PIC16LC621-04/P - 4MHz 8-bit OTP MCU, 1.75KB, 18-DIP | Microchip
MPN: PIC16LC621-04/P ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.7 | $2.70 |
| 10 | $2.45 | $24.50 |
| 100 | $2.17 | $217.00 |
| 500 | $1.92 | $960.00 |
| 1,000 | $1.65 | $1,650.00 |
PIC16LC621-04/P Overview
An 8-bit microcontroller (MCU) is a single-chip computer that combines a CPU, RAM, non-volatile program memory, and peripheral I/O on one die. Within the broader taxonomy it sits under microprocessor -> microcontroller -> 8-bit MCU -> CMOS RISC MCU. The PIC16LC62x family in particular is part of Microchip's mid-range PIC architecture, which uses a Harvard-style separate program/data bus and a small, deterministic instruction set well-suited to real-time control. The LC (low-power CMOS) suffix indicates the part is optimized for low quiescent current and supports a wide supply range, making it appropriate for battery-powered and industrial systems.
Key features include 35 single-cycle instructions (only program branches take two cycles), 12 I/O pins with individual direction control, a two-level deep hardware stack, and support for direct, indirect, and relative addressing modes. The device has seven or eight special function hardware registers and an integrated power-on reset / brown-out detection block (typical for the family). The 'LC' process node enables supply operation from approximately 2.5 V to 6.25 V with reduced active current compared to the standard 'C' EPROM variants.
Architecturally the PIC16LC621 uses a RISC core with a fixed 14-bit instruction word and 8-bit data path, giving it deterministic interrupt latency and instruction timing - a key reason these MCUs remain popular in cost-sensitive motor control, sensor conditioning, and appliance designs. The 4 MHz speed grade in this part denotes a maximum oscillator input of 4 MHz, yielding a 200 ns instruction cycle. The OTP (One-Time Programmable) program memory is windowless and intended for production volumes where code is finalized.
Typical applications include low-cost white goods control (washing machines, microwave ovens), HVAC fan and damper control, simple sensor interface boards, IR remote receivers, and small appliance key-scan matrices. The wide 2.5-6.25 V supply range also makes it suitable for 3.3 V or 5 V industrial sensor nodes.
When designing with this MCU, allocate the 1.75 KB program memory carefully - it accommodates roughly 1K single-word instructions. Because this is an OTP part, code must be fully debugged before programming; use the UV-erasable PIC16C621 windowed variant during development, then move to PIC16LC621-04/P for production.
This page synthesizes current distributor pricing, drop-in alternative listings (same-brand first), and practical design notes not aggregated on any single manufacturer or distributor page, providing a single reference for engineers qualifying the PIC16LC621-04/P.
Drop-in alternatives for PIC16LC621-04/P — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with PIC16LC621-04/P (same form factor and footprint) — differing in Core Architecture, Instruction Cycle Time, Operating Temperature Range, Package Type, Program Memory Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC621A-04/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC620A-04/P
✅ Drop-In✓ In Stock
$1.3 / Unit
View Datasheet →PIC16LC620-04/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC621-04I/P
✅ Drop-In✓ In Stock
$2.54 / Unit
View Datasheet →PIC16LC621A-04I/P
✅ Drop-In✓ In Stock
$1.01 / Unit
View Datasheet →PIC16LC621-04/P Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 8-bit RISC |
| Program Memory Type | OTP (EPROM-based) |
| Program Memory Size | 1.75 KB (1K x 14) |
| RAM Size | 80 bytes |
| Maximum Clock Frequency | 4 MHz |
| Instruction Cycle Time | 200 ns (single cycle) |
| Instruction Set Size | 35 instructions |
| Supply Voltage Range | 2.5 V to 6.25 V |
| I/O Pins | 13 |
