PIC16C621T-20/SO - 8-Bit 20MHz OTP MCU 1.75KB | Microchip
MPN: PIC16C621T-20/SO β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.18 | $5.18 |
| 10 | $4.66 | $46.60 |
| 100 | $4.14 | $414.00 |
| 500 | $3.62 | $1,810.00 |
| 1,000 | $3.11 | $3,110.00 |
PIC16C621T-20/SO Overview
An OTP microcontroller is a CMOS device whose program memory can be written only once via a programming cycle - the bit cells use EPROM (erasable programmable read-only memory) technology that is electrically programmed but not UV-erasable. Once programmed, the firmware is permanent; this makes OTP parts ideal for cost-sensitive high-volume production where code is finalized before tooling. In the broader hierarchy, OTP MCUs sit between one-time-programmable EPROM-based devices and modern Flash-based MCUs (e.g., PIC16F) - they share the same PIC16C instruction set but are limited to a single programming event.
Key features include a wide 3.0V to 6.0V operating voltage range, an internal oscillator option, low-power consumption, and CMOS RISC architecture with only 35 single-word instructions. The PIC16C core executes one instruction per instruction cycle (4 clock cycles), giving an effective throughput of 5 million instructions per second at 20MHz. Brown-out Detect/Reset and Power-On Reset combine to give reliable startup behavior in electrically noisy environments.
The 18-pin SOIC (Small Outline Integrated Circuit) package is part of the SOIC family within surface-mount plastic packages and supports hand-soldering as well as standard reflow profiles. Compared to the 18-pin PDIP counterpart, the SOIC variant enables higher board density and lower assembly cost in automated SMT lines.
Typical applications include industrial control logic, sensor signal conditioning, low-cost consumer appliances, automotive body electronics, and discrete replacement of TTL/CMOS glue logic. The combination of OTP code security, wide voltage range, and on-chip peripherals reduces external component count.
When designing with the PIC16C621T-20/SO, note that OTP memory cannot be re-programmed - plan firmware revision strategy accordingly or consider the flash-based PIC16F621 for prototyping. Decoupling capacitors of 0.1uF should be placed as close as possible to VDD and VSS pins.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes for the PIC16C621T-20/SO not found in the manufacturer datasheet alone, including cross-package, cross-temperature, and same-family PIC16C620A/PIC16C622A migration paths.
Drop-in alternatives for PIC16C621T-20/SO β 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-20/SO (same form factor and footprint) β differing in Program Memory Size, RAM Size, Program Memory Type, MSL Level, Operating Temperature.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PIC16C621T-20I/SO
β Drop-Inβ In Stock
$1.95 / Unit
View Datasheet βPIC16C621T-20E/SO
β Drop-Inβ In Stock
$1.72 / Unit
View Datasheet βPIC16C621T-20C/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C621-20I/SO
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
PIC16C621A-20I/SS
β Drop-Inπ Reference alternative (not in catalog)
PIC16F628A-I/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C621T-20/SO Maximum Ratings & Electrical Characteristics
| Manufacturer | Microchip Technology |
| Series | PIC 16C |
| Core Processor | PIC |
| Core Size | 8-Bit |
| Maximum Clock Frequency | 20 MHz |
| Program Memory Size | 1.75 KB (1K x 14) OTP |
| RAM Size | 80 x 8 (80 bytes) |
| Number of I/O Pins | 13 |
| Operating Voltage Range | 3.0 V to 6.0 V |
| Operating Temperature Range | 0 C to +70 C (Commercial) |
| Package / Case | 18-SOIC (7.50 mm Width, 0.295") |
| Mounting Type | Surface Mount |
| Terminal Form | Gull Wing |
| Peripherals | Brown-out Detect/Reset, POR, WDT |
| Program Memory Type | OTP (EPROM) |
| Temperature Grade | Commercial |
| MSL Level | 1 (Unlimited) |
PIC16C621T-20/SO Pin Configuration
| Pin 1 | RA2/AN2/VREF β Port A bit 2 / Analog input 2 / Voltage reference |
| Pin 2 | RA3/AN3 β Port A bit 3 / Analog input 3 |
| Pin 3 | RA4/T0CKI β Port A bit 4 / Timer 0 clock input |
| Pin 4 | RA5/MCLR/VPP β Port A bit 5 / Master Clear reset input / Programming voltage |
| Pin 5 | VSS β Ground reference |
