DM74123N

DM74123N Datasheet

DM74123 Dual Retriggerable One-Shot with Clear and Complementary Outputs

Part	Datasheet
DM74123N	DM74123N (pdf)

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DM74123 Dual Retriggerable One-Shot with Clear and Complementary Outputs DM74123 Dual Retriggerable One-Shot with Clear and Complementary Outputs The DM74123 is a dual retriggerable monostable multivibrator capable of generating output pulses from a few nano-seconds 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 active-LOW transition trigger input and pin B is an activeHIGH transition trigger input. A LOW at the clear CLR input terminates the output pulse which also inhibits triggering. An internal connection from CLR to the input gate makes it possible to trigger the circuit by a positive-going signal on CLR as shown in the Truth Table. To obtain the best and trouble free operation from this device please read the Operating Rules as well as the Application Notes carefully and observe recommendations. s DC triggered from active-HIGH transition or active-LOW transition inputs s Retriggerable to 100% duty cycle s Direct reset terminates output pulse s Compensated for VCC and temperature variations s DTL, TTL compatible s Input clamp diodes Ordering Code: Order Number Package Number Package Description DM74123N N16E 16-Lead Plastic Dual-In-Line Package PDIP , JEDEC MS-001, Wide Connection Diagram 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 Triggering Truth Table Inputs H = HIGH Voltage Level L = LOW Voltage Level X = Immaterial CLR L X H X Response No Trigger No Trigger No Trigger transition 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. 2001 Fairchild Semiconductor Corporation DS006539 DM74123 Operating Rules An external resistor RX and 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. 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 Figure However, its use in general is not recommended with retriggerable operation. The output pulse width TW for CX > 1000 pF is defined as follows: TW = K RX CX 1 + 0.7/RX where [RX is in Kilo-ohm] [CX is in pico Farad] [TW is in nano second] FIGURE For CX < 1000 pF see Figure 2 for TW vs. CX family curves with RX as a parameter: Pulse Width vs. RX and CX To obtain variable pulse width by remote trim- ming, the following circuit is recommended: Note “Rremote” should be as close to the one-shot as possible. FIGURE The retriggerable pulse width is calculated as shown below: T = TW + tPLH = Kx RX x CX + tPLH The retriggered pulse width is equal to the pulse width plus a delay time period Figure FIGURE Under any operating condition CX and RX must be kept as close to the one-shot device

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DM74123 Dual Retriggerable One-Shot with Clear and Complementary Outputs

DM74123 Dual Retriggerable One-Shot with Clear and Complementary Outputs

The DM74123 is a dual retriggerable monostable multivibrator capable of generating output pulses from a few nano-seconds 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 active-LOW transition trigger input and pin B is an activeHIGH transition trigger input. A LOW at the clear CLR input terminates the output pulse which also inhibits triggering. An internal connection from CLR to the input gate makes it possible to trigger the circuit by a positive-going signal on CLR as shown in the Truth Table.

To obtain the best and trouble free operation from this device please read the Operating Rules as well as the Application Notes carefully and observe recommendations.
s DC triggered from active-HIGH transition or active-LOW transition inputs
s Retriggerable to 100% duty cycle s Direct reset terminates output pulse s Compensated for VCC and temperature variations s DTL, TTL compatible s Input clamp diodes
Ordering Code:

Order Number Package Number

Package Description

DM74123N

N16E
16-Lead Plastic Dual-In-Line Package PDIP , JEDEC MS-001, Wide

Connection Diagram

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

Triggering Truth Table

Inputs

H = HIGH Voltage Level L = LOW Voltage Level X = Immaterial

CLR L X H X

Response

No Trigger No Trigger No Trigger
transition 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.
2001 Fairchild Semiconductor Corporation DS006539

DM74123

Operating Rules

An external resistor RX and 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.

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 Figure However, its use in general is not recommended with retriggerable operation.

The output pulse width TW for CX > 1000 pF is defined as follows:

TW = K RX CX 1 + 0.7/RX
where [RX is in Kilo-ohm]
[CX is in pico Farad]
[TW is in nano second]

FIGURE

For CX < 1000 pF see Figure 2 for TW vs. CX
family curves with RX as a parameter:

Pulse Width vs. RX and CX

To obtain variable pulse width by remote trim-
ming, the following circuit is recommended:

Note “Rremote” should be as close to the one-shot as possible.

FIGURE

The retriggerable pulse width is calculated as
shown below:

T = TW + tPLH = Kx RX x CX + tPLH

The retriggered pulse width is equal to the pulse width plus a delay time period Figure

FIGURE

Under any operating condition CX and RX
must be kept as close to the one-shot device

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Datasheet ID: DM74123N 513616