PIC16C621-20I/P - 8-Bit OTP MCU 1.75KB 20MHz 18-DIP | Microchip
MPN: PIC16C621-20I/P ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.7536 | $4.75 |
| 10 | $4.28 | $42.80 |
| 100 | $3.82 | $382.00 |
| 500 | $3.42 | $1,710.00 |
| 1,000 | $3.05 | $3,050.00 |
PIC16C621-20I/P Overview
A PIC16C-series microcontroller is an 8-bit RISC Harvard-architecture MCU built on Microchip's OTP EPROM/ROM CMOS process. Within the broader taxonomy, it sits at the bottom of the PIC12/PIC16/PIC18 hierarchy, designed for cost-sensitive embedded control tasks that need more I/O than a PIC12 can offer but do not require the peripheral richness of a PIC18. Compared with PIC16F flash variants, the PIC16C OTP line is intended for mature, stable production designs where firmware is finalized and code-protection is desirable.
Key features of this part include a wide 2.5V to 6.0V operating voltage range, fully static design (clock from DC up to 20 MHz), 15 uA typical current at 5V/4 MHz and 1 uA typical at 3V/32 kHz for low-power sleep operation, an external oscillator interface, and 13 bidirectional digital I/O pins with programmable direction. Industrial temperature grade (-40C to +85C) makes it suitable for harsh-environment deployments.
The PIC16C621 uses a 14-bit instruction word with a RISC-like instruction set optimized for compact code density and deterministic interrupt response. Peripherals on this die include a core timer/counter, watchdog timer, and brown-out reset depending on silicon revision. The 20 MHz top speed at 5V gives 5 MIPS of throughput, which is sufficient for simple control loops, user-interface scanning, and protocol bridging.
Typical applications for the PIC16C621-20I/P include consumer appliance control, security and access-control panels, lighting controllers, low-end sensor signal-conditioning front ends, and replacement designs for legacy through-hole PIC16C production lines. Its 18-DIP footprint and industrial temperature grade specifically suit through-hole industrial boards and retrofit designs.
A key design consideration for OTP PIC16C parts is that firmware can only be programmed once and cannot be updated in-circuit. Designers should finalize firmware revision before committing to the C-series, or move to the PIC16F flash equivalent (e.g. PIC16F684-I/P) if field-upgrade capability is mandatory. The 18-DIP footprint remains compatible with PIC16F684-I/P, easing migration when OTP stock is exhausted.
This page synthesizes distributor pricing, drop-in alternatives, application guidance, and practical design notes that are not bundled in the manufacturer datasheet, helping engineers select, source, and design with the PIC16C621-20I/P efficiently.
Drop-in alternatives for PIC16C621-20I/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 PIC16C621-20I/P (same form factor and footprint) — differing in Program Memory Type, Watchdog Timer, RAM Size, Core Architecture, Instruction Set Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C621A-20I/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621-20/P
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →PIC16C621-04I/P
✅ Drop-In✓ In Stock
$1.38 / Unit
View Datasheet →PIC16C621-20E/SS
✅ Drop-In✓ In Stock
$2.45 / Unit
View Datasheet →PIC16C620A-20I/P
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →PIC16F684-I/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16F628A-I/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621-20I/P Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit RISC (PIC16C family, 14-bit instruction word) |
| Program Memory Type | OTP EPROM (One-Time-Programmable) |
| Program Memory Size | 1.75 KB (1K x 14) |
| RAM Size | 80 bytes (80 x 8) |
| EEPROM | None |
| Maximum CPU Frequency | 20 MHz |
| Operating Voltage Range | 2.5 V to 6.0 V |
| Number of I/O Pins | 13 |
| Number of Timers | 1 (TMR0) |
| Oscillator Type | External |
| Brown-out Reset | Yes |
| Watchdog Timer | Yes |
| Package | 18-DIP (0.300 inch / 7.62 mm pitch) |
| Mounting Type | Through-Hole |
| Operating Temperature Range | -40 C to +85 C (Industrial grade) |
| Typical Current at 5V/4 MHz | 15 uA |
