74121中文资料

© 1999 Fairchild Semiconductor Corporation DS006538June 1989Revised November 1999DM74121 One-Shot with Clear and Complementary OutputsDM74121One-Shot with Clear and Complementary OutputsGeneral DescriptionThe DM74121 is a monostable multivibrator featuring both positive and negative edge triggering with complementary outputs. An internal 2k Ω timing resistor is provided for design convenience minimizing component count and lay-out problems. this device can be used with a single exter-nal capacitor. Inputs (A) are active-LOW trigger transition inputs and input (B) is and active-HIGH transition Schmitt-trigger input that allows jitter-free triggering from inputs with transition rates as slow as 1 volt/second. A high immunity to V CC noise of typically 1.5V is also provided by internal circuitry at the input stage.To obtain optimum and trouble free operation please read operating rules and one-shot application notes carefully and observe recommendations.Featuress Triggered from active-HIGH transition or active-LOW transition inputs s Variable pulse width from 30 ns to 28 seconds s Jitter free Schmitt-trigger input s Excellent noise immunity typically 1.2V s Stable pulse width up to 90% duty cycle s TTL, DTL compatibles Compensated for V CC and temperature variations s Input clamp diodesOrdering Code:Connection Diagram Function TableH = HIGH Logic Level ↑ = Positive Going Transition L = LOW Logic Level↓ = Negative Going TransitionX = Can Be Either LOW or HIGH = A Positive Pulse = A Negative PulseFunctional DescriptionThe basic output pulse width is determined by selection of an internal resistor R INT or an external resistor (R X ) and capacitor (C X ). Once triggered the output pulse width is independent of further transitions of the inputs and is func-tion of the timing components. Pulse width can vary from afew nano-seconds to 28 seconds by choosing appropriate R X and C X combinations. There are three trigger inputs from the device, two negative edge-triggering (A) inputs,one positive edge Schmitt-triggering (B) input.Order Number Package NumberPackage DescriptionDM74121NN14A14-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 WideInputsOutputsA1A2B Q Q L X H L H X L H L H X X L L H H H X LHH ↓H ↓H H ↓↓H L X ↑ XL↑ 2D M 74121Operating Rules1.To use the internal 2 k Ω timing resistor, connect theR INT pin to V CC .2.An external resistor (R X ) or the internal resistor (2 k Ω)and an external capacitor (C X ) are required for proper operation. The value of C X may vary from 0 to any nec-essary value. For small time constants use high-quality mica, glass, polypropylene, polycarbonate, or polysty-rene capacitors. For large time constants use solid tan-talum or special aluminum capacitors. If the timing capacitors have leakages approaching 100 nA or if stray capacitance from either terminal to ground is greater than 50 pF the timing equations may not repre-sent the pulse width the device generates.3.The pulse width is essentially determined by externaltiming components R X and C X . For C X < 1000 pF see Figure 1 design curves on t W as function of timing com-ponents value. For C X > 1000 pF the output is defined as:t W = K R X C Xwhere [R X is in Kilo-ohm][C X is in pico Farad][t W is in nano second][K ≈ 0.7]4.If C X is an electrolytic capacitor a switching diode isoften required for standard TTL one-shots to prevent high inverse leakage current Figure 2.5.Output pulse width versus V CC and operation tempera-tures: Figure 3 depicts the relationship between pulse width variation versus V CC. Figure 4 depicts pulse width variation versus ambient temperature.6.The “K” coefficient is not a constant, but varies as afunction of the timing capacitor C X . Figure 5 details this characteristic.7.Under any operating condition C X and R X must be keptas close to the one-shot device pins as possible to min-imize stray capacitance, to reduce noise pick-up, and to reduce I X R and Ldi/dt voltage developed along their connecting paths. If the lead length from C X to pins (10) and (11) is greater than 3 cm, for example,the output pulse width might be quite different from val-ues predicted from the appropriate equations. A non-inductive and low capacitive path is necessary to ensure complete discharge of C X in each cycle of its operation so that the output pulse width will be accu-rate.8.V CC and ground wiring should conform to good high-frequency