PIC18LF4321-I/ML - 8KB Flash 8-bit MCU 40MHz | Microchip
MPN: PIC18LF4321-I/ML ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.92 | $6.92 |
| 10 | $6.23 | $62.30 |
| 100 | $5.54 | $554.00 |
| 500 | $4.98 | $2,490.00 |
| 1,000 | $4.43 | $4,430.00 |
PIC18LF4321-I/ML Overview
An 8-bit microcontroller (MCU) is a single-chip computer built around an 8-bit data path, optimized for deterministic real-time control in cost-sensitive embedded applications. Within the broader taxonomy it falls under microcontroller -> embedded processor -> semiconductor IC, and the PIC18 family specifically targets mid-range control tasks with enhanced instruction sets and C-friendly architecture. The "LF" prefix designates the extended low-voltage operating variant, while the "F" indicates Flash-based reprogrammable program memory.
Key specifications include 77 single-word instructions, 16-bit wide instructions for improved code density, an internal 31 kHz to 8 MHz oscillator, and hardware multiply support. The PIC18LF4321 supports 4.2 V to 5.5 V supply operation in LF mode (with PIC18F4321 covering the wider 2.0 V to 5.5 V range), nanoWatt Technology for sleep currents below 1 uA, and a 10-bit ADC with up to 13 input channels depending on package. The 44-QFN package supports up to 34 digital I/O pins.
The device integrates Enhanced Capture/Compare/PWM (ECCP) modules, a USART with LIN support, an MSSP module for SPI and I2C, two analog comparators, and a programmable LVD module. Its RISC architecture with hardware multiply makes it efficient for closed-loop control, sensor interfacing, and small protocol stacks.
Typical applications include industrial sensor conditioning, HVAC actuator control, low-power remote sensing nodes, USB-less human-interface appliances, and motor-control pre-drivers. The wide peripheral mix lets a single MCU handle analog sensing, PWM drive, and serial communication without external glue logic.
Design tip: when migrating between PIC18F4321 (F) and PIC18LF4321 (LF), verify the supply-rail upper bound and the brown-out reset trip points - LF parts lose operation above 5.5 V. The exposed thermal pad on the QFN must be soldered to a sufficient copper pour to meet theta_JA targets.
This page combines distributor stock, drop-in alternatives, and engineering guidance not assembled in the manufacturer datasheet alone, giving procurement and design teams a single reference for sourcing, substitution, and implementation decisions.
Drop-in alternatives for PIC18LF4321-I/ML — 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 PIC18LF4321-I/ML (same form factor and footprint) — differing in Package, ADC, Program Memory (Flash), Timers, Operating Temperature.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18F4321-I/ML
✅ Drop-In✓ In Stock
$1.22 / Unit
View Datasheet →PIC18LF4320-I/ML
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18LF4523-I/ML
✅ Drop-In✓ In Stock
$4.12 / Unit
View Datasheet →PIC18F4331-I/ML
✅ Drop-In✓ In Stock
$5.32 / Unit
View Datasheet →PIC18F4523-I/ML
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4320-I/ML
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18LF4321-I/ML Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC18 RISC |
| Program Memory | 8 KB (4K x 16) Flash |
| Data RAM | 512 bytes |
| Data EEPROM | 256 bytes |
| Maximum Clock Frequency | 40 MHz |
| Performance | 10 MIPS |
| Instruction Set | 77 single-word instructions (16-bit wide) |
| Supply Voltage Range (LF) | 4.2 V to 5.5 V |
| I/O Pins | 34 |
| ADC | 10-bit, up to 13 channels |
| Timers | Multiple 8-bit and 16-bit |
| Communication | EUSART, MSSP (SPI/I2C) |
| PWM Channels | Enhanced CCP, multiple outputs |
| Package | 44-pin QFN (HVQCCN) 8x8 mm with exposed pad |
| Operating Temperature | -40C to +85C (Industrial) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
| Lead-Free | Yes |
PIC18LF4321-I/ML 44-pin qfn (hvqccn) 8x8 mm with exposed pad Pin Configuration Guide
Pin configuration for PIC18LF4321-I/ML (44-pin qfn (hvqccn) 8x8 mm with exposed pad package). This digital IC includes GPIO, communication interfaces (UART, SPI, I2C), and power pins. Refer to the manufacturer datasheet for alternate pin functions and configuration options. Essential for embedded system design and PCB layout.
No detailed pinout data available for PIC18LF4321-I/ML.
Refer to the datasheet for full pin configuration.
