PIC16LC621A-04I/P - 4MHz 8-bit OTP MCU 1.75KB | Microchip
MPN: PIC16LC621A-04I/P β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.1 | $2.10 |
| 10 | $1.85 | $18.50 |
| 100 | $1.55 | $155.00 |
| 500 | $1.3 | $650.00 |
| 1,000 | $1.01 | $1,010.00 |
PIC16LC621A-04I/P Overview
An 8-bit microcontroller (MCU) is a small computer-on-a-chip that integrates a CPU, program memory, RAM, and peripherals into a single package. The PIC16C series uses a RISC-based Harvard architecture with 12-bit wide instructions and an 8-bit wide data path, which simplifies firmware development while delivering deterministic real-time response for embedded control. The PIC16LC621A belongs to the Microchip mid-range PIC16 family, occupying the low-power (LC) tier optimized for battery-operated and industrial applications where minimal quiescent current matters.
Key features include an internal comparator with programmable reference, 13 digital I/O lines capable of sourcing/sinking 25 mA per pin, a watchdog timer with its own on-chip RC oscillator for reliable operation, and a power-on reset (POR) circuit. The device supports in-circuit serial programming (ICSP) via two pins, allowing firmware updates without removing the chip from the board, which is invaluable in field-deployed equipment. Two 8-bit timers plus one watchdog timer provide flexible event scheduling.
The PIC16LC621A-04I/P uses a CMOS process with EPROM-based program memory, which makes it one-time-programmable (OTP). This is preferred in low-volume or industrial control applications where firmware is finalized in production and field updates are not expected. The LC variant (low-power CMOS) draws roughly half the operating current of the standard PIC16C621A, extending battery life in remote sensor nodes. Direct, indirect, and relative addressing modes give the compiler flexibility in code generation.
Typical applications include industrial control logic, appliance controllers (washing machines, microwave ovens, HVAC), remote sensor interfaces, low-end automotive body modules, and general-purpose embedded control where simplicity, deterministic timing, and cost-effectiveness outweigh the need for larger memory. Its wide voltage range also suits battery-powered products. As a drop-in successor to older PIC16C621A-04/P designs, the LC variant is commonly specified for new low-power designs and legacy refresh programs.
When designing with this part, ensure the system clock configuration matches the 4 MHz maximum for the -04 speed grade, and budget adequate supply decoupling (100 nF ceramic plus 10 uF bulk) close to VDD/VSS pins. The OTP memory means firmware must be fully validated before programming - there are no field re-program cycles. For higher memory or in-system re-programmability, consider the PIC16F family (Flash-based) as a future-proof migration path on the same 18-pin footprint.
This page synthesizes distributor pricing from Mouser/DigiKey/LCSC, drop-in same-package alternatives, and practical engineering guidance not found in the manufacturer datasheet alone.
Drop-in alternatives for PIC16LC621A-04I/P β 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 PIC16LC621A-04I/P (same form factor and footprint) β differing in Core Architecture, Operating Temperature Range, Program Memory Size, Program Memory Type, RAM Size.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PIC16LC621A-04/P
β Drop-Inπ Reference alternative (not in catalog)
PIC16LC621A-04E/P
β Drop-Inπ Reference alternative (not in catalog)
PIC16LC620A-04/P
β Drop-Inβ In Stock
$1.3 / Unit
View Datasheet βPIC16LC621-04/P
β Drop-Inβ In Stock
$1.65 / Unit
View Datasheet βPIC16LC621-04I/P
β Drop-Inπ Reference alternative (not in catalog)
PIC16C621A-04/P
β Drop-Inπ Reference alternative (not in catalog)
PIC16LC621A-04I/P Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC RISC (Harvard) |
| Instruction Set | 35 single-word instructions |
| Instruction Cycle Time | 200 ns at 4 MHz |
| Maximum Clock Frequency | 4 MHz |
| Program Memory Size | 1.75 KB (1K x 14) OTP/EPROM |
| Data RAM | 96 bytes |
| Data EEPROM | Not present (OTP only) |
| I/O Pins | 13 |
| Timers | 2 x 8-bit + 1 x WDT |
| Analog Comparator | Yes, internal with programmable reference |
| Hardware Stack | 2 levels deep |
| Addressing Modes | Direct, Indirect, Relative |
| Supply Voltage (VDD) | 2.5 V to 6.25 V |
| Package Type | 18-pin PDIP (P) through-hole |
| Operating Temperature Range | -40 C to +85 C (industrial, 'I' grade) |
| Watchdog Timer | Yes, with dedicated on-chip RC oscillator |
