PIC16C621T-04/SO - 8-Bit 4MHz 1.75KB OTP MCU 18-SOIC | Microchip
MPN: PIC16C621T-04/SO ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.25 | $2.25 |
| 10 | $2.1 | $21.00 |
| 100 | $1.95 | $195.00 |
| 500 | $1.8 | $900.00 |
| 1,000 | $1.65 | $1,650.00 |
PIC16C621T-04/SO Overview
A PIC16C-series microcontroller belongs to the 8-bit microcontroller category (hypernym hierarchy: PIC16C -> PIC16 -> PIC -> 8-bit MCU -> microcontroller -> embedded processor -> semiconductor IC). It is a Harvard-architecture RISC device with separate program and data buses, optimized for deterministic real-time control and low-cost embedded designs where OTP memory provides cost-effective one-time code storage for mature, fixed-function products.
Key features of this part include 35 single-word instructions, a 14-bit instruction word, two 8-bit timer/counters, a watchdog timer, an internal 4 MHz RC oscillator option, and a wide 3.0 V to 6.0 V operating voltage range suitable for both 3.3 V and 5 V rails. The OTP program memory enables low-cost firmware storage while the 80-byte RAM footprint is sized for compact control loops. The 18-SOIC package offers a 300-mil body width for hand-solder-friendly prototyping and high-volume surface-mount assembly.
The architecture uses a 14-bit instruction set with most instructions executing in a single instruction cycle (4 oscillator clocks), giving an effective throughput of 1 MIPS at 4 MHz. Peripherals include a comparator module (the PIC16C621 variant includes dual comparators), programmable I/O with individual direction control, and power-on reset / brown-out detection support on selected family members.
Typical applications include consumer appliance controls, simple sensor interfaces, automotive body electronics (non-safety), low-end motor control, and industrial control subsystems. The wide voltage tolerance allows direct 5 V operation from unregulated supplies. Note that the OTP nature means firmware cannot be updated in-circuit; flash-based PIC16F equivalents exist where in-system reprogrammability is required.
Drop-in alternatives for PIC16C621T-04/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-04/SO (same form factor and footprint) — differing in Program Memory Size, Program Memory Type, RAM Size, Operating Temperature Range, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C621-04/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C620T-04/SO
✅ Drop-In✓ In Stock
$2.78 / Unit
View Datasheet →PIC16C621AT-20I/SO
✅ Drop-In✓ In Stock
$2.3 / Unit
View Datasheet →PIC16C621AT-20E/SO
✅ Drop-In✓ In Stock
$2.18 / Unit
View Datasheet →PIC16C620-04I/SO
✅ Drop-In✓ In Stock
$1.65 / Unit
View Datasheet →PIC16C621T-04/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 8-bit RISC (Harvard) |
| Family | PIC16C |
| Program Memory Type | OTP (One-Time Programmable) |
| Program Memory Size | 1.75 KB (1K x 14) |
| RAM Size | 80 bytes |
| Maximum Clock Frequency | 4 MHz |
| Instruction Word Width | 14 bits |
| Operating Supply Voltage | 3.0 V to 6.0 V |
| Number of I/O Pins | 13 |
| Timers | 2 x 8-bit (Timer0, Timer1) |
| Watchdog Timer | Yes |
| Oscillator Type | External/internal selectable |
| Package | 18-pin SOIC (300 mil, SO) |
| Mounting Type | Surface Mount |
| Operating Temperature Range | -40C to +85C (industrial, per family) |
| Lead-Free / RoHS | Compliant (per DigiKey listing) |
| Speed Grade Suffix | -04 = 4 MHz |
| Packaging Suffix | T = Tape and Reel |
PIC16C621T-04/SO Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O port A bit 2 |
| Pin 2 | RA3 — Bidirectional I/O port A bit 3 |
| Pin 3 | RA4/T0CKI — Bidirectional I/O / Timer0 clock input |
| Pin 4 | MCLR — Master Clear reset input (active low) |
| 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 (3.0 V to 6.0 V) |
| Pin 15 | OSC2/CLKOUT — Oscillator crystal output / clock output |
| Pin 16 | OSC1/CLKIN — Oscillator crystal input / external clock input |
| Pin 17 | RA0 — Bidirectional I/O port A bit 0 |
| Pin 18 | RA1 — Bidirectional I/O port A bit 1 |
Typical Applications
PIC16C621T-04/SO is suitable for 7 applications: Consumer Appliance Control, Industrial Sensor Interface Module, Automotive Body Electronics (Non-Safety), Low-End Motor Speed Control, Remote Control Transmitter, LED Display Driver Controller, Smart Home Sensor Node.