Typical Applications
PIC18LF4321-I/ML is suitable for 6 applications: Industrial Sensor Conditioning and Control, Low-Power Remote Sensing Nodes, HVAC Actuator and Damper Control, Small Appliance User Interface and Control, Automotive Body and Interior Modules (Non-Safety), Educational and Prototyping Development Platforms.
Industrial Sensor Conditioning and Control
The PIC18LF4321-I/ML fits industrial sensor conditioning because it combines a 10-bit ADC with up to 13 input channels, hardware multiply for calibration math, and an industrial -40C to +85C operating range. With 8 KB Flash and 512 bytes RAM it can host linearization tables and digital filters for thermocouple, RTD, or strain-gauge front ends. The 40 MHz / 10 MIPS performance sustains 1 ms PID loops on multiple channels simultaneously. Its nanoWatt Technology idle modes drop quiescent draw below 1 uA, enabling 4-20 mA loop-powered sensor heads. Place the MCU on the 5V rail with a 100 nF decoupling cap near each VDD pin and route analog traces away from PWM outputs to preserve ADC accuracy.
Recommended
Low-Power Remote Sensing Nodes
The PIC18LF4321-I/ML is well suited for battery-powered remote sensor nodes because nanoWatt Technology brings sleep current below 1 uA, while 8 KB Flash and 256 bytes EEPROM let the firmware store configuration and calibration persistently across deep-sleep cycles. The integrated EUSART and MSSP support SPI/I2C sensors and low-power radio modules like the MRF24J40. At a 1% duty cycle with periodic wake-and-transmit, average current stays under 50 uA, giving multi-year life on two AA cells. Use the MSSP in I2C mode to interface digital temperature, humidity, and pressure sensors, and the 10-bit ADC for battery voltage monitoring. Select the internal 31 kHz LF oscillator during sleep and switch to the 8 MHz HF oscillator only for active measurements.
Recommended
HVAC Actuator and Damper Control
The PIC18LF4321-I/ML drives HVAC actuators and dampers using its Enhanced CCP module to generate complementary PWM outputs with programmable dead-band, which prevents shoot-through in half-bridge motor and valve drivers. Its 10-bit ADC samples thermistor or 0-10 V feedback, while the EUSART links to a building automation bus. The industrial temperature grade supports rooftop and basement equipment enclosures, and the 5V supply range simplifies integration with legacy HVAC control boards. With 77 single-word instructions and hardware multiply, the 4321 executes PID loops for variable-air-volume boxes in well under 1 ms. Provide a 10 uF bulk capacitor at the motor-driver supply and keep PWM traces short to limit EMI.
Recommended
Small Appliance User Interface and Control
The PIC18LF4321-I/ML powers small appliance user interfaces by scanning up to 8x5 matrix keypads, driving character LCDs via I2C with the MSSP, and controlling triac-fired heaters or universal motors via the Enhanced CCP PWM. Its 8 KB Flash accommodates menu state machines plus fault-logging EEPROM storage (256 bytes). The 4.2 V to 5.5 V supply works directly off rectified mains-derived 5V rails. With 34 I/O pins the MCU replaces dedicated UI controllers while also serving as the main system MCU. Add zero-cross detection to the CCP capture input for triac phase-angle control and use the analog comparators for overcurrent shutdown.
Recommended
Automotive Body and Interior Modules (Non-Safety)
The PIC18LF4321-I/ML is used in non-safety automotive body modules such as mirror adjusters, interior lighting controllers, and seat-position memories. The 5V supply range aligns with body-electronics rails, and the Enhanced CCP module produces the PWM signals needed for LED dimming and small motor drive. The 256-byte EEPROM stores seat-position presets without battery backup. For AEC-Q100 qualified body-electronics designs, choose the automotive-graded PIC18F4321-I/ML variant instead. Add ESD protection (TVS diodes) on connector pins and isolate the MCU analog ground from the load-drive ground.
Recommended
Educational and Prototyping Development Platforms
The PIC18LF4321-I/ML serves as an educational platform in universities and maker labs because of its balanced mix of peripherals (ADC, PWM, EUSART, MSSP, ECCP) and free Microchip toolchain (MPLAB X IDE plus XC8 compiler). Students learn C programming, interrupt-driven design, and peripheral configuration on a single chip with 8 KB Flash for moderately sized assignments. The 44-QFN package, however, is challenging for hand-soldering; pair the MCU with a QFN-to-DIP carrier board for breadboard prototyping. The PICkit 3 or PICkit 4 programmer/debugger provides in-circuit debugging for student projects.