| Pin 6 | RB0/INT β Port B bit 0 / External interrupt input |
| Pin 7 | RB1 β Port B bit 1 |
| Pin 8 | RB2 β Port B bit 2 |
| Pin 9 | RB3 β Port B bit 3 |
| Pin 10 | RB4 β Port B bit 4 |
| Pin 11 | RB5 β Port B bit 5 |
| Pin 12 | RB6 β Port B bit 6 |
| Pin 13 | RB7 β Port B bit 7 |
| Pin 14 | VDD β Positive supply voltage (3.0V to 6.0V) |
| Pin 15 | OSC2/CLKOUT β Oscillator output / Clock out |
| Pin 16 | OSC1/CLKIN β Oscillator input / Clock in |
| Pin 17 | RA0/AN0 β Port A bit 0 / Analog input 0 |
| Pin 18 | RA1/AN1 β Port A bit 1 / Analog input 1 |
Typical Applications
PIC16C621T-20/SO is suitable for 7 applications: Industrial Control Logic, Sensor Signal Conditioning, Low-Cost Consumer Appliances, Automotive Body Electronics, TTL/CMOS Glue Logic Replacement, Security & Surveillance Sensors, Battery-Operated Remote Controls.
Industrial Control Logic
The PIC16C621T-20/SO fits industrial control logic boards because its 13 digital I/O pins, 3.0V to 6.0V supply tolerance, and on-chip Brown-out Detect/Reset tolerate the wide supply variation and motor-drive noise typical of 24V industrial rails. With 20 MHz core clock delivering 5 MIPS effective throughput, the part can scan digital inputs and drive relays within tight control-loop deadlines while consuming only a few mA. Compared to discrete TTL/CMOS glue logic, this OTP MCU replaces several packages, reduces board area, and provides firmware-configurable I/O mapping.
Recommended
Sensor Signal Conditioning
For sensor signal conditioning front-ends, the PIC16C621T-20/SO offers 13 I/O that can be partitioned between analog sensor excitation, digital thresholding, and PWM drive outputs. Its wide 3.0V to 6.0V operating range matches typical transducer supply rails, while the 80-byte RAM handles small state machines that buffer sensor data before downstream transmission. The Brown-out Detect feature prevents corruption of calibration coefficients during supply brown-outs, which is critical for factory-calibrated sensor modules.
Recommended
Low-Cost Consumer Appliances
In low-cost consumer appliances such as coffee makers, microwave ovens, and small kitchen tools, the PIC16C621T-20/SO delivers 1.75 KB of OTP program memory - enough to implement user-interface scanning, timer control, and relay sequencing without external memory. The 18-SOIC package is compatible with automated SMT lines, reducing per-unit assembly cost; 35 single-word RISC instructions shorten firmware development time. For appliance designers, the OTP memory also provides firmware security since the program cannot be read back once locked.
Recommended
Automotive Body Electronics
Although the PIC16C621T-20/SO is commercial-temperature graded, the same die in industrial grade (-I/SO suffix) supports automotive body electronics such as interior lighting controllers, seat-position memories, and mirror-adjustment modules. The 20 MHz instruction throughput handles LIN-bus bit timing, while on-chip Power-On Reset and Brown-out Detect/Reset ensure reliable startup across automotive cranking transients. The 13 I/O pins are sufficient for switch matrix scanning and H-bridge enable signals.
Recommended
TTL/CMOS Glue Logic Replacement
The PIC16C621T-20/SO can replace 3 to 5 packages of discrete TTL/CMOS glue logic (gates, flip-flops, one-shots, counters) in legacy board designs, reducing PCB area and BOM count. Its 13 programmable I/O pins implement custom sequential logic, debounced switch inputs, and small state machines without external PLDs. OTP memory ensures that the equivalent logic function is locked at production time, eliminating field-reprogramming risk and matching the lifecycle of fixed-function logic replacements.
Recommended
Security & Surveillance Sensors
For security and PIR-based intrusion sensors, the PIC16C621T-20/SO offers 1.75 KB OTP to hold detection algorithms, communication timing, and tamper logic while running on a single 3V to 6V supply. The Watchdog Timer guards against firmware lock-up in unattended installations, and the Brown-out Detect/Reset prevents false alarms during supply dips. The 18-SOIC footprint enables miniaturized sensor housings, and OTP code protection prevents reverse engineering of proprietary detection firmware.
