0 50.0 75.0 100.0 125.0 temperature ( c) normalized frequency stability as a function of t emperature (astable mode) v dd = 18v v dd = 5v v dd = 2v r a = r b = 1k w c = 0.1 m f t a = +25 c t a = +125 c t a = 55 c t a = +25 c r a = r b = 10k w c = 0.1 m f
philips semiconductors linear products product specification icm7555 general purpose cmos timer august 31, 1994 344 typical performance characteristics (continued) free-running frequency as a function of r a , r b , and c monostable time delay vs r a and c 100.0 10.0 1.0 0.1 0.01 0.001 0.0001 0.0 0.1 1.0 10 100 1k 10k 100k 1m 10m capacitance ( f) m frequency (hz) 100.0 10.0 1.0 0.1 0.01 0.001 0.0001 0.0 capacitance ( f) m time delay 100ns 1ms 10ms 100ms 1s 10s 1 m s 10 m s 100 m s v dd = 5v t a = +25 c v dd = 5v t a = +25 c (r a + 2r b ) 1k w 10k w 100k w 1m w 10m w 1k w 10k w 100k w 1m w 10m w r a figure 1. supply current transient compared with a standard bipolar 555 during an output transition 500 400 300 200 100 0 0 200 400 600 800 supply current (ma) time (ns) t a = +25 c ne/se555 icm7555 application notes general the icm7555 device is, in most instances, a direct replacement for the ne/se555 device. however, it is possible to effect economies in the external component count using the icm7555. because the bipolar 555 device produces large crowbar currents in the output driver , it is necessary to decouple the power supply lines with a good capacitor close to the device. the 7555 device produces no such transients. see figure 1. the icm7555 produces supply current spikes of only 2-3ma instead of 300-400ma and supply decoupling is normally not necessary . secondly, in most instances, the control voltage decoupling capacitors are not required since the input impedance of the cmos comparators on chip are very high. thus, for many applications, 2 capacitors can be saved using an icm7555. power supply considerations although the supply current consumed by the icm7555 device is very low , the total system supply can be high unless the timing components are high impedance. therefore, high values for r and low values for c in figures 2 and 3 are recommended. output drive capability the output driver consists of a cmos inverter capable of driving most logic families including cmos and ttl. as such, if driving cmos, the output swing at all supply voltages will equal the supply voltage. at a supply voltage of 4.5v or more, the icm7555 will drive at least 2 standard ttl loads.
philips semiconductors linear products product specification icm7555 general purpose cmos timer august 31, 1994 345 astable operation if the circuit is connected as shown in figure 2, it will trigger itself and free run as a multivibrator. the external capacitor charges through r a and r b and discharges through r b only. thus, the duty cycle (d) may be precisely set by the ratio of these two resistors. in this mode of operation, the capacitor charges and discharges between 1/3 v dd and 2/3 v dd . since the charge rate and the threshold levels are directly proportional to the supply voltage, the frequency of oscillation is independent of the supply voltage. 1.38 (r a + 2r b ) r a + 2r b f = c d = r a + r b monostable operation in this mode of operation, the timer functions as a one-shot. initially , the external capacitor (c) is held discharged by a transistor inside the timer . upon application of a negative pulse to pin 2,trigger , the internal flip-flop is set which releases the low impedance on discharge; the external capacitor charges and drives the output high. the voltage across the capacitor increases exponentially with a time constant t = r a c. when the voltage across the capacitor equals 2/3 v + , the comparator resets the flip-flop, which in turn discharges the capacitor rapidly and also drives the output to its low state. trigger must return to a high state before the output can return to a low state. control voltage the control volt age terminal permits the two trip voltages for the threshold and trigger internal comparators to be controlled. this provides the possibility of oscillation frequency modulation in the astable mode, or even inhibition of oscillation, depending on the applied voltage. in the monostable mode, delay times can be changed by varying the applied voltage to the control voltage pin. reset the reset terminal is designed to have essentially the same trip voltage as the standard bipolar 555, i.e., 0.6 to 0.7v . at all supply voltages it represents an extremely high input impedance. the mode of operation of the reset function is, however, much improved over the standard bipolar 555 in that it controls only the internal flip-flop, which in turn controls simultaneously the state of the output and discharge pins. this avoids the multiple threshold problems sometimes encountered with slow falling edges in the bipolar devices. 1 2 3 4 8 7 6 5 gnd trigger output reset dishcarge threshold control voltage output v dd r a b r v dd v dd c figure 2. astable operation 1 2 3 4 8 7 6 5 trigger output reset dishcarge threshold control voltage v dd c optional capacitor v dd < 18v t = 1.05 r a c r a figure 3. monostable operation
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