Consumer Appliance Control
The PIC16C621T-04/SO fits consumer appliance control boards (rice cookers, washing machines, microwave ovens) thanks to its 13 I/O pins for relay drivers and sensor inputs, 1.75 KB of OTP memory sized for typical control firmware, and 3.0-6.0 V supply tolerance that accepts unregulated 5 V rails. Its 4 MHz core delivers 1 MIPS, enough for PWM motor control and user-interface scanning. The 18-SOIC package withstands high-volume SMT reflow and the OTP memory protects intellectual property in mature products. Compared with newer flash PICs, this part offers a proven, cost-optimized platform for fixed-function appliances where firmware is finalized.
Recommended
Industrial Sensor Interface Module
For industrial sensor interfaces (proximity, optical, temperature), the PIC16C621T-04/SO provides two 8-bit timers for pulse-counting, a watchdog timer for fault recovery in factory environments, and 13 I/O for multiplexed analog sensor inputs via external ADC or comparator logic. The 3.0-6.0 V range tolerates 24 V industrial rails stepped down by simple linear regulators. OTP memory is appropriate because sensor calibration firmware is finalized at production. The 18-SOIC footprint is industry standard for these small interface modules. Engineers should add TVS diodes and bulk caps per Microchip EMC guidelines for harsh industrial sites.
Recommended
Automotive Body Electronics (Non-Safety)
The PIC16C621T-04/SO can drive non-safety automotive body modules such as interior lighting controllers, seat-position switches, and HVAC blend-door actuators, where its 13 I/O pins interface with 5 V Hall sensors, the 3-6 V supply rail accommodates 12 V battery transients after regulation, and the watchdog timer resets the MCU on EMI-induced lockup. According to the Microchip datasheet, OTP memory prevents unauthorized firmware reflash on dealer-serviceable parts. Note this part lacks AEC-Q100 qualification; for safety-critical automotive use, select AEC-Q100-qualified PIC16F or dsPIC parts. The 18-SOIC package is compatible with high-temperature automotive reflow profiles.
Recommended
Low-End Motor Speed Control
The PIC16C621T-04/SO is well suited to small brushed-DC or low-frequency motor speed controllers in fans, pumps, and small appliances. Its two 8-bit timers generate PWM at 4 MHz core clock with 8-bit duty resolution, 13 I/O pins accept tachometer feedback and direction commands, and 80 bytes of RAM suffice for closed-loop PI control loops. The 3.0-6.0 V supply accepts 5 V motor drivers directly. OTP memory locks in validated motor-control firmware, reducing warranty risk. For higher-resolution PWM or FOC, upgrade to a PIC16F or dsPIC33 part, but this MCU hits the sweet spot for cost-driven variable-speed applications.
Recommended
Remote Control Transmitter
The PIC16C621T-04/SO powers simple IR or RF remote controls thanks to its low pin count, 1.75 KB OTP memory sized for fixed command libraries, and ultra-low-cost 18-SOIC footprint enabling sub-$1 BOM. Sleep mode via the SLEEP instruction drops current consumption during standby, extending battery life in handheld transmitters. The 4 MHz internal oscillator option eliminates external crystals. OTP memory protects the encoding scheme from cloning. Per Microchip datasheet, the device supports interrupt-driven wake-up from sleep for low-power standby operation. This application is a textbook fit for an 8-bit 18-pin OTP MCU.
Recommended
LED Display Driver Controller
For 7-segment or dot-matrix LED display drivers (clocks, counters, signage), the PIC16C621T-04/SO provides 13 I/O pins capable of multiplexing 4-6 digits directly via external transistor drivers, two 8-bit timers for refresh-rate generation and timekeeping, and 1.75 KB OTP for character-lookup tables. The 3.0-6.0 V supply accepts 5 V LED anodes with appropriate current-limiting resistors. OTP locks in the display font and animation logic, protecting OEM branding. Compared with specialized LED-driver ICs, this part adds display-logic flexibility for custom characters. The 18-SOIC footprint is common in handheld LED products.
