PIC16LC621T-04/SO - 8-Bit PIC MCU, 4MHz, 1.75KB OTP | Microchip
MPN: PIC16LC621T-04/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.2 | $3.20 |
| 10 | $2.95 | $29.50 |
| 100 | $2.55 | $255.00 |
| 500 | $2.2 | $1,100.00 |
| 1,000 | $1.95 | $1,950.00 |
PIC16LC621T-04/SO Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, working RAM, and configurable I/O peripherals. The PIC16C family from Microchip is built on a Harvard-architecture RISC core with separate program and data buses, 12-bit-wide instructions and an 8-bit-wide data path. Inside the PIC16LC621 the core is paired with seven (or eight) special-function hardware registers, a two-level-deep hardware stack, and direct/indirect/relative addressing modes that map efficiently onto compiled C and assembly source.
Key features include a 4 MHz maximum clock, 12 CMOS-compatible I/O lines, OTP program memory suited to fixed-code production runs, internal oscillator support, and power-saving SLEEP mode. The 'LC' supply range of 2.5 V to 6.25 V lets the part run directly from a 3.3 V or 5 V rail without a separate regulator. Compared with flash-based PIC16F parts, the OTP variant reduces unit cost in mature, code-stable products where in-field firmware updates are not required.
Typical applications include appliance controls, sensor signal conditioning, low-end remote keyless entry transmitters, automotive body modules, and simple logic-replacement glue. The 18-SOIC footprint remains popular for through-hole-free board designs that migrate from DIP-18 prototypes.
When designing with this device, observe the maximum clock versus supply-voltage derating in the datasheet, keep RESET/MCLR decoupling tight, and reserve the OTP programmer footprint on first-article builds. Migration to the flash-based PIC16F627 (same pinout) is recommended for new designs that need firmware iteration.
This page synthesises distributor pricing, drop-in same-package alternatives, and engineering design notes for the PIC16LC621T-04/SO that are not found in a single manufacturer datasheet.
Drop-in alternatives for PIC16LC621T-04/SO — 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 PIC16LC621T-04/SO (same form factor and footprint) — differing in Package, Program Memory Size, Program Memory Type, RAM Size, I/O Pins.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC621A-04/SO
✅ Drop-In✓ In Stock
$1.75 / Unit
View Datasheet →PIC16LC621AT-04I/SO
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →PIC16LC621-04/SO
✅ Drop-In✓ In Stock
$2.1 / Unit
View Datasheet →PIC16LC621T-04I/SO
✅ Drop-In✓ In Stock
$2.52 / Unit
View Datasheet →PIC16F627-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16F628-04/SO
✅ Drop-In✓ In Stock
$1.05 / Unit
View Datasheet →PIC16LC621T-04/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 8-bit RISC (Harvard) |
| Core Size | 8-bit |
| Series | PIC 16C |
| Maximum Clock Speed | 4 MHz |
| Program Memory Size | 1.75 KB (1K x 14) OTP |
| RAM Size | 80 bytes |
| Supply Voltage Range | 2.5 V to 6.25 V |
| Number of I/O Pins | 13 (12 per alternate source listings) |
| Package | 18-pin SOIC (SO-18, 0.300 inch) |
| Mounting Type | Surface Mount |
| Instruction Word Width | 12-bit |
| Hardware Stack Depth | 2 levels |
| Memory Type | OTP (One-Time Programmable) |
PIC16LC621T-04/SO Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O port A bit 2 |
| Pin 2 | RA3 — Bidirectional I/O port A bit 3 |
| Pin 3 | RA4/T0CKI — I/O port A bit 4 / Timer0 clock input |
| Pin 4 | MCLR/VPP — Master Clear reset (active low) / Programming voltage input |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — I/O port B bit 0 / External interrupt input |
| Pin 7 | RB1 — Bidirectional I/O port B bit 1 |
| Pin 8 | RB2 — Bidirectional I/O port B bit 2 |
| Pin 9 | RB3 — Bidirectional I/O port B bit 3 |
| Pin 10 | RB4 — Bidirectional I/O port B bit 4 |
| Pin 11 | RB5 — Bidirectional I/O port B bit 5 |
| Pin 12 | RB6 — I/O port B bit 6 / ICSP clock |
| Pin 13 | RB7 — I/O port B bit 7 / ICSP data |
| Pin 14 | VDD — Positive supply voltage (2.5 V to 6.25 V) |
| Pin 15 | OSC2/CLKOUT — Oscillator crystal output / Clock output |
| Pin 16 | OSC1/CLKIN — Oscillator crystal input / External clock input |
| Pin 17 | RA0 — Bidirectional I/O port A bit 0 |
| Pin 18 | RA1 — Bidirectional I/O port A bit 1 |
Typical Applications
PIC16LC621T-04/SO is suitable for 7 applications: Appliance Control Boards, Remote Keyless Entry (RKE) Transmitters, Automotive Body Modules, Sensor Signal Conditioning, Logic Replacement / Glue Controller, Low-End Consumer Electronics, Industrial Control Panels (HMI).