| Data Bus Width | 8-bit |
| Instruction Word Width | 14-bit |
| Stack Depth | 2 levels (hardware) |
| Package Type | 18-pin PDIP (DIP-18, 0.300 inch) |
| Mounting Type | Through-Hole |
| Operating Temperature Range | 0C to +70C (Commercial) |
| Address Modes | Direct, Indirect, Relative |
| Special Function Registers | 7 to 8 |
PIC16LC621-04/P Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O, PORTA bit 2 |
| Pin 2 | RA3 — Bidirectional I/O, PORTA bit 3 |
| Pin 3 | RA4/T0CKI — Bidirectional I/O / Timer0 clock input |
| Pin 4 | MCLR/VPP — Master Clear (Reset) / Programming voltage |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Bidirectional I/O / External interrupt |
| Pin 7 | RB1 — Bidirectional I/O, PORTB bit 1 |
| Pin 8 | RB2 — Bidirectional I/O, PORTB bit 2 |
| Pin 9 | RB3 — Bidirectional I/O, PORTB bit 3 |
| Pin 10 | RB4 — Bidirectional I/O, PORTB bit 4 |
| Pin 11 | RB5 — Bidirectional I/O, PORTB bit 5 |
| Pin 12 | RB6 — Bidirectional I/O, PORTB bit 6 |
| Pin 13 | RB7 — Bidirectional I/O, PORTB bit 7 |
| Pin 14 | VDD — Positive supply voltage |
| Pin 15 | OSC2/CLKOUT — Oscillator crystal output / Clock out |
| Pin 16 | OSC1/CLKIN — Oscillator crystal input / External clock in |
| Pin 17 | RA0 — Bidirectional I/O, PORTA bit 0 |
| Pin 18 | RA1 — Bidirectional I/O, PORTA bit 1 |
Typical Applications
PIC16LC621-04/P is suitable for 6 applications: White Goods Control, IR Remote Receiver Decoder, HVAC Fan and Damper Control, Small Appliance Key-Scan Matrix, Industrial Sensor Interface Board, Battery-Powered Sensor Node.
White Goods Control
The PIC16LC621-04/P's 1.75 KB OTP program memory and 13 GPIO pins make it well suited for low-cost white goods controllers such as microwave ovens, washing machines, and dishwashers. Its 4 MHz core delivers a 200 ns instruction cycle, fast enough for keypad scanning, relay sequencing, and triac-based heater control loops typical in appliance main boards. The wide 2.5 V to 6.25 V supply tolerance allows direct connection to rectified 5 V or 3.3 V rails without additional regulators, simplifying the BOM.
Recommended
IR Remote Receiver Decoder
With 35 single-cycle instructions and a deterministic 200 ns instruction cycle, the PIC16LC621-04/P can decode common IR protocols (RC5, NEC, Sony SIRC) directly in software using a single external interrupt pin. The 80-byte RAM is sufficient for protocol state machines and timing buffers, while the OTP program memory locks the decoded command set against field tampering. Its 13 GPIO pins comfortably drive status LEDs and relay outputs.
Recommended
HVAC Fan and Damper Control
The PIC16LC621-04/P's CMOS LC process supports the wide 2.5-6.25 V supply range needed for 24 V industrial HVAC control boards with simple LDO regulation. Its 13 GPIO pins can drive multiple TRIAC optocouplers for fan speed selection and damper actuators, while the 4 MHz clock enables precise PWM-based motor control. The OTP memory prevents firmware tampering in field-deployed HVAC systems.
Recommended
Small Appliance Key-Scan Matrix
For small kitchen and personal-care appliances, the PIC16LC621-04/P can scan a 4x4 or larger key matrix using its 13 GPIO pins with minimal external components. The Harvard architecture and predictable interrupt response allow deterministic debounce handling and multi-key rollover detection. OTP memory keeps per-SKU firmware locked at production cost, ideal for high-volume appliance lines.
Recommended
Industrial Sensor Interface Board
The PIC16LC621-04/P's 13 GPIO pins and 80-byte RAM support simple 4-20 mA or 0-10 V sensor signal conditioning boards that require local display driving and relay outputs. The 4 MHz instruction cycle allows polling of multiple sensor channels at sub-millisecond rates. Its commercial 0C to +70C operating range and through-hole PDIP package suit industrial control panels where socketed replacement and hand-prototyping remain common.
