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Dual non-retriggerable monostable multivibrator with reset

The 74HC/74HCT221 are high-speed Si-gate CMOS devices and are pin compatible with low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A.

The 74HC/HCT221 are dual non-retriggerable monostable multivibrators. Each multivibrator features an active LOW-going edge input (nA) and an active HIGH-going edge input (nB), either of which can be used as an enable input.

Pulse triggering occurs at a particular Voltage level and is not directly related to the transition time of the input pulse. Schmitt-trigger input circuitry for the nB inputs allow jitter-free triggering from inputs with slow transition rates, providing the circuit with excellent noise immunity.

Once triggered, the outputs (nQ, nQ) are independent of further transitions of nA and nB inputs and are a function of the timing components. The output pulses can be terminated by the overriding active LOW reset inputs (nR D ). Input pulses may be of any duration relative to the output pulse.

Pulse width stability is achieved through internal compensation and is virtually independent of VCC and temperature. In most applications pulse stability will only be limited by the accuracy of the external timing components.

The output pulse width is defined by the following relationship:



Pin assignments for the '221' are identical to those of the '123' so that the '221' can be substituted for those products in systems not using the retrigger by merely changing the value of REXT and/or CEXT.

Orderable parts

Type number Orderable part number Ordering code (12NC) Package Buy from distributors
74HCT221D 74HCT221D,118 933715110118 SOT109-1 Order product

Features and benefits

  • Pulse width variance is typically less than ± 5%
  • Pin-out identical to '123'
  • Overriding reset terminates output pulse
  • nB inputs have hysteresis for improved noise immunity
  • Output capability: standard (except for nREXT /CEXT)
  • ICC category: MSI



Type numberProduct statusVCC (V)Logic switching levelsOutput drive capability (mA)tpd (ns)Power dissipation considerationsTamb (°C)Rth(j-a) (K/W)Ψth(j-top) (K/W)Rth(j-c) (K/W)Package name
74HCT221DProduction4.5 - 5.5TTL± 432low-40~125621.019SO16


Type numberOrderable part number, (Ordering code (12NC))StatusMarkingPackagePackage informationReflow-/Wave solderingPacking
( 9337 151 10118 )
Reel 13" Q1/T1

The variants in the table below are discontinued. See the table Discontinuation information for more information.

Type numberOrderable part number, (Ordering code (12NC))StatusMarkingPackagePackage informationReflow-/Wave solderingPacking
( 9337 151 10112 )
Discontinued / End-of-life74HCT221D
Bulk Pack

Discontinuation information

Type numberOrderable part numberOrdering codeLast time buy dateLast time delivery dateReplacement productStatusComments

Quality, reliability & chemical content

Type numberOrderable part numberChemical contentRoHS / RHFEFRIFRMTBF (hour)MSLMSL leadfree

The variants in the table below are discontinued. See the table Discontinuation information for more information.

Type numberOrderable part numberChemical contentRoHS / RHFEFRIFRMTBF (hour)MSLMSL leadfree
Quality and reliability disclaimer

Documentation (6)

File nameTitleTypeDate
74HCT221Dual non-retriggerable monostable multivibrator with resetData sheet2017-03-17
AN11044Pin FMEA 74HC/74HCT familyApplication note2019-01-09
HCT_USER_GUIDEHC/T User GuideUser manual1997-10-31
SO-SOJ-REFLOWFootprint for reflow solderingReflow soldering2009-10-08
SO-SOJ-WAVEFootprint for wave solderingWave soldering2009-10-08
WAVE_BG-BD-1Wave soldering profileWave soldering2021-09-08


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Ordering, pricing & availability

Type numberOrderable part numberOrdering code (12NC)PackingBuy online
74HCT221D74HCT221D,118933715110118Reel 13" Q1/T1Order product


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