PIC18F4221-I/ML - 40MHz 8-bit MCU 4KB Flash 44-QFN | Microchip
MPN: PIC18F4221-I/ML ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.1 | $6.10 |
| 10 | $5.42 | $54.20 |
| 100 | $4.65 | $465.00 |
| 500 | $4.05 | $2,025.00 |
| 1,000 | $3.5 | $3,500.00 |
PIC18F4221-I/ML Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program and data memory, peripherals, and I/O on a single die. The PIC18F family sits in Microchip's 8-bit enhanced architecture tier, offering C compiler-friendly instruction set, hardware multiplier, linear program memory up to 2 MB, and the nanoWatt Technology power-management suite for low-power designs.
Key features include thirteen 10-bit ADC channels, two analog comparators, two capture/compare/PWM modules, an MSSP configurable as SPI or I2C, an EUSART, 36 digital I/O lines, and self-programming support for in-application firmware upgrades. nanoWatt Technology provides multiple idle and sleep modes (Run, Idle, Sleep, RC_RUN, RC_IDLE) with fast wake-up, making the device suitable for battery-powered embedded products.
The enhanced Harvard architecture delivers up to 10 MIPS at 40 MHz while maintaining deterministic interrupt latency. Internal oscillator options and wide operating voltage (4.2V-5.5V) eliminate external clock hardware in cost-sensitive designs, and the 10-bit ADC at up to 30 ksps supports sensor-conditioning and closed-loop control tasks.
Typical applications include industrial sensor interfaces, appliance control panels, HVAC fan controllers, low-end consumer devices, USB-less embedded controls, and automotive body modules (under-the-hood parts require AEC-Q100 grade). The 36 I/O count and 10-bit ADC make it a balanced general-purpose MCU.
When designing with this part, ensure 5V supply regulation within 4.2V-5.5V and provide adequate decoupling. The QFN-44 exposed pad must be soldered to the ground plane for thermal dissipation; failure to do so derates thermal performance significantly.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for PIC18F4221-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 PIC18F4221-I/ML (same form factor and footprint) — differing in Operating Temperature, Package, Program Memory (Flash), Self-Programming.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18F4220-I/ML
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$3.97 / Unit
View Datasheet →PIC18F4321-I/ML
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$1.22 / Unit
View Datasheet →PIC18F4221-I/PT
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4420-I/ML
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
PIC18F46K22-I/ML
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$3.08 / Unit
View Datasheet →PIC18F4221-I/ML Maximum Ratings & Electrical Characteristics
| Core | PIC18F 8-bit enhanced Harvard |
| Maximum Clock Frequency | 40 MHz |
| MIPS | 10 MIPS |
| Program Memory (Flash) | 4 KB (2K x 16) |
| Data SRAM | 512 bytes |
| Data EEPROM | 256 bytes |
| Operating Voltage | 4.2 V to 5.5 V |
| Operating Temperature | -40 C to +85 C (industrial) |
| I/O Pins | 36 |
| ADC | 10-bit, 13 channels |
| Analog Comparators | 2 |
| CCP/PWM Modules | 2 |
| MSSP | 1 (SPI or I2C) |
| EUSART | 1 |
| Package | 44-pin QFN (8x8 mm) with EP |
| Mounting Type | Surface Mount |
| MSL Level | 3 (168 hours) |
| Lead-Free / RoHS | Yes / Compliant |
| Power-Saving Modes | Run, Idle, Sleep, RC_RUN, RC_IDLE (nanoWatt) |
| Self-Programming | Yes (ICSP) |
PIC18F4221-I/ML Pin Configuration
| Pin 1 | MCLR/VPP/RE3 — Master clear / programming voltage / digital I/O RE3 |
| Pin 2 | RA0/AN0 — Digital I/O RA0 / analog input AN0 |
| Pin 3 | RA1/AN1 — Digital I/O RA1 / analog input AN1 |
| Pin 4 | RA2/AN2/VREF- — Digital I/O RA2 / analog input AN2 / ADC VREF- |
| Pin 5 | RA3/AN3/VREF+ — Digital I/O RA3 / analog input AN3 / ADC VREF+ |
| Pