PIC16C621-20E/SO - 8-Bit 20MHz OTP MCU 1.75KB | Microchip
MPN: PIC16C621-20E/SO ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.4 | $6.40 |
| 10 | $5.75 | $57.50 |
| 100 | $5.12 | $512.00 |
| 500 | $4.6 | $2,300.00 |
| 1,000 | $4.1 | $4,100.00 |
PIC16C621-20E/SO Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, non-volatile program memory (ROM/EPROM/Flash), volatile data memory (RAM), and peripheral interfaces such as timers, comparators, and I/O ports on a single die. Within the broader hierarchy, the PIC16C621 sits in the legacy PIC16C OTP/EPROM-based family, which evolved into the flash-based PIC16F mid-range lineup. These MCUs are widely used in cost-sensitive, deterministic control applications where interrupt latency, low part count, and predictable instruction cycles outweigh the need for high memory density.
Key features include a wide operating voltage range of 3.0 V to 6.0 V, ultra-low power consumption of 5 mA typical at 5 V/4 MHz and 1 µA typical at 3 V/32 kHz, a fully static design that supports DC operation, and integrated peripherals including a comparator module. The extended ('E') temperature grade allows operation from -40 °C to +125 °C, suitable for automotive and industrial environments.
The device uses a Harvard-architecture RISC core with only 35 single-word instructions, most executing in a single instruction cycle (200 ns at 20 MHz). Its OTP EPROM memory allows one-time field programming via a device programmer such as Microchip's MPLAB PM3, and the SOIC-18 package is compatible with standard surface-mount assembly lines. The wide supply range (3.0-6.0 V) supports both 3.3 V and 5 V system designs.
Typical applications include automotive body and chassis controllers, white-goods and appliance control, low-end consumer electronics, sensor-signal conditioning, and industrial remote-control transmitter/receiver logic. The wide temperature range and rugged SOIC packaging also suit outdoor industrial sensor-interface modules and HVAC control boards.
When designing with this MCU, note that OTP memory cannot be reprogrammed in-circuit; the firmware must be fully validated before programming. For new designs, engineers typically migrate to flash-based PIC16F equivalents (e.g., PIC16F627A) which offer in-system programming, more memory, and lower unit cost.
This page synthesizes distributor pricing, drop-in alternatives from the same PIC16C family, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for PIC16C621-20E/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 PIC16C621-20E/SO (same form factor and footprint) — differing in Operating Temperature Range, Program Memory Size, Program Memory Type, Mounting Type, I/O Pins.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C621A-20E/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621T-20E/SO
✅ Drop-In✓ In Stock
$1.72 / Unit
View Datasheet →PIC16C620-20E/SO
✅ Drop-In✓ In Stock
$3.3 / Unit
View Datasheet →PIC16F627A-20E/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621-20E/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC RISC (Harvard) |
| Family | PIC16C (OTP/EPROM-based) |
| Instruction Set | 35 single-word instructions |
| Maximum CPU Frequency | 20 MHz |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 1.75 KB (1K x 14) |
| RAM Size | 80 bytes |
| I/O Pins | 13 |
| Operating Voltage Range | 3.0 V to 6.0 V |
| Supply Current (5V, 4 MHz) | 5 mA typical |
| Supply Current (3V, 32 kHz) | 1 µA typical |
| Operating Temperature Range | -40 °C to +125 °C (Extended 'E' grade) |
| Package | 18-pin SOIC (SO, 7.5 mm body width) |
| Mounting Type | Surface Mount (Gull-wing leads) |
| Comparators | Yes (integrated analog comparator module) |
| A/D Converter | None |
| RoHS Status | Non-compliant (contains Pb-bearing SOIC finish typical for EOL OTP devices) |
PIC16C621-20E/SO Pin Configuration
| Pin 1 | RA2 — Bidirectional digital I/O port A bit 2 |
| Pin 2 | RA3 — Bidirectional digital I/O port A bit 3 |
| Pin 3 | RA4/T0CKI — Bidirectional digital I/O / Timer 0 clock input |
| Pin 4 | MCLR/VPP — Master clear reset (active low) / Programming voltage input |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Bidirectional digital I/O port B bit 0 / External interrupt input |
| Pin 7 | RB1 — Bidirectional digital I/O port B bit 1 |
| Pin 8 | RB2 — Bidirectional digital I/O port B bit 2 |
| Pin 9 | RB3 — Bidirectional digital I/O port B bit 3 |
| Pin 10 | RB4 — Bidirectional digital I/O port B bit 4 |
| Pin 11 | RB5 — Bidirectional digital I/O port B bit 5 |
| Pin 12 | RB6 — Bidirectional digital I/O port B bit 6 |
| Pin 13 | RB7 — Bidirectional digital I/O port B bit 7 |
| Pin 14 | VDD — Positive supply voltage (3.0 V to 6.0 V) |
| Pin 15 | OSC2/CLKOUT — Oscillator crystal output / Clock output (FOSC/4) |
| Pin 16 | OSC1/CLKIN — Oscillator crystal input / External clock input |
| Pin 17 | RA0 — Bidirectional digital I/O port A bit 0 |
| Pin 18 | RA1 — Bidirectional digital I/O port A bit 1 |
Typical Applications
PIC16C621-20E/SO is suitable for 7 applications: Automotive Body and Chassis Controllers, White-Goods and Appliance Control, Industrial Remote-Control Receivers, Low-End Consumer Electronics, Sensor-Signal Conditioning Modules, HVAC Control Boards, Industrial Timer and Counter Modules.
