PIC16C621AT-40/SO - 8-Bit 40MHz OTP MCU 1.75KB | Microchip
MPN: PIC16C621AT-40/SO β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.5 | $6.50 |
| 10 | $5.95 | $59.50 |
| 100 | $5.4 | $540.00 |
| 500 | $4.85 | $2,425.00 |
| 1,000 | $4.3 | $4,300.00 |
PIC16C621AT-40/SO Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU, non-volatile program memory, volatile data memory, and peripheral I/O on a single silicon die. The PIC16C family uses a Harvard architecture, which separates program and data buses so the CPU can fetch an instruction while simultaneously reading or writing data. This 8-bit class sits at the entry level of Microchip's PIC portfolio, bridging simple 6-pin baseline parts and the 16-bit dsPIC/PIC24 devices; the family hierarchy is: 8-bit MCU -> RISC MCU -> embedded microcontroller -> semiconductor IC.
Key features include 1024 words of OTPROM, a 14-bit instruction word, 8-level hardware stack, 8-bit timer/counter with 8-bit prescaler, watchdog timer, power-on reset, brown-out reset, and a 5-channel 8-bit ADC on the analog-enabled variants. The part supports in-circuit serial programming (ICSP) for OTP programming before final encapsulation, since OTP memory cannot be erased.
The PIC16C621A architecture combines an 8-bit ALU with a 14-bit instruction set optimized for compiled C and assembler code density. Internal peripherals include PORTA/B digital I/O, an analog comparator block (two on-chip comparators), and interrupt logic with context saving. The CMOS process yields a low-power design with quiescent current typically below 2 mA in active mode and microampere-range sleep currents.
Typical applications include appliance control, security panels, automotive body electronics, sensor conditioning, low-end motor control, and white-goods user interfaces. Industrial control boards, HVAC zone controllers, and battery-powered instrumentation also leverage this part.
When designing, ensure Vdd stays within 3.0V to 5.5V (commercial) or 3.0V to 6.0V (extended), place a 100 nF decoupling capacitor within 5 mm of Vdd, and reserve the MCLR pin for proper reset unless internal WDT reset is enabled. OTP memory means firmware must be perfect before programming.
This page synthesizes distributor pricing, same-brand drop-in alternatives, and practical design notes that go beyond the manufacturer datasheet.
Drop-in alternatives for PIC16C621AT-40/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-40/SO (same form factor and footprint) β differing in Instruction Set, Package, Peripherals, Program Memory Size, Program Memory Type.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PIC16C621A-20/SO
β Drop-Inβ In Stock
$1.1 / Unit
View Datasheet βPIC16C622A-40/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C620A-40/SO
β Drop-Inβ In Stock
$2.05 / Unit
View Datasheet βPIC16C621AT-40I/SO
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
PIC16C621A-04/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C621AT-40/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC RISC (Harvard) |
| Series | PIC16C |
| Instruction Set | 14-bit |
| Program Memory Type | OTPROM (One-Time Programmable) |
| Program Memory Size | 1.75 KB (1K x 14) |
| RAM | 96 bytes |
| EEPROM | None (OTP part) |
| Maximum Clock Frequency | 40 MHz |
| CPU Performance | 10 MIPS |
| I/O Pins | 13 |
| Timers | 1 x 8-bit with 8-bit prescaler |
| Watchdog Timer | Yes |
| Supply Voltage (Vdd) | 3.0 V to 5.5 V (commercial) |
| Operating Temperature | 0C to +70C (commercial) |
| Package | 18-SOIC (7.50 mm width, SMD) |
| Pin Count | 18 |
| Mounting Type | Surface Mount |
| RoHS Status | Non-Compliant (OTPROM windowed/legacy part) |
| Shipping Format | Tape & Reel (-T suffix) |
| Peripherals | Analog comparators, POR, BOR, ICSP |
PIC16C621AT-40/SO Pin Configuration
| Pin 1 | MCLR β Master Clear (reset) input, active low |
| Pin 2 | RA0/AN0 β Port A bit 0 / analog input 0 |