| In-Circuit Serial Programming (ICSP) | Yes |
| Power-On Reset (POR) | Yes |
| RoHS Status | Compliant |
| Lead-Free | Yes (per LCSC product page) |
PIC16LC621A-04I/P Pin Configuration
| Pin 1 | MCLR/Vpp β Master Clear (Reset) input / Programming voltage input |
| Pin 2 | RA0 β Port A bit 0 / Analog comparator output |
| Pin 3 | RA1 β Port A bit 1 / Analog comparator negative input |
| Pin 4 | RA2 β Port A bit 2 / Analog comparator positive input |
| Pin 5 | RA3 β Port A bit 3 (input only) / Vref input |
| Pin 6 | RA4 β Port A bit 4 / Timer0 clock input |
| Pin 7 | RA5 β Port A bit 5 / Master Clear (alternate) |
| Pin 8 | VSS β Ground reference |
| Pin 9 | OSC1/CLKIN β Oscillator crystal input / External clock input |
| Pin 10 | OSC2/CLKOUT β Oscillator crystal output / Clock output (Fosc/4) |
| Pin 11 | RC0 β Port C bit 0 |
| Pin 12 | RC1 β Port C bit 1 |
| Pin 13 | RC2 β Port C bit 2 |
| Pin 14 | RC3 β Port C bit 3 |
| Pin 15 | RC4 β Port C bit 4 |
| Pin 16 | RC5 β Port C bit 5 |
| Pin 17 | RC6 β Port C bit 6 |
| Pin 18 | RC7 β Port C bit 7 |
| Pin VDD | VDD β Positive supply voltage (2.5V to 6.25V) |
Typical Applications
PIC16LC621A-04I/P is suitable for 7 applications: Industrial Control Logic, Appliance Controllers, Remote Sensor Interfaces, Low-End Automotive Body Modules, Battery-Powered Devices, General-Purpose Embedded Control, HVAC Thermostat Controls.
Industrial Control Logic
The PIC16LC621A-04I/P's 4 MHz clock with 200 ns deterministic instruction cycle, 13 digital I/O lines capable of 25 mA sink/source, and internal analog comparator make it well-suited for industrial control panels, relay drivers, and machine interlocks. The wide 2.5V-6.25V supply tolerance accommodates 24V industrial bus systems with simple linear regulation. Its industrial -40 C to +85 C temperature grade ensures reliable operation in factory automation cells, conveyor control modules, and PLC expansion I/O boards where ambient temperatures fluctuate widely. The on-chip watchdog timer with dedicated RC oscillator provides autonomous fault recovery without external components.
Recommended
Appliance Controllers
White goods such as washing machines, microwave ovens, dishwashers, and HVAC thermostats benefit from the PIC16LC621A-04I/P's low cost, OTP memory for finalized firmware, and 35-instruction RISC architecture that simplifies firmware development. The internal analog comparator enables direct sensor interfacing for temperature, humidity, or pressure without external op-amps. With 13 I/O pins, the MCU can drive multiplexed LED displays, keypads, triac control outputs, and buzzer feedback. The 2.5V-6.25V supply range simplifies power supply design from rectified mains.
Recommended
Remote Sensor Interfaces
The PIC16LC621A-04I/P's low-power CMOS (LC) variant draws roughly half the operating current of standard PIC16C621A, extending battery life in remote sensor nodes deployed in agricultural, environmental, or building automation monitoring. The internal analog comparator with programmable voltage reference allows direct threshold detection of sensor signals without external components, while 13 I/O pins support multiple sensor channels or low-power RF modules. Industrial temperature grade and wide supply tolerance ensure reliable operation in outdoor enclosures subject to temperature swings.
Recommended
Low-End Automotive Body Modules
Automotive body electronics such as interior lighting controllers, seat position memory, mirror adjustment, and simple door modules can use the PIC16LC621A-04I/P for cost-sensitive applications. The industrial temperature grade (-40 C to +85 C) covers cabin environments; for under-hood or harsher locations, AEC-Q100 qualified parts are required. The MCU's 13 I/O lines drive relay coils and LED indicators while the analog comparator monitors current-sense signals. Wide supply tolerance accommodates 12V automotive bus transients when paired with appropriate TVS protection.
Recommended
Battery-Powered Devices
Handheld instruments, remote controls, and portable measurement tools benefit from the PIC16LC621A-04I/P's low-power CMOS architecture which significantly reduces current consumption compared to standard PIC16C621A. The 2.5V minimum supply voltage allows direct operation from 2x AA alkaline cells down to their end-of-discharge voltage. Sleep-mode current is minimal because the watchdog timer uses its own dedicated RC oscillator, allowing the main oscillator to shut down completely. The 1.75KB OTP memory holds compact firmware for typical portable device control loops.
