PIC16LC621AT-04E/SS - 8-Bit OTP MCU, 4MHz, 1.75KB | Microchip
MPN: PIC16LC621AT-04E/SS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.42 | $3.42 |
| 10 | $3.07 | $30.70 |
| 100 | $2.74 | $274.00 |
| 500 | $2.46 | $1,230.00 |
| 1,000 | $2.19 | $2,190.00 |
PIC16LC621AT-04E/SS Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, memory, and I/O peripherals on one die. The PIC16LC621AT belongs to the EPROM/OTP branch of the PIC16 mid-range architecture, which uses a 14-bit wide instruction set with separate 8-bit data paths, a two-level deep hardware stack, and direct/indirect/relative addressing. The PIC16 family sits within Microchip's broader PIC microcontroller hierarchy (PIC10/12/16/18/24/32) and is one of the longest-running 8-bit MCU lines in the industry.
Key features of this device include 12 I/O pins, two 8-bit timer/counters, a watchdog timer, Power-On Reset (POR), Brown-out Detect/Reset, and a programmable code protection mechanism. The OTP program memory allows one-time field programming via standard PIC programmers, making the device well suited to low-volume production runs where mask-ROM volume is not justified. With 12-bit wide instructions and 35 single-word instructions, the core delivers predictable deterministic execution at 250 ns per instruction at 4MHz.
Typical applications include low-cost consumer appliances, sensor signal conditioning front-ends, simple motor control loops, automotive body electronics (non-safety), remote-control transmitters, and battery-powered instruments where the wide 2.5V-6.25V supply range provides flexibility across 3.3V and 5V rails. The extended temperature grade permits operation from -40C to +125C, fitting industrial and automotive underhood environments.
When designing with this part, note that OTP memory cannot be erased - firmware must be fully validated before programming. The device is in production but has been superseded in many designs by the Flash-based PIC16F628 (pin-compatible upgrade path), and the PIC16LC621AT remains the preferred choice only when OTP cost advantages or security requirements matter.
This page synthesizes distributor stock and pricing data, drop-in compatible alternatives in the 20-SSOP footprint, and practical design notes not collected in a single place in the manufacturer datasheet, helping procurement and design engineers shortlist compatible parts faster.
Drop-in alternatives for PIC16LC621AT-04E/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-04E/SS (same form factor and footprint) — differing in Operating Temperature Range, Package, Program Memory Size, Program Memory Type, Peripherals.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC621A-04E/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC621A-04I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC621AT-04I/SS
✅ Drop-In✓ In Stock
$2.46 / Unit
View Datasheet →PIC16LC620AT-04I/SS
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
PIC16LC620AT-04E/SS
✅ Drop-In✓ In Stock
$2.45 / Unit
View Datasheet →PIC16F628A-I/SS
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$1.41 / Unit
View Datasheet →PIC16LC621AT-04E/SS Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC16 (8-bit) mid-range |
| Instruction Set Width | 14-bit |
| Program Memory Type | OTP (One-Time Programmable EPROM) |
| Program Memory Size | 1.75 KB (1K x 14) |
| RAM Size | 96 bytes |
| Data EEPROM | Not present |
| Maximum Clock Speed | 4 MHz |
| Instruction Cycle Time | 1 us at 4 MHz (4 TOSC) |
| Supply Voltage (Vdd) | 2.5 V to 6.25 V |
| I/O Pins | 12 |
| Timers | 1 x 8-bit Timer0, 1 x 8-bit Timer1 (per datasheet family) |
| Watchdog Timer | Yes (independent WDT with on-chip RC oscillator) |
| Brown-out Reset (BOR) | Yes |
| Power-On Reset (POR) | Yes |
| Code Protection | Programmable |
| Operating Temperature | -40 C to +125 C (Extended, 'E' suffix) |
| Package | 20-pin SSOP (5.30 mm body) |
| Mounting Type | Surface Mount |
| MSL Level | 1 |
| Lead Finish | Matte Tin |
PIC16LC621AT-04E/SS Pin Configuration
| Pin 1 | RA2/AN2 — Bidirectional I/O / analog input (where supported) |
| Pin 2 | RA3/AN3 — Bidirectional I/O / analog input (where supported) |
| Pin 3 | RA4/T0CKI — Bidirectional I/O / Timer0 clock input |
| Pin 4 | RA5/MCLR/Vpp — Bidirectional I/O / Master Clear (reset) / programming voltage input |
