PIC16C621T-04I/SO - 8-bit OTP MCU, 4MHz, 1.75KB | Microchip
MPN: PIC16C621T-04I/SO ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.533 | $4.53 |
| 10 | $4.08 | $40.80 |
| 100 | $3.62 | $362.00 |
| 500 | $3.2 | $1,600.00 |
| 1,000 | $2.85 | $2,850.00 |
PIC16C621T-04I/SO Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, RAM, non-volatile program memory, and peripheral I/O on one die. It belongs to the broader hierarchy of microcontrollers -> embedded processors -> semiconductors, and serves as the central control element in countless embedded designs. The PIC16C family specifically uses a Harvard RISC architecture with 14-bit wide instruction words, optimizing code efficiency over pure data throughput.
Key features include 80 bytes of RAM, 13 digital I/O pins, an integrated analog comparator module, internal watchdog timer, and 1,000,000 erase/write cycle endurance on the OTP program memory. The part operates from 3.0V to 6.0V supply voltage and supports both RC and crystal clock modes, enabling low-cost oscillator designs. Its 18-pin SOIC footprint places it in the small-outline surface-mount family (SOIC -> SMD -> SMT), suited for automated assembly.
Architecturally, the PIC16C621 separates program memory (1K x 14 OTP) from data memory (80 bytes RAM plus a 7-byte common RAM area), accessed through separate buses. This Harvard approach allows instruction fetch and data access to occur simultaneously, accelerating execution. The integrated analog comparator with programmable reference voltage eliminates the need for an external analog front end in many applications.
Typical applications include appliance control, security sensor interfaces, low-cost remote controls, smoke detectors, and small industrial controllers. The wide SOIC package and broad third-party tool support (MPLAB PM3, ICD programmers) make it easy to prototype and produce. Designers choose the PIC16C621 family for its mature ecosystem, deterministic instruction timing, and abundant reference designs from Microchip's application notes.
When designing with the PIC16C621, configure the configuration fuses carefully, since OTP memory cannot be reprogrammed. Ensure decoupling capacitors are placed within 5mm of VDD/VSS pins, and follow Microchip's AN577 'PIC16C5X/XX Design Considerations' for brown-out and EMI guidance. Note that the 'T' suffix indicates tape-and-reel, important for high-volume SMT assembly.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for PIC16C621T-04I/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 PIC16C621T-04I/SO (same form factor and footprint) — differing in Program Memory Size, Program Memory Type, RAM Size, RoHS Status, Timers.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C621-04I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621T-04/SO
✅ Drop-In✓ In Stock
$1.65 / Unit
View Datasheet →PIC16C620T-04/SO
✅ Drop-In✓ In Stock
$2.78 / Unit
View Datasheet →PIC16C621AT-20I/SO
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.3 / Unit
View Datasheet →PIC16C621AT-04I/SO
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
PIC16C621T-04I/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC RISC (Harvard) |
| Program Memory Size | 1.75 KB (1K x 14) OTP |
| RAM Size | 80 bytes |
| Number of I/O Pins | 13 |
| Core Frequency | 4 MHz |
| Instruction Word Width | 14-bit |
| Supply Voltage Range | 3.0 V to 6.0 V |
| Operating Temperature Range | -40 C to +85 C (Industrial) |
| Package / Case | 18-SOIC (0.295, 7.50 mm Width) |
| Mounting Type | Surface Mount |
| Packaging Type (T suffix) | Tape & Reel |
| Analog Comparator | Yes, integrated |
| Watchdog Timer | Yes, internal |
| Clock Modes | RC / External Crystal |
| Program Memory Type | OTP (One-Time-Programmable) |
| RoHS Status | Compliant |
PIC16C621T-04I/SO Pin Configuration
| Pin 1 | RA2/AN2 — Bidirectional I/O pin / analog comparator input |
| Pin 2 | RA3 — Bidirectional I/O pin |
| Pin 3 | RA4/T0CKI — Bidirectional I/O pin / Timer 0 clock input |
| Pin 4 | MCLR/VPP — Master Clear (reset) input / programming voltage input |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Bidirectional I/O pin / external interrupt input |
| Pin 7 | RB1 — Bidirectional I/O pin |
| Pin 8 | RB2 — Bidirectional I/O pin |
| Pin 9 | RB3 — Bidirectional I/O pin |
| Pin 10 | RB4 — Bidirectional I/O pin |
| Pin 11 | RB5 — Bidirectional I/O pin |
| Pin 12 | RB6 — Bidirectional I/O pin |
| Pin 13 | RB7 — Bidirectional I/O pin |
| Pin 14 | VDD — Positive supply voltage |
| Pin 15 | OSC2/CLKOUT — Oscillator crystal connection / clock output |
| Pin 16 | OSC1/CLKIN — Oscillator crystal connection / external clock input |
| Pin 17 | RA0/AN0 — Bidirectional I/O pin / analog comparator input |
| Pin 18 | RA1/AN1 — Bidirectional I/O pin / analog comparator input |
Typical Applications
PIC16C621T-04I/SO is suitable for 6 applications: Appliance Control, Security Sensor Interface, Remote Control Transmitters, Smoke Detector Controllers, Small Motor Driver Controllers, Industrial Sensor Modules.
