PIC16LC621T-04/SS - 8-Bit 4MHz OTP MCU, 1.75KB | Microchip
MPN: PIC16LC621T-04/SS ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.45 | $3.45 |
| 10 | $3.1 | $31.00 |
| 100 | $2.75 | $275.00 |
| 500 | $2.4 | $1,200.00 |
| 1,000 | $2.1 | $2,100.00 |
PIC16LC621T-04/SS Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, non-volatile program memory, RAM, and programmable peripherals. The PIC16LC621 belongs to the mid-range PIC16 family — a Harvard-architecture RISC controller that executes one instruction per cycle (except branches) and uses a 14-bit instruction word with an 8-bit data path. Within the broader taxonomy, this part sits between simple PIC10/PIC12 8-pin devices and higher-pin-count PIC18/PIC24 parts, optimized for cost-sensitive embedded control.
Key features include 13 general-purpose digital I/O pins, a Watchdog Timer (WDT) for code-flow integrity, Power-On Reset (POR), Brown-out Detect/Reset (BOR) for safe operation across fluctuating supplies, and a two-level hardware stack. The device is fabricated on a low-power CMOS process, allowing deep sleep modes for battery-friendly applications, and supports both 3.3 V and 5 V operation. Integrated peripherals include a Timer0 8-bit counter/timer with programmable prescaler, and analog comparators suitable for sensor interfaces.
The PIC16LC621 uses a RISC core with 35 single-word instructions, two-level deep hardware stack, and seven special function hardware registers. Direct, indirect, and relative addressing modes are supported. The 'LC' suffix indicates the low-voltage CMOS variant, optimized for operation down to 2.5 V, while the 'T' tape-and-reel suffix and '04' speed grade denote 4 MHz operation in surface-mount shipping format.
Typical applications include low-cost consumer appliances, sensor interface modules, simple motor-control driver boards, LED lighting controllers, IR remote-control transmitters/receivers, and battery-powered portable instruments. The 13-I/O count and small SSOP-20 footprint suit designs where PCB area is constrained but digital I/O and basic analog comparator functions are required.
When designing with this part, note that OTP memory can be programmed only once — production units must be pre-programmed or use the equivalent Flash-based PIC16F62X family for iterative development. Ensure decoupling capacitors are placed close to VDD/VSS, and that the MCLR reset pin is pulled high through a proper resistor for reliable startup.
This page synthesizes distributor pricing, drop-in pin-compatible alternatives (same SSOP-20 footprint), and practical engineering notes not found in the manufacturer datasheet alone.
Drop-in alternatives for PIC16LC621T-04/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-04/SS (same form factor and footprint) — differing in Package, Operating Temperature Range, Program Memory Size, RAM Size, Core Architecture.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC621AT-04I/SS
✅ Drop-In✓ In Stock
$2.46 / Unit
View Datasheet →PIC16LC621AT-04E/SS
✅ Drop-In✓ In Stock
$2.19 / Unit
View Datasheet →PIC16LC620T-04I/SS
✅ Drop-In✓ In Stock
$1.75 / Unit
View Datasheet →PIC16LC620A-04/SS
✅ Drop-In✓ In Stock
$2.74 / Unit
View Datasheet →PIC16LC620-04/SS
✅ Drop-In✓ In Stock
$2.95 / Unit
View Datasheet →PIC16LC621T-04/SS Maximum Ratings & Electrical Characteristics
| Core Processor | PIC |
| Core Size | 8-Bit |
| Series | PIC16C |
| Maximum Clock Speed | 4 MHz |
| Program Memory Size | 1.75 KB (1K x 14) |
| Program Memory Type | OTP (One-Time Programmable) EPROM |
| Supply Voltage Range | 2.5 V to 6.0 V |
| Number of I/O Pins | 13 |
| Package | 20-SSOP (5.30 mm width) |
| Mounting Type | Surface Mount |
| Operating Temperature Range | 0 °C to +70 °C |
| Peripherals | Brown-out Detect/Reset, POR, WDT |
| Instruction Set | 35 single-word instructions, 14-bit wide |
| Data Path Width | 8-bit |
| Stack Depth | 2-level hardware stack |
| Speed Grade | 04 (4 MHz) |
| Shipping Format | Tape & Reel (T suffix) |
| RoHS Status | Compliant |
PIC16LC621T-04/SS Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O port A bit 2 / analog comparator output |
| Pin 2 | RA3 — Bidirectional I/O port A bit 3 / analog comparator non-inverting input |
| Pin 3 | RA4/T0CKI — Bidirectional I/O port A bit 4 / Timer0 clock input (open-drain) |