Recommended
Recommended Products Summary
Engineering reference data for PIC18LF4321-I/ML — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18F4321-I/ML | PIC18LF4320-I/ML | PIC18LF4523-I/ML | PIC18F4331-I/ML | PIC18F4523-I/ML | PIC18F4320-I/ML |
|---|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 44-QFN (HVQCCN) 8x8 mm | 44-QFN (HVQCCN) 8x8 mm - same | 44-QFN (HVQCCN) 8x8 mm - same | 44-QFN (HVQCCN) 8x8 mm - same | 44-QFN (HVQCCN) 8x8 mm - same | 44-QFN (HVQCCN) 8x8 mm - same | 44-QFN (HVQCCN) 8x8 mm - same |
| Program Memory | 8 KB Flash | 8 KB Flash | 8 KB Flash | 16 KB Flash | 8 KB Flash | 16 KB Flash | 8 KB Flash |
| Data RAM | 512 bytes | 512 bytes | 512 bytes | 768 bytes | 512 bytes | 768 bytes | 512 bytes |
| Supply Voltage | 4.2 V to 5.5 V | 2.0 V to 5.5 V | 4.2 V to 5.5 V | 4.2 V to 5.5 V | 2.0 V to 5.5 V | 2.0 V to 5.5 V | 2.0 V to 5.5 V |
| Max Clock Frequency | 40 MHz | 40 MHz | 40 MHz | 40 MHz | 40 MHz | 40 MHz | 40 MHz |
| ADC | 10-bit, up to 13 channels | 10-bit, up to 13 channels | 10-bit, up to 13 channels | 12-bit ADC | 12-bit ADC | 12-bit ADC | 10-bit, up to 13 channels |
| Enhanced CCP / PWM | Yes (ECCP) | Yes (ECCP) | No (standard CCP) | Yes (ECCP) | Yes (motor-control PWM) | Yes (ECCP) | No (standard CCP) |
| Operating Temperature | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) |
Key Differentiators
- Extended low-voltage 4.2V-5.5V LF specification (vs PIC18F4321-I/ML (2.0V-5.5V))
- Enhanced CCP module for advanced PWM (vs PIC18LF4320-I/ML)
- Balanced 8 KB Flash / 512 RAM for moderate code size (vs PIC18LF4523-I/ML (16 KB Flash / 768 RAM))
- Standard 10-bit ADC sufficient for most sensor readings (vs PIC18F4331-I/ML (12-bit ADC + 3 op-amps))
Design Notes
Estimated: at 40 MHz and 5.0 V the PIC18LF4321 typically draws 12-15 mA active and below 1 uA in Sleep. Place a 100 nF ceramic decoupling capacitor within 5 mm of each VDD/VDDCORE pin and a 10 uF bulk capacitor at the regulator output. The LF variant requires VDD stay within 4.2 V to 5.5 V - brown-out resets are configured in CONFIG2L for safe thresholds.
The 44-pin QFN (HVQCCN) package dissipates heat primarily through the exposed thermal pad. Solder the EP to a copper pour of at least 1 square inch to keep theta_JA below 30 C/W. In enclosed industrial enclosures above 60 C ambient, derate clock frequency to 32 MHz or provide forced-air cooling. Estimated junction temperature at 25 C ambient, 40 MHz: below 35 C rise.
Route the analog ADC inputs (AN0-AN12) away from PWM and switching traces. Use a separate analog ground island joined to the digital ground at a single point near the MCU GND pin. The 44-QFN pad layout uses a 0.5 mm pitch and 8x8 mm body; refer to Microchip package drawing C04-188 for land pattern dimensions.
Common pitfalls include: (1) forgetting to disable the WDT in CONFIG2H when unused, which causes unintended resets; (2) configuring the LFINTOSC without trimming the TUN<5:0> register, which can leave the clock 5-10% off; (3) using the F-variant firmware voltage thresholds on an LF part, causing brown-out at 5V rails; (4) leaving the MCLR pin floating - always pull MCLR high through a 10 kohm resistor.
Keep the 40 MHz crystal traces (OSC1/OSC2) shorter than 10 mm and symmetric. Use guard traces grounded on both sides for EMI-sensitive designs. Place the ICSP programming header (PGD/PGC) at the board edge so the PICkit can connect without removing the enclosure. Reserve area for a 2-pin SOT-23 footprint in case of future crystal-to-internal-oscillator migration.
Compliance Information
RoHS and lead-free compliance per Microchip product page. Industrial -40C to +85C grade; not AEC-Q100 qualified (choose automotive variant for AEC-Q).