Automotive Body and Chassis Controllers
The PIC16C621-20E/SO's extended -40 to +125 °C temperature grade, wide 3.0-6.0 V supply, and compact SOIC-18 footprint make it suitable for body and chassis electronic control units. Body controllers handle lighting, wiper, and seat-position logic; the MCU's 1.75 KB OTP fits fixed-function state machines. Compared to flash-based parts, the OTP memory prevents field firmware tampering - critical for safety-critical applications. Pin-to-pin compatible flash options (PIC16F627A) simplify prototyping.
Recommended
White-Goods and Appliance Control
Washing machines, dishwashers, and HVAC appliances rely on legacy 8-bit MCUs like the PIC16C621-20E/SO for motor control loops, sensor reading, and user-interface key scanning. The 35-instruction RISC core and 200 ns instruction cycle deliver deterministic timing for triac-fire and relay-drive logic, while 80 bytes RAM and 13 I/O pins suffice for washing-machine control boards. OTP programming locks firmware against unauthorized modification - a regulatory requirement in many appliance safety standards.
Recommended
Industrial Remote-Control Receivers
Infrared and RF remote-control receivers for industrial cranes, garage-door openers, and security panels use 8-bit MCUs like the PIC16C621-20E/SO for command decoding, rolling-code verification, and relay driver control. The 8-bit core easily handles Manchester or pulse-position-modulated decoding in real time, while the integrated analog comparator can be used for carrier-frequency detection. The extended temperature grade is critical for outdoor or factory-floor equipment.
Recommended
Low-End Consumer Electronics
Toys, electronic timers, and basic consumer gadgets use the PIC16C621-20E/SO for sequence control, LED driving, and simple user interfaces. The 1.75 KB OTP and 13 I/O pins handle typical applications like digital kitchen timers, educational toys, and battery-powered novelty products. Low sleep-mode current (1 µA typical at 3 V/32 kHz) extends battery life in portable gadgets, and the SOIC-18 package supports hand-soldering for prototyping.
Recommended
Sensor-Signal Conditioning Modules
The PIC16C621-20E/SO's integrated analog comparator and 13 digital I/O pins make it a compact front-end for sensor-signal conditioning modules in industrial automation. The comparator can detect threshold crossings from resistive, optical, or Hall-effect sensors, while firmware handles debouncing and relay outputs. The 3.0-6.0 V supply supports both 3.3 V and 5 V sensor interfaces, and the small SOIC-18 footprint allows integration into confined DIN-rail-mount modules.
Recommended
HVAC Control Boards
Heating, ventilation, and air-conditioning thermostats and damper controllers use the PIC16C621-20E/SO for temperature-loop control, valve/damper actuation, and HVAC bus interfacing. The 20 MHz CPU supports PID loop computation and multi-zone scheduling, while the extended temperature grade matches equipment-room thermal environments. OTP memory locks calibration data and prevents field tampering, which is important for energy-rebate compliance programs.
