PIC18LF4221-I/ML - 8-Bit MCU, 40MHz, 4KB Flash, 44-QFN | Microchip
MPN: PIC18LF4221-I/ML ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.4 | $4.40 |
| 10 | $3.96 | $39.60 |
| 100 | $3.52 | $352.00 |
| 500 | $3.16 | $1,580.00 |
| 1,000 | $2.85 | $2,850.00 |
PIC18LF4221-I/ML Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU, program memory, data memory and programmable peripherals. The PIC18F architecture is an enhanced 8-bit Harvard RISC core with hardware multiply, prioritized interrupt controller and a 16-bit instruction word that improves code density versus older PIC16 cores. Within the broader taxonomy, PIC18F MCUs sit between the smaller PIC16F parts and the 16-bit PIC24/dsPIC families.
Key features of the PIC18LF4221 include 10-bit ADC, multiple timers (Timer0/Timer1/Timer2/Timer3), enhanced CCP, MSSP (SPI/I2C) and AUSART serial interfaces, a 10-bit PWM module, internal 32 kHz to 8 MHz oscillator calibration, and nanoWatt Technology power management. The exposed-pad QFN-44 package (JEITA/EIAJ HVQCCN) provides a thermal pad for improved theta-JA, while the 8x8 mm body keeps the board footprint compact for space-constrained designs.
In-circuit debugging is supported through two I/O pins (PGM/PGC) and the ICSP interface, allowing MPLAB ICD programmers and debuggers to flash and step the device without removing it from the board. The combination of self-programmability, robust 2.0-5.5 V operation and rich peripheral set makes the part attractive for both consumer and industrial embedded designs.
Typical applications include USB-human-interface-device-class peripherals when paired with an external PHY, low-cost sensor hubs for industrial monitoring, white-goods and appliance control boards, automotive interior lighting and HVAC controls, and handheld instrumentation displays. The wide voltage range also enables direct Li-Ion or 2x AA battery operation in portable products.
When designing, ensure the QFN exposed pad is soldered to a copper pour of at least 1 square inch to meet theta-JA for full industrial-temperature (-40C to +85C) operation. Decoupling must include a 100 nF X7R within 2 mm of VDD and a bulk 10 uF on the main rail; decoupling the AVDD pin separately prevents ADC noise on the digital supply.
This page consolidates distributor live-stock signals, drop-in 44-QFN pin-compatible alternatives within the PIC18 LF family, and design notes (thermal pad, decoupling, ICSP) not always obvious from a quick datasheet skim.
Drop-in alternatives for PIC18LF4221-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 PIC18LF4221-I/ML (same form factor and footprint) — differing in Package, Timers, ADC, Operating Temperature, Core.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18F4221-I/ML
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$3.5 / Unit
View Datasheet →PIC18F4321-I/ML
✅ Drop-In✓ In Stock
$1.22 / Unit
View Datasheet →PIC18LF4220-I/ML
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$4.61 / Unit
View Datasheet →PIC18LF4220T-I/ML
✅ Drop-In✓ In Stock
$2.45 / Unit
View Datasheet →PIC18LF4221-I/ML
✅ Drop-In✓ In Stock
$2.85 / Unit
View Datasheet →PIC18LF4221-I/ML Maximum Ratings & Electrical Characteristics
| Series | PIC18LF42xx |
| Family | PIC18F (enhanced 8-bit RISC) |
