PIC16LC621AT-04I/SS - 8-Bit 4MHz OTP MCU 1.75KB 20-SSOP | Microchip
MPN: PIC16LC621AT-04I/SS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.85 | $3.85 |
| 10 | $3.46 | $34.60 |
| 100 | $3.08 | $308.00 |
| 500 | $2.77 | $1,385.00 |
| 1,000 | $2.46 | $2,460.00 |
PIC16LC621AT-04I/SS Overview
A PIC microcontroller (MCU) is a compact, self-contained computer-on-a-chip combining an 8-bit CPU, non-volatile program memory (here, OTP), volatile RAM, and configurable I/O peripherals on a single die. PIC MCUs sit in the broader hierarchy of embedded controllers -> microcontrollers -> 8-bit microcontrollers -> RISC microcontrollers -> semiconductors, and are widely used in cost-sensitive consumer and industrial control products. The 'C' in PIC16C indicates an OTP EPROM-based program memory architecture, distinguishing it from flash-based PIC16F variants.
Key features of the PIC16LC621AT-04I/SS include 12-bit wide instruction set with an 8-bit data path, seven or eight special function hardware registers, direct/indirect/relative addressing modes, and CMOS low-power technology supporting the wide 2.5 V to 6.25 V supply range. The /SS suffix denotes the 20-pin SSOP (Shrink Small Outline Package) form factor, and the '04' speed grade specifies 4 MHz maximum clock. The 'I' industrial temperature grade supports -40C to +85C ambient operation. According to the Microchip datasheet, this part belongs to the mid-range PIC16C6xx family and is suitable for products where one-time programmable memory and a small footprint are acceptable.
Typical applications span white goods and small appliance controllers, automotive body electronics (non-AEC-Q100), simple sensor interfaces, consumer remote controls, low-end timer/sequencer logic, and replacement of discrete logic in cost-optimized designs. For applications requiring in-system reprogrammability, designers should migrate to a flash-based PIC16F equivalent instead. The 20-SSOP package offers a compact 0.209 inch (5.30 mm) body width for high-density board layouts.
When designing with this device, carefully verify that OTP programming is acceptable for your production flow, since OTP parts cannot be erased or rewritten. Plan for adequate supply decoupling and ensure the WDT is enabled or disabled intentionally per the application requirement. According to the Microchip datasheet, the PIC16LC621A family is mature and may be subject to lifecycle transitions; verify current availability with Microchip before committing to new designs.
Drop-in alternatives for PIC16LC621AT-04I/SS — 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 PIC16LC621AT-04I/SS (same form factor and footprint) — differing in Operating Temperature Range, Program Memory Size, Core Architecture, Package, RAM Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC621A-04I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC621AT-04E/SS
✅ Drop-In✓ In Stock
$2.19 / Unit
View Datasheet →PIC16LC621AT-04I/SO
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →PIC16LC620A-04I/SS
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →PIC16LC621A-04I/P
✅ Drop-In✓ In Stock
$1.01 / Unit
View Datasheet →PIC16LC621AT-04I/SS Maximum Ratings & Electrical Characteristics
| Core Processor | PIC |
| Core Size | 8-Bit |
| Core Architecture | RISC |
| Series | PIC® 16C |
| Clock Speed (Max) | 4 MHz |
| Program Memory Size | 1.75 KB (1K x 14) |
| Program Memory Type | OTP (One-Time Programmable) |
| RAM Size | 96 bytes |
| Number of I/O Pins | 13 |
| Supply Voltage Range | 2.5 V to 6.25 V |
| Operating Temperature Range | -40C to +85C (Industrial) |
| Package / Case | 20-SSOP (0.209 inch, 5.30 mm body width) |
| Mounting Type | Surface Mount |
| Instruction Set Width | 12-bit |
| Data Path Width | 8-bit |
| Stack Depth | 2-level hardware stack |
| Peripherals | Brown-out Detect (BOD), Power-On Reset (POR), Watchdog Timer (WDT) |
| Addressing Modes | Direct, Indirect, Relative |
| Number of Special Function Registers | 7 or 8 |
| RoHS Status | Compliant |
PIC16LC621AT-04I/SS Pin Configuration
| Pin 1 | RA2 — GPIO / analog input |
| Pin 2 | RA3 — GPIO / analog input |
| Pin 3 | RA4 — GPIO / T0CKI |
| Pin 4 | MCLR — Master Clear (Reset, active low) |
| Pin 5 | VSS — Ground |
| Pin 6 | RB0 — GPIO / INT |
| Pin 7 | RB1 — GPIO |
| Pin 8 | RB2 — GPIO |
| Pin 9 | RB3 — GPIO |
| Pin 10 | RB4 — GPIO |
| Pin 11 | RB5 — GPIO |
| Pin 12 | RB6 — GPIO |
| Pin 13 | RB7 — GPIO |
| Pin 14 | VDD — Positive supply voltage |
| Pin 15 | OSC2 — Oscillator output |
| Pin 16 | OSC1 — Oscillator input |
| Pin 17 | RA0 — GPIO / analog input |
| Pin 18 | RA1 — GPIO / analog input |
| Pin 19 | RC0 — GPIO |
| Pin 20 | RC1 — GPIO |
Typical Applications
PIC16LC621AT-04I/SS is suitable for 6 applications: White Goods and Small Appliance Control, Automotive Body Electronics (Non-Safety), Consumer Remote Controls and IR Transmitters, Industrial Sensor Interface and Signal Conditioning, LED Lighting Controllers and Drivers, Battery-Powered Timers and Sequencers.
