PIC16C621A-20I/SO - 8-bit OTP MCU 1.75KB EPROM 20MHz | Microchip
MPN: PIC16C621A-20I/SO ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.2 | $4.20 |
| 10 | $3.78 | $37.80 |
| 100 | $3.36 | $336.00 |
| 500 | $2.97 | $1,485.00 |
| 1,000 | $2.65 | $2,650.00 |
PIC16C621A-20I/SO Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, working RAM, and peripherals such as timers, comparators, and I/O. The PIC16C621A belongs to the PIC16C family of OTP microcontrollers, which sit in the hierarchy of microcontrollers > 8-bit MCUs > PIC16C family > PIC16C62X sub-family > CMOS OTP-based RISC microcontrollers. OTP devices are programmed once and retain code for the life of the part, which is a cost-optimized choice for high-volume, stable-firmware products.
Key features include 1.75KB EPROM program memory, 96 bytes of static RAM, two on-chip analog comparators with programmable reference, a watchdog timer, power-on reset, brown-out reset, and 13 bidirectional I/O pins with individual direction control. The Harvard RISC architecture separates program and data buses, allowing simultaneous instruction fetch and operand access for predictable cycle-time behavior. The 8-bit core, 14-bit instruction word, and 35-instruction set simplify code generation in MPLAB and the legacy PIC assembler toolchains.
Typical applications span industrial control logic, appliance controllers, sensor signal conditioning front-ends, low-cost remote controls, security keypads, simple user-interface boards, and replacement of 555-timer glue logic with programmable timing sequences. For designers choosing between this part and its flash-based PIC16F or PIC16C cousins, the trade-off is one-time programmability versus in-system reprogrammability; the PIC16C621A is preferred where code stability, lower unit cost, and code-protection via OTP are acceptable.
Drop-in alternatives for PIC16C621A-20I/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 PIC16C621A-20I/SO (same form factor and footprint) — differing in Package, Core Architecture, Program Memory Size, Analog Comparators, Watchdog Timer.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C621A-20I/SO
✅ Drop-In✓ In Stock
$2.65 / Unit
View Datasheet →PIC16C621A-20I/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C620A-20I/SO
✅ Drop-In✓ In Stock
$1.31 / Unit
View Datasheet →PIC16C621-20I/P
✅ Drop-In✓ In Stock
$3.05 / Unit
View Datasheet →PIC16C620A-20I/SS
✅ Drop-In✓ In Stock
$2.15 / Unit
View Datasheet →PIC16C621A-20E/SS
✅ Drop-In✓ In Stock
$4.12 / Unit
View Datasheet →PIC16C621A-20I/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 8-bit RISC (Harvard) |
| Program Memory Size | 1.75 KB (1K x 14) OTP EPROM |
| RAM Size | 96 bytes |
| Data EEPROM | 0 bytes (none on this die) |
| Number of I/O Pins | 13 |
| Maximum Clock Frequency | 20 MHz |
| Instruction Execution Time | 100 ns (at 20 MHz) |
| Instruction Set Size | 35 single-word instructions |
| Operating Voltage Range | 2.5 V to 5.5 V |
| Analog Comparators | 2 (on-chip) |
| ADC | None (0 channels, 0-bit resolution) |
| Communication Interfaces | None (no UART, SPI, or I2C) |
| PWM Channels | 0 (none) |
| Package | 18-pin SOIC (SO), 0.295 inch / 7.50 mm width |
| Operating Temperature Range (Industrial) | -40 C to +85 C |
| Mounting Type | Surface Mount |
PIC16C621A-20I/SO Pin Configuration
| Pin 1 | RA2 — I/O pin / analog comparator output |
| Pin 2 | RA3 — I/O pin / comparator reference input |
| Pin 3 | RA4 — I/O pin / Timer0 clock input |
| Pin 4 | MCLR — Master clear reset input (active low) |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0 — I/O pin / interrupt-on-change |
| Pin 7 | RB1 — I/O pin / interrupt-on-change |
| Pin 8 | RB2 — I/O pin / interrupt-on-change |
| Pin 9 | RB3 — I/O pin / interrupt-on-change / low-voltage programming |
| Pin 10 | RB4 — I/O pin / interrupt-on-change |
| Pin 11 | RB5 — I/O pin / interrupt-on-change |
| Pin 12 | RB6 — I/O pin / interrupt-on-change / serial programming clock |
| Pin 13 | RB7 — I/O pin / interrupt-on-change / serial programming data |
| Pin 14 | VDD — Positive supply voltage (2.5 V to 5.5 V) |
| Pin 15 | OSC2 — Oscillator output / RC clock output |
| Pin 16 | OSC1 — Oscillator input / external clock input |
| Pin 17 | RA0 — I/O pin / analog comparator input 1 |
| Pin 18 | RA1 — I/O pin / analog comparator input 2 |
Typical Applications
PIC16C621A-20I/SO is suitable for 6 applications: Industrial Control Logic Replacement, Appliance User Interface Controller, Sensor Threshold Detector Front-End, Security Keypad and Access Controller, Remote Control and IR Transmitter, Low-Cost Display and Indicator Driver.