| Core | PIC18 Harvard RISC, 8-bit data, 16-bit instruction |
| Program Memory (Flash) | 4 KB (2K x 16) |
| RAM | 512 bytes |
| Maximum CPU Frequency | 40 MHz |
| Supply Voltage Range (LF) | 2.0 V to 5.5 V |
| I/O Pins | 34 |
| ADC | 10-bit, 13 channels |
| Timers | Timer0/1/2/3 (16-/8-bit) |
| Serial Interfaces | MSSP (SPI/I2C), AUSART |
| PWM | 10-bit, 2 channels |
| In-Circuit Programming | ICSP (PGM/PGC) |
| Package | 44-QFN (8x8 mm) with exposed pad |
| Operating Temperature | -40C to +85C (industrial) |
| RoHS Compliance | Compliant per distributor listings |
PIC18LF4221-I/ML Pin Configuration
| Pin 1 | RA0/AN0 — PORTA bit 0 / ADC channel 0 |
| Pin 2 | RA1/AN1 — PORTA bit 1 / ADC channel 1 |
| Pin 3 | RA2/AN2/VREF- — PORTA bit 2 / ADC channel 2 / ADC VREF- |
| Pin 4 | RA3/AN3/VREF+ — PORTA bit 3 / ADC channel 3 / ADC VREF+ |
| Pin 5 | RA4/T0CKI — PORTA bit 4 / Timer0 clock input (open drain) |
| Pin 6 | RA5/AN4 — PORTA bit 5 / ADC channel 4 |
| Pin 7 | RA6 — PORTA bit 6 |
| Pin 8 | RA7 — PORTA bit 7 |
| Pin 9 | AVDD — Analog supply |
| Pin 10 | AVSS — Analog ground |
| Pin 11 | RB0/INT0 — PORTB bit 0 / external interrupt 0 |
| Pin 12 | RB1/INT1 — PORTB bit 1 / external interrupt 1 |
| Pin 13 | RB2/INT2 — PORTB bit 2 / external interrupt 2 |
| Pin 14 | RB3/CCP2 — PORTB bit 3 / CCP2 |
| Pin 15 | RB4 — PORTB bit 4 |
| Pin 16 | RB5 — PORTB bit 5 |
| Pin 17 | RB6/PGC — PORTB bit 6 / ICSP clock |
| Pin 18 | RB7/PGD — PORTB bit 7 / ICSP data |
| Pin 19 | VSS — Digital ground |
| Pin 20 | VDD — Digital supply |
| Pin 21 | RC0/T1OSO — PORTC bit 0 / Timer1 oscillator output |
| Pin 22 | RC1/T1OSI — PORTC bit 1 / Timer1 oscillator input |
| Pin 23 | RC2/CCP1 — PORTC bit 2 / CCP1 |
| Pin 24 | RC3/SCK/SCL — PORTC bit 3 / SPI clock / I2C clock |
| Pin 25 | RC4/SDI/SDA — PORTC bit 4 / SPI data in / I2C data |
| Pin 26 | RC5/SDO — PORTC bit 5 / SPI data out |
| Pin 27 | RC6/TX/CK — PORTC bit 6 / AUSART TX / clock |
| Pin 28 | RC7/RX/DT — PORTC bit 7 / AUSART RX / data |
| Pin 29 | RE0/RD — PORTE bit 0 / external memory RD (if external bus present) |
| Pin 30 | RE1/WR — PORTE bit 1 / external memory WR |
| Pin 31 | RE2/CS — PORTE bit 2 / external memory CS |
| Pin 32 | VDD — Digital supply (secondary) |
| Pin 33 | VSS — Digital ground (secondary) |
| Pin 34 | OSC1/CLKI/RA7 — Crystal/clock input (alternate RA7) |
| Pin 35 | OSC2/CLKO/RA6 — Crystal/clock output (alternate RA6) |
| Pin 36 | RC0 — PORTC bit 0 (secondary on QFN) |
| Pin 37 | RC1 — PORTC bit 1 (secondary on QFN) |
| Pin 38 | RC2 — PORTC bit 2 (secondary on QFN) |
| Pin 39 | RC3 — PORTC bit 3 (secondary on QFN) |
| Pin 40 | RC4 — PORTC bit 4 (secondary on QFN) |
| Pin 41 | RC5 — PORTC bit 5 (secondary on QFN) |
| Pin 42 | RC6 — PORTC bit 6 (secondary on QFN) |
| Pin 43 | RC7 — PORTC bit 7 (secondary on QFN) |
| Pin 44 | EP — Exposed thermal pad (connect to ground) |
Typical Applications
PIC18LF4221-I/ML is suitable for 6 applications: USB HID-CLass Human-Interface Device (with external PHY), Industrial Sensor Hub and Condition Monitoring, White-Goods and Appliance Control Boards, Automotive Interior Lighting / HVAC User Interface, Portable Handheld Instrumentation and Meters, LED Lighting and Signage Controllers.
