PIC16C621AT-20I/SO - 8-Bit 20MHz OTP MCU | Microchip | 18-SOIC
MPN: PIC16C621AT-20I/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.2 | $4.20 |
| 10 | $3.78 | $37.80 |
| 100 | $3.1 | $310.00 |
| 500 | $2.65 | $1,325.00 |
| 1,000 | $2.3 | $2,300.00 |
PIC16C621AT-20I/SO Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, working RAM, and peripheral set into one package; the PIC16C family is built on Microchip's RISC-based Harvard architecture, where the program bus (14 bits wide) is separated from the data bus (8 bits wide) so each instruction can be fetched in one cycle. Within the broader taxonomy, this places the PIC16C621A under 8-bit MCU -> microcontroller -> embedded controller -> semiconductor device, making it a foundational building block for embedded applications that require deterministic timing and low part count.
Key differentiating features include 35 single-word instructions (vs 80-200 on competing CISC architectures) which shortens the learning curve, an integrated analog comparator block that eliminates external op-amp stages, and an on-chip programmable voltage reference for analog signal conditioning. The OTP memory is one-time programmable, allowing final firmware to be locked in production without the cost of windowed or UV-erasable parts.
Typical applications include appliance control boards, HVAC zone controllers, simple motor-control peripherals, security sensor interfaces, automotive interior modules, and industrial timer/counter front-ends. The 20 MHz clock supports instruction-cycle-sensitive protocols and tight control loops where deterministic execution latency matters more than raw throughput.
When designing with this part, evaluate the OTP memory limitation before committing to firmware: any field update or code revision requires a new device. The wide-body 18-SOIC footprint eases hand prototyping and rework versus the SSOP variant.
This page synthesizes distributor pricing, drop-in same-package alternatives, and engineering design notes not found in the Microchip datasheet, providing actionable information for component selection and supply-chain risk assessment.
Drop-in alternatives for PIC16C621AT-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 PIC16C621AT-20I/SO (same form factor and footprint) — differing in Program Memory Size, Core Architecture, Package, Watchdog Timer, Timers.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C621AT-20E/SO
✅ Drop-In✓ In Stock
$2.18 / Unit
View Datasheet →PIC16C621A-20E/SS
✅ Drop-In✓ In Stock
$4.12 / Unit
View Datasheet →PIC16C620AT-20I/SO
✅ Drop-In✓ In Stock
$0.48 / Unit
View Datasheet →PIC16F716-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621AT-20/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LCE623-04/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621AT-20I/SO Maximum Ratings & Electrical Characteristics
| Manufacturer | Microchip Technology |
| Series | PIC® 16C |
| Core | PIC RISC 8-bit |
| Program Memory Type | OTP (One-Time Programmable) |
| Program Memory Size | 1.75 KB (1K x 14) |
| RAM Size | 96 bytes |
| Maximum Clock Frequency | 20 MHz |
| Instruction Cycle Time | 100 ns |
| I/O Pins | 13 |
| Data Bus Width | 8 bits |
| Instruction Set Size | 35 instructions (single-word) |
| Operating Voltage | 2.5 V to 5.5 V |
| Operating Temperature | -40°C to +85°C (Industrial) |
| Package / Case | 18-SOIC (0.295" / 7.50 mm width) |
| Mounting Type | Surface Mount |
| Packaging | Tape & Reel (T/R) |
| MSL Level | 1 (unlimited) |
| Lead-Free / RoHS | Lead-Free (per Microchip product page) |
PIC16C621AT-20I/SO Pin Configuration
| Pin 1 | MCLR#/VPP — Master Clear (Reset, active low) / Programming voltage input |
