A 74HC595 and a 74HC165 serve different data-direction roles, so they should be requested as separate BOM items. For either device, the complete manufacturer ordering code, logic family and package are essential. Confirm availability through a quotation for the required variant rather than a generic request for an eight-bit shift register.
Identify the direction and control signals
Nexperia describes the 74HC595 and 74HCT595 as serial-input shift registers with output latches, while its 74HC165 and 74HCT165 datasheet covers parallel-input, serial-output operation. These distinct functions matter when expanding outputs or reading multiple inputs from a processor.
Document the clock, data, load, latch and enable signals used by the board. Check their active levels and how the firmware sequences them. A replacement must preserve both the data path and the control behavior expected by the application.
Compare logic levels and loading
Record the register supply and the voltage levels produced by the controlling processor. Compare those conditions with the specific input thresholds. Do not treat HC and HCT versions as identical merely because the numerical device function is the same.
For output expansion, review per-output current and the total current permitted by the package. Identify any LEDs, transistors or other loads attached to the outputs. For input expansion, check pull-ups, switch bounce and the timing of the parallel capture. Validate the maximum intended clock rate with the actual chain length and wiring.
Specify the quotation and production test
Include manufacturer, full suffix, package, temperature grade, packing format and quantity. Ask the supplier to identify any offered alternate explicitly. Keep approved substitutions separate from parts still awaiting electrical or firmware evaluation.
Test reset or startup behavior and exercise all bits in the chain, including patterns that switch many outputs at once. Confirm that software reads inputs in the intended order and that output latching does not create unwanted intermediate states. Retain the board revision and test sequence with the approved ordering code.
Frequently asked questions
Can 74HC595 and 74HC165 replace one another?
No. Their primary data-direction and control functions differ. Select the device that matches the schematic and firmware operation.
Can a shift register drive a load directly?
Only when the load fits the device’s specified current, voltage and total package limits. Otherwise, design and qualify an appropriate output driver.
Send SENICO a shift-register RFQ with the complete part numbers and required arrival date. Availability, price and shipment details require quotation confirmation.