General purpose CMOS timer

Transcription

1 DESCIPTION The 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 THESHOLD, TIGGE, and currents, no crowbarring of the supply current during output transitions, higher frequency performance and no requirement to decouple CONTOL VOLTAGE for stable operation. The 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 CONTOL VOLTAGE terminal need not be decoupled with a capacitor. The TIGGE and 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. PIN CONFIGUATION GND TIGGE D and N Packages DISCHAGE THESHOLD CONTOL VOLTAGE Timing from microseconds through hours Operates in both astable and monostable modes Adjustable duty cycle High output source/sink driver can drive TTL/CMOS Typical temperature stability of.5%/ o C at 5 C ail-to-rail outputs FEATUES Exact equivalent in most applications for NE/SE555 Low supply current: 8µA (typ) Extremely low trigger, threshold, and reset currents: (typ) High-speed operation: khz guaranteed Wide operating supply voltage range guaranteed to V 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 APPLICATIONS Precision timing Pulse generation Sequential timing Time delay generation Pulse width modulation Pulse position modulation Missing pulse detector ODEING INFOMATION DESCIPTION TEMPEATUE ANGE ODE CODE DWG # 8-Pin Plastic Dual In-Line Package (DIP) to +7 C CN B 8-Pin Plastic Small Outline (SO) Package to +7 C CD 7C 8-Pin Plastic Dual In-Line Package (DIP) - to +85 C IN B 8-Pin Plastic Small Outline (SO) Package - to +85 C ID 7C August,

2 EQUIVALENT BLOCK DIAGAM 8 FLIP FLOP THESHOLD CONTOL VOLTAGE TIGGE 5 COMPAATO A + COMPAATO B + DIVES DISCHAGE 7 N NOTE: UNUSED INPUTS SHOULD BE CONNECTED TO APPOPIATE VOLTAGE FOM TUTH TABLE. TUTH TABLE THESHOLD VOLTAGE TIGGE VOLTAGE DISCHAGE SWITCH DON T CAE DON T CAE LOW LOW ON >/(V+) > /(V+) HIGH LOW ON V TH < / V T > / HIGH STABLE STABLE DON T CAE </(V+) HIGH HIGH OFF NOTES:. will dominate all other inputs: TIGGE will dominate over THESHOLD. ABSOLUTE MAXIMUM ATINGS SYMBOL PAAMETE ATING UNITS Supply voltage +8 V V TIG Trigger input voltage V CV Control voltage > -. to V TH Threshold input voltage < +. V V ST input voltage I OUT Output current ma P DMAX Maximum power dissipation, TA = 5 C (still air) N package mw D package 78 mw T STG Storage temperature range -5 to + C T SOLD Lead temperature (Soldering s) C NOTES:. Due to the SC structure inherent in the CMOS process used to fabricate these devices, connecting any terminal to a voltage greater than +.V or less than GND -.V may cause destructive latch-up. For this reason it is recommended that no inputs from external sources not operating from the same power supply be applied to the device before its power supply is established. In multiple systems, the supply of the must be turned on first.. Derate above 5 C, at the following rates: N package at 9.mW/ C D package at.mw/ C. See Power Dissipation Considerations section. August, 99 8

3 DC AND AC ELECTICAL CHAACTEISTICS T A = 5 C unless otherwise specified. LIMITS SYMBOL PAAMETE TEST CONDITIONS UNITS MIN TYP MAX Supply voltage T MIN < T A < T MAX V I DD Supply current = V MIN = V MAX 8 Astable mode timing Initial accuracy Drift with supply voltage Drift with temperature A, B = k to k, C = µf 5V < <5V = V = 5V µa µa % %/V ppm/ o C ppm/ o C ppm/ o C V TH Threshold voltage..5.7 x V TIG Trigger voltage.9.. x I TIG Trigger current = V TIG = V MAX = V TIG = 5V = V TIG = V MIN I TH Threshold current = V TH = V MAX = V TH = 5V = V TH = V MIN = V ST = V MAX I ST eset current = V ST = 5V = V ST = V MIN V ST eset voltage = V MIN and V MAX..7 V V CV Control voltage..5.7 x V V OL Output voltage (low) DD = V MAX, I SINK =.ma. V, I SINK =.ma.. V V OH Output voltage (high) = V MAX, I SOUCE = -ma, I SOUCE = -ma V DIS Discharge output voltage, I DIS =.ma.. V t ise time of output L = MΩ, C L = pf, = 5V 5 75 ns t F Fall time of output L = MΩ, C L = pf, = 5V 75 ns F MAX Maximum oscillator frequency (astable mode) khz NOTES:. The supply current value is essentially independent of the TIGGE, THESHOLD, and voltages..8. Astable timing is calculated using the following equation: f =. The components are defined in Figure. ( A + B )C. Parameter is not % tested. August, 99 9

