PIC16C621AT-20E/SO - 8-Bit 20MHz OTP MCU, 1.75KB, 13 I/O | Microchip
MPN: PIC16C621AT-20E/SO β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.45 | $3.45 |
| 10 | $3.1 | $31.00 |
| 100 | $2.78 | $278.00 |
| 500 | $2.46 | $1,230.00 |
| 1,000 | $2.18 | $2,180.00 |
PIC16C621AT-20E/SO Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, program memory, RAM, and peripherals onto one silicon die, forming the lowest tier of the embedded processor taxonomy: 8-bit MCU -> microcontroller -> embedded processor -> semiconductor. The PIC16C62x series specifically targets cost-sensitive applications that need precise timing, low power, and a small footprint, while offering analog comparators and capture/compare/PWM peripherals typically absent from simpler 8-bit parts.
Key features include 35 single-word instructions with 200 ns instruction cycle at 20 MHz, 14-bit wide instructions for compact code, two analog comparators with programmable on-chip voltage reference, one 8-bit timer/counter (TMR0) with an 8-bit prescaler, one 16-bit timer/counter (TMR1), a Watchdog Timer with its own on-chip RC oscillator for reliable operation, and thirteen digital I/O pins with high-current sink/source capability. The CMOS OTP process delivers low power consumption typical of PIC mid-range parts.
Architecturally, the PIC16C621A uses a Harvard-style memory map with separate program and data buses, an 8-level deep hardware stack, and direct/indirect addressing modes. The Enhanced Mid-Range core introduces interrupt handling improvements and additional peripheral control registers compared to the original PIC16C5x baseline, while preserving instruction-set compatibility for migration of legacy code bases.
Typical applications include automotive body electronics and sensor interfaces, white goods and appliance controls, industrial sensors and simple closed-loop regulators, low-end security panels, battery chargers, and consumer remote controls. The PIC16C621A is widely used in designs originally prototyped on the PIC16C621, where the 'A' silicon revision and OTP program memory offered a balance of cost, code security, and field upgradability.
When designing with this part, observe the Extended temperature range rating of -40C to +125C for automotive under-hood or industrial environments, and ensure the supply voltage stays within the 3.0 V to 5.5 V range. OTP memory cannot be re-programmed, so plan code development on a windowed or flash equivalent (e.g., PIC16F62x) before committing to the OTP device for production.
This page synthesizes current distributor pricing, drop-in same-family alternatives from the Site MPN catalog, and practical engineering guidance not consolidated in the manufacturer datasheet, helping engineers evaluate the PIC16C621AT-20E/SO against its 16C62x siblings and modern flash-based replacements.
Drop-in alternatives for PIC16C621AT-20E/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 PIC16C621AT-20E/SO (same form factor and footprint) β differing in Program Memory Size, RAM Size, Core Architecture, Operating Temperature Range, Package / Case.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PIC16C621AT-20/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C621A-04E/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C620A-20E/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16F627-20E/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16F628-20E/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C621A-20I/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C621AT-20E/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit Enhanced Mid-Range PIC |
| Program Memory Type | OTP (One-Time-Programmable) |
| Program Memory Size | 1.75 KB (1K x 14 words) |
| RAM | 96 bytes |
| Maximum CPU Clock | 20 MHz |
| Instruction Cycle | 200 ns at 20 MHz |
| Instruction Set Width | 14 bits |
| I/O Pins | 13 |
| Timers | TMR0 (8-bit), TMR1 (16-bit) |
| Analog Comparators | 2 with programmable voltage reference |
| Watchdog Timer | Yes, with dedicated on-chip RC oscillator |
| Supply Voltage | 3.0 V to 5.5 V |
| Operating Temperature Range | -40C to +125C (Extended, 'E' suffix) |
| Package | 18-pin SOIC (SO) |
| Mounting Type | Surface Mount |
| Lead Finish / RoHS | Matte Tin / Compliant |
| MSL Level | 1 (per JEDEC J-STD-020) |
| Data EEPROM | None (OTP program memory only) |
PIC16C621AT-20E/SO Pin Configuration
| Pin 1 | RA2 β PORTA bit 2 / analog comparator input |
| Pin 2 | RA3 β PORTA bit 3 / analog comparator input |
| Pin 3 | RA4 β PORTA bit 4 (open-drain) / T0CKI clock input |
| Pin 4 | MCLR β Master Clear reset input (active low) |
| Pin 5 | VSS β Ground reference |
| Pin 6 | RB0 β PORTB bit 0 / INT external interrupt |
| Pin 7 | RB1 β PORTB bit 1 |
| Pin 8 | RB2 β PORTB bit 2 |
| Pin 9 | RB3 β PORTB bit 3 |
| Pin 10 | RB4 β PORTB bit 4 |
| Pin 11 | RB5 β PORTB bit 5 |
| Pin 12 | RB6 β PORTB bit 6 / ICSCLK |
| Pin 13 | RB7 β PORTB bit 7 / ICSDAT |
| Pin 14 | VDD β Positive supply (3.0 V to 5.5 V) |
| Pin 15 | OSC2 β Oscillator output / RA6 |
| Pin 16 | OSC1 β Oscillator input / RA7 |
| Pin 17 | RA0 β PORTA bit 0 / analog comparator input |
| Pin 18 | RA1 β PORTA bit 1 / analog comparator input |
Typical Applications
PIC16C621AT-20E/SO is suitable for 6 applications: Automotive Body Electronics, White Goods and Appliance Control, Industrial Sensor Signal Conditioning, Battery Chargers and Power Management, Consumer Remote Controls and IR Links, Security and Alarm Panels.