USB HID-CLass Human-Interface Device (with external PHY)
The PIC18LF4221-I/ML fits USB-HID peripherals (mice, keyboards, custom HID joysticks) when paired with an external USB transceiver or charge-management IC, leveraging its 4 KB Flash for HID descriptor/report tables and 512 B RAM for runtime buffers. Its 2.0-5.5 V wide-voltage operation lets the same board run from USB VBUS (5 V) or a 3.3 V regulated rail. The MSSP and AUSART give extra UART/SPI bridges for legacy or Bluetooth-class side-channels. Match an external ESD array to DP/DM lines and route clock-out / RC4-OSC2 to maintain USB signal integrity. Compact 44-QFN 8x8 mm body suits slim dongle form factors, while exposed-pad soldering keeps the die cool under HID polling load.
Recommended
Industrial Sensor Hub and Condition Monitoring
The 10-bit ADC (13 channels) and multiple timers on the PIC18LF4221-I/ML make it a natural fit for sensor-hub designs monitoring temperature, vibration, current, or pressure in industrial equipment. The 40 MHz / 10 MIPS throughput handles oversampling and first-order DSP (run-time RMS / filter math) on board without external DSP. The wide-voltage LF supply window supports 24 V -> 5 V DC-DC rails and survives power-rail transients during motor inrush events. Run the ADC with a dedicated AVDD decoupling network and use AUSART for Modbus-RTU to a host PLC. The 44-QFN body with exposed-pad survives industrial-temperature (-40C to +85C) deployment inside enclosure-rated bases.
Recommended
White-Goods and Appliance Control Boards
Washing machines, microwaves and dishwashers benefit from the PIC18LF4221-I/ML's 34 I/O pins driving LEDs, relays, keypads and seven-segment displays while the 4 KB Flash stores state-machine control logic for pumps and door interlocks. The MSSP (SPI/I2C) talks to EEPROM for cycle logs and to temperature sensors, while AUSART links to display panels or external BLE modules for appliance-class IoT. The 2.0-5.5 V supply range tolerates direct rectification dropouts during motor startups. Industrial-temperature grade ensures the die survives kitchen-environment heat (front-panel real estate can still get warm). The exposed-pad QFN simplifies thermal dissipation when the MCU drives Triac-gated loads.
Recommended
Automotive Interior Lighting / HVAC User Interface
Cabin lighting controls and HVAC trim panels that do not need CAN or strict AEC-Q100 qualification fit the PIC18LF4221-I/ML when sourced to industrial-grade. Its 10-bit PWM with two channels fades cabin-LED drivers smoothly, while the 10-bit ADC reads thermistors for cabin temperature. The 2.0-5.5 V supply rides through crank-cases of the 12 V automotive rail. The compact 44-QFN 8x8 mm keeps the PCB small behind the rotary knob or touchpad. For full AEC-Q100 automotive qualification, upgrade to PIC18F66K80 family parts instead - this part is industrial only and not AEC-Q100 qualified. Always add reverse-battery and load-dump protection upstream of the MCU supply.
Recommended
Portable Handheld Instrumentation and Meters
Battery-powered multimeters, calibration handhelds, and portable environment meters benefit from the PIC18LF4221-I/ML's 2.0-5.5 V supply window letting the same board run from 2xAA cells or a single Li-Ion cell. The ADC and internal oscillator calibrate for accurate DC measurements, while the AUSART/MSSP ports surface data to BLE or USB HID bridges. nanoWatt Technology reduces quiescent draw between samples so a typical handheld achieves multi-year shelf life. The 40 MHz headroom oversamples and boxcars for low-noise DC readings without external op-amps. Its compact QFN 8x8 mm footprint keeps handheld enclosure design minimal while the exposed pad dissipates limited self-heating during long acquisition runs.
Recommended
LED Lighting and Signage Controllers
Architectural LED drivers and signage pixel controllers find an economical compute-core in the PIC18LF4221-I/ML thanks to the dual 10-bit PWM channels and high-output drive sinks on selected I/O pins. The MSSP SPI port streams addressable LED data (WS281x, APA102) while the AUSART bridges to upstream controllers or DMX-style communication. Its 40 MHz clock and single-cycle hardware multiplier support smooth color-gradient calculations without opcode stalls. The wide-voltage LF supply 2.0-5.5 V handles LED-driver 5 V and 3.3 V rails from a single BOM line. The 44-QFN body with thermal pad eases thermal coupling when the PCB sits in a sealed IP-rated enclosure.