White Goods and Small Appliance Control
The PIC16LC621AT-04I/SS suits white goods and small appliance controllers where final firmware is locked and per-unit cost matters. Its 1.75 KB OTP program memory is sufficient for state machines controlling relays, triacs, and sensor inputs in microwaves, washing machines, and coffee makers. The 4 MHz clock handles slow electromechanical sequencing (timer ticks, button debounce, mode selection) without taxing the budget. The 13 GPIO pins map directly to keypad rows, LED indicators, and motor-driver enable lines; brown-out detect prevents erratic operation during brown-outs in mains-powered systems. Wide 2.5 V to 6.25 V supply tolerance lets the MCU run directly from rectified 5 V or 3.3 V rails. Industrial -40C to +85C support covers garage and laundry-room environments.
Recommended
Automotive Body Electronics (Non-Safety)
The PIC16LC621AT-04I/SS fits non-safety automotive body modules such as interior lighting controllers, mirror adjusters, seat-position memory, and accessory timing modules where AEC-Q100 qualification is not strictly required. Its 2.5 V to 6.25 V supply range tolerates 12 V battery cranking transients when paired with external regulators. The 4 MHz clock and 96 bytes RAM are adequate for PWM-based LED dimming, debounced switch inputs, and CAN/LIN slave tasks in body networks. The -40C to +85C industrial range covers cabin environments. Designers targeting AEC-Q100 should evaluate Microchip's automotive-grade PIC16F or dsPIC families instead, since this part lacks formal automotive qualification.
Recommended
Consumer Remote Controls and IR Transmitters
The PIC16LC621AT-04I/SS is well-suited for consumer IR remote controls, RF key fobs, and simple wireless transmitters where ultra-low cost and small footprint dominate. The 1.75 KB OTP stores IR protocol tables (RC5, NEC, SIRC), button-scanning routines, and battery-saving sleep routines. 96 bytes of RAM covers the transmit buffer and timing variables. The 4 MHz clock generates accurate 38 kHz / 40 kHz carrier frequencies via timer interrupts for IR LED modulation. Wide 2.5 V to 6.25 V operation runs directly from 2 x AAA or coin-cell batteries. The 20-SSOP package fits inside slim remote enclosures. Power-on reset and watchdog timer prevent lock-ups on weak batteries.
Recommended
Industrial Sensor Interface and Signal Conditioning
The PIC16LC621AT-04I/SS serves as a low-cost front-end for industrial sensor modules reading thermocouples, RTDs, switches, or 4-20 mA loops. Its 13 GPIO pins accept multiple digital inputs and drive indicator LEDs or relay coils. The integrated brown-out detect and power-on reset protect against unstable 24 V industrial rails when fed through a 5 V regulator. 1.75 KB of OTP accommodates linearization tables and HART-style request handling. The 4 MHz clock provides ample timing resolution for polled sensors at sub-kHz rates. Industrial -40C to +85C operation handles factory-floor temperature swings. Watchdog timer recovers from EMI-induced firmware stalls common in motor cabinets.