Automotive Body Electronics
The PIC16C621AT-20E/SO fits automotive body electronics such as seat controllers, mirror adjusters, lighting modules, and HVAC damper actuators. Its Extended -40C to +125C operating temperature range survives under-hood thermal stress, and the 20 MHz CPU clock delivers deterministic timing for LIN-style or direct-wired control loops. The two on-chip analog comparators enable low-cost current sensing for motor stall detection without an external op-amp, while the 13 GPIO pins drive relays, LEDs, and H-bridge MOSFETs directly. Place 100 nF decoupling caps adjacent to VDD (pin 14) and VSS (pin 5), and use the Watchdog Timer with its dedicated RC oscillator to recover from automotive load-dump-induced brown-outs. The 18-SOIC package is compatible with lead-free automotive reflow profiles per JEDEC J-STD-020.
Recommended
White Goods and Appliance Control
Washing machines, dishwashers, ovens, and refrigerators commonly use the PIC16C621A as the main control MCU thanks to its low cost, robust I/O, and analog comparators. The 20 MHz instruction cycle drives simple state machines for motor speed and door-lock interlocks within tight real-time budgets, while the two comparators sense water level, temperature via NTC, and door-latch position. The 96-byte RAM is sufficient for parameter storage in EEPROM-backed variable locations, and the 13 GPIO pins multiplex keypad inputs, triac firing pulses, and seven-segment displays. OTP memory secures the firmware against unauthorized copying. Layout the 18-SOIC footprint so the optional 32.768 kHz watch crystal on RA6/RA7 is reserved for future low-power migration, and place a series ferrite bead on VDD to suppress relay transient noise.
Recommended
Industrial Sensor Signal Conditioning
In 4-20 mA loop-powered sensor transmitters, photoelectric sensor amplifiers, and limit-switch interfaces, the PIC16C621AT-20E/SO performs analog threshold detection, linearization, and PWM or UART output. The internal analog comparators with programmable voltage reference let the firmware implement hysteresis and threshold switching without an external op-amp, reducing BOM cost and PCB area. The 13 GPIO drive RS-485 direction control, status LEDs, and push-pull outputs up to 25 mA per pin. The 14-bit instruction width keeps the calibration lookup-table code compact in the 1.75 KB OTP. Use TMR1 with an external 32.768 kHz crystal for accurate sample intervals, and route the comparator inputs (RA0/RA1/RA2/RA3) on short, guarded traces to avoid switching-noise pickup.
Recommended
Battery Chargers and Power Management
Low-end NiCd/NiMH and lead-acid chargers for portable tools, e-bikes, and backup power systems use the PIC16C621A to implement CC/CV profiles, temperature foldback, and termination detection. The two comparators sense battery voltage across a resistor divider and current via a low-side shunt, while TMR1 generates PWM to drive a MOSFET or a hysteretic controller. The 5.5 V maximum VDD allows direct connection to a 4-cell NiMH pack through a regulator. The Watchdog Timer protects against charger latch-up if firmware enters an illegal state. For higher power applications, add an external current-sense amplifier and use the spare GPIO for relay cutoff and LED status indication. Migration to PIC16F88 or PIC16F628A is recommended for designs needing firmware flexibility.
Recommended
Consumer Remote Controls and IR Links
The PIC16C621AT-20E/SO is widely used in TV, set-top box, and air-conditioner remote controls where the 1.75 KB OTP holds the entire IR protocol stack (RC-5, NEC, SIRC, or proprietary). TMR0 generates the 36-58 kHz carrier via PWM or bit-banging while the CPU encodes the command frame, and the 13 GPIO drive the keypad matrix and IR LED. Sleep current with the Watchdog Timer running on its internal RC oscillator is below 1 uA typical, extending battery life over years. The 5 V tolerance and wide operating temperature range survive temperature swings in living-room and outdoor use. Migrate to PIC16F628A for designs that need firmware updates without case opening.
