PIC16LC621AT-04I/SO - 8-Bit 4MHz OTP MCU 18-SOIC | Microchip
MPN: PIC16LC621AT-04I/SO ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.85 | $2.85 |
| 10 | $2.45 | $24.50 |
| 100 | $1.95 | $195.00 |
| 500 | $1.72 | $860.00 |
| 1,000 | $1.55 | $1,550.00 |
PIC16LC621AT-04I/SO Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, working RAM, and peripheral I/O on one die. The PIC16C family uses a RISC Harvard architecture with separate program and data buses, a fixed 12-bit-wide instruction word, an 8-bit-wide data path, two-level deep hardware stack, and seven/eight special function registers. Direct, indirect, and relative addressing modes are supported. As part of the broader hierarchy, this PIC16 MCU sits under: microcontroller -> embedded MCU -> microprocessor-based system -> semiconductor. Synonyms: MCU, microcontroller unit, embedded controller.
Key features include 13 general-purpose digital I/O pins (12 I/O ports per datasheet overview), a 4 MHz internal/external oscillator option, low-power CMOS construction with typical sleep currents in the microamp range, and an on-chip watchdog timer for safety-critical embedded control. The OTP program memory allows one-time field programming using standard PIC development tools, which is well-suited to mature production designs where code is finalized.
The architecture is built around a 14-bit instruction set optimized for compact code density, allowing simple control loops, state machines, and peripheral driving tasks to fit in the small 1K instruction-word memory. Brown-out reset, power-on reset, and a programmable code-protect bit are provided. The '04' speed grade (4 MHz) is the lowest clock speed in the family and yields the lowest dynamic power consumption.
Typical applications include appliance control (washing machines, microwave ovens, HVAC fan control), industrial sensor interfaces, low-cost remote controls, automotive interior subsystems (non-safety), battery-powered metering, and consumer white goods. The wide 2.5-6.25V supply tolerance makes the part tolerant of unregulated wall-adapter rails.
When designing with this device, pay attention to the OTP nature of program memory - firmware must be fully validated before programming because re-programming in-circuit is not possible. A 100 nF decoupling capacitor placed within 5 mm of VDD and a 10-100 uF bulk capacitor on the supply rail are recommended. MCLR must be pulled high through a 10 kohm resistor for normal operation.
This page synthesizes distributor pricing from DigiKey, Mouser, LCSC, and Octopart, cross-references drop-in same-package alternatives from the PIC16C621A family, and provides practical design notes not consolidated in the manufacturer datasheet alone.
Drop-in alternatives for PIC16LC621AT-04I/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 PIC16LC621AT-04I/SO (same form factor and footprint) — differing in Program Memory Size, Core Architecture, Instruction Set Width, Operating Temperature Range, RAM Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC621A-04I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC621A-04E/SO
✅ Drop-In✓ In Stock
$2.25 / Unit
View Datasheet →PIC16LC621AT-04E/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC620AT-04I/SO
✅ Drop-In✓ In Stock
$1.62 / Unit
View Datasheet →PIC16LC621AT-04I/SO Maximum Ratings & Electrical Characteristics
| Core Processor | PIC |
| Core Size | 8-Bit |
| Series | PIC 16C |
| Program Memory Size | 1.75 KB (1K x 14) |
| Program Memory Type | OTP (One-Time Programmable) |
| RAM Size | 96 x 8 bytes |
| EEPROM Size | None |
| Clock Speed (Maximum) | 4 MHz |
| 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 | 18-SOIC (0.295 inch, 7.50 mm width) |
| Mounting Type | Surface Mount |
| Instruction Set Width | 12-bit |
| Data Path Width | 8-bit |
| Hardware Stack Depth | 2 levels |
| Connectivity | GPIO only |
| Peripherals | Brown-out Detect/Reset, POR, WDT |
| Oscillator Type | External |
| RoHS Status | unknown |
PIC16LC621AT-04I/SO Pin Configuration
| Pin 1 | RA2 — General-purpose I/O port A bit 2 |
| Pin 2 | RA3 — General-purpose I/O port A bit 3 |
| Pin 3 | RA4/T0CKI — General-purpose I/O / Timer0 clock input |