Appliance Control
The PIC16C621T-04I/SO fits appliance control boards through its combination of 13 digital I/O pins (each capable of 20 mA source/sink), integrated analog comparator for sensor signal conditioning, and 4MHz core sufficient for simple state-machine logic. The 1.75KB OTP memory holds washing machine, dishwasher, or microwave oven control firmware with deterministic timing. Industrial temperature grade ensures reliable operation in kitchen environments where ambient temperatures can exceed 70C near heating elements. The 18-SOIC package supports automated SMT assembly for high-volume appliance manufacturing. Compared to modern Cortex-M0 alternatives, the PIC16C621T-04I/SO offers lower unit cost and a mature MPLAB toolchain that engineering teams already know, making it practical for cost-sensitive appliance designs.
Recommended
Security Sensor Interface
The PIC16C621T-04I/SO serves as the central controller in PIR motion detectors, smoke alarms, and door/window contact sensors through its low 3.0V-6.0V operating range suitable for battery-powered wireless security nodes. The integrated analog comparator directly interfaces with PIR sensor signals, eliminating an external op-amp and reducing BOM cost by $0.10-$0.30 per unit. The 80-byte RAM is adequate for short event buffers and timing variables, while the 1.75KB OTP holds motion-discrimination firmware. Industrial temperature rating ensures reliable operation in outdoor security cameras and perimeter sensors. The 4MHz core provides 1 MIPS performance, sufficient for simple FIR filtering of sensor signals to reduce false alarms.
Recommended
Remote Control Transmitters
The PIC16C621T-04I/SO is well-suited for IR/RF remote control transmitters where 13 I/O pins drive button matrix scanning, LED indicators, and encoder outputs. The 4MHz core and 1.75KB OTP firmware memory comfortably hold RC5/RC6/SIRC encoding algorithms plus custom protocol extensions. Operating from a single CR2032 coin cell (3V) through its 3.0V minimum supply rating, the PIC16C621T-04I/SO achieves multi-year battery life in intermittent-duty remote designs. The integrated analog comparator can monitor battery voltage for low-battery warning LEDs. Tape-and-reel packaging (T suffix) supports high-volume SMT production lines used by consumer electronics manufacturers.
Recommended
Smoke Detector Controllers
The PIC16C621T-04I/SO functions as the main controller in ionization and photoelectric smoke detectors, using its 13 I/O pins to interface with the smoke chamber sensor, sounder driver, LED indicator, and test button. The integrated analog comparator continuously monitors the photoelectric chamber's IR photodiode current, detecting smoke particles via light scattering. Industrial temperature range (-40C to +85C) is essential for smoke detectors installed in attics, basements, and unconditioned spaces. The watchdog timer ensures the sounder activates in the rare event of firmware lockup, a critical safety function. OTP memory prevents accidental field reprogramming that could compromise detector calibration.
