PIC16C621A-20/SO - 8-Bit 20MHz OTP MCU 1.75KB | Microchip
MPN: PIC16C621A-20/SO ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.83 | $1.83 |
| 10 | $1.65 | $16.50 |
| 100 | $1.45 | $145.00 |
| 500 | $1.28 | $640.00 |
| 1,000 | $1.1 | $1,100.00 |
PIC16C621A-20/SO Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, RAM, and peripheral interfaces such as timers, comparators, and I/O ports. The PIC16C621A sits in the PIC16C family of OTP-based mid-range microcontrollers, a category below flash-based PIC16F parts in reprogrammability but above baseline PIC10/12/16 devices in peripheral integration. OTP means the program memory is written once and is not erasable, making the part suited to production-run embedded control where firmware is finalized before manufacture.
Key features include a 14-bit instruction word, 35 single-word instructions, 100 ns instruction execution at 20 MHz, two analog comparators with programmable reference, a Watchdog Timer with its own on-chip RC oscillator, and brown-out reset support. The device operates from 2.5V to 6.0V across commercial 0C to +70C temperature range, drawing low operating current suitable for battery-influenced designs. Internal oscillator and power-on reset circuitry minimize external component count.
Architecturally, the PIC16C621A separates program and data memory (Harvard architecture), allowing simultaneous instruction fetch and data access for deterministic throughput. The RISC-style core achieves 200 ns instruction cycles at 20 MHz oscillator (one instruction cycle per four oscillator clocks), enabling responsive control loops in motor, power, and sensor applications without DSP-class complexity.
Typical applications include appliance control, sensor signal conditioning, low-cost motor drivers, security alarm panels, and small consumer electronics. The integrated comparators make it well suited to threshold detection and battery monitoring. The PIC16C621A-20/SO is the surface-mount SOIC-18 variant of the family for commercial-temperature applications.
When designing with this device, account for OTP programming: firmware must be fully verified before production programming, since OTP cannot be re-written. Use the MCLR, WDT, and POR features together for reliable reset behavior in noisy industrial environments.
This page synthesizes distributor pricing, drop-in package equivalents, and design considerations not found on a single manufacturer or distributor datasheet page, giving procurement and engineering teams a single reference for evaluating the PIC16C621A-20/SO.
Drop-in alternatives for PIC16C621A-20/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-20/SO (same form factor and footprint) — differing in Package, Program Memory Size, Core Architecture, RAM Size, Program Memory Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C621A-20I/SO
✅ Drop-In✓ In Stock
$2.65 / Unit
View Datasheet →PIC16C621A-20E/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C620A-20/SO
✅ Drop-In✓ In Stock
$2.04 / Unit
View Datasheet →PIC16C620A-20I/SO
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$1.31 / Unit
View Datasheet →PIC16F628A-20/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621-20I/P
✅ Drop-In✓ In Stock
$3.05 / Unit
View Datasheet →PIC16C621A-20/SO Maximum Ratings & Electrical Characteristics
| Product Family | PIC 16C Microcontroller |
| Core | 8-bit PIC16C RISC |
| Maximum Clock Frequency | 20 MHz |
| Program Memory Size | 1.75 KB (1K x 14) OTP |
| RAM Size | 96 bytes |
| Data EEPROM | Not present (OTP family) |
| I/O Pins | 13 |
| Instruction Set | 35 single-word instructions, 14-bit |
| Instruction Cycle | 200 ns at 20 MHz |
| Supply Voltage | 2.5 V to 6.0 V |
| Operating Temperature | 0 C to +70 C (Commercial) |
| Package | SOIC-18 (208 mil) |
| Mounting Type | Surface Mount |
| Comparators | 2 on-chip analog comparators |
| Watchdog Timer | Yes, with dedicated RC oscillator |
| Brown-out Reset | Yes |
| Power-on Reset | Yes |
PIC16C621A-20/SO Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O port A bit 2 / AN2 / VREF- |
| Pin 2 | RA3 — Bidirectional I/O port A bit 3 / AN3 / VREF+ |
| Pin 3 | RA4/T0CKI — Bidirectional I/O port A bit 4 / Timer0 clock input |
| Pin 4 | RA5 — Bidirectional I/O port A bit 5 |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Bidirectional I/O port B bit 0 / external interrupt |
| 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 — Bidirectional I/O port B bit 6 |
| Pin 13 | RB7 — Bidirectional I/O port B bit 7 |
| Pin 14 | VDD — Positive supply voltage |
| Pin 15 | OSC2/CLKOUT — Oscillator output / clock out |
| Pin 16 | OSC1/CLKIN — Oscillator input / external clock |
| Pin 17 | RA0/AN0 — Bidirectional I/O port A bit 0 / analog input 0 |
| Pin 18 | RA1/AN1 — Bidirectional I/O port A bit 1 / analog input 1 |
Typical Applications
PIC16C621A-20/SO is suitable for 7 applications: Appliance Control Boards, Security Alarm Panels, Low-Cost Motor Drivers, Battery-Powered Sensor Nodes, Automotive Aftermarket Accessories, Consumer Remote Controls, Power Supply Monitoring Modules.