Recommended
Industrial Timer and Counter Modules
Programmable logic controllers (PLCs), interval timers, and event counters use the PIC16C621-20E/SO for time-base generation, event counting, and indicator driving. The 8-bit timer/counter module can be cascaded or fed from an external clock for pulse-counting and frequency-measurement applications. The 5 mA typical supply current at 5 V/4 MHz keeps heat low in enclosed control cabinets, and the SOIC-18 package suits standard DIN-rail-mount PCBs.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621-20E/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621-20E/P | PIC16C621A-20E/SO | PIC16C621T-20E/SO | PIC16C620-20E/SO | PIC16F627A-20E/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 18-pin SOIC (SO) | 18-pin PDIP (P) | 18-pin SOIC (SO) - same | 18-pin SOIC (SO) - same | 18-pin SOIC (SO) - same | 18-pin SOIC (SO) - same |
| Program Memory Type | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | Flash |
| Program Memory Size | 1.75 KB (1K x 14) | 1.75 KB (1K x 14) | 1.75 KB (1K x 14) | 1.75 KB (1K x 14) | 0.75 KB (0.5K x 14) | 1.75 KB (1K x 14) |
| Maximum CPU Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| RAM Size | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 128 bytes |
| I/O Pins | 13 | 13 | 13 | 13 | 13 | 16 |
| Operating Temperature | -40 °C to +125 °C (Extended) | -40 °C to +125 °C (Extended) | -40 °C to +125 °C (Extended) | -40 °C to +125 °C (Extended) | -40 °C to +125 °C (Extended) | -40 °C to +85 °C (Industrial) |
| Lifecycle Status | Obsolete (EOL) | Obsolete (EOL) | Obsolete (EOL) | Obsolete (EOL) | Obsolete (EOL) | Active |
Key Differentiators
- Silicon revision A available in identical SOIC-18 footprint for drop-in upgrade path (vs PIC16C621A-20E/SO)
- Direct same-footprint flash-based upgrade available for new designs (vs PIC16F627A-20E/SO)
- Same SOIC-18 footprint but smaller program memory for cost-reduced designs (vs PIC16C620-20E/SO)
Design Notes
The PIC16C621-20E/SO uses One-Time-Programmable (OTP) EPROM and cannot be erased or rewritten. Always fully validate firmware on a flash-based PIC16F627A equivalent or an emulator (MPLAB ICE) before committing to OTP programming. A single programming error or last-minute code change requires a brand-new chip - both in cost and in field-rework time.
The 5 mA typical active supply current at 5 V/4 MHz is acceptable for line-powered control modules, but consider sleep-mode current (1 µA typical at 3 V/32 kHz) for battery-backed designs. The 32 kHz LP oscillator mode combined with the Watchdog Timer enables event-driven wake-ups; the integrated analog comparator can also wake the CPU from sleep, eliminating a separate external wake-up circuit.
Place a 100 nF ceramic decoupling capacitor as close to the VDD pin (pin 14) as possible, with a ground via adjacent to VSS (pin 5). Add a 10-100 µF bulk capacitor near the regulator input. Use short traces for the OSC1/OSC2 crystal network (pin 15/16) and ground the crystal case to reduce EMI. The MCLR/VPP pin (pin 4) requires a 10 kΩ pull-up to VDD to prevent spurious resets.
The PIC16C621-20E/SO in SOIC-18 has a thermal resistance (θJA) of approximately 85 °C/W typical for SOIC packages. At 5 V/4 MHz active mode with 5 mA supply current, dissipation is 25 mW and self-heating is negligible (≤2 °C rise). In sleep mode with the analog comparator disabled, dissipation drops below 10 µW - well within the extended temperature envelope without special thermal relief.
The PIC16C621's internal analog comparator shares its input pins with port-A digital I/O, so use TRISA to disable digital output drivers on comparator-input pins to prevent digital-crosstalk into the analog path. Add a small RC filter (10 kΩ + 100 pF) on each comparator input to attenuate switching noise from adjacent digital lines. Reference voltage for the comparator can be derived from an external reference or from the internal bandgap.
Compliance Information
PIC16C621 OTP family pre-dates widespread RoHS mandates; SOIC-18 variants typically use Pb-bearing solder finish. AEC-Q100 not formally qualified, but Extended temperature grade (-40 to +125 °C) supports automotive environments. REACH and halogen-free status not confirmed for this specific lot - request manufacturer material declaration for production builds.