| Pin 4 | MCLR — Master Clear reset input (active low) |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — General-purpose I/O / external interrupt input |
| Pin 7 | RB1 — General-purpose I/O port B bit 1 |
| Pin 8 | RB2 — General-purpose I/O port B bit 2 |
| Pin 9 | RB3 — General-purpose I/O port B bit 3 |
| Pin 10 | RB4 — General-purpose I/O port B bit 4 |
| Pin 11 | RB5 — General-purpose I/O port B bit 5 |
| Pin 12 | RB6 — General-purpose I/O port B bit 6 |
| Pin 13 | RB7 — General-purpose I/O port B bit 7 |
| Pin 14 | VDD — Positive supply voltage (2.5V to 6.25V) |
| Pin 15 | OSC2/CLKOUT — Oscillator crystal output / clock out |
| Pin 16 | OSC1/CLKIN — Oscillator crystal input / external clock in |
| Pin 17 | RA0 — General-purpose I/O port A bit 0 |
| Pin 18 | RA1 — General-purpose I/O port A bit 1 |
Typical Applications
PIC16LC621AT-04I/SO is suitable for 6 applications: White Goods Appliance Control, Battery-Powered Remote Control, Industrial Sensor Interface Module, HVAC Fan and Damper Controller, Automotive Interior Lighting Controller, Consumer White-Goods Timer.
White Goods Appliance Control
The PIC16LC621AT-04I/SO fits white-goods appliance control (washing machines, microwave ovens, dishwashers) because its 1.75 KB OTP, 13 I/O, and 2.5-6.25V supply tolerance directly support relay drivers, LED indicators, and button-matrix keypads. The 'LC' CMOS variant minimizes idle current so door-sensor polling draws minimal standby power across long idle periods. Industrial -40C to +85C operation tolerates kitchen-cabinet thermal rise. Compared with a 32-bit MCU, this PIC's 4 MHz / 1 MIPS throughput is sufficient for sequential relay-state machines with debounced mechanical switches. Place optocouplers between AC-line-driven relays and the MCU's GPIO pins for safety isolation; MCLR must be pulled high through a 10 kohm resistor for normal operation.
Recommended
Battery-Powered Remote Control
The PIC16LC621AT-04I/SO suits battery-powered IR/RF remote controls because its CMOS 'LC' core draws microamp-level sleep current, preserving coin-cell life across years of standby. The 1.75 KB OTP is adequate for fixed infrared protocol encoding (RC-5, NEC, SIRC) and button-matrix scanning, while 13 I/O is sufficient for 4x4 keypads plus status LEDs. The 2.5V minimum supply supports 2x AA alkaline cells down to end-of-life voltage. Compared with newer PIC16F parts, the OTP variant offers no in-field reprogramming, which is acceptable for shipped consumer products. Decouple VDD with a 100 nF ceramic capacitor within 5 mm of the IC, and put a 10 uF bulk capacitor across the battery terminals for inductive load transients.
Recommended
Industrial Sensor Interface Module
The PIC16LC621AT-04I/SO works well in industrial sensor-interface modules (4-20 mA loop converters, RTD conditioners, photoelectric sensor signal processors) because its 13 I/O can scan multiple analog signals via external multiplexer ICs and its 2.5-6.25V supply range accepts 24V industrial rails after a simple linear regulator. The hardware watchdog timer and brown-out reset provide fault recovery needed for unattended field installations. Industrial -40C to +85C operation covers outdoor enclosures. Compared with a Cortex-M0 module, this PIC's 1 MIPS is adequate for polled sensor readout every 10 ms. Use the GPIO's weak pull-ups for switch-type sensor inputs; reserve MCLR for in-circuit programming header only if not using the OTP-revision-locked variant.
Recommended
HVAC Fan and Damper Controller
The PIC16LC621AT-04I/SO fits HVAC fan-speed and damper-position controllers because its 13 I/O can drive triac-gate optocouplers, read thermistor dividers through GPIO, and pulse-stepper motor drivers. The 4 MHz instruction rate executes proportional control loops at 1 kHz update rates with margin. 2.5-6.25V supply tolerance accommodates 24 VAC-derived DC rails after rectification, simplifying HVAC control-board design. The -40C to +85C industrial range covers attic-installed HVAC equipment. The hardware watchdog catches firmware lockups caused by EMI from relay switching, important in this noisy environment. Add a TVS diode across the triac for transient suppression, and a ferrite bead on the supply input to reduce conducted EMI.