Recommended
LED Lighting Controllers and Drivers
The PIC16LC621AT-04I/SS drives LED lighting controllers for decorative strips, signage, and architectural fixtures. Its 13 GPIO pins directly switch MOSFETs or constant-current LED drivers via PWM at the 4 MHz CPU clock, generating accurate dimming waveforms at audio-band rates. 1.75 KB OTP stores color-sequence tables, fade curves, and DMX-512 slave parsing logic. The 2.5 V to 6.25 V supply range accommodates 3.3 V logic or 5 V regulated supplies in LED drivers. Industrial -40C to +85C range covers outdoor enclosures and ceiling-fixture thermal loads. Brown-out detect ensures clean resets during mains dips in triac-dimmable installations.
Recommended
Battery-Powered Timers and Sequencers
The PIC16LC621AT-04I/SS powers battery-operated timer modules, irrigation controllers, and watch-dog sequencers where OTP cost savings and wide-voltage operation matter. The 4 MHz CPU clock drives RTC-style counters from a 32.768 kHz crystal via timer0, while GPIO outputs trigger relays or MOSFETs at scheduled times. 96 bytes RAM holds current timer state and user-set variables stored in EEPROM emulation. The 2.5 V to 6.25 V supply range runs directly from 2 x AA alkaline cells down to end-of-life voltage. Brown-out detect prevents EEPROM corruption as batteries deplete. Industrial -40C to +85C range supports outdoor and automotive-cabin installations.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621AT-04I/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621A-04I/SS | PIC16LC621AT-04E/SS | PIC16LC621AT-04I/SO | PIC16LC620A-04I/SS | PIC16LC621A-04I/P |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 20-SSOP | 20-SSOP - same | 20-SSOP - same | 20-SOIC - same pinout, larger body | 20-SSOP - same | 20-PDIP - same pinout, through-hole |
| Clock Speed (Max) | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 0.875 KB OTP | 1.75 KB OTP |
| RAM Size | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 80 bytes | 96 bytes |
| Supply Voltage Range | 2.5 V to 6.25 V | 2.5 V to 6.25 V | 2.5 V to 6.25 V | 2.5 V to 6.25 V | 2.5 V to 6.25 V | 2.5 V to 6.25 V |
| Operating Temperature | -40C to +85C (Industrial) | -40C to +85C | -40C to +125C (Extended) | -40C to +85C | -40C to +85C | -40C to +85C |
| Number of I/O Pins | 13 | 13 | 13 | 13 | 13 | 13 |
Key Differentiators
- Industrial temperature grade with wide voltage tolerance (vs PIC16LC620A-04I/SS)
- Compact 20-SSOP footprint for space-constrained designs (vs PIC16LC621A-04I/P)
- Wide 2.5 V to 6.25 V supply tolerance supports both 3.3 V and 5 V rails (vs PIC16LC621AT-04E/SS)
Design Notes
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 battery-powered designs, add a 10 uF bulk capacitor on the VDD rail to handle transient loads when GPIO banks switch simultaneously. The PIC16LC621AT-04I/SS's brown-out detect (BOD) protects against code corruption when VDD drops below the BOD threshold; configure the BOD via configuration bits during programming. Always hold MCLR high through a 10 kohm pull-up resistor for normal operation.
Remember that OTP (One-Time Programmable) memory cannot be erased or rewritten once programmed - unlike flash-based PIC16F parts. Plan for prototype validation on a flash equivalent (e.g., PIC16F716-I/SO) before committing to OTP for production. Verifying OTP-programmed units requires physical destruction or dedicated verification routines. Programming failures on OTP parts result in scrap, so invest in programmer calibration and socket testing before any production run.
Route the OSC1/OSC2 crystal traces (pins 16/15) short and symmetric, with the crystal placed within 5 mm of the MCU. Keep high-frequency switching traces (PWM outputs, relay drive lines) away from the oscillator loop to avoid injection-locking or extra jitter. The 20-SSOP package's 0.65 mm pitch requires fine-pitch PCB fabrication; use ENIG surface finish and 0.1 mm solder mask dams between pads. Provide a copper pour on the top layer tied to VSS for thermal dissipation and ground return.
Compliance Information
RoHS compliant per Microchip product page and distributor listings. Not AEC-Q100 qualified - choose automotive-grade PIC16F or dsPIC variants for AEC-Q100 designs. Halogen-free status not explicitly stated in provided data.