Industrial Control Logic Replacement
The PIC16C621A-20I/SO replaces discrete 555-timer and CMOS-logic glue circuits in industrial controllers, where its 20 MHz core executes deterministic 100 ns instructions and its two on-chip analog comparators handle threshold sensing. The 13 I/O pins drive relays, opto-isolators, and indicator LEDs directly via 25 mA sink capability on selected pins. Industrial temperature grade -40 C to +85 C ensures operation in factory-floor cabinets. Housed in 18-pin SOIC, it drops onto existing control boards using the same footprint.
Recommended
Appliance User Interface Controller
White-goods appliances such as washing machines, dishwashers, and microwave ovens use the PIC16C621A-20I/SO to scan keypads, drive seven-segment displays, and sequence motor-control relays. The 35-instruction RISC set keeps the firmware footprint under 1.75 KB, while the 96 bytes of RAM buffer key-debounce state and timer variables. Two analog comparators monitor line-voltage zero-cross events for synchronous triac drive. The 18-SOIC package and 2.5 V to 5.5 V supply match 5 V appliance rails directly.
Recommended
Sensor Threshold Detector Front-End
The PIC16C621A-20I/SO serves as a low-cost sensor front-end, with its two on-chip analog comparators providing window-comparison or single-threshold detection for thermistors, photodiodes, or pressure transducers. The 13 I/O lines drive status LEDs and a 1-Wire or I/O-bit-banged interface to a host MCU. Operating from 2.5 V to 5.5 V, the part can be battery-powered or share a sensor-bridge supply. Industrial temperature rating supports outdoor and HVAC deployments in the same 18-SOIC footprint.
Recommended
Security Keypad and Access Controller
Access-control keypads and alarm panels use the PIC16C621A-20I/SO to scan 4x4 matrix keypads via 13 I/O pins, debounce entries in 96 bytes of RAM, and drive a relay or buzzer output. The OTP program memory holds the access-code table and lockout logic immutably, preventing firmware tampering. The two comparators monitor backup-battery voltage and tamper switches. Wide 2.5 V to 5.5 V supply lets the same board run from 5 V wall adapter or 3.3 V battery backup in an 18-pin SOIC.
Recommended
Remote Control and IR Transmitter
Battery-powered remote controls use the PIC16C621A-20I/SO to read button matrices, encode IR protocols via software bit-banging on a single I/O pin, and enter sleep mode between button events for long battery life. The 100 ns instruction execution at 20 MHz gives precise 38 kHz carrier timing for consumer IR standards. Industrial temperature grade suits automotive-garage and outdoor-environment remotes. Small 18-SOIC footprint fits slim handset enclosures with 2.5 V to 5.5 V battery compatibility.
