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DM74121 One-Shot with Clear and Complementary Outputs
June 1989 Revised July 2001
DM74121 One-Shot with Clear and Complementary Outputs
General Description
The DM74121 is a monostable multivibrator featuring both positive and negative edge triggering with complementary outputs. An internal 2k timing resistor is provided for design convenience minimizing component count and layout problems. this device can be used with a single external capacitor. Inputs (A) are active-LOW trigger transition inputs and input (B) is and active-HIGH transition Schmitttrigger input that allows jitter-free triggering from inputs with transition rates as slow as 1 volt/second. A high immunity to VCC 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.
Features
s 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 compatible s Compensated for VCC and temperature variations s Input clamp diodes
Ordering Code:
Order Number DM74121N Package Number N14A Package Description 14-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
Connection Diagram
Function Table
Inputs A1 L X X H H A2 X L X H B H H L X H H H Q L L L Outputs Q H H H
H

L X
X L

H = HIGH Logic Level L = LOW Logic Level X = Can Be Either LOW or HIGH = A Positive Pulse = A Negative Pulse

Functional Description
The basic output pulse width is determined by selection of an internal resistor RINT or an external resistor (RX) and capacitor (CX). Once triggered the output pulse width is independent of further transitions of the inputs and is function of the timing components. Pulse width can vary from a
= Positive Going Transition = Negative Going Transition

L

H
few nano-seconds to 28 seconds by choosing appropriate RX and CX combinations. There are three trigger inputs from the device, two negative edge-triggering (A) inputs, one positive edge Schmitt-triggering (B) input.
(c) 2001 Fairchild Semiconductor Corporation
DS006538
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DM74121
Operating Rules
1. To use the internal 2 k timing resistor, connect the RINT pin to VCC. 2. An external resistor (RX) or the internal resistor (2 k) 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 use high-quality mica, glass, polypropylene, polycarbonate, or polystyrene capacitors. For large time constants use solid 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. 3. The pulse width is essentially determined by external timing components RX and CX. For CX < 1000 pF see Figure 1 design curves on tW as function of timing components value. For CX > 1000 pF the output is defined as: t W = K RX CX where [RX is in Kilo-ohm] [CX is in pico Farad] [tW is in nano second] [K 0.7] 4. If CX is an electrolytic capacitor a switching diode is often required for standard TTL one-shots to prevent high inverse leakage current Figure 2. 5. Output pulse width versus VCC and operation temperatures: Figure 3 depicts the relationship between pulse width variation versus VCC. Figure 4 depicts pulse width variation versus ambient temperature. 6. The "K" coefficient is not a constant, but varies as a function of the timing capacitor CX. Figure 5 details this characteristic. 7. 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 X R and Ldi/dt voltage developed along their connecting paths. If the lead length from CX to pins (10) and (11) is greater than 3 cm, for example, the output pulse width might be quite different from values predicted from the appropriate equations. A noninductive 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. 8. VCC and ground wiring should conform to good highfrequency standards and practices so that switching transients on the VCC and ground return leads do not cause interaction between one-shots. A 0.01 F to 0.10 F 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. For further detailed device characteristics and output performance please refer to the one-shot application note, AN366. FIGURE 5. FIGURE 3. FIGURE 2.
FIGURE 1.
FIGURE 4.
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DM74121
Absolute Maximum Ratings(Note 1)
Supply Voltage Input Voltage Operating Free Air Temperature Range Storage Temperature Range 7V 5.5V 0C to +70C
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.
-65C to +150C
Recommended Operating Conditions
Symbol VCC VT+ VT- VT+ VT- IOH IOL tW dV/dt dV/dt REXT CEXT DC TA Parameter Supply Voltage Positive-Going Input Threshold Voltage at the A Input (VCC = Min) Negative-Going Input Threshold Voltage at the A Input (VCC = Min) Positive-Going Input Threshold Voltage at the B Input (VCC = Min) Negative-Going Input Threshold Voltage at the B Input (VCC = Min) HIGH Level Output Current LOW Level Output Current Input Pulse Width (Note 2) Rate of Rise or Fall of Schmidt Input (B) (Note 2) Rate of Rise or Fall of Schmidt Input (A) (Note 2) External Timing Resistor (Note 2) External Timing Capacitance (Note 2) Duty Cycle (Note 2) Free Air Operating Temperature RT = 2 k RT = REXT (Max) 0
Note 2: TA = 25C and VCC = 5V
Min 4.75
Nom 5 1.4
Max 5.25 2
Units V V V
0.8
1.4 1.5 2
V V
0.8
1.3
-0.4
16 40 1 1 1.4 0 40 1000 67 90 70
mA mA ns V/s V/s k
F
%
C
Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted) Symbol VI VOH VOL II IIH IIL IOS ICC Parameter Input Clamp Voltage HIGH Level Output Voltage LOW Level Output Voltage Input Current @ Max Input Voltage HIGH Level Input Current LOW Level Input Current Short Circuit Output Current Supply Current VCC = Max, VI = 2.4V VCC = Max, VI = 0.4V VCC = Max (Note 4) VCC = Max Quiescent Triggered
Note 3: All typicals are at VCC = 5V, TA = 25C. Note 4: Not more than one output should be shorted at a time.
Conditions VCC = Min, II = -12 mA VCC = Min, IOH = Max, VIL = Max, VIH = Min VCC = Min, IOL = Max, VIH = Max, VIL = Min VCC = Max, VI = 5.5V A1, A2 B A1, A2 B
Min
Typ (Note 3) 3.4
Max -1.5
Units V V
2.4
0.2
0.4 1 40 80 -1.6 -3.2
V mA A mA mA mA
-18 13 23
-55 25 40
3
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DM74121
Switching Characteristics
At VCC = 5V and TA = 25C (See Test Waveforms and Output Load Section) From (Input) Symbol Parameter To (Output) tPLH tPLH tPHL tPHL tW(OUT) Propagation Delay Time LOW-to-HIGH Level Output Propagation Delay Time LOW-to-HIGH Level Output Propagation Delay Time HIGH-to-LOW Level Output Propagation Delay Time HIGH-to-LOW Level Output Output Pulse Width Using the Internal Timing Resistor tW(OUT) Output Pulse Width Using Zero Timing Capacitance tW(OUT) Output Pulse Width Using External Timing Resistor A1, A2 to Q, Q A1, A2 to Q, Q A1, A2 to Q, Q A1, A2 to Q B to Q A1, A2 to Q B to Q A1, A2 or B to Q, Q CEXT = 80 pF RINT to VCC RL = 400 CL = 15 pF CEXT = 0 pF RINT to VCC RL = 400 CL = 15 pF CEXT = 100pF RINT = 10 k RL = 400 CL = 15pF CEXT = 1 F RINT = 10 k RL = 400 CL = 15 pF 6 8 ms 600 800 ns 50 ns 70 150 ns Conditions CEXT = 80 pF RINT to VCC CL = 15 pF RL = 400 Min Max 70 55 80 65 Units ns ns ns ns
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DM74121 One-Shot with Clear and Complementary Outputs
Physical Dimensions inches (millimeters) unless otherwise noted
14-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide Package Number N14A
Fairchild 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 POLICY FAIRCHILD'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 reasonably expected to result in a significant injury to the user. 5 2. A critical component in 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. www.fairchildsemi.com
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