DM74LS123 Dual Retriggerable One-Shot with Clear and Complementary Outputs Y General Description Y The DM74LS123 is a dual retriggerable monostable multivibrator capable of generating output pulses from a few nanoseconds to extremely long duration up to 100% duty cycle. Each device has three inputs permitting the choice of either leading edge or trailing edge triggering. Pin (A) is an activelow transition trigger input and pin (B) is an active-high transition trigger input. The clear (CLR) input terminates the output pulse at a predetermined time independent of the timing components. The clear input also serves as a trigger input when it is pulsed with a low level pulse transition (ß). To obtain the best trouble free operation from this device please read the operating rules as well as the NSC one-shot application notes carefully and observe recommendations. Y Y Compensated for VCC and temperature variations Triggerable from CLEAR input DTL, TTL compatible Input clamp diodes Functional Description The basic output pulse width is determined by selection of an external resistor (RX) and capacitor (CX). Once triggered, the basic pulse width may be extended by retriggering the gated active-low transition or active-high transition inputs or be reduced by use of the active-low or CLEAR input. Retriggering to 100% duty cycle is possible by application of an input pulse train whose cycle time is shorter than the output cycle time such that a continuous ‘‘HIGH’’ logic state is maintained at the ‘‘Q’’ output. Features Y Y DC triggered from active-high transition or active-low transition inputs Retriggerable to 100% duty cycle Connection Diagram Function Table Dual-In-Line Package Inputs Outputs CLEAR A B Q Q L X X H H X H X L X X L v u L L L L É É É H H H ß ß ß u H H H e High Logic Level L e Low Logic Level X e Can Be Either Low or High u e Positive Going Transition v e Negative Going Transition É e A Positive Pulse ß e A Negative Pulse TL/F/6386 – 1 Order Number DM74LS123M or DM74LS123N See NS Package Number M16A or N16E C1995 National Semiconductor Corporation TL/F/6386 RRD-B30M105/Printed in U. S. A. DM74LS123 Dual Retriggerable One-Shot with Clear and Complementary Outputs March 1991 Absolute Maximum Ratings (Note) Note: 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’’ table are not guaranteed at the absolute maximum ratings. The ‘‘Recommended Operating Conditions’’ table will define the conditions for actual device operation. If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/Distributors for availability and specifications. Supply Voltage Input Voltage Operating Free Air Temperature Range Storage Temperature 7V 7V 0§ C to a 70§ C b 65§ C to a 150§ C Recommended Operating Conditions Symbol Parameter Min Nom Max Units 4.75 5 5.25 V 0.8 V High Level Output Current b 0.4 mA Low Level Output Current 8 mA VCC Supply Voltage VIH High Level Input Voltage VIL Low Level Input Voltage IOH IOL tW Pulse Width (Note 6) 2 A or B High REXT External Timing Resistor CEXT External Timing Capacitance CWIRE Wiring Capacitance at REXT/CEXT Terminal TA Free Air Operating Temperature Electrical Characteristics Symbol Parameter V 40 A or B Low 40 Clear Low 40 ns 5 260 No Restriction 0 kX mF 50 pF 70 §C over recommended operating free air temperature range (unless otherwise noted) Conditions Min Typ (Note 1) Max Units b 1.5 V VI Input Clamp Voltage VOH High Level Output Voltage VCC e Min, II e b18 mA VCC e Min, IOH e Max VIL e Max, VIH e Min VOL Low Level Output Voltage VCC e Min, IOL e Max VIL e Max, VIH e Min 0.35 0.5 IOL e 4 mA, VCC e Min 0.25 0.4 2.7 3.4 V V II Input Current @ Max Input Voltage VCC e Max, VI e 7V IIH High Level Input Current VCC e Max, VI e 2.7V 20 mA IIL Low Level Input Current VCC e Max, VI e 0.4V b 0.4 mA IOS Short Circuit Output Current VCC e Max (Note 2) b 100 mA Supply Current VCC e Max (Notes 3,4 and 5) 20 mA ICC 0.1 b 20 12 mA Note 1: All typicals are at VCC e 5V, TA e 25§ C. Note 2: Not more than one output should be shorted at a time, and the duration should not exceed one second. Note 3: Quiescent ICC is measured (after clearing) with 2.4V applied to all clear and A inputs, B inputs grounded, all outputs open, CEXT e 0.02 mF, and REXT e 25 kX. Note 4: ICC is measured in the triggered state with 2.4V applied to all clear and B inputs, A inputs grounded, all outputs open, CEXT e 0.02 mF, and REXT e 25 kX. Note 5: With all outputs open and 4.5V applied to all data and clear inputs, ICC is measured after a momentary ground, then 4.5V is applied to the clock. Note 6: TA e 25§ C and VCC e 5V. 2 Switching Characteristics at VCC e 5V and TA e 25§ C RL e 2 kX Symbol Parameters From (Input) To (Output) CL e 15pF CEXT e 0 pF, REXT e 5 kX Min Max CL e 15pF CEXT e 1000 pF, REXT e 10 KX Min Units Max tPLH Propagation Delay Time Low to High Level Output A to Q 33 ns tPLH Propagation Delay Time Low to High Level Output