| Typical Current at 3V/32 kHz | 1 uA |
| Pin Count | 18 |
| Packaging | Tube |
| Lead Free / RoHS | Lead-free process, RoHS status per lot - verify with distributor |
PIC16C621-20I/P Pin Configuration
| Pin 1 | MCLR/Vpp — Master clear reset (active low) / programming voltage input |
| Pin 2 | RA0/AN0 — Port A bit 0 / analog comparator input 0 |
| Pin 3 | RA1/AN1 — Port A bit 1 / analog comparator input 1 |
| Pin 4 | RA2/AN2 — Port A bit 2 / analog comparator output |
| Pin 5 | RA3/AN3 — Port A bit 3 / analog comparator input 3 |
| Pin 6 | RA4/T0CKI — Port A bit 4 / Timer0 clock input (open-drain output) |
| Pin 7 | RB0/INT — Port B bit 0 / external interrupt input |
| Pin 8 | RB1 — Port B bit 1 |
| Pin 9 | RB2 — Port B bit 2 |
| Pin 10 | RB3 — Port B bit 3 |
| Pin 11 | RB4 — Port B bit 4 |
| Pin 12 | RB5 — Port B bit 5 |
| Pin 13 | RB6 — Port B bit 6 |
| Pin 14 | RB7 — Port B bit 7 |
| Pin 15 | Vss — Ground |
| Pin 16 | VDD — Positive supply voltage (2.5V to 6.0V) |
| Pin 17 | OSC2/CLKOUT — Oscillator output / clock output |
| Pin 18 | OSC1/CLKIN — Oscillator input / external clock input |
Typical Applications
PIC16C621-20I/P is suitable for 6 applications: Security and Access Control Panels, Consumer Appliance Control Boards, Lighting Controllers and Dimmers, Sensor Signal-Conditioning Front Ends, Automotive Aftermarket Electronics, Industrial Control and Legacy Replacement.
Security and Access Control Panels
The PIC16C621-20I/P suits keypad entry controllers, magnetic-card readers, and PIR sensor interfaces thanks to its 13 I/O lines that directly scan 4x4 matrices, drive relay coils, and read digital sensors without external logic. With 1.75KB OTP it can host the full keypad-decode, debounce, and lock-actuation state machine while the 20MHz clock gives 5MIPS of deterministic interrupt response. Industrial temperature grade (-40C to +85C) survives unheated vestibules and outdoor junction boxes. Estimated: with code size typically 700-1200 instructions, the 1024-word OTP has 10-30% headroom for protocol additions like Wiegand output or EEPROM emulation on the I/O pins.
Recommended
Consumer Appliance Control Boards
The PIC16C621-20I/P drives washing-machine control boards, microwave keypads, dishwasher user interfaces, and HVAC zone controllers because its 13 I/O can directly multiplex 7-segment displays and triac-fire outputs while the 20MHz clock services zero-crossing interrupts in real time. The 80-byte RAM holds running timers, mode flags, and button-debounce counters without overflow. Its industrial temperature grade tolerates the heat soak inside an appliance chassis. The PIC16C6x instruction set is optimized for bit-banging, so a single I/O line can generate the precise pulse trains needed for IR remote, triac phase-angle control, or tone generation.
Recommended
Lighting Controllers and Dimmers
The PIC16C621-20I/P is well-suited to DMX512 lighting fixtures, architectural dimmer packs, and LED driver controllers because its 13 I/O can decode a single DMX universe (8 channels per port) and drive 0-10V analog outputs via PWM-filtered I/O. The 20MHz clock performs accurate phase-angle triac dimming at 50/60Hz with sub-microsecond jitter. The comparator input can monitor zero-crossing directly for synchronous triac firing. The 80-byte RAM keeps running scene states for 8-16 lighting zones without external storage. Industrial temperature grade handles ceiling-fixture heat-rise during continuous LED driver operation.
Recommended
Sensor Signal-Conditioning Front Ends
The PIC16C621-20I/P serves as a smart sensor front-end for thermocouples, RTDs, thermistors, and 4-20mA loops where the on-chip comparator and 13 I/O can digitize analog signals via slope/dual-slope conversion before serializing data on an I/O pin. The 20MHz clock converts analog readings at >1kHz rates while maintaining 14-bit effective resolution through oversampling. The wide 2.5-6.0V supply range accepts 3.3V or 5V sensor rails directly. Estimated: a typical RTD signal chain running 10 conversions per second consumes under 1mA active and 5uA standby, well within the PIC16C621 power budget.
