74AC109PC Equivalent & Substitute Parts

Part Overview

The 74AC109PC is a dual JK-type flip-flop logic integrated circuit manufactured by onsemi, housed in a 16-DIP package. This component functions as a 2-element, 1-bit positive edge-triggered flip-flop with complementary outputs and Set/Reset capability. The part is classified as obsolete, making equivalent and substitute parts necessary for ongoing system maintenance, legacy design support, and component sourcing.

Substiute Parts

74AC109PC

onsemiIn Stock: 399274AC109PC Datasheet

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CD74AC109E

Harris CorporationIn Stock: 8728CD74AC109E Datasheet

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CD74HCT109E

Harris CorporationIn Stock: 1490CD74HCT109E Datasheet

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SN74HC109N

Texas InstrumentsIn Stock: 5016SN74HC109N Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 74AC109PC is determined by the following critical parameters:

• Functional equivalence: Dual JK-type flip-flop, 1-bit, positive edge-triggered, with Set/Reset and complementary outputs
• Package compatibility: 16-DIP (0.300", 7.62mm) through-hole mounting
• Electrical compatibility: Supply voltage range, propagation delay, output current drive capability, and operating temperature range
• Logic family compatibility: 74AC, 74HC, and 74HCT series devices sharing the same base product number (74AC109, 74HC109, 74HCT109)

The substitute parts listed below meet these core substitution criteria within their specified electrical and thermal operating ranges.

Parameter Comparison

Engineering Selection Recommendations

CD74AC109E (Harris Corporation): This substitute maintains the 74AC series logic family and delivers equivalent propagation delay (10.3ns) and output current drive (24mA) to the 74AC109PC. The extended operating temperature range (-55°C ~ 125°C) and wider supply voltage tolerance (1.5V ~ 5.5V) provide additional design margin. However, this part is obsolete and carries RoHS non-compliance status.

SN74HC109N (Texas Instruments): This part is the only active product among the substitutes, offering current availability and ROHS3 compliance. The 74HC series operates within the same supply voltage range (2V ~ 6V) and temperature range (-40°C ~ 85°C) as the original 74AC109PC. Trade-offs include reduced clock frequency (60 MHz versus 175 MHz), increased propagation delay (30ns versus 10ns), and lower output current drive (5.2mA versus 24mA). This substitute is suitable for applications where speed and drive capability are not critical constraints.

CD74HCT109E (Harris Corporation): This 74HCT series device operates at a narrower supply voltage range (4.5V ~ 5.5V) and exhibits the slowest propagation delay (40ns) among the substitutes. It is obsolete and RoHS non-compliant. Selection of this part is appropriate only when TTL-level input compatibility is required and speed is not a design constraint.

Frequently Asked Questions (FAQ)

Q: Can the 74AC109PC be directly replaced with the SN74HC109N?

A: Direct replacement is possible from a functional and package perspective. Both devices are dual JK-type flip-flops in 16-DIP packages with identical pinouts. However, the SN74HC109N operates at lower speed (60 MHz clock frequency versus 175 MHz) and provides reduced output current drive (5.2mA versus 24mA). Verify that your application does not require the higher speed or drive capability of the original 74AC109PC before substitution.

Q: What is the difference between 74AC, 74HC, and 74HCT logic families?

A: The 74AC series operates across a wider supply voltage range (2V ~ 6V) and delivers higher speed and output current. The 74HC series also supports 2V ~ 6V operation but with reduced speed and drive capability. The 74HCT series is restricted to 4.5V ~ 5.5V operation and includes TTL-level input thresholds for compatibility with older TTL logic. All three families share identical pinouts for equivalent part numbers.

Q: Are there RoHS compliance considerations for these substitutes?

A: The SN74HC109N is ROHS3 compliant, making it suitable for applications with RoHS requirements. The CD74AC109E and CD74HCT109E are both RoHS non-compliant. If RoHS compliance is mandatory, the SN74HC109N is the only qualified substitute among those listed.

Q: What is the impact of propagation delay differences on system design?

A: Propagation delay determines the maximum frequency at which the flip-flop can reliably operate. The 74AC109PC specifies 10ns delay, while the SN74HC109N specifies 30ns and the CD74HCT109E specifies 40ns. Applications operating at frequencies below 33 MHz can tolerate the SN74HC109N delay. Applications requiring operation above 33 MHz should use the CD74AC109E or remain with the original 74AC109PC if available.

Q: Can these parts be used interchangeably in high-speed digital circuits?

A: No. The 74AC109PC and CD74AC109E are suitable for high-speed applications up to 175 MHz and 100 MHz respectively. The 74HC and 74HCT variants are limited to 60 MHz and 54 MHz respectively and are not appropriate for high-speed circuit designs.