Appliance Control Boards
The PIC16LC621T-04/SO's 1.75 KB OTP program memory and 13 CMOS I/O lines fit appliance controls such as washing-machine front panels, microwave user interfaces and small kitchen appliances. The 4 MHz core delivers enough MIPS for keypad scanning, LED multiplexing and basic relay timing, while OTP keeps the per-unit cost low in high-volume SKUs. Operating from 2.5 V to 6.25 V lets the part share a 5 V or 3.3 V rail with the rest of the appliance's analog circuitry, simplifying the BOM. Designers should reserve the ICSP pins (RB6/RB7 + MCLR) so first-article boards can be programmed before OTP locking.
Recommended
Remote Keyless Entry (RKE) Transmitters
The PIC16LC621T-04/SO is well matched to low-end RKE transmitter keyfobs where low cost, low standby current and a small 18-SOIC footprint outweigh the need for in-field firmware updates. SLEEP mode plus the 2.5-6.25 V supply range lets the part run directly from a CR2032 coin cell for multi-year battery life. The OTP memory locks the rolling-code algorithm at production, preventing firmware tampering, and 13 I/O pins are sufficient for 4-5 button inputs plus an LED indicator and SAW-transmitter enable line.
Recommended
Automotive Body Modules
For non-safety automotive body functions (interior lighting controllers, mirror-adjust modules, seat-position switches) the PIC16LC621T-04/SO provides adequate processing at the lowest BOM cost. The wide 2.5 V to 6.25 V supply tolerance survives 12 V automotive transients when paired with an external TVS clamp. For AEC-Q100 qualified designs engineers should migrate to the PIC16LC621AT-04I/SO industrial-grade variant, which shares the same 18-SOIC footprint and is qualified to higher automotive reliability standards. OTP memory is acceptable because body-module firmware rarely changes once the part is in production.
Recommended
Sensor Signal Conditioning
The PIC16LC621T-04/SO serves as a low-cost front-end controller for sensor signal conditioning boards (thermistor linearisation, NTC thermometry, simple 4-20 mA loop trim). The 13 I/O pins handle multiplexed analog switch control, reference voltage switching and a one-wire UART output back to a host PLC. The 1.75 KB OTP accommodates calibration lookup tables for a few sensor types, while the 4 MHz core runs the linearisation math in real time at typical loop rates of 100 Hz to 1 kHz. Operating from a 3.3 V or 5 V loop supply, the part avoids the cost of an extra LDO on the sensor board.
Recommended
Logic Replacement / Glue Controller
Designers often drop a PIC16LC621T-04/SO onto a board to replace a handful of 74HC logic gates and a discrete timing RC network. The 1.75 KB OTP stores a custom state machine that handles power-up sequencing, watchdog timing and interlock logic in one 18-SOIC package. The 2.5-6.25 V supply range lets the MCU share the existing 3.3 V or 5 V logic rail with no extra regulator. OTP ensures the logic-replacement firmware is locked at production, simplifying end-product certification.