| Pin 4 | MCLR/VPP — Master Clear reset input (active low) / programming voltage input |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Bidirectional I/O port B bit 0 / external interrupt input |
| Pin 7 | RB1 — Bidirectional I/O port B bit 1 |
| Pin 8 | RB2 — Bidirectional I/O port B bit 2 |
| Pin 9 | RB3 — Bidirectional I/O port B bit 3 |
| Pin 10 | RB4 — Bidirectional I/O port B bit 4 |
| Pin 11 | RB5 — Bidirectional I/O port B bit 5 |
| Pin 12 | RB6 — Bidirectional I/O port B bit 6 |
| Pin 13 | RB7 — Bidirectional I/O port B bit 7 |
| Pin 14 | VDD — Positive supply voltage (2.5 V to 6.0 V) |
| Pin 15 | OSC2/CLKOUT — Oscillator crystal output / CLKOUT in RC mode |
| Pin 16 | OSC1/CLKIN — Oscillator crystal input / external clock input |
| Pin 17 | RC0 — Bidirectional I/O port C bit 0 |
| Pin 18 | RC1 — Bidirectional I/O port C bit 1 |
| Pin 19 | RC2 — Bidirectional I/O port C bit 2 |
| Pin 20 | RA0/AN0 — Bidirectional I/O port A bit 0 / analog comparator inverting input |
Typical Applications
PIC16LC621T-04/SS is suitable for 6 applications: Consumer Appliance Control, IR Remote Control Transmitter, LED Lighting Controller, Sensor Interface Module, Battery-Powered Portable Instrument, Simple Motor Control Driver Board.
Consumer Appliance Control
The PIC16LC621T-04/SS fits consumer appliance control because its 13 digital I/O lines can directly drive relays, triac interfaces, LED indicators, and key-scan matrices used in washing machines, microwave ovens, and rice cookers. The 4 MHz core executes 1 MIPS, sufficient for state-machine control loops typical of appliance firmware, and the integrated Brown-out Detect/Reset prevents erratic behavior during brown-out events when motors induce supply dips. The 2.5 V to 6.0 V supply range simplifies designs that must work across both 3.3 V logic and 5 V relay-driver rails, reducing BOM cost by avoiding separate voltage regulators.
Recommended
IR Remote Control Transmitter
The PIC16LC621T-04/SS suits IR remote-control transmitters because its low-power CMOS design and 2.5 V minimum supply permit operation from two AAA cells via a simple boost or direct connection. The 13 I/O pins handle the keypad matrix (4x4 = 8 lines) plus IR LED driver and status LED, while the Watchdog Timer recovers from battery-induced glitches. The 4 MHz speed grade provides adequate timing precision for 38 kHz carrier generation used in standard RC5/ NEC protocols. The SSOP-20 footprint keeps the PCB small enough for slim remote housings, and OTP memory suffices for fixed-function code.
Recommended
LED Lighting Controller
The PIC16LC621T-04/SS works in LED lighting controllers by using its PWM-capable Timer0 to dim LED strings via MOSFET drivers, while its 13 I/O drive address-selection switches and status indicators. The wide 2.5 V to 6.0 V supply lets the controller run directly from 5 V USB or 3.3 V battery packs, supporting portable task lamps and architectural fixtures. Brown-out Reset prevents flicker during power transitions, and the Watchdog Timer recovers the controller from ESD-induced firmware lockups. The SSOP-20 package enables slim in-line LED driver PCB designs.
Recommended
Sensor Interface Module
The PIC16LC621T-04/SS serves sensor interface modules well because its on-chip analog comparator directly accepts signals from thermistors, photodiodes, or Hall-effect sensors without an external op-amp. The 13 I/O handle SPI or I2C communication to a host controller plus discrete sensor-enable lines. With 4 MHz operation, the MCU can poll sensors at 10 kHz rates while leaving cycles for digital filtering. The 2.5 V to 6.0 V range supports both 3.3 V digital sensors and legacy 5 V analog front-ends, and the small SSOP-20 package fits inside sensor probe housings.
Recommended
Battery-Powered Portable Instrument
The PIC16LC621T-04/SS is well-suited to battery-powered portable instruments because the low-power CMOS core draws minimal current at 4 MHz, extending battery life in handheld DMMs, thermometers, and stud finders. The 2.5 V minimum supply permits operation from two AA cells even near end-of-life, and the integrated Brown-out Detect triggers a clean shutdown before undervoltage causes memory corruption. The Watchdog Timer recovers from firmware hangs caused by static discharge. With 1.75 KB OTP program memory, code for ADC scanning, LCD driving, and keypad debouncing fits comfortably within the 1K x 14 instruction budget.