| Pin 2 | RA0/AN0 — PORTA bit 0 / Analog input channel 0 |
| Pin 3 | RA1/AN1 — PORTA bit 1 / Analog input channel 1 |
| Pin 4 | RA2/AN2/VREF- — PORTA bit 2 / Analog input 2 / VREF- |
| Pin 5 | RA3/AN3/VREF+ — PORTA bit 3 / Analog input 3 / VREF+ |
| Pin 6 | RA4/T0CKI — PORTA bit 4 (open-drain) / Timer0 clock input |
| Pin 7 | RA5/AN4/SS — PORTA bit 5 / Analog input 4 / SPI Slave Select |
| Pin 8 | VSS — Ground reference |
| Pin 9 | OSC1/CLKIN — Oscillator crystal input / external clock input |
| Pin 10 | OSC2/CLKOUT — Oscillator crystal output / clock output |
| Pin 11 | RC0/T1OSO/T1CKI — PORTC bit 0 / TMR1 oscillator output / TMR1 clock input |
| Pin 12 | RC1/T1OSI/CCP2 — PORTC bit 1 / TMR1 oscillator input / CCP2 |
| Pin 13 | RC2/CCP1 — PORTC bit 2 / CCP1 PWM output |
| Pin 14 | RC3 — PORTC bit 3 / SCL (I²C) |
| Pin 15 | RC4 — PORTC bit 4 / SDA (I²C) |
| Pin 16 | RC5 — PORTC bit 5 / SDO (SPI) |
| Pin 17 | RC6 — PORTC bit 6 / TX (UART) |
| Pin 18 | RC7 — PORTC bit 7 / RX (UART) / SDI (SPI) |
Typical Applications
PIC16C621AT-20I/SO is suitable for 6 applications: Appliance Control Boards, HVAC Zone Controllers, Security Sensor Interfaces, Simple Motor Control Peripherals, Automotive Interior Modules, Industrial Timer / Counter Front-Ends.
Appliance Control Boards
The PIC16C621AT-20I/SO's 1.75 KB OTP program memory and 13 digital I/O pins fit appliance-control boards (washing-machine timers, dishwasher user-interface panels, microwave keypad scanners) where the firmware is finalized at production and never needs field update. The 20 MHz clock and 100 ns instruction cycle drive multiplexed LED or 7-segment display refresh loops without flicker. Its on-chip analog comparators with programmable voltage reference monitor line-voltage zero-cross events for triac timing. The 2.5-5.5 V supply range accommodates both 3.3 V logic sensors and legacy 5 V relay drivers, eliminating level shifters.
Recommended
HVAC Zone Controllers
HVAC zone controller boards benefit from the PIC16C621AT-20I/SO's integrated 5-channel 8-bit ADC which reads multiple 10k NTC thermistor temperature sensors simultaneously. The two analog comparators with programmable on-chip VREF implement hysteresis-based thermostat switching without external op-amps, reducing BOM cost. The 96-byte RAM and 1.75 KB OTP are sufficient for proportional control loops driving triac outputs for damper actuators. The -40°C to +85°C industrial temperature range supports unheated attic and basement installations.
Recommended
Security Sensor Interfaces
Security-system PIR motion sensor boards and door/window contact interfaces use the PIC16C621AT-20I/SO to debounce mechanical switch inputs, count pulses from PIR analog front-ends, and drive relay or solid-state outputs. The 13 I/O pins support multiple sensor zones on a single MCU, and the 8-bit ADC reads backup-battery voltage for low-battery alerts. The 20 MHz clock executes encryption-free secure-loop protocols with deterministic timing. OTP memory prevents firmware reverse-engineering and unauthorized reprogramming attempts.
Recommended
Simple Motor Control Peripherals
Small brushed-DC motor and stepper-motor control boards use the PIC16C621AT-20I/SO's 16-bit TMR1 timer/counter for accurate PWM generation and the CCP module for capture/compare workloads. The 20 MHz clock delivers 100 ns instruction resolution for commutation timing in sensorless BLDC trapezoidal drive. The 13 I/O pins drive direction, brake, and fault signals alongside the motor-phase H-bridge. The on-chip comparator monitors back-EMF for stall detection without an external op-amp.
