PIC16LC621T-04I/SS - 4MHz 8-Bit OTP MCU, 20-SSOP | Microchip
MPN: PIC16LC621T-04I/SS ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.5 | $5.50 |
| 10 | $5 | $50.00 |
| 100 | $4.45 | $445.00 |
| 500 | $3.95 | $1,975.00 |
| 1,000 | $3.55 | $3,550.00 |
PIC16LC621T-04I/SS Overview
An 8-bit microcontroller (MCU) is a single-chip computer integrating a CPU, program memory, RAM, and peripherals onto one die. The PIC 16C architecture belongs to the broader RISC microcontroller family within the wider microcontroller -> embedded processor -> semiconductor taxonomy. 8-bit MCUs remain the workhorses of low-cost embedded control because they offer deterministic instruction execution, very low quiescent current, and a mature toolchain. The 'LC' suffix identifies the low-voltage, low-power process node used by this device, optimized for designs previously served by discrete logic or earlier PIC12/PIC16 baselines.
Key features of the PIC16LC621T-04I/SS include 12 to 13 general-purpose digital I/O pins (sources vary slightly), a two-level deep hardware stack, seven or eight special-function hardware registers, and direct/indirect/relative addressing modes. The instruction word is 14 bits wide while the data path is 8 bits wide, a hallmark of mid-range PIC devices. Brown-out Detect/Reset, Power-On Reset (POR), and a Watchdog Timer (WDT) are integrated on-chip, allowing the device to recover from low-voltage brown-out events and runaway code without external supervisory components.
The PIC 16C core is a Harvard-architecture RISC processor: separate program and data buses permit simultaneous instruction fetch and data access. Each instruction executes in a single instruction cycle (four oscillator clocks), which simplifies deterministic timing analysis. The device requires an external oscillator and offers flexible clock source selection, enabling the designer to trade EMI, cost, and power consumption by choosing RC, crystal, or resonator timing references.
Typical applications for the PIC16LC621T-04I/SS include industrial control logic, appliance and white-goods subsystems, simple sensor interfaces, automotive body controllers (non-safety), remote controls, and battery-powered instrumentation. Its OTP memory makes it well-suited to high-volume, cost-sensitive products where firmware is finalized at production.
A key design consideration is that OTP (One-Time Programmable) memory cannot be reprogrammed in-circuit; prototypes should be developed on the windowed (JW) or UV-erasable variant or a pin-compatible Flash device such as the PIC16F baseline. Designers should also budget for the external RC or crystal oscillator components required by this device.
This page synthesizes distributor pricing, pin-compatible drop-in alternatives, lifecycle status, and practical design notes not found on the manufacturer datasheet's first page.
Drop-in alternatives for PIC16LC621T-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 PIC16LC621T-04I/SS (same form factor and footprint) — differing in Operating Temperature Range, RAM Size, Mounting Type, Program Memory Type, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC621T-04/SS
✅ Drop-In✓ In Stock
$2.1 / Unit
View Datasheet →PIC16LC621AT-04I/SS
✅ Drop-In✓ In Stock
$2.46 / Unit
View Datasheet →PIC16LC621A-04I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC620A-04I/SS
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$1.55 / Unit
View Datasheet →PIC16LC620T-04I/SS
✅ Drop-In✓ In Stock
$1.75 / Unit
View Datasheet →PIC16LC621T-04I/SS Maximum Ratings & Electrical Characteristics
| Core Processor | PIC |
| Core Size | 8-Bit |
| Core Series | PIC® 16C |
| Maximum Clock Speed | 4 MHz |
| Program Memory Size | 1.75 KB (1K x 14) |
| Program Memory Type | OTP (One-Time Programmable) |
| RAM Size | 80 bytes |
| Number of I/O Pins | 12 to 13 (sources vary, datasheet authoritative) |
| Supply Voltage (Vdd) | 2.5 V to 6.25 V |
| Operating Temperature Range | -40 C to +85 C (Industrial, 'I' suffix) |
| Package / Case | 20-SSOP (0.209 inch / 5.30 mm body width) |
| Mounting Type | Surface Mount (Gull Wing) |
| Instruction Word Width | 14 bits |
| Data Path Width | 8 bits |
| Hardware Stack Depth | 2 levels |
| Oscillator Type | External (RC, Crystal, or Resonator) |
