60 MHz positive-edge JK — the toggle-rate ceiling for your counter chain
The SN74HC109D is a dual positive-edge-triggered JK flip-flop from the 74HC family, clocked at 60 MHz max. That 60 MHz figure is the toggle-rate ceiling at which the internal master-slave latch reliably captures the J and K inputs — above it, the setup-hold window closes and the output state becomes unpredictable. For a synchronous binary counter running at 50 MHz, this part fits; for a 100 MHz data pipeline, it does not. Supply range is 2 V to 6 V, so the same BOM line serves both a 3.3 V FPGA interface and a 5 V legacy backplane without a level translator between the rails. The 4 µA quiescent current makes it viable in a battery-backed counter that sleeps between events.
Timing budget — 30 ns propagation delay at 6 V
Max propagation delay is 30 ns at 6 V with a 50 pF load. That 30 ns is the time from clock edge to output valid — budget it into the daisy-chain timing of a shift register or the feedback path of a state machine. At 3.3 V the delay rises; the 74HC family's propagation delay increases as supply voltage drops, so a 3.3 V design should derate by roughly 1.5× versus the 6 V figure. Output drive is 5.2 mA source and sink at the rated supply — enough to switch one standard TTL load or drive the input of another HC gate, but not a 50 Ω backplane. The complementary outputs (Q and Q-bar) eliminate the need for an external inverter in divide-by-2 or toggle configurations. Input capacitance is 3 pF typical — negligible in a clock-tree fan-out calculation until the trace count exceeds eight loads, at which point the cumulative load starts to round the clock edge.
Active production — no last-time-buy clock ticking
ROHS3 compliance is confirmed — no exemptions that could expire and force a supply discontinuity.
Industrial temperature grade — -40 to 85 °C
Operating temperature range is -40 °C to 85 °C ambient. That covers the industrial equipment floor — factory-floor PLC cabinets, outdoor telecom shelters, and HVAC controllers. The 74HC family's CMOS logic levels are ratiometric with the supply rail, so the noise margin stays consistent across the temperature span as long as the supply stays regulated. The 16-SOIC package is a surface-mount footprint with 1.27 mm pitch — standard for automated pick-and-place assembly. The supplier device package is listed as 16-SOIC, matching the JEDEC MS-012 variation. No exposed thermal pad; junction-to-ambient thermal resistance follows the standard SOIC-16 profile.