Recommended
Smart Home Sensor Node
In wireless smart-home sensor nodes (temperature, humidity, door/window sensors), the PIC16C621T-04/SO handles sensor I/O and simple protocol logic while a companion RF module handles wireless transmission. The MCU's 13 I/O accept I2C/SPI sensors, watchdog timer recovers from RF glitches, and sleep mode drops supply current for multi-year battery life. OTP memory at $2.25 BOM keeps node cost below competing SoCs. According to the Microchip datasheet, the device wakes from sleep in microseconds via interrupt. For Zigbee/Thread nodes, evaluate the PIC16F or SAM R34 series instead, but for sub-GHz or Wi-Fi-bridged designs, this part is a competent host controller.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621T-04/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621-04/SO | PIC16C620T-04/SO | PIC16C621AT-20I/SO | PIC16C620-04I/SO |
|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 18-SOIC (300 mil) | 18-SOIC (300 mil) | 18-SOIC (300 mil) | 18-SOIC (300 mil) | 18-SOIC (300 mil) |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 0.875 KB OTP | 2 KB OTP | 0.875 KB OTP |
| RAM | 80 bytes | 80 bytes | 64 bytes | 128 bytes | 64 bytes |
| Max Clock Speed | 4 MHz | 4 MHz | 4 MHz | 20 MHz | 4 MHz |
| I/O Pins | 13 | 13 | 13 | 13 | 13 |
| Supply Voltage | 3.0 V to 6.0 V | 3.0 V to 6.0 V | 3.0 V to 6.0 V | 3.0 V to 6.0 V | 3.0 V to 6.0 V |
| Operating Temperature | -40C to +85C (per family) | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
Key Differentiators
- Industry-standard 18-SOIC pinout shared across PIC16C62x family (vs PIC16C621-04/SO (tube version))
- Wide 3.0-6.0 V supply tolerates unregulated 5 V rails (vs PIC16C620-04I/SO)
- Mature OTP platform with proven long-term reliability (vs Newer PIC16F flash MCUs)
Design Notes
Decouple VDD (pin 14) with a 100 nF ceramic capacitor placed within 5 mm of the pin and a 10 uF bulk capacitor at the board supply entry. The PIC16C621T-04/SO supply range of 3.0 V to 6.0 V allows direct 5 V regulator operation, but add a series ferrite bead if the supply shares a noisy digital rail. Hold MCLR high through a 10 kohm pull-up to VDD; add a 100 nF cap from MCLR to ground for brown-out reset filtering. Estimated: with 4 MHz active current draw of approximately 2 mA from the datasheet, the 10 uF bulk cap supports 5 ms of hold-up - sufficient for typical power glitches.
Keep the 18-SOIC footprint on a 300-mil land pattern per JEDEC MS-013; the SOIC gull-wing leads require fillets of approximately 0.4 mm height for reliable reflow. Place a ground pour under the package for thermal spreading and EMI shielding, though the MCU dissipates under 100 mW so no thermal via array is needed. Isolate the oscillator pins (OSC1/OSC2) trace routing with a guard ring and keep them short; long traces couple noise into the 4 MHz clock and degrade timer accuracy.
Do not attempt to reprogram the OTP memory in-circuit - the PIC16C621 is one-time programmable only. Engineers accustomed to flash MCUs sometimes try to re-flash via ICSP after code revision, which fails. Plan firmware revisions before programming or migrate to a PIC16F flash equivalent for development flexibility. Also verify the CONFIG word fuse settings (watchdog timer, oscillator mode, code protection) are correct before mass programming; a misconfigured oscillator selection can prevent the device from booting.
Compliance Information
RoHS and lead-free compliance per DigiKey product listing 320217. PIC16C621T-04/SO is not AEC-Q100 qualified; not recommended for safety-critical automotive. REACH compliance per Microchip product declaration; conflict-minerals compliance per Microchip CMRT filings.