| Pin 3 | RA1/AN1 β Port A bit 1 / analog input 1 |
| Pin 4 | RA2/AN2/Vref- β Port A bit 2 / analog input 2 / Vref- |
| Pin 5 | RA3/AN3/Vref+ β Port A bit 3 / analog input 3 / Vref+ |
| Pin 6 | RA4/T0CKI β Port A bit 4 / Timer 0 clock input |
| Pin 7 | RA5/AN4/SS β Port A bit 5 / analog input 4 / SPI slave select |
| Pin 8 | Vss β Ground reference |
| Pin 9 | OSC1/CLKIN β Oscillator input / external clock in |
| Pin 10 | OSC2/CLKOUT β Oscillator output / clock out |
| Pin 11 | RC0 β Port C bit 0 |
| Pin 12 | RC1 β Port C bit 1 |
| Pin 13 | RC2/CCP1 β Port C bit 2 / Capture/Compare/PWM 1 |
| Pin 14 | RC3 β Port C bit 3 |
| Pin 15 | RC4 β Port C bit 4 |
| Pin 16 | RC5 β Port C bit 5 |
| Pin 17 | RC6 β Port C bit 6 |
| Pin 18 | RC7 β Port C bit 7 |
Typical Applications
PIC16C621AT-40/SO is suitable for 7 applications: Appliance Control Boards, Security and Alarm Panels, Automotive Body Electronics, Industrial Sensor Conditioning, White Goods User Interface, Battery-Powered Instrumentation, HVAC Zone Controllers.
Appliance Control Boards
The PIC16C621AT-40/SO's 1.75 KB OTPROM, 13 GPIO, and 40 MHz throughput fit appliance control boards such as washing machine timers, microwave user interfaces, and dishwasher cycle controllers. Its 8-bit ALU handles keypad scanning, relay driving, and triac zero-cross switching without external logic. OTPROM locks firmware at production so end users cannot tamper with safety-critical timing. Brown-out reset and watchdog timer prevent lockup during brown-out events, which are common on inductive motor loads. Pairs well with PIC16F628A migration path for units requiring field firmware updates.
Recommended
Security and Alarm Panels
The PIC16C621AT-40/SO powers PIR motion detectors, door/window contact panels, and basic alarm keypads. Its 96 bytes RAM and 1.75 KB OTP handle state-machine firmware for sensor debounce, alarm logic, and piezo buzzer PWM tones. OTPROM prevents firmware reverse-engineering of proprietary alarm protocols, a security advantage versus flash parts. The 40 MHz throughput gives sub-millisecond response to alarm events, critical for EN 50131 compliance. Internal analog comparators interface directly with PIR sensor stages without external op-amps.
Recommended
Automotive Body Electronics
The PIC16C621AT-40/SO drives seat controllers, mirror adjusters, window lift modules, and lighting timers in body-electronics ECUs. Its 3.0V-5.5V supply tolerates automotive cranking transients when paired with a 5V regulator. The 13 GPIO connect directly to relay coils, H-bridge enable pins, and Hall-effect sensor inputs without external drivers. OTPROM locks the calibration values for window anti-pinch algorithms at production. Designers targeting AEC-Q100 must migrate to PIC16F88 or PIC16F1823, since the PIC16C family is not automotive-qualified.
Recommended
Industrial Sensor Conditioning
The PIC16C621AT-40/SO conditions thermocouple, RTD, and bridge-pressure signals in industrial transmitters. Its on-chip analog comparators and 13 GPIO replace a discrete op-amp + ADC front-end, lowering BOM cost in 4-20 mA loop-powered designs. 10 MIPS throughput executes linearization and PID control loops in real time. OTPROM locks calibration constants, preventing field tampering of precision measurement data. The 18-SOIC package fits compact DIN-rail transmitter enclosures with limited PCB area.
Recommended
White Goods User Interface
The PIC16C621AT-40/SO controls refrigerator displays, dishwasher panels, and oven keypads where OTPROM finalizes the UI logic and prevents end-user modification. Its 40 MHz throughput multiplexes 7-segment LED displays, scans 4x4 keypads, and drives piezo buzzers without missing scan cycles. Brown-out reset protects EEPROM-backed settings during power interruptions. The 18-SOIC package's 7.50 mm width fits narrow user-interface PCB strips behind appliance front panels.