| Pin 5 | Vss — Ground reference |
| Pin 6 | RB0/INT — Bidirectional I/O / external interrupt |
| Pin 7 | RB1 — Bidirectional I/O |
| Pin 8 | RB2 — Bidirectional I/O |
| Pin 9 | RB3 — Bidirectional I/O |
| Pin 10 | RB4 — Bidirectional I/O / interrupt-on-change |
| Pin 11 | RB5 — Bidirectional I/O / interrupt-on-change |
| Pin 12 | RB6 — Bidirectional I/O / ICSP clock |
| Pin 13 | RB7 — Bidirectional I/O / ICSP data |
| Pin 14 | Vdd — Positive supply (2.5 V to 6.25 V) |
| Pin 15 | OSC2/CLKOUT — Crystal/ceramic oscillator output or clock-out |
| Pin 16 | OSC1/CLKIN — Crystal/ceramic oscillator input or external clock in |
| Pin 17 | RA0/AN0 — Bidirectional I/O / analog input (where supported) |
| Pin 18 | RA1/AN1 — Bidirectional I/O / analog input (where supported) |
| Pin 19 | RA6 — Bidirectional I/O (oscillator function on some variants) |
| Pin 20 | RA7 — Bidirectional I/O (oscillator function on some variants) |
Typical Applications
PIC16LC621AT-04E/SS is suitable for 6 applications: Low-Cost Consumer Appliance Control, Remote Control Transmitter / Receiver Pair, Automotive Body Electronics (Non-Safety), Sensor Signal Conditioning Front-End, Battery-Powered Instrumentation, Simple Motor / Fan Speed Controller.
Low-Cost Consumer Appliance Control
The PIC16LC621AT-04E/SS fits low-cost consumer appliance control because its 1.75KB OTP memory holds compact state-machine firmware, its 2.5V-6.25V supply range accommodates 3.3V or 5V power rails, and its on-chip Brown-out Reset plus Power-On Reset guarantee clean starts after brownouts. The 12 I/O pins directly drive seven-segment displays, keypads, and triac-based heater controls. The 4MHz instruction rate at 250ns/instruction handles multiplexed LED scanning loops without flicker, while the extended -40C to +125C temperature grade survives under-cabinet or motor-compartment heat. Compared with discrete logic replacements, the PIC16LC621AT reduces BOM count by half and lets engineers revise behavior via firmware without re-spinning the PCB.
Recommended
Remote Control Transmitter / Receiver Pair
The PIC16LC621AT-04E/SS suits handheld remote-control transmitters because its 2.5V minimum supply runs directly from 2x AA cells, the 4MHz clock provides ample timing resolution for IR or RF carrier generation, and the watchdog timer recovers the device from static-discharge upsets. The 12 I/O lines easily interface with 4x4 matrix keypads, status LEDs, and an encoder IC. OTP code protection prevents firmware cloning by competitors. The 20-SSOP package fits into slim enclosures, and the 4MHz instruction cycle delivers sub-microsecond key-debounce timing for responsive user feel. Industrial temperature rating ensures operation in outdoor or garage environments where temperatures swing widely.
Recommended
Automotive Body Electronics (Non-Safety)
The PIC16LC621AT-04E/SS handles non-safety automotive body modules such as mirror adjusters, seat controllers, and lighting timers because it tolerates the 12V automotive supply through an external 5V regulator, the -40C to +125C extended temperature range covers underhood conditions, and on-chip POR + BOR survive cranking transients. The 1.75KB OTP accommodates the small instruction footprint of body-control state machines, and code protection locks the algorithm against unauthorized cloning. Note: this part is NOT AEC-Q100 qualified; for safety-critical functions, use PIC16F1xxx or dsPIC family with explicit Q100 status. For non-safety body modules with existing firmware, the PIC16LC621AT remains cost-effective and well-proven in field.
Recommended
Sensor Signal Conditioning Front-End
The PIC16LC621AT-04E/SS functions as a sensor-conditioning front-end in industrial loops because its 12 I/O pins read multiple switches or analog sensors (via external ADC), its 4MHz core executes linearization and averaging routines in real time, and the 2.5V-6.25V supply tolerates 24V industrial rail conversions down to 5V. The watchdog timer recovers from EMI-induced lockups common in motor cabinets, while on-chip BOR prevents latch-up during brownouts. The 20-SSOP footprint allows the controller to sit directly behind the sensor connector, minimizing analog-loop trace length. For higher-resolution conditioning, an external 10-12 bit ADC companion is recommended since this part lacks an internal ADC.