B to Q 44 ns tPHL Propagation Delay Time High to Low Level Output A to Q 45 ns tPHL Propagation Delay Time High to Low Level Output B to Q 56 ns tPLH Propagation Delay Time Low to High Level Output Clear to Q 45 ns tPHL Propagation Delay Time High to Low Level Output Clear to Q 27 ns tWQ(Min) Minimum Width of Pulse at Output Q A or B to Q 200 ns tW(out) Output Pulse Width A or B to Q 4 5 ms Operating Rules 3. For CX ll 1000 pF the output pulse width (TW) is defined as follows: TW e KRX CX where [RX is in kX] [CX is in pF] [TW is in ns] K & 0.37 1. An external resistor (RX) and an external capacitor (CX) are required for proper operation. The value of CX may vary from 0 to any necessary value. For small time constants high-grade mica, glass, polypropylene, polycarbonate, or polystyrene material capacitors may be used. For large time constants use tantalum 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 represent the pulse width the device generates. 2. When an electrolytic capacitor is used for CX a switching diode is often required for standard TTL one-shots to prevent high inverse leakage current. This switching diode is not needed for the ’LS123 one-shot and should not be used. In general the use of the switching diode is not recommended with retriggerable operation. Furthermore, if a polarized timing capacitor is used on the ’LS123 the negative terminal of the capacitor should be connected to the ‘‘CEXT’’ pin of the device (Figure 1 ). 4. The multiplicative factor K is plotted as a function of CX below for design considerations: TL/F/6386 – 2 FIGURE 2 TL/F/6386 – 8 FIGURE 1 3 Operating Rules (Continued) 5. For CX k 1000 pF see Figure 3 for TW vs CX family curves with RX as a parameter: TL/F/6386 – 7 FIGURE 7 9. Under any operating condition CX and RX must be kept as close to the one-shot device pins as possible to minimize stray capacitance, to reduce noise pick-up, and to reduce I-R and Ldi/dt voltage developed along their connecting paths. If the lead length from CX to pins (6) and (7) or pins (14) and (15) is greater than 3 cm, for example, the output pulse width might be quite different from values predicted from the appropriate equations. A non-inductive and low capacitive path is necessary to ensure complete discharge of CX in each cycle of its operation so that the output pulse width will be accurate. 10. The CEXT pins of this device are internally connected to the internal ground. For optimum system performance they should be hard wired to the system’s return ground plane. 11. VCC and ground wiring should conform to good high-frequency standards and practices so that switching transients on the VCC and ground return leads do not cause interaction between one-shots. A 0.01 mF to 0.10 mF bypass capacitor (disk ceramic or monolithic type) from VCC to ground is necessary on each device. Furthermore, the bypass capacitor should be located as close to the VCC-pin as space permits. TL/F/6386 – 3 FIGURE 3 6. To obtain variable pulse widths by remote trimming, the following circuit is recommended: TL/F/6386 – 4 FIGURE 4 Note: ‘‘Rremote’’ should be as close to the device pin as possible. 7. The retriggerable pulse width is calculated as shown below: T e TW a tPLH e K c RX c CX a tPLH The retriggered pulse width is equal to the pulse width plus a delay time period (Figure 5). For further detailed device characteristics and output performance please refer to the NSC one-shot application note AN-372. TL/F/6386 – 5 FIGURE 5 8. Output pulse width variation versus VCC and temperatures: Figure 6 depicts the relationship between pulse width variation versus VCC, and Figure 7 depicts pulse width variation versus temperatures. TL/F/6386 – 6 FIGURE 6 4 Physical Dimensions inches (millimeters) 16-Lead Small Outline Molded Package Order Number DM74LS123M NS Package Number M16A 5 DM74LS123 Dual Retriggerable One-Shot with Clear and Complementary Outputs Physical Dimensions inches (millimeters) (Continued) 16-Lead Molded Dual-In-Line Package (N) Order Number DM74LS123N NS Package Number N16E LIFE SUPPORT POLICY NATIONAL’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 NATIONAL 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 whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation 1111 West Bardin Road Arlington, TX 76017 Tel: 1(800) 272-9959 Fax: 1(800) 737-7018 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Europe Fax: (a49) 0-180-530 85 86 Email: cnjwge @ tevm2.nsc.com Deutsch Tel: (a49) 0-180-530 85 85 English Tel: (a49) 0-180-532 78 32 Fran3ais Tel: (a49) 0-180-532 93 58 Italiano Tel: (a49) 0-180-534 16 80 National Semiconductor Hong Kong Ltd. 13th Floor, Straight Block, Ocean Centre, 5 Canton Rd. Tsimshatsui, Kowloon Hong Kong Tel: (852) 2737-1600 Fax: (852) 2736-9960 National Semiconductor Japan Ltd. Tel: 81-043-299-2309 Fax: 81-043-299-2408 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.