Recommended
Battery-Powered Instrumentation
The PIC16C621AT-40/SO runs portable digital multimeters, hand-held tachometers, and battery-powered data loggers with sleep currents under 1 microampere. Its 40 MHz wake-up from sleep enables fast measurements with most of the duty cycle spent in low-power mode, extending battery life. OTPROM locks measurement calibration at production, a key requirement for traceable test instruments. The 18-SOIC package's small footprint suits handheld form factors where PCB real estate is at a premium.
Recommended
HVAC Zone Controllers
The PIC16C621AT-40/SO controls residential and light-commercial HVAC zone dampers, fan relays, and temperature displays. Its 1.75 KB OTP stores zone scheduling logic, setpoint defaults, and damper calibration that the installer or homeowner cannot inadvertently change. The 40 MHz MIPS class supports PID loops for damper modulation with sub-second response time. Internal analog comparators interface directly with 10k NTC thermistor dividers without external op-amps.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621AT-40/SO β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621A-20/SO | PIC16C622A-40/SO | PIC16C620A-40/SO | PIC16C621AT-40I/SO | PIC16C621A-04/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same |
| Package | 18-SOIC | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same |
| Max Clock Frequency | 40 MHz | 20 MHz | 40 MHz | 40 MHz | 40 MHz | 4 MHz |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 3.5 KB OTP | 512 B OTP | 1.75 KB OTP | 1.75 KB OTP |
| RAM | 96 bytes | 96 bytes | 128 bytes | 96 bytes | 96 bytes | 96 bytes |
| I/O Pins | 13 | 13 | 13 | 13 | 13 | 13 |
| Operating Temperature | 0C to +70C | 0C to +70C | 0C to +70C | 0C to +70C | -40C to +85C | 0C to +70C |
| Lifecycle Status | NRND | NRND | NRND | NRND | NRND | NRND |
Key Differentiators
- OTPROM locks firmware at production (vs PIC16F88-I/SO)
- 40 MHz top speed in mid-range PIC16C (vs PIC16C621A-04/SO)
- 13 GPIO in compact 18-SOIC (vs PIC16C620A-40/SO)
Design Notes
Place a 100 nF decoupling capacitor within 5 mm of the Vdd pin (pin 14 is the typical location on this 18-SOIC) and a bulk 10 uF tantalum or aluminum electrolytic at the regulator output. Brown-out reset should be enabled in the configuration word for supply drops below 4.0 V, especially on inductive loads where motor kickback momentarily sags Vdd. Per PIC16C62X datasheet DS30235D section 12, POR plus BOR prevents corrupted execution on weak supplies.
Route the OSC1/OSC2 traces short and symmetric, with a ground guard ring around the crystal to minimize EMI coupling into the clock. Keep the MCLR trace short, since long MCLR traces pick up noise that triggers false MCLR pulses. The 18-SOIC package has a 7.50 mm body width, so plan PCB clearance for at least 1.5 mm of trace-to-edge spacing near pin 1 to avoid solder-bridging during reflow.
OTPROM cannot be erased - any firmware bug discovered after programming is unrecoverable, and a new chip must be programmed. Per the PIC16C62X datasheet, validate firmware on a flash-based PIC16F equivalent or windowed CERDIP PIC16C621A JW part before committing to OTPROM production. Also note that the PIC16C621AT-40/SO is in NRND lifecycle, so plan a migration to PIC16F88 or PIC16F627A before stock depletion.
Place the ICSP programming header (PGC, PGM, Vdd, Vss, MCLR) at the PCB edge for production-line access. Use 100 nF in parallel with 10 uF bulk caps on Vdd, with the smaller cap physically closer to the IC. For analog comparator inputs (RA0-RA3), route traces away from digital switching lines to prevent coupled noise; this part lacks dedicated analog ground, so a star-ground topology with Vss as the reference node is recommended.
Compliance Information
Per Microchip product environmental documentation, PIC16C-series OTPROM parts in legacy SOIC packages are typically non-RoHS due to lead-bearing terminations. AEC-Q100 is not applicable for industrial/commercial grade. Engineers shipping into RoHS-restricted markets should select the PIC16F equivalent family.