Recommended
Security and Alarm Panels
Wired PIR motion detectors, glass-break sensors, and door/window contact interfaces use the PIC16C621A for low-power signal conditioning and alarm decision logic. The two analog comparators detect PIR amplifier output transitions and supervise the wired loop for tamper, while TMR1 debounces mechanical reed switches and supervises the Watchdog Timer for fail-safe operation. The 13 GPIO drive alarm relays, status LEDs, and optional keypad input. Low sleep current is achieved by halting the CPU between sensor events and waking on comparator change. The OTP memory secures the alarm logic against cloning. Add a piezo buzzer driver transistor for local alarm and a serial EEPROM companion for event logging; migrate to PIC16F88 for designs requiring encrypted firmware or remote firmware updates.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621AT-20E/SO β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621AT-20/SO | PIC16C621A-04E/SO | PIC16C620A-20E/SO | PIC16F627-20E/SO | PIC16F628-20E/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | 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 | 18-SOIC - same |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 0.875 KB OTP | 1.75 KB Flash | 3.5 KB Flash |
| Max CPU Clock | 20 MHz | 20 MHz | 4 MHz | 20 MHz | 20 MHz | 20 MHz |
| RAM | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 128 bytes | 224 bytes |
| Operating Temperature | -40C to +125C (Extended) | -40C to +85C (Industrial) | -40C to +125C (Extended) | -40C to +125C (Extended) | -40C to +125C (Extended) | -40C to +125C (Extended) |
| Program Memory Type | OTP | OTP | OTP | OTP | Flash + 128B EEPROM | Flash + 224B EEPROM |
| USART | No | No | No | No | No | Yes (hardware USART) |
| Lifecycle Status | NRND | NRND | NRND | NRND | Active | Active |
Key Differentiators
- Extended temperature grade for automotive/industrial use (vs PIC16C621AT-20/SO)
- Highest speed in the 18-SOIC 16C62x family (vs PIC16C621A-04E/SO)
- Largest OTP program memory in the 16C620A/621A pair (vs PIC16C620A-20E/SO)
- Drop-in path to flash memory for field upgrades (vs PIC16F627-20E/SO)
Design Notes
Place a 100 nF X7R decoupling capacitor within 5 mm of the VDD pin (pin 14) and a bulk 10 uF tantalum or ceramic at the board input. The PIC16C621AT-20E/SO draws up to 2 mA at 5 V/20 MHz and as little as 1 uA in sleep with Watchdog Timer running on its internal RC. Add a 10 kohm pull-up on MCLR (pin 4) to keep reset stable during power-up; an optional diode from VDD to MCLR enables faster brown-out recovery.
The 18-SOIC footprint fits a 1.27 mm pitch SOIC land pattern with 0.41 mm x 1.5 mm pads; reserve a copper pour under the package thermal pad area if migrating to the SSOP variant. Keep the OSC1/OSC2 traces (pins 15/16) under 10 mm and guard them from switching signals to avoid radiated EMI pickup. Route RA0-RA3 (pins 17, 18, 1, 2) on the analog side of the board with a separate analog ground island that joins VSS at a single point to keep comparator thresholds clean.
OTP memory cannot be re-programmed; a single bad write wastes the device. Always program using a verified hex file on a windowed PIC16C621A JW or flash-equivalent PIC16F627 for code development, then commit to OTP only for production. The Extended temperature grade 'E' variant is required for automotive under-hood use - substituting the Industrial 'I' version (-40C to +85C) fails AEC-Q100 thermal stress tests. Always configure the Watchdog Timer in long-timeout mode if your firmware has interrupt latency above 18 ms, otherwise spurious resets occur.
The PIC16C621A's analog comparators have a typical propagation delay of 200-400 ns; for high-speed events, use TMR1 capture mode instead. The internal voltage reference for the comparators has a +/- 5% tolerance across temperature, so calibrate thresholds in firmware using the bandgap or an external reference for precision applications. The I/O pins source/sink up to 25 mA but the total package dissipation is limited to 800 mW; budget current accordingly when driving multiple LEDs or relays.
Compliance Information
RoHS compliant per Microchip product page; lead-free matte-tin finish. Not AEC-Q100 qualified, but Extended -40C to +125C temperature grade supports many automotive cabin and industrial applications. For AEC-Q100 designs, the PIC16F627-I/SO is the recommended Microchip path.