Recommended
General-Purpose Embedded Control
Educational kits, hobby projects, and small-volume commercial products leverage the PIC16LC621A-04I/P's mature development ecosystem, abundant code examples, and low-cost entry point. The 35-instruction RISC architecture is widely documented with free MPLAB X IDE support and HI-TECH C compiler compatibility. The 13 I/O pins plus internal comparator handle typical embedded tasks such as button input, LED output, PWM via timer, and analog threshold detection. Its 18-pin PDIP through-hole package simplifies breadboarding and hand-soldering for prototypes and educational use.
Recommended
HVAC Thermostat Controls
Heating, ventilation, and air conditioning (HVAC) thermostat and zone controller applications benefit from the PIC16LC621A-04I/P's analog comparator for temperature sensor interfacing, timer resources for PWM-driven TRIAC control of heating elements, and 13 I/O pins for keypad, LCD, and relay drivers. The industrial -40 C to +85 C temperature grade covers equipment-room environments. The OTP memory is ideal for HVAC firmware that is finalized at production and does not require field updates, keeping unit costs low.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621A-04I/P β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621A-04/P | PIC16LC621A-04E/P | PIC16LC620A-04/P | PIC16LC621-04/P | PIC16C621A-04/P |
|---|---|---|---|---|---|---|
| Package | PDIP-18 (P) | PDIP-18 - same | PDIP-18 - same | PDIP-18 - same | PDIP-18 - same | PDIP-18 - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 0.5 KB OTP (-71%) | 1.75 KB OTP | 1.75 KB OTP |
| RAM | 96 bytes | 96 bytes | 96 bytes | 64 bytes (-33%) | 96 bytes | 96 bytes |
| Maximum Clock | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| 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 | 3.0 V to 6.0 V |
| Temperature Grade | Industrial (-40 C to +85 C) | Commercial (0 C to +70 C) | Industrial (-40 C to +85 C) | Commercial (0 C to +70 C) | Commercial (0 C to +70 C) | Commercial (0 C to +70 C) |
| Quiescent Current | Low (LC process) | Low (LC process) - same | Lower (enhanced CMOS, ~25% less) | Low (LC process) | Low (LC process, original) | Higher (~2x vs LC variant) |
Key Differentiators
- Industrial temperature grade in standard 18-pin PDIP package (vs PIC16LC621A-04/P)
- Low-power CMOS (LC) process for battery applications (vs PIC16C621A-04/P)
- Larger program memory versus PIC16LC620A family (vs PIC16LC620A-04/P)
Design Notes
Place a 100 nF ceramic decoupling capacitor as close as physically possible to the VDD pin (pin 14 equivalent, sharing the VDD bond with VSS). Add a bulk 10 uF tantalum or aluminum electrolytic capacitor on the same supply rail near the MCU. For battery-powered designs, add a small (1-10 uF) reservoir capacitor to handle inrush when the MCU wakes from sleep. The LC variant's low quiescent current makes supply decoupling more critical because switching noise from other board sections can couple through the supply pin into the analog comparator reference.
Keep the crystal or ceramic resonator within 5 mm of the OSC1/OSC2 pins (pins 9 and 10). Route the oscillator traces short and surround them with a ground pour to minimize EMI pickup. For CMOS oscillator configuration using a single resistor (typically 10-100 kOhm) between OSC1 and VDD, ensure no high-frequency signals pass near the oscillator pins. Add a guard ring around the oscillator traces if the board has switching power converters nearby.
Critical: PIC16LC621A uses EPROM/OTP memory which is one-time programmable - there is no field re-programming without UV erasure. Ensure firmware is fully validated before programming production units. Also, the MCLR pin (pin 1) must NOT be left floating; tie it to VDD through a 10 kOhm resistor or directly if not using external reset. A floating MCLR pin can cause spurious resets from injected noise. Finally, configure the watchdog timer (WDTE fuse) appropriately - leaving it enabled with a short timeout in development can make debugging frustrating, while disabling it in production compromises reliability.
For analog comparator applications, route the comparator input pins (RA1, RA2) away from digital switching lines and the oscillator traces to minimize coupled noise. The analog reference voltage pin (RA3/Vref) should be bypassed with a 100 nF capacitor if used as a reference. Keep ground return paths short - use a single-point ground topology where the MCU's VSS pin ties to the system ground at the same point as the bulk decoupling capacitor's ground lead. This minimizes ground bounce during I/O transitions.
Compliance Information
RoHS compliant and lead-free per LCSC and Microchip product documentation. NOT AEC-Q100 qualified - for AEC-Q100 automotive applications, use PIC16F1823-I/P or similar qualified parts. Halogen-free status not explicitly stated in available data.