Appliance Control Boards
The PIC16C621A-20/SO's 1.75 KB OTP program memory, 96 bytes RAM, and 13 I/O pins make it well suited to fixed-function appliance controls such as washing-machine timers, microwave keypads, and HVAC damper drivers. Its two on-chip analog comparators enable direct sensing of temperature thermistors or current-shunt thresholds without external op-amps, reducing BOM cost. The 20 MHz instruction rate provides 200 ns cycle time, sufficient for real-time motor-control PWM loops. Engineers should account for OTP one-time programming: firmware must be fully validated before production runs because OTP cells cannot be re-written. Brown-out reset and watchdog timer with dedicated RC oscillator protect against brown-outs and software lockups in line-powered appliance environments where mains transients are common.
Recommended
Security Alarm Panels
Security alarm panels require a deterministic, low-power MCU to scan multiple zones, drive piezo sirens, and read keypad matrices. The PIC16C621A-20/SO's 13 I/O lines can scan a 4x4 keypad matrix and read 8-12 zone inputs without external mux logic. Its 96-byte RAM accommodates a small event buffer and the 1.75 KB OTP holds the alarm state machine. Two integrated comparators enable direct interface to PIR motion sensors and glass-break transducers producing analog envelopes. Operating voltage from 2.5V to 6.0V supports both 5V logic and 3.3V battery backup. The brown-out reset ensures clean recovery from backup-battery sag. For new designs, migrate to PIC16F628A for in-circuit firmware updates that field-installers need for code-revision changes.
Recommended
Low-Cost Motor Drivers
Small brushed DC and unipolar stepper motor drivers in consumer products rely on an MCU that can output PWM signals, read Hall-effect sensors, and time commutation events. The PIC16C621A-20/SO's 20 MHz clock generates PWM at 8-bit resolution with sub-microsecond edge accuracy, and its comparators handle Hall-sensor threshold detection directly. The 13 I/O lines drive direction and enable signals for a single H-bridge plus auxiliary indicator LEDs. OTP memory locks the motor-control algorithm into production silicon, preventing end-user firmware modification that could damage the motor. Industrial users should specify the PIC16C621A-20I/SO variant for -40C to +85C operation in automotive or outdoor applications. Pair with a TLP521 optocoupler or HIP4081 driver for mains-isolated designs.
Recommended
Battery-Powered Sensor Nodes
Distributed sensor monitoring in industrial plants and remote telemetry uses low-cost MCUs to digitize analog inputs and forward data over a serial link. The PIC16C621A-20/SO consumes minimal operating current and supports sleep modes suitable for battery-influenced deployments. Its two comparators can directly sense battery voltage divider for low-battery warning without an ADC. The 96-byte RAM is sufficient for small data buffers and the 1.75 KB OTP hosts sensor-linearization tables and protocol handlers. Operating voltage from 2.5V to 6.0V accepts 3.3V and 5V battery stacks. For solar-powered nodes, the watchdog timer with internal RC oscillator allows long sleep intervals between measurements. When migrating to flash-based designs, the PIC16F628A-20/SO offers the same pinout plus a hardware USART for serial telemetry.
Recommended
Automotive Aftermarket Accessories
Aftermarket automotive accessories such as alarm add-ons, lighting controllers, and auxiliary gauge drivers benefit from the PIC16C621A-20/SO's industrial-temperature sibling, the PIC16C621A-20I/SO. That variant operates from -40C to +85C, tolerating under-hood and dashboard thermal extremes. The 13 I/O pins read switches and drive relays or MOSFET gates for lighting control. Built-in comparators monitor battery voltage via a divider for under-voltage cutoff. Brown-out reset and watchdog timer provide robustness against cranking transients and load-dump events. While not AEC-Q100 qualified, the industrial-grade device is widely used in non-safety automotive accessories. Designers of new products should evaluate AEC-Q100 qualified PIC18F alternatives for safety-relevant functions.