Recommended
Simple Motor Control Driver Board
The PIC16LC621T-04/SS drives simple brushed-DC or small stepper motors via its 13 I/O pins, with enough bandwidth at 4 MHz to generate step pulses and direction signals for low-RPM positioning applications such as valve actuators and small fans. The Brown-out Reset protects the motor driver stage from MCU glitches during supply transients caused by motor inrush currents. The integrated Watchdog Timer recovers from software faults without external supervisor ICs, reducing BOM cost. The SSOP-20 footprint is small enough to fit alongside driver FETs on a compact motor-control PCB, and the wide supply range supports both 5 V logic-level and 3.3 V battery-fed designs.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621T-04/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621AT-04I/SS | PIC16LC621AT-04E/SS | PIC16LC620T-04I/SS | PIC16LC620A-04/SS | PIC16LC620-04/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 |
| Program Memory | 1.75 KB OTP | 1.75 KB Flash | 1.75 KB Flash | 896 B OTP | 896 B Flash | 896 B OTP |
| Memory Type | OTP EPROM | Flash (reprogrammable) | Flash (reprogrammable) | OTP EPROM | Flash (reprogrammable) | OTP EPROM |
| Clock Speed | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| Supply Voltage | 2.5 V to 6.0 V | 2.5 V to 6.0 V | 2.5 V to 6.0 V | 2.5 V to 6.0 V | 2.5 V to 6.0 V | 2.5 V to 6.0 V |
| I/O Pins | 13 | 13 | 13 | 13 | 13 | 13 |
| Operating Temperature | 0 C to +70 C | -40 C to +85 C (industrial) | -40 C to +125 C (extended) | -40 C to +85 C (industrial) | 0 C to +70 C | 0 C to +70 C |
| Lifecycle Status | Obsolete | Active | Active | Obsolete | Active | Obsolete |
Key Differentiators
- Reprogrammable Flash memory vs one-time programmable EPROM (vs PIC16LC621AT-04I/SS)
- Wider temperature range for harsh environments (vs PIC16LC621AT-04E/SS)
- Lower cost via reduced memory in cost-optimized variants (vs PIC16LC620T-04I/SS)
Design Notes
Decouple VDD (pin 14) with a 100 nF ceramic capacitor placed within 5 mm of the pin, plus a bulk 10 uF tantalum or aluminum electrolytic capacitor on the same supply rail. The PIC16LC621T-04/SS draws short current spikes during internal clock edges, and inadequate decoupling causes erratic resets via the integrated Brown-out Detect. The MCLR pin (pin 4) must be pulled to VDD through a 10 kohm resistor; do not tie it directly to VDD because the programmer needs to drive it for in-circuit serial programming.
Place the 20-SSOP footprint on a board with at least 0.2 mm clearance between SSOP leads and adjacent traces to prevent solder bridges during reflow. The exposed pad of the SSOP is not present on this part (unlike QFN packages), so all thermal dissipation occurs through the standard gull-wing leads. Keep high-frequency switching traces (relay coils, motor drivers) at least 5 mm away from the OSC1/OSC2 crystal pins to avoid injecting noise into the clock circuit. Use a ground pour on the top layer under the MCU to reduce EMI.
Do not exceed the absolute maximum VDD of 7.0 V on PIC16LC621T-04/SS; transients above this level permanently damage the EPROM cell oxide. Configuration bits must be set correctly: enable the Watchdog Timer only if the firmware periodically clears it, or the MCU will reset every 18 ms nominal. The two-level hardware stack means deeply nested CALL chains corrupt the return address — limit subroutine depth to two. OTP memory cannot be erased, so develop firmware on the Flash-based PIC16LC621A or PIC16F62X equivalent first.
Keep the oscillator traces (OSC1 pin 16, OSC2 pin 15) short, symmetric, and surrounded by a ground guard ring. For crystal operation, place load capacitors (typically 15-33 pF) directly between each oscillator pin and ground. For RC oscillator mode, the resistor connects between OSC1 and VDD, and OSC2 can be left open or used as CLKOUT. Avoid routing digital signal traces under the crystal or its capacitors, as capacitive loading shifts the oscillation frequency and may prevent startup at low supply voltages.
Compliance Information
RoHS and lead-free status confirmed via distributor listings. Halogen-free status not explicitly stated in provided data. AEC-Q100 not applicable for commercial-grade MCU.