Recommended
Battery-Operated Remote Controls
In battery-operated remote controls and handheld tools, the PIC16C621T-20/SO provides low active current and supports operation from 2xAA cells via its wide 3.0V to 6.0V range. The 13 I/O pins scan key matrices up to 4x4, drive IR LEDs or 2.4 GHz transmitter enables, and handle sleep-mode wakeup. The Watchdog Timer and Power-On Reset extend battery life by allowing long sleep periods between user inputs, while OTP memory protects the proprietary RF protocol code from external read-out.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621T-20/SO β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621T-20I/SO | PIC16C621T-20E/SO | PIC16C621A-20I/SS | PIC16F628A-I/SO |
|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 18-SOIC | 18-SOIC (same) | 18-SOIC (same) | 18-SOIC (same) | 18-SOIC (same) |
| Core | 8-bit PIC16C | 8-bit PIC16C | 8-bit PIC16C | 8-bit PIC16C (enhanced) | 8-bit PIC16F (Flash) |
| Max Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP (enhanced) | 2 KB Flash (re-programmable) |
| RAM Size | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 224 bytes (+180%) |
| I/O Pins | 13 | 13 | 13 | 13 | 16 (+23%) |
| Operating Temperature | 0 C to +70 C (Commercial) | -40 C to +85 C (Industrial) | -40 C to +125 C (Extended) | -40 C to +85 C (Industrial) | -40 C to +85 C (Industrial) |
| Peripherals | BOD, POR, WDT | BOD, POR, WDT | BOD, POR, WDT | BOD, POR, WDT, comparator | BOD, POR, WDT, USART, CCP, comparator |
Key Differentiators
- On-chip Brown-out Detect and Power-On Reset (vs PIC16C620A-20I/SO)
- 20 MHz speed grade with 5 MIPS throughput (vs PIC16C621-04I/P)
- Reprogrammable Flash memory option (vs PIC16F628A-I/SO)
Design Notes
The OTP program memory of PIC16C621T-20/SO can only be written ONCE - after programming and code protection, the firmware is permanent. Do not use this part for prototype firmware that will require iteration; develop on PIC16F628A-I/SO (Flash, same 18-SOIC pinout) and port the final code to OTP only for production. Estimated: this single pitfall causes the majority of field returns on PIC16C62X designs.
Place a 0.1 uF decoupling capacitor as close as possible to the VDD pin (pin 14) with a short ground return to VSS (pin 5). For designs with high-current digital outputs switching simultaneously, add a bulk 10 uF tantalum or aluminum capacitor near the MCU. The MCLR/VPP pin (pin 4) should be tied to VDD through a 10 kohm resistor for normal operation; a 100 nF cap from MCLR to VSS improves noise immunity during voltage transients.
Brown-out Detect/Reset (BOD) on the PIC16C621T-20/SO holds the MCU in reset when VDD drops below the BOD threshold (~4.0V on the 5V configuration). Enable BOD for any application where VDD can dip during motor inrush or inductive load switching. The POR circuit (Power-On Reset) initializes registers on VDD rise; combined with BOD, it provides reliable startup behavior. Estimated: with BOD disabled, an estimated 15-25% of brown-out events corrupt the program counter and cause lockups.
The PIC16C621T-20/SO in the 18-SOIC package dissipates under 200 mW even at 20 MHz active operation, so no heatsink is required. However, for industrial temperature designs (-40 C to +85 C), use the PIC16C621T-20I/SO suffix instead of the /SO commercial grade, since the commercial part's 0 C to +70 C range will fail above +70 C. The extended PIC16C621T-20E/SO reaches +125 C for under-hood or harsh industrial environments.
Compliance Information
PIC16C621T-20/SO is a legacy OTP product predating widespread RoHS reporting; RoHS/REACH/lead-free status was not present in the Verified Web Data and is marked unknown. AEC-Q100 is not applicable to this commercial-temperature 8-bit MCU; for automotive designs use PIC16C621T-20I/SO or migrate to AEC-Q100 qualified PIC16F628A-I/SO.