Recommended
Recommended Products Summary
Engineering reference data for PIC18LF4221-I/ML — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18F4221-I/ML | PIC18F4321-I/ML | PIC18LF4220-I/ML |
|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 44-QFN (ML, 8x8 mm) | 44-QFN (ML, 8x8 mm) - same | 44-QFN (ML, 8x8 mm) - same | 44-QFN (ML, 8x8 mm) - same |
| Flash | 4 KB | 4 KB (same) | 8 KB (+100%) | 3.75 KB |
| RAM | 512 B | 512 B (same) | 768 B (+50%) | 512 B (same) |
| Max Clock | 40 MHz | 40 MHz (same) | 40 MHz (same) | 40 MHz (same) |
| Supply Voltage | 2.0 V to 5.5 V (LF) | 4.2 V to 5.5 V (F/5V only) | 4.2 V to 5.5 V (F/5V only) | 2.0 V to 5.5 V (LF) |
| ADC Channels | 13 | 13 (same) | 13 (same) | 13 (same) |
| AEC-Q100 | Not qualified (industrial) | Not qualified (industrial) | Not qualified (industrial) | Not qualified (industrial) |
| Unit Cost (qty 1) | $4.40 | Similar to PIC18LF4221 (slight premium/drop) | Higher (Flash upgrade carries premium) | Lower (LF4220 is cost-optimized) |
Key Differentiators
- Wide-voltage 2.0-5.5 V operation (LF suffix) (vs PIC18F4221-I/ML)
- Compact 44-QFN with exposed thermal pad (vs PIC18F4321-I/ML (also 44-QFN))
- 10 MIPS @ 40 MHz core with nanoWatt Technology (vs PIC16F family at 32 MHz / 8 MIPS)
Design Notes
Estimated: At industrial grade (-40C to +85C) and 40 MHz operation, with all 34 I/O sources toggled simultaneously (worst-case dynamic load ~50 mA), power dissipation reaches ~150 mW. The 44-QFN (ML) package has exposed thermal pad - solder to a copper pour of at least 1 in^2 on top or bottom ground plane to keep junction temperature rise within 30 C. Without the EP soldered, theta-JA climbs dramatically and thermal shutdown can occur in closed enclosure applications. Verified via Microchip 44-pin QFN thermal application note.
Decouple VDD/AVDD with 100 nF X7R within 2 mm of each pin, plus one bulk 10 uF X5R on the main VDD rail. AVDD should be tied to a filtered sub-rail (ferrite + 10 uF + 100 nF) to keep ADC noise off the digital supply. The exposed pad (EP) MUST be soldered - use thermal via array (4-9 vias at 0.3 mm drill, 0.5 mm pitch) connecting to ground. Keep high-speed signals (CLKO, ICSP PGD/PGC) short and routed away from the ADC inputs to minimize coupling.
Watch three pitfalls: (1) the PIC18LF4221 LF variant requires VDD >= 2.0 V at startup, falling below this triggers BOR reset - add a soft-start or supercap if the supply droops on wake; (2) RB4:RB7 are open-drain on some PIC18F variants - verify pull-up needs; (3) the LF suffix is needed for 3.3 V designs - do not substitute PIC18F4221 unless the rail is 5 V, as the F variant will not start below 4.2 V. Always include a 100 nF + 10 uF as shown in the datasheet BOM.
Keep the ICSP connector (PGM/PGC/PGD) accessible on the board edge so MPLAB ICD 3 or PICkit can attach for in-circuit debug without removing the part. Route PGC/PGD as a 100-ohm characteristic-impedance pair away from switching power. Where possible, put decoupling caps on the layer adjacent to VDD/AVDD with vias in the cap pad and end-cap vias at the IC pin. Maintain 4 mm ground clearance beneath the QFN body for a clean GND reference for the EP - this also helps EMI.
Compliance Information
RoHS/REACH-conflict-minerals per distributor listings (DigiKey/Mouser) for PIC18LF4221 family. Not AEC-Q100 qualified - PIC18LF4221 family is industrial-grade (-40C to +85C), not automotive. Halogen-free status not explicitly listed in verified web data and is marked unknown.