4 TYPICAL PEFOMANCE CHAACTEISTICS 5 SUPPLY CUENT (I DD ) ( µ A) T A = 55 C T A = +5 C T A = +5 C SUPPLY VOLTAGE ( ) Supply Current vs Supply Voltage. T A = +5 C SOUCE CUENT 9mA). = 8V = V. V OUT (V) High Output Voltage Drop vs Output Source Current August, 99

5 TYPICAL PEFOMANCE CHAACTEISTICS (continued). = 8V T A = 5 C DISCHAGE CUENT (ma). = V. DISCHAGE VOLTAGE (V) Discharge Low Output Voltage vs Discharge Sink Current. T A = +5 C CUENT (ma). = 8V = V. VOLTAGE (V) Low Output Voltage vs Output Sink Current August, 99

6 TYPICAL PEFOMANCE CHAACTEISTICS (continued). T A = 5 C CUENT (ma). = 8V = V. VOLTAGE (V) Low Output Voltage vs Output Sink Current. = 8V T A = -55 C CUENT (ma). = V. VOLTAGE (V) Low Output Voltage vs Output Sink Current PULSE WIDTH FO TIGGE (ns) = V = 8V LOWEST LEVEL OF TIGGE PULSE (% ) Minimum Pulse Width for Triggering August, 99

7 TYPICAL PEFOMANCE CHAACTEISTICS (continued) POPAGATION DELAY (ns) 7... T A = +5 C T A = +5 C T A = 55 C. LOWEST VOLTAGE OF TIGGE PULSE (% ) Propagation Delay vs Voltage Level of Trigger Pulse NOMALIZED FEQUENCY (%) T A = +5 C A = B = kω C = µf 5 5 SUPPLY VOLTAGE ( ) Normalized Frequency Stability as a Function of Supply Voltage (Astable Mode) NOMALIZED FEQUENCY (%) = 8V = V A = B = kω C = µf 5.E.5E TEMPEATUE ( C) Normalized Frequency Stability as a Function of Temperature (Astable Mode) August, 99

8 TYPICAL PEFOMANCE CHAACTEISTICS (continued).. ( A + B ) T A = +5 C CAPACITANCE ( µ F)... kω kω kω MΩ MΩ. k k k M M FEQUENCY (Hz) Free-unning Frequency as a Function of A, B, and C.. T A = +5 C CAPACITANCE ( µ F)... A kω kω kω MΩ MΩ SUPPLY CUENT (ma). T A = +5 C ns µs µs µs ms ms ms s s TIME DELAY 8 TIME (ns) Figure. Supply Current Transient Compared With a Standard Bipolar 555 During an Output Transition APPLICATION NOTES NE/SE555 General The 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. Because the Monostable Time Delay vs A and C 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. The produces supply current spikes of only -ma instead of -ma and supply decoupling is normally not necessary. Secondly, in most instances, the CONTOL VOLTAGE decoupling capacitors are not required since the input impedance of the CMOS comparators on chip are very high. Thus, for many applications, capacitors can be saved using an. Power Supply Considerations Although the supply current consumed by the device is very low, the total system supply can be high unless the timing components are high impedance. Therefore, high values for and low values for C in Figures and 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.5v or more, the will drive at least standard TTL loads. August, 99

9 Astable Operation If the circuit is connected as shown in Figure, it will trigger itself and free run as a multivibrator. The external capacitor charges through A and B and discharges through 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 / and /. 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..8 F = A + B D = ( A + B ) C A + B improved over the standard bipolar 555 in that it controls only the internal flip-flop, which in turn controls simultaneously the state of the and DISCHAGE pins. This avoids the multiple threshold problems sometimes encountered with slow falling edges in the bipolar devices. A GND TIGGE DISHCAGE THESHOLD 8 7 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,TIGGE, the internal flip-flop is set which releases the low impedance on DISCHAGE; the external capacitor charges and drives the High. The voltage across the capacitor increases exponentially with a time constant t = A C. When the voltage across the capacitor equals / V +, the comparator resets the flip-flop, which in turn discharges the capacitor rapidly and also drives the to its low state. TIGGE must return to a high state before the can return to a low state. Control Voltage The CONTOL VOLTAGE terminal permits the two trip voltages for the THESHOLD and TIGGE 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 CONTOL VOLTAGE pin. The terminal is designed to have essentially the same trip voltage as the standard bipolar 555, i.e.,. to.7v. At all supply voltages it represents an extremely high input impedance. The mode of operation of the function is, however, much < 8V B t = 5 A C C CONTOL VOLTAGE Figure. Astable Operation TIGGE DISHCAGE THESHOLD CONTOL VOLTAGE Figure. Monostable Operation A 5 OPTIONAL CAPACITO C August, 99 5