| Integrated Peripherals | Brown-out Detect/Reset, POR, Watchdog Timer (WDT) |
| Addressing Modes | Direct, Indirect, Relative |
| Special Function Registers | 7 to 8 |
| Lifecycle Status | Obsolete |
| Packaging Form | Tape & Reel ('T' suffix) |
PIC16LC621T-04I/SS Pin Configuration
| Pin 1 | RA2 — General-purpose I/O / analog input |
| Pin 2 | RA3 — General-purpose I/O / MCLR shared |
| Pin 3 | RA4 — General-purpose I/O / T0CKI |
| Pin 4 | MCLR/Vpp — Master Clear (reset) / programming voltage |
| Pin 5 | Vss — Ground reference |
| Pin 6 | RB0 — General-purpose I/O / INT |
| Pin 7 | RB1 — General-purpose I/O |
| Pin 8 | RB2 — General-purpose I/O |
| Pin 9 | RB3 — General-purpose I/O |
| Pin 10 | RB4 — General-purpose I/O |
| Pin 11 | RB5 — General-purpose I/O |
| Pin 12 | RB6 — General-purpose I/O / PGC |
| Pin 13 | RB7 — General-purpose I/O / PGD |
| Pin 14 | Vdd — Positive supply voltage (2.5 V to 6.25 V) |
| Pin 15 | OSC2 — Oscillator output / clock out |
| Pin 16 | OSC1 — Oscillator input / external clock in |
| Pin 17 | RA0 — General-purpose I/O |
| Pin 18 | RA1 — General-purpose I/O |
| Pin 19 | RA5 — General-purpose I/O |
| Pin 20 | Vdd — Positive supply (alternate Vdd pin) |
Typical Applications
PIC16LC621T-04I/SS is suitable for 6 applications: Industrial Control Logic, Appliance and White Goods Subsystems, Battery-Powered Remote Controls, Simple Sensor Interface Modules, Automotive Body Controllers (Non-Safety), Consumer Toy and Hobby Electronics.
Industrial Control Logic
The PIC16LC621T-04I/SS fits industrial control logic roles where its 4 MHz 8-bit core, 1.75 KB OTP program memory, and integrated Brown-out Reset plus Watchdog Timer deliver deterministic control of relays, solenoids, and indicator LEDs. The 2.5 V to 6.25 V supply range accepts both 3.3 V and 5 V rails from industrial 24 V-to-DC subsystems, and the -40 C to +85 C industrial temperature grade covers factory-floor enclosures. With 12-13 GPIO pins it can directly drive small signal-conditioning front-ends, opto-isolators, and discrete outputs without external logic. Designers should pair the MCU with bulk 10 uF plus 100 nF decoupling and follow the SSOP-20 land pattern recommended by Microchip application note AN578.
Recommended
Appliance and White Goods Subsystems
In washing machines, dishwashers, and microwave ovens the PIC16LC621T-04I/SS handles button-debounce, LED/LCD segment driving, and relay sequencing. Its 14-bit instruction width and 1.75 KB OTP memory hold complete user-interface state machines including timer logic, mode selection, and fault detection. The integrated Watchdog Timer recovers the appliance if firmware enters an illegal state, and Brown-out Reset handles AC-line sag events common in motor-start transients. OTP memory is appropriate because finished appliance firmware rarely changes. Reference designs in Microchip application note AN529 demonstrate similar PIC16C5x/LC6xx usage in washing-machine control boards.
Recommended
Battery-Powered Remote Controls
Battery-powered remote controls benefit from the PIC16LC621T-04I/SS low-voltage CMOS process, which lets the MCU operate down to 2.5 V from two alkaline or NiMH cells in series. The 4 MHz clock and modest 1 MIPS throughput deliver responsive IR or RF transmission without draining the battery, while the integrated Watchdog Timer and Brown-out Reset protect against low-cell lockups. With only 12-13 GPIO available, designers use direct port-pin PWM or bit-banged protocols for IR encoding. OTP memory keeps the unit cost low for high-volume consumer SKUs. Microchip application note AN543 discusses low-power PIC16 design patterns for battery-powered remotes.
Recommended
Simple Sensor Interface Modules
Sensor interface modules for thermistors, photocells, and simple switches use the PIC16LC621T-04I/SS to digitize analog signals via external RC timing tricks (no internal ADC) and to format data for downstream UART or one-wire links. The 80 bytes RAM hold recent samples, and the 1.75 KB OTP memory hosts linearization tables for the sensor. Wide 2.5 V to 6.25 V supply lets the module share power with 3.3 V sensors or 5 V analog front-ends. Brown-out Reset prevents data corruption when batteries weaken, and the small 20-SSOP footprint keeps the module compact.
