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Dual precision monostable multivibrator

The HEF4538B is a dual retriggerable-resettable monostable multivibrator. Each multivibrator has an active LOW trigger/retrigger input (nA), an active HIGH trigger/retrigger input (nB), an overriding active LOW direct reset input (nCD), an output (nQ) and its complement (nQ), and two pins (nREXT/CEXT, and nCEXT, always connected to ground) for connecting the external timing components CEXT and REXT. Typical pulse width variation over the specified temperature range is ±0.2%.

The multivibrator may be triggered by either the positive or the negative edges of the input pulse and will produce an accurate output pulse with a pulse width range of 10 μs to infinity. The duration and accuracy of the output pulse are determined by the external timing components CEXT and REXT. The output pulse width (tW) is equal to REXT× CEXT. The linear design techniques in LOCMOS (Local Oxide CMOS) guarantee precise control of the output pulse width. A LOW level at nCD terminates the output pulse immediately. The trigger inputs’ Schmitt trigger action makes the circuit highly tolerant of slower rise and fall times.

It operates over a recommended VDD power supply range of 3 V to 15 V referenced to VSS (usually ground). Unused inputs must be connected to VDD, VSS or another input.

Orderable parts

Type number Orderable part number Ordering code (12NC) Package Buy from distributors
HEF4538BT HEF4538BT,653 933507970653 SOT109-1 Order product
HEF4538BT HEF4538BT,652 933507970652 SOT109-1 Order product

Features and benefits

  • Tolerant of slow trigger rise and fall times
  • Fully static operation
  • 5 V, 10 V, and 15 V parametric ratings
  • Standardized symmetrical output characteristics
  • Specified from -40 °C to +85 °C and -40 °C to +125 °C
  • Complies with JEDEC standard JESD 13-B



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
HEF4538BTProduction4.5 - 15.5CMOS± 2.460medium-40~85783.537SO16


Type numberOrderable part number, (Ordering code (12NC))StatusMarkingPackagePackage informationReflow-/Wave solderingPacking
( 9335 079 70653 )
Reel 13" Q1/T1 CECC
( 9335 079 70652 )
ActiveHEF4538BTBulk Pack, CECC

Quality, reliability & chemical content

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

Documentation (4)

File nameTitleTypeDate
HEF4538BDual precision monostable multivibratorData sheet2018-10-19
AN11051Pin FMEA HEF4000 familyApplication note2019-01-09
SO-SOJ-REFLOWFootprint for reflow solderingReflow soldering2009-10-08
SO-SOJ-WAVEFootprint for wave solderingWave soldering2009-10-08


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Ordering, pricing & availability

Type numberOrderable part numberOrdering code (12NC)PackingBuy online
HEF4538BTHEF4538BT,653933507970653Reel 13" Q1/T1 CECCOrder product
HEF4538BTHEF4538BT,652933507970652Bulk Pack, CECCOrder product


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Sample orders normally take 2-4 days for delivery.

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