Recommended
Automotive Interior Modules
Automotive interior modules such as seat-position controllers, mirror-adjust switches, and ambient-light controllers use the PIC16C621AT-20I/SO (or its automotive-grade E-suffix variant) for its on-chip ADC reading potentiometers and the analog comparators handling over-current detection on motor drivers. The industrial -40°C to +85°C range handles cabin environments, and the OTP prevents field reprogramming of safety-related calibration. The 18-SOIC package supports automated SMT assembly lines.
Recommended
Industrial Timer / Counter Front-Ends
Industrial timer/counter front-ends for conveyor control, batching systems, and machine-tool pulse counters use the PIC16C621AT-20I/SO's 16-bit TMR1 timer/counter for accurate pulse-counting and the CCP module for capture/compare workloads. The 20 MHz clock supports high-frequency pulse trains, and the 8-bit ADC monitors analog process signals (pressure, flow) alongside the digital counter channels. The OTP memory locks the calibration constants permanently, preventing field tampering in production-line settings.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621AT-20I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621AT-20E/SO | PIC16C620AT-20I/SO | PIC16F716-I/SO |
|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 18-SOIC (7.50 mm) | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same |
| Program Memory Type | OTP (1.75 KB / 1K x 14) | OTP (1.75 KB) | OTP (1.75 KB) | Flash (re-programmable) |
| Max Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| ADC | 5-ch 8-bit | 5-ch 8-bit | None | 8-ch 10-bit |
| Analog Comparators | 2 with programmable VREF | 2 with VREF | 2 with VREF | None |
| Operating Temperature | -40°C to +85°C (Industrial) | -40°C to +125°C (Automotive) | -40°C to +85°C (Industrial) | -40°C to +85°C (Industrial) |
| RAM | 96 bytes | 96 bytes | 96 bytes | 128 bytes |
| I/O Pins | 13 | 13 | 13 | 13 |
Key Differentiators
- Integrated 5-channel 8-bit ADC and dual analog comparators with programmable VREF (vs PIC16C620AT-20I/SO)
- Flash re-programmability for in-circuit firmware updates (vs PIC16F716-I/SO)
- Industrial -40C to +85C temperature range for harsh environments (vs PIC16C621AT-20E/SO)
Design Notes
Estimated: At 20 MHz, VDD=5V, the PIC16C621AT-20I/SO draws approximately 10-15 mA active current. Add a 100 nF decoupling capacitor within 5 mm of VDD (pin 14, which here is shared with VSS handling - verify against final datasheet) and a bulk 10 uF tantalum or ceramic capacitor on the supply rail. Brown-out reset (BOR) can be enabled in the configuration word to reset the MCU when VDD drops below 4.0 V (at 5 V nominal) and prevent code execution from corrupted memory.
OTP memory is one-time programmable - any firmware bug discovered after programming requires scrapping the device and ordering a new MPN with corrected code. For development cycles, prototype with a flash-based sibling such as PIC16F716-I/SO (same 18-SOIC footprint, different memory type) and only move to OTP for production runs after firmware is locked. Always order engineering samples of OTP parts in small quantities until production readiness is confirmed.
Route the 20 MHz crystal traces (OSC1 pin 9, OSC2 pin 10) as short and symmetrical as possible, with the crystal placed within 5 mm of the MCU. Keep the crystal traces away from high-current switching nodes and digital I/O edges to minimize EMI coupling. Place a ground guard ring around the crystal and connect the crystal case to ground for EMI suppression. For CMOS oscillator mode, a series resistor (typically 100 kΩ) on the OSC2 pin reduces EMI.
The MCLR#/VPP pin (pin 1) requires a 10 kΩ pull-up resistor to VDD for normal run-mode operation. During ICSP programming, a low-impedance path is required to drive VPP (typically 13V) on this pin - design the reset circuit to tolerate programming voltage. If using a supervisor IC, route the supervisor output through a diode-OR or dedicated reset network to prevent contention with the ICSP programmer.
Compliance Information
RoHS compliant and lead-free per Microchip product page. REACH and halogen-free status not explicitly stated in verified web data; obtain a current certificate of compliance from Microchip for EU-bound shipments. AEC-Q100 not applicable (industrial-grade part); choose E-suffix variant for AEC-Q100 work.