Recommended
Automotive Body Controllers (Non-Safety)
Non-safety automotive body controllers - interior lighting, accessory delay timers, and simple door-lock sequencers - use the PIC16LC621T-04I/SS for its industrial temperature grade, integrated Brown-out Reset for crank-cycle voltage drops, and OTP memory that locks firmware against field tampering. The 4 MHz clock is more than adequate for body-controller timing functions, and the 20-SSOP package supports compact PCB modules behind dashboard trim. Note that AEC-Q100 qualification is NOT claimed on this part - for safety-critical or AEC-Q100-required designs, choose the PIC16F88T-I/SS or another automotive-grade PIC.
Recommended
Consumer Toy and Hobby Electronics
Consumer toys, model trains, and hobby electronics kits use the PIC16LC621T-04I/SS to drive small DC motors via PWM bit-banging, decode RC-servo pulses, and sequence LED animations. The 1.75 KB OTP memory holds multi-pattern sequences, while 12-13 GPIO connect directly to H-bridge drivers and LED arrays. Operating voltage down to 2.5 V supports 2-cell battery packs, and the industrial temperature grade tolerates storage in unheated garages. OTP memory prevents hobbyists from accidentally bricking units with errant code; commercial kits can program the device once at production and ship without further firmware risk.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621T-04I/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621T-04/SS | PIC16LC621AT-04I/SS | PIC16LC621A-04I/SS | PIC16LC620A-04I/SS | PIC16LC620T-04I/SS |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 20-SSOP | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same |
| Core / Architecture | PIC16C 8-bit, Harvard, 14-bit instruction | PIC16C 8-bit - same | PIC16C 8-bit - same | PIC16C 8-bit - same | PIC16C 8-bit - same | PIC16C 8-bit - same |
| Max Clock Speed | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| Program Memory Size | 1.75 KB (1K x 14) | 1.75 KB - same | 1.75 KB - same | 1.75 KB - same | 512 bytes (-71%) | 512 bytes (-71%) |
| Program Memory Type | OTP | OTP - same | EPROM (UV-erasable) | OTP - same | OTP - same | OTP - same |
| RAM Size | 80 bytes | 80 bytes - same | 80 bytes - same | 80 bytes - same | 80 bytes - same | 80 bytes - same |
| Supply Voltage | 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 | -40 C to +85 C (Industrial) | 0 C to +70 C (Commercial) | -40 C to +85 C (Industrial) | -40 C to +85 C (Industrial) | -40 C to +85 C (Industrial) | -40 C to +85 C (Industrial) |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete |
Key Differentiators
- OTP memory locks firmware against post-production tampering (vs PIC16LC621AT-04I/SS)
- Lowest cost variant in the LC621 family with industrial temperature grade (vs PIC16LC621T-04/SS)
- Smallest die in the 20-SSOP PIC16C footprint with full 1.75 KB program memory (vs PIC16LC620T-04I/SS)
Design Notes
Estimated: at 4 MHz and 5 V supply the PIC16LC621T-04I/SS typically draws 2 mA active and 1 uA sleep. Place a 100 nF ceramic decoupling capacitor as close as possible to the Vdd pin (pin 14) and a bulk 10 uF tantalum or ceramic on the same supply trace. Connect both Vdd pins (14 and 20) to the same rail with a short trace to avoid voltage differential that can trigger Brown-out Reset.
Because the PIC16LC621T-04I/SS uses OTP memory, firmware cannot be patched in-circuit after programming. Develop on the PIC16LC621AT-04I/SS (EPROM, UV-erasable) or PIC16F88-I/SS (Flash) and only freeze the OTP device after firmware is fully validated. Brown-out Reset defaults to enabled at the lowest threshold; ensure the BOR voltage setting matches the lowest valid Vdd in your system to avoid spurious resets during power-up ramp.
The 20-SSOP package has a 0.65 mm lead pitch and 5.30 mm body width. Follow Microchip SSOP-20 land pattern recommendations (IPC-SM-782) with at least 0.2 mm solder mask expansion. Keep the OSC1/OSC2 traces short (<5 mm) and surround them with a ground pour to reduce EMI pickup. Place the MCLR pull-up resistor (typically 10 kohm) close to the MCLR pin (pin 4) to improve reset noise immunity.
OSC1 is the high-impedance oscillator input and is sensitive to noise coupling. Route the crystal or resonator traces on the top layer only, keep them short, and guard-band with ground pour on adjacent layers. If using an external clock source, drive OSC1 with a CMOS buffer and leave OSC2 floating per datasheet; failure to do so can cause oscillator startup failures at low Vdd.
Compliance Information
RoHS, REACH, lead-free, and halogen-free status are not specified in the verified distributor data; consult Microchip's product environmental compliance page for authoritative declaration. AEC-Q100 automotive qualification is NOT claimed on this part - it is industrial-grade only.