Recommended
Automotive Interior Lighting Controller
The PIC16LC621AT-04I/SO can drive automotive interior lighting (ambient LED strips, dome-light delay, puddle lamps) because its 13 I/O can PWM LED drivers via external MOSFETs and read door-switch signals with internal weak pull-ups. The 2.5-6.25V supply range tolerates 12V automotive cranking transients after a simple LDO, and the -40C to +85C range suits cabin installations. The 'LC' core draws low quiescent current during parked-vehicle standby. Note: this part is not AEC-Q100 qualified, so for OEM automotive designs the Q-graded PIC16F628AT-I/SO is preferred. Decouple VDD with reverse-polarity protection diode and 100 nF ceramic; place ESD protection on external connector pins.
Recommended
Consumer White-Goods Timer
The PIC16LC621AT-04I/SO is well-suited to microwave-oven, rice-cooker, and bread-machine countdown timers because its OTP memory permanently stores the validated cooking profile, eliminating field reprogramming risk and reducing firmware-update support costs. The 13 I/O handles 7-segment LED multiplexing, membrane keypad scanning, buzzer drive, and relay control. The 4 MHz clock generates accurate timing via the 8-bit Timer0 with prescaler. The 2.5-6.25V supply range accepts rectified mains after a small transformer and regulator. Compared with a modern RTC + MCU combo, integrating timing and control in one PIC16 reduces BOM cost by 30-40% in this cost-sensitive segment.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621AT-04I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621A-04I/SO | PIC16LC621A-04E/SO | PIC16LC621AT-04E/SO | PIC16LC620AT-04I/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 |
| Program Memory | 1.75 KB (1K x 14) OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 0.875 KB OTP (-50%) |
| Clock Speed (Maximum) | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| 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 |
| Operating Temperature | -40C to +85C (Industrial) | -40C to +85C | -40C to +125C (Extended) | -40C to +125C (Extended) | -40C to +85C |
| I/O Pins | 13 | 13 | 13 | 13 | 13 |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete |
| Packaging Form | Tape & Reel | Tube | Tube | Tape & Reel | Tape & Reel |
Key Differentiators
- Low-power CMOS 'LC' core with sub-mA active current (vs PIC16C621A-04/P (PDIP))
- Industrial temperature range -40C to +85C (vs PIC16LC621A-04E/SO (Extended temp))
- Tape-and-reel packaging for high-volume SMD assembly (vs PIC16LC621A-04I/SO (tube))
Design Notes
Place a 100 nF ceramic decoupling capacitor within 5 mm of the VDD pin (pin 14) with a short, wide trace to VSS (pin 5). Add a 10-100 uF bulk aluminum-polymer capacitor on the supply rail near the IC to absorb relay and motor-switching transients. The 'LC' CMOS core draws typical operating current below 2 mA at 4 MHz, so even small decoupling capacitors easily handle the ripple budget.
The PIC16LC621AT-04I/SO is OTP (One-Time Programmable); once programmed it cannot be erased or rewritten. Production firmware must be fully validated on a windowed or flash-equivalent PIC16F variant before committing the OTP. For prototypes, use PIC16F628A-I/SO which shares the same 18-SOIC pinout and lets you iterate firmware freely, then migrate to the OTP version only for production runs.
Keep the oscillator traces (pins 15 OSC2 and 16 OSC1) short - under 10 mm total loop length - and surround them with a ground pour to minimize radiated EMI. If using an external crystal, place the load capacitors (typically 15-33 pF) within 3 mm of the OSC pins. For external clock input mode, drive OSC1 with a clean CMOS rail-to-rail signal and leave OSC2 floating. MCLR (pin 4) requires a 10 kohm pull-up to VDD for normal operation; add a 100 nF capacitor from MCLR to VSS only if you need a clean power-on-reset delay.
Compliance Information
RoHS, REACH, lead-free, and halogen-free status were not present in the verified distributor snippets and are set to unknown. The part is not AEC-Q100 qualified per Octopart comparison data; for automotive OEM designs use the Q-suffix PIC16F628AT-I/SO instead.