Recommended
Low-End Consumer Electronics
The PIC16LC621T-04/SO fits low-end consumer products such as electronic toys, novelty LED gadgets, simple remote controls and personal-care devices. The 4 MHz core runs PWM for LED dimming and tone generation for piezo buzzers, while 13 I/O pins drive keypad scanning and segment-LCD multiplexing via external transistors. OTP keeps the unit cost low enough for sub-USD 10 retail products, and the 18-SOIC footprint is friendly to small two-layer PCBs. Designers should reserve the ICSP header on prototype runs to enable last-minute firmware tweaks before OTP lockdown.
Recommended
Industrial Control Panels (HMI)
The PIC16LC621T-04/SO is used in operator-interface panels where it scans a small matrix keypad, drives a multiplexed seven-segment display and communicates with a host PLC over UART or RS-485. The 4 MHz core and 1 MIPS throughput comfortably handle 4-digit multiplexed displays at > 100 Hz refresh, eliminating visible flicker. The 2.5-6.25 V supply lets the MCU run from the same 24 V-to-5 V rail as the rest of the panel electronics. For panels that may need firmware updates the PIC16F627-I/SO is the recommended flash-based drop-in replacement in the same 18-SOIC footprint.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621T-04/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621A-04/SO | PIC16LC621AT-04I/SO | PIC16LC621-04/SO | PIC16LC621T-04I/SO | PIC16F627-I/SO | PIC16F628-04/SO |
|---|---|---|---|---|---|---|---|
| Package | 18-SOIC (SO-18) | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Core / Series | 8-bit PIC 16C | 8-bit PIC 16C | 8-bit PIC 16C | 8-bit PIC 16C | 8-bit PIC 16C | 8-bit PIC 16F (flash) | 8-bit PIC 16F (flash) |
| Max Clock Speed | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 20 MHz | 4 MHz grade |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB Flash | 3.5 KB Flash |
| RAM | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 224 bytes | 224 bytes |
| 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 | 2.0 V to 5.5 V | 2.0 V to 5.5 V |
| Memory Type | OTP | OTP | OTP | OTP | OTP | Flash | Flash |
| Temperature Grade | Commercial | Commercial | Industrial (-40C to +85C) | Commercial | Industrial (-40C to +85C) | Industrial (-40C to +85C) | Commercial |
Key Differentiators
- Same-die 'A' silicon revision with internal oscillator calibration (vs PIC16LC621A-04/SO)
- Industrial temperature grade option in the same 18-SOIC footprint (vs PIC16LC621AT-04I/SO)
- Direct flash-based migration path in same footprint (vs PIC16F627-I/SO)
- Lowest unit cost for fixed-code production (vs PIC16F627-I/SO / PIC16F628-04/SO)
Design Notes
Place a 0.1 uF ceramic decoupling capacitor as close as possible to the VDD pin (pin 14) of the PIC16LC621T-04/SO, with a 10 uF bulk capacitor on the supply rail. Although the device draws only a few mA at 4 MHz, OTP programming pulses on MCLR/VPP inject high di/dt transients that can corrupt logic operation if VDD is not well bypassed. For battery-powered designs leverage the SLEEP mode and verify the wake-up timing against the 4 MHz oscillator start-up specification in the Microchip datasheet.
Keep the trace between the crystal (or ceramic resonator) and the OSC1/OSC2 pins (15, 16) under 10 mm and surround them with a ground pour to minimise oscillator pickup of switching noise. The MCLR/VPP pin (pin 4) needs its own 10 kohm pull-up to VDD and a 100 nF cap to ground for in-circuit serial programming (ICSP). Reserve an unpopulated 6-pin ICSP header on prototype boards so OTP locking can be deferred until final firmware sign-off.
Remember that OTP memory on the PIC16LC621T-04/SO can only be programmed once - any code change after lockdown requires a new physical part. Always validate firmware on a flash-based PIC16F627-I/SO development board before committing to OTP programming. Also note that the maximum clock rate (4 MHz) is derated at lower VDD; consult the Fmax-versus-VDD graph in the datasheet to avoid oscillator failure at 3.0 V operation.
Compliance Information
Standard PIC16LC621T-04/SO is commercial temperature grade; for AEC-Q100 qualified automotive designs migrate to the PIC16LC621AT-04I/SO variant. RoHS / lead-free / halogen-free status was not provided in the verified web data and is flagged [DATA_NEEDED] in the specs array.