Recommended
Small Motor Driver Controllers
The PIC16C621T-04I/SO controls low-power brushless DC and stepper motors in small appliances, fans, and toys through its 13 I/O pins driving H-bridge FET gate signals and Hall sensor inputs. The 4MHz core provides adequate PWM resolution for speed control loops up to 10 kHz switching frequency. The integrated analog comparator simplifies back-EMF zero-crossing detection in sensorless BLDC designs, reducing external component count by 3-4 devices. The industrial temperature grade handles motor self-heating in enclosed driver housings. With 1.75KB OTP, the firmware fits sensorless startup ramps, commutation tables, and fault protection routines for a complete motor controller in a single IC.
Recommended
Industrial Sensor Modules
The PIC16C621T-04I/SO serves in industrial 4-20mA sensor transmitters, RTD signal conditioners, and discrete I/O modules where its industrial temperature rating (-40C to +85C) and integrated analog comparator provide robust signal handling. The 13 I/O pins drive relay coils, status LEDs, and communication lines while reading sensor inputs. The 1.75KB OTP holds linearization tables for thermocouples, RTDs, and bridge pressure sensors. The 3.0V-6.0V supply range supports both 3.3V and 5V industrial backplanes. In legacy factory automation systems where PIC16C621 firmware has been qualified and certified, the PIC16C621T-04I/SO provides continued production availability without requalification.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621T-04I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621-04I/SO | PIC16C621T-04/SO | PIC16C620T-04/SO | PIC16C621AT-20I/SO | PIC16C621AT-04I/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 18-SOIC (7.50mm) | 18-SOIC (7.50mm) - same | 18-SOIC (7.50mm) - same | 18-SOIC (7.50mm) - same | 18-SOIC (7.50mm) - same | 18-SOIC (7.50mm) - same |
| Core Frequency | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 20 MHz | 4 MHz |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP |
| RAM Size | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 80 bytes |
| I/O Pins | 13 | 13 | 13 | 13 | 13 | 13 |
| Temperature Grade | Industrial (-40C to +85C) | Industrial (-40C to +85C) | Commercial (0C to +70C) | Commercial (0C to +70C) | Industrial (-40C to +85C) | Industrial (-40C to +85C) |
| Analog Comparator | Yes (integrated) | Yes | Yes | No | Yes | Yes |
| Memory Type | OTP | OTP | OTP | OTP | OTP | OTP |
Key Differentiators
- Industrial temperature range in tape-and-reel packaging (vs PIC16C621T-04/SO)
- Integrated analog comparator eliminates external op-amp (vs PIC16C620T-04/SO)
- Pin-compatible 5x faster upgrade path available (vs PIC16C621AT-20I/SO)
Design Notes
The PIC16C621T-04I/SO operating voltage is 3.0V to 6.0V. Place a 100nF ceramic decoupling capacitor within 5mm of the VDD pin (14) and VSS pin (5), with a 10uF bulk capacitor on the same supply rail. For battery-powered designs operating below 4.5V, enable the brown-out reset (BOR) configuration fuse to ensure defined startup behavior when batteries approach end-of-life. The internal comparator draws approximately 1 mA when active; disable it via CMCON register when not in use to reduce quiescent current for low-power sensor applications.
Route the OSC1/OSC2 traces (pins 15, 16) as short as possible and keep them away from high-current switching nodes to minimize EMI coupling. If using a crystal oscillator, place the load capacitors (typically 15-22 pF) close to the crystal and the IC pins. The MCLR pin (4) requires a 10k pull-up resistor to VDD for normal operation; add a 100nF capacitor to ground only if MCLR rise time must be slowed to avoid spurious resets in noisy environments.
OTP memory on the PIC16C621T-04I/SO can be programmed only ONCE per address - configuration word, ID locations, and program memory cannot be erased. Verify all firmware thoroughly using a Flash-based equivalent (PIC16F630) or windowed PIC16C621 before committing to OTP production. The analog comparator output must be read via the CMCON register and not the GPIO register when used in analog mode, otherwise reads will return 0 regardless of the actual comparator state.
Compliance Information
RoHS and REACH compliant per Microchip product page. Not AEC-Q100 qualified - not recommended for safety-critical automotive applications. Lead-free and halogen-free per Microchip packaging specifications.