Recommended
Automotive Aftermarket Electronics
The PIC16C621-20I/P is used in aftermarket automotive modules such as alarm systems, remote-start controllers, and gauge-cluster retrofits because its industrial -40C to +85C temperature range covers under-dash environments and its 13 I/O drive relay drivers, LED indicators, and ignition-switch inputs. The 20MHz instruction cycle services debounced switch inputs in real time. The OTP memory prevents field-tampering of alarm codes. Where AEC-Q100 automotive qualification is required, designers should migrate to PIC16F684-I/P or PIC16F628A-I/P since the C-series is not AEC-Q qualified despite its industrial temperature grade.
Recommended
Industrial Control and Legacy Replacement
The PIC16C621-20I/P is used to maintain legacy industrial controllers, PLC I/O modules, and SCADA remote-terminal units (RTUs) that were originally designed around the PIC16C6x family and where firmware is locked-in OTP for tamper resistance. Its 13 I/O can replace discontinued discrete-logic glue, its 20MHz clock handles Modbus RTU frame timing, and its 18-DIP through-hole form factor is repairable in the field with standard sockets. Industrial temperature grade matches factory-floor and outdoor-cabinet conditions. Replacement and migration to PIC16F628A-I/P or PIC16F684-I/P is recommended for new designs.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621-20I/P — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621A-20I/P | PIC16C621-20/P | PIC16C621-04I/P | PIC16F684-I/P | PIC16F628A-I/P |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 18-DIP | 18-DIP - same | 18-DIP - same | 18-DIP - same | 18-DIP - same | 18-DIP - same |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 2 KB Flash | 3.5 KB Flash |
| RAM | 80 B | 80 B | 80 B | 80 B | 256 B | 224 B |
| I/O Pins | 13 | 13 | 13 | 13 | 12 | 16 |
| Max Clock | 20 MHz | 20 MHz | 20 MHz | 4 MHz | 20 MHz | 20 MHz |
| Program Type | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | Flash | Flash |
| Temperature Grade | Industrial -40C to +85C | Industrial -40C to +85C | Commercial 0C to +70C | Industrial -40C to +85C | Industrial -40C to +85C | Industrial -40C to +85C |
Key Differentiators
- Pin-compatible silicon-updated alternative available (vs PIC16C621A-20I/P)
- Flash migration target available in same footprint (vs PIC16F684-I/P)
- Industrial temperature range and 20MHz throughput (vs PIC16C621-04I/P)
Design Notes
PIC16C621-20I/P uses One-Time-Programmable EPROM - firmware cannot be erased or rewritten after programming. Verify firmware revision and timing margins exhaustively before committing to OTP. For field-updatable designs, migrate to PIC16F684-I/P or PIC16F628A-I/P. Estimated: design cycle should include at least 3 firmware-rebuild rounds on a windowed/UV-erasable PIC16C621JW before locking the OTP mask.
Power the PIC16C621-20I/P from a regulated 5.0V +/- 5% supply. Brown-out reset is enabled in the configuration word by default; configure BOR voltage threshold below Vdd_min to avoid unintended reset. Decoupling: place a 100 nF ceramic between Vdd (pin 16) and Vss (pin 15) within 5 mm of the pins. For low-power sleep applications, gate the external oscillator off via a load-switch since current draw drops to ~1 uA at 32 kHz.
MCLR (pin 1) requires a 10 kohm pull-up to Vdd and a 100 nF cap-to-ground for noise immunity - directly tying MCLR to Vdd risks spurious resets from EMI. Route the external oscillator traces (OSC1/OSC2, pins 17/18) short and adjacent to ground; place the crystal or resonator within 10 mm of the pins. Keep high-current switching traces (relay coils, triacs) at least 25 mm away from the OSC traces to avoid clock jitter.
The PIC16C621-20I/P is not 5V-tolerant on I/O when powered at 3.3V - driving a 5V input into a 3.3V-powered PIC will forward-bias the ESD clamp and may damage the device. For 5V-tolerant I/O at 3.3V supply, migrate to PIC16F684-I/P which has Schmitt-trigger inputs with input-clamp diodes. For comparator inputs AN0/AN1 (pins 2/3), add a 100 ohm series resistor to limit input current during fault conditions.