standards and practices so that switching transients on the V CC and ground return leads do not cause interaction between one-shots. A 0.01 µF to 0.10µF bypass capacitor (disk ceramic or monolithic type)from V CC to ground is necessary on each device. Fur-thermore, the bypass capacitor should be located as close to the V CC -pin as space permits.For further detailed device characteristics and output per-formance please refer to the one-shot application note, AN-366.FIGURE 1.FIGURE 2.FIGURE 3. FIGURE 4.FIGURE 5.DM74121Absolute Maximum Ratings (Note 1)Note 1: The Absolute Maximum Ratings are those values beyond which the safety of the device cannot be guaranteed. The device should not be operated at these limits. The parametric values defined in the Electrical Characteristics tables are not guaranteed at the absolute maximum ratings.The Recommended Operating Conditions table will define the conditions for actual device operation.Recommended Operating ConditionsNote 2: T A = 25°C and V CC = 5VElectrical Characteristicsover recommended operating free air temperature range (unless otherwise noted)Note 3: All typicals are at V CC = 5V, T A = 25°C.Note 4: Not more than one output should be shorted at a time.Supply Voltage 7V Input Voltage5.5VOperating Free Air Temperature Range 0°C to +70°C Storage Temperature Range−65°C to +150°CSymbol ParameterMin Nom Max Units V CC Supply Voltage4.755 5.25V V T +Positive-Going Input Threshold Voltage 1.42V at the A Input (V CC = Min)V T −Negative-Going Input Threshold Voltage 0.8 1.4Vat the A Input (V CC = Min)V T +Positive-Going Input Threshold Voltage 1.52V at the B Input (V CC = Min)V T −Negative-Going Input Threshold Voltage 0.8 1.3Vat the B Input (V CC = Min)I OH HIGH Level Output Current −0.4mA I OL LOW Level Output Current 16mA t W Input Pulse Width (Note 2)40nsdV/dt Rate of Rise or Fall of 1V/s Schmidt Input (B) (Note 2)dV/dt Rate of Rise or Fall of 1V/µs Schmidt Input (A) (Note 2)R EXT External Timing Resistor (Note 2) 1.440k ΩC EXT External Timing Capacitance (Note 2)01000µF DC Duty Cycle (Note 2)R T = 2 k Ω67%R T = R EXT (Max)90T AFree Air Operating Temperature70°CSymbol ParameterConditionsMinTyp (Note 3)Max Units V I Input Clamp Voltage V CC = Min, I I = −12 mA −1.5V V OH HIGH Level Output V CC = Min, I OH = Max, 2.4 3.4VVoltageV IL = Max, V IH = Min V OL LOW Level Output V CC = Min, I OL = Max,0.20.4V Voltage V IH = Max, V IL = Min I I Input Current @V CC = Max, V I = 5.5V 1mA Max Input Voltage I IH HIGH Level V CC = Max,A1, A240µA Input Current V I = 2.4V B 80I IL LOW Level V CC = Max,A1, A2−1.6mA Input CurrentV I = 0.4VB−3.2I OS Short Circuit Output Current V CC = Max (Note 4)−18−55mA I CCSupply CurrentV CC = MaxQuiescent 1325mATriggered2340 4D M 74121Switching CharacteristicsAt V CC = 5V and T A = 25°C (See Test Waveforms and Output Load Section)Symbol ParameterFrom (Input)Conditions MinMax Units To (Output)t PLH Propagation Delay Time A1, A2C EXT = 80 pF 70ns LOW-to-HIGH Level Output to Q R INT to V CC t PLH Propagation Delay Time B to C L = 15 pF 55ns LOW-to-HIGH Level Output Q R L = 400Ωt PHL Propagation Delay Time A1, A280ns HIGH-to-LOW Level Output to Q t PHL Propagation Delay Time B 65nsHIGH-to-LOW Level Output to Q t W(OUT)Output Pulse A1, A2 or B C EXT = 80 pF 70150nsWidth Using the to Q, QR INT to V CC Internal Timing ResistorR L = 400ΩC L = 15 pF t W(OUT)Output Pulse A1, A2C EXT = 0 pF 50nsWidth Using Zero to Q, Q R INT to V CC Timing CapacitanceR L = 400ΩC L = 15 pF t W(OUT)Output Pulse A1, A2C EXT = 100pF 600800nsWidth Using External to Q, Q R INT = 10 k ΩTiming ResistorR L = 400ΩC L = 15pF A1, A2C EXT = 1 µF 68msto Q, Q R INT = 10 k ΩR L = 400ΩC L = 15 pF5DM74121 One-Shot with Clear and Complementary OutputsPhysical Dimensions inches (millimeters) unless otherwise noted14-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 WidePackage Number N14AFairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and Fairchild reserves the right at any time without notice to change said circuitry and specifications.LIFE SUPPORT POLICYFAIRCHILD ’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein:1.Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be rea-sonably expected to result in a significant injury to the user.2. A critical component in any component of a life support device or system whose failure to perform can be rea-sonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.。