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
74HCT221D 74HCT221D,112 933715110112 SOT109-1 Order product


  • 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

Target applications


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))StatusMarkingPackageOutline versionReflow-/Wave solderingPacking
( 9337 151 10118 )
Reel 13" Q1/T1
( 9337 151 10112 )
Active74HCT221DBulk Pack

Quality, reliability & chemical content

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

Documentation (7)

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
SOT109-1_118SO16; Reel pack; SMD, 13" Q1/T1 Standard product orientation Orderable part number ending ,118 or J Ordering code (12NC) ending 118Packing2013-04-24
SOT109-1plastic, small outline package; 16 leads; 1.27 mm pitch; 9.9 mm x 3.9 mm x 1.35 mm bodyOutline drawing2018-10-18


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Ordering, pricing & availability

Type numberOrderable part numberOrdering code (12NC)PackingBuy online
74HCT221D74HCT221D,118933715110118Reel 13" Q1/T1Order product
74HCT221D74HCT221D,112933715110112Bulk PackOrder product


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