Recommended
Battery-Powered Sensor Node
The 'LC' low-power CMOS process of the PIC16LC621-04/P reduces active current draw versus standard CMOS variants, making it usable in battery-powered wireless sensor transmitters and remote controls. The 2.5 V to 6.25 V supply range allows direct operation from 2xAA alkaline or single Li-ion cells. Its 13 GPIO pins can wake from sleep on a sensor event and drive an RF transmitter for short-range data links.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621-04/P — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621A-04/P | PIC16LC620A-04/P | PIC16LC620-04/P | PIC16LC621-04I/P | PIC16LC621A-04I/P |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 18-pin PDIP (DIP-18) | 18-pin PDIP (DIP-18) | 18-pin PDIP (DIP-18) | 18-pin PDIP (DIP-18) | 18-pin PDIP (DIP-18) | 18-pin PDIP (DIP-18) |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 896 B OTP | 896 B OTP | 1.75 KB OTP | 1.75 KB OTP |
| RAM | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 80 bytes |
| Maximum Clock | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| I/O Pins | 13 | 13 | 13 | 13 | 13 | 13 |
| Supply Voltage | 2.5 V to 6.25 V | 2.5 V to 6.25 V | 2.5 V to 6.25 V | 2.5 V to 6.25 V | 2.5 V to 6.25 V | 2.5 V to 6.25 V |
| Temperature Grade | Commercial (0C to +70C) | Commercial | Commercial | Commercial | Industrial (-40C to +85C) | Industrial (-40C to +85C) |
| Mounting Type | Through-Hole (PDIP) | Through-Hole (PDIP) | Through-Hole (PDIP) | Through-Hole (PDIP) | Through-Hole (PDIP) | Through-Hole (PDIP) |
Key Differentiators
- Enhanced CMOS revision with identical footprint (vs PIC16LC621A-04/P)
- Industrial temperature grade variant available (vs PIC16LC621-04I/P)
- Lower-memory variant in same package (vs PIC16LC620A-04/P)
Design Notes
PIC16LC621-04/P is OTP (One-Time Programmable) - firmware cannot be erased or rewritten. Develop and debug firmware on the UV-erasable windowed PIC16C621 variant or on a Flash-based PIC16F84A/16F88 development platform first. Once programmed into the OTP LC621, any code bug requires a new chip, increasing rework cost on production lines. Always verify code with the MPLAB simulator and an emulator or ICD before committing.
PIC16LC621-04/P lacks an internal voltage regulator, so VDD must be tightly regulated to within 2.5 V to 6.25 V. Add a 100 nF decoupling capacitor close to VDD (pin 14) and a 10 uF bulk capacitor on the supply rail. Brown-out reset is selectable via configuration fuses; enable BOR for reliable operation in electrically noisy environments like motor control or relay-driven systems. For battery-powered designs, leverage the SLEEP instruction to reduce quiescent current to typical LC-family levels.
The 18-pin PDIP through-hole package accommodates both wave soldering and hand-prototyping with DIP sockets - use machined-pin sockets for production programming and field replacement. Keep the 4 MHz crystal or resonator (typically a 4.000 MHz AT-cut type with 22-33 pF loading caps) within 5 mm of OSC1/OSC2 pins to minimize EMI and start-up issues. Route the MCLR/VPP pin with a 10 kΩ pullup to VDD and place the reset circuit close to the MCU to avoid spurious triggering.
Estimate: PORTB internal weak pull-ups (typically 50-100 kΩ) can source limited current - do not use them to drive LEDs directly without a buffer transistor. For high-current loads (relays, solenoids, triacs), use a dedicated driver IC such as a ULN2003 or MOC3021 optocoupler on the GPIO pin. Isolate noisy analog sections from the MCU's digital traces with a ground plane and keep the crystal traces short and symmetric to reduce radiated EMI.
Compliance Information
RoHS and lead-free compliance per Microchip product page. PIC16LC621-04/P is not AEC-Q100 qualified - choose automotive-grade PIC variants for vehicle applications. Halogen-free status not explicitly stated in the verified data.