Recommended
Low-Cost Display and Indicator Driver
The PIC16C621A-20I/SO drives multiplexed LED or seven-segment displays by sequencing digit-select lines and segment data through its 13 I/O pins. The 35-instruction RISC set supports software-PWM brightness control and blinking patterns without external driver ICs. Two comparators can monitor supply current or temperature for fault indication. The 2.5 V to 5.5 V supply matches 3.3 V or 5 V LED rails, and 18-SOIC surface-mount packaging supports high-volume automated assembly in price-sensitive signage.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621A-20I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621A-20I/P | PIC16C620A-20I/SO | PIC16C621-20I/P | PIC16C620A-20I/SS | PIC16C621A-20E/SS |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 18-SOIC (SO) | 18-DIP (P) - different footprint | 18-SOIC (SO) - same | 18-DIP (P) - different footprint | 18-SSOP (SS) - different footprint | 18-SSOP (SS) - different footprint |
| Program Memory | 1.75 KB OTP EPROM | 1.75 KB OTP EPROM | 1.75 KB OTP EPROM | 1.75 KB OTP EPROM | 1.75 KB OTP EPROM | 1.75 KB OTP EPROM |
| RAM Size | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 96 bytes |
| Analog Comparators | 2 | 2 | 0 | 2 | 0 | 2 |
| Max Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| Operating Voltage | 2.5 V to 5.5 V | 2.5 V to 5.5 V | 2.5 V to 5.5 V | 2.5 V to 5.5 V | 2.5 V to 5.5 V | 2.5 V to 5.5 V |
| Temperature Grade | Industrial (-40 C to +85 C) | Industrial | Industrial | Industrial | Industrial | Extended |
| Lifecycle Status | NRND | NRND | NRND | NRND | NRND | NRND |
Key Differentiators
- Two on-chip analog comparators vs none on PIC16C620A (vs PIC16C620A-20I/SO)
- A-silicon revision with improved brown-out and lower ICC (vs PIC16C621-20I/P)
- Industrial temperature grade vs commercial (vs PIC16C621A-20/SO)
Design Notes
Estimated: at 20 MHz and 5 V supply with all 13 I/O pins driving 5 mA loads, the PIC16C621A-20I/SO draws approximately 15 mA active and below 1 uA in sleep. Decouple VDD with a 100 nF ceramic capacitor placed within 5 mm of pin 14, plus a bulk 10 uF tantalum or aluminum cap if the supply is shared with relay coils. The MCLR pin (pin 4) requires a 10 kohm pull-up to VDD for normal operation; add a 100 nF cap from MCLR to VSS to filter noise.
Keep the 18-SOIC land pattern 7.50 mm body width with 1.27 mm pitch per JEDEC SO-018. Route the oscillator traces (OSC1/OSC2) short and surround with a ground guard ring to reduce EMI pickup. Place the decoupling cap on VDD (pin 14) within one trace-width of the pin, and keep the MCLR pull-up close to pin 4. If using a crystal, place load capacitors within 3 mm of OSC1 and OSC2 to minimize parasitic loop inductance.
Do not assume in-system programmability - PIC16C621A uses OTP EPROM and requires a high-voltage (typically 13 V) parallel programmer. Code-protect fuses cannot be un-set once programmed. The two comparators share pins with general I/O, so configuring them for analog disables digital reads on those pins. Brown-out reset and watchdog timer must be enabled in configuration words before firmware writes; if omitted, the MCU may hang on power-up glitches or runaway code.
Estimated: at 20 MHz, 5 V VDD, and 15 mA active ICC, the device dissipates roughly 75 mW. The 18-SOIC package has theta_JA of approximately 70 C/W in still air, giving a junction rise of about 5 C above ambient, well inside the 85 C industrial ceiling. For high-I/O-count designs with all outputs toggling at full 25 mA, total dissipation may reach 250 mW; in that case increase PCB copper area or use the 18-DIP package for better thermal conduction.
Compliance Information
RoHS, REACH, halogen-free, and conflict-mineral status not present in the verified web data and marked unknown. Lead-free is assumed yes per Microchip's standard OTP product line. AEC-Q100 not applicable for industrial-grade non-automotive MCU.