Recommended
Consumer Remote Controls
Universal remote controls and IR-RF transmitters require a small MCU with low standby current and sufficient I/O for key matrix scanning. The PIC16C621A-20/SO's 13 I/O pins scan a 4x4 or 5x3 key matrix and drive an IR LED through a single transistor. OTP memory locks the protocol stack so the manufacturer controls the firmware after production. Sleep current in the microamp range extends battery life across years of typical use. The two on-chip comparators handle end-of-battery detection via a divider tied to VDD. Operating voltage 2.5V to 6.0V supports 3V coin-cell and 4.5V alkaline battery packs. For designs requiring field firmware updates, the flash-based PIC16F628A-20/SO provides identical pinout and adds USART for in-system programming.
Recommended
Power Supply Monitoring Modules
Standalone PSU monitor modules in telecom, industrial, and server applications sense voltage rails, current, and temperature and report status via LEDs or relays. The PIC16C621A-20/SO's two analog comparators directly interface to a current-shunt amplifier and a temperature thermistor, providing under-voltage, over-current, and over-temperature trip points without external ADC. The 13 I/O pins drive status LEDs and a fault relay, while 96-byte RAM buffers recent fault events. Brown-out reset ensures clean restart after a power glitch. Operating voltage 2.5V to 6.0V supports both 3.3V and 5V logic. For new designs requiring firmware flexibility for different trip thresholds, the flash-based PIC16F628A-20/SO is the recommended migration with the same SOIC-18 footprint.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621A-20/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621A-20I/SO | PIC16C621A-20E/SO | PIC16C620A-20/SO | PIC16C620A-20I/SO | PIC16F628A-20/SO |
|---|---|---|---|---|---|---|
| Package | SOIC-18 | SOIC-18 | SOIC-18 | SOIC-18 | SOIC-18 | SOIC-18 |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 3.5 KB Flash |
| RAM Size | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 128 bytes |
| Analog Comparators | 2 | 2 | 2 | 0 | 0 | 2 |
| Operating Temperature | 0C to +70C | -40C to +85C | -40C to +125C | 0C to +70C | -40C to +85C | -40C to +85C |
| Max Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Active |
Key Differentiators
- On-chip dual analog comparators with programmable voltage reference (vs PIC16C620A-20/SO)
- Flash-based migration path with identical SOIC-18 footprint (vs PIC16C620A-04/SO)
- Wide 2.5V to 6.0V supply supports both 3.3V and 5V designs (vs PIC16C55-XT/SO)
Design Notes
The PIC16C621A uses One-Time-Programmable (OTP) memory, which cannot be erased or rewritten. Estimated: every firmware revision requires a new blank device, so production programmers should be configured with batch serialization. Validate firmware on a windowed ceramic (JW) sample or a flash-based development board (PIC16F628A) before committing to OTP volume. Skipping this step risks scrapping fully assembled boards if a bug is found in the field.
Place a 0.1 uF decoupling capacitor as close as possible to the VDD pin (pin 14) and a 10 uF bulk capacitor on the same supply trace. The PIC16C621A's analog comparators draw brief current spikes during switching, and an under-decoupled supply can cause the brown-out reset to mis-trigger. For battery-influenced designs, pair the MCU with a low-quiescent LDO such as the MCP1700 to extend sleep-mode battery life. Estimated: typical operating current at 5V, 20 MHz is approximately 5-10 mA, falling to microamps in sleep mode.
Route the OSC1/OSC2 oscillator traces short and symmetric, with the crystal or resonator placed within 5 mm of the MCU to minimize parasitic capacitance. Estimated: at 20 MHz, each millimeter of trace adds roughly 1-2 pF of stray capacitance, which can detune the oscillator or cause start-up failure at cold temperatures. Use a ground guard ring around the oscillator area and avoid routing signal traces beneath the crystal to prevent crosstalk. For EMI-sensitive applications, add a 4.7 k-ohm feedback resistor across OSC1/OSC2 to bias the inverter into its linear region.
The PIC16C621A's analog comparators share input pins with digital I/O (RA0/RA1 and RA2/RA3). To prevent digital switching noise from corrupting comparator thresholds, configure unused comparator channels as digital outputs and avoid toggling them near the active comparator input. Estimated: comparator response time at 5V is approximately 400 ns; faster toggling can cause false trips. For precision threshold detection, add an RC low-pass filter (10 k-ohm + 0.1 uF) on each analog input to reject high-frequency noise.
Compliance Information
Lifecycle status marked obsolete on Microchip product page. RoHS, REACH, lead-free, and halogen-free status not confirmed in the verified web data; consult Microchip product page or distributor listings for current compliance attestations.