Recommended
Battery-Powered Instrumentation
The PIC16LC621AT-04E/SS enables battery-powered portable instruments because it draws microamp-level sleep currents (with the watchdog off), runs directly from 2x AA / 2x AAA cells through its 2.5V minimum Vdd, and integrates BOR + WDT without external supervisor chips. The 4MHz mode supports medium-speed measurement and display-refresh tasks, and lower-clock SLEEP modes extend shelf life. The 20-SSOP package suits thin handheld enclosures, and the OTP code protection prevents firmware theft. For multi-year battery life, pair with a low-quiescent LDO and consider a Flash-based PIC16LF1554 for development before committing OTP volumes.
Recommended
Simple Motor / Fan Speed Controller
The PIC16LC621AT-04E/SS delivers basic BLDC or brushed-motor commutation for low-power fans and pumps because the 4MHz instruction rate produces 5-10 kHz PWM at 8-bit resolution, the 12 I/O lines drive phase-control FETs directly via gate drivers, and the watchdog timer recovers from commutation glitches. The extended temperature grade handles motor-bearing heat, and Brown-out Reset prevents undefined behavior during motor startup inrush. The 1.75KB OTP holds a complete PID loop plus commutation table for small motors. For high-current 3-phase BLDC, use a dedicated motor-control MCU; this part excels in cost-sensitive single- or dual-phase small-motor loops like PC case fans or appliance pumps.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621AT-04E/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621A-04E/SS | PIC16LC621AT-04I/SS | PIC16LC620AT-04E/SS | PIC16F628A-I/SS |
|---|---|---|---|---|---|
| Brand | 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 |
| Program Memory | 1.75 KB OTP (1K x 14) | 1.75 KB OTP (same) | 1.75 KB OTP (same) | 0.875 KB OTP (half) | 3.5 KB Flash (2x) |
| Memory Type | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | Flash (reprogrammable) |
| Maximum Clock | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 20 MHz |
| RAM | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 224 bytes |
| 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 | 2.0 V to 5.5 V |
| Operating Temperature | -40 C to +125 C (E) | -40 C to +125 C (E) | -40 C to +85 C (I) | -40 C to +125 C (E) | -40 C to +85 C (I) |
| Internal ADC | Not present | Not present | Not present | Not present | No internal ADC |
Key Differentiators
- Extended -40 C to +125 C temperature range ('E' suffix) (vs PIC16LC621AT-04I/SS)
- 1.75 KB OTP memory vs 0.875 KB on smaller siblings (vs PIC16LC620AT-04E/SS)
- Field-programmable via ICSP without removing the part (vs Mask-ROM PIC16C621 equivalents)
Design Notes
OTP memory cannot be erased after programming. Validate firmware on a Flash-equivalent PIC16F628A-I/SS before committing OTP volumes - any code bug discovered post-programming wastes the part. Use Microchip's MPLAB X IDE simulator with the PIC16F628A as a stand-in, since both share the PIC16 mid-range core. If a development cycle is anticipated, buy a PIC16F628A-I/SS for engineering and qualify the PIC16LC621AT-04E/SS only for production.
Place a 0.1 uF ceramic decoupling capacitor within 5 mm of the Vdd pin (pin 14) and a 10 uF bulk capacitor near the supply input. The PIC16LC621AT's Brown-out Reset and Power-On Reset need a clean Vdd ramp slower than 50 ms - if your regulator has a 1 ms soft-start, add RC delay on MCLR to avoid missing-reset edge cases. Watchdog timer must be cleared in firmware within its ~18 ms (typical) window or the part resets.
Estimated: with the 20-SSOP package and a 4 MHz oscillator, the OSC1/OSC2 traces (pins 15-16) should be kept under 10 mm and surrounded by a ground pour to avoid coupling noise into the internal clock. Place the crystal or resonator within 5 mm of the pins with short, symmetrical traces. Avoid routing RB6/RB7 (ICSP) near switching power traces - ICSP programming can be corrupted by high dV/dt on adjacent nets.
Compliance Information
RoHS and REACH compliant per Microchip product declaration. Matte-tin lead finish. Not AEC-Q100 qualified; for automotive safety use a Q100-qualified successor. Halogen-free status not explicitly declared in verified data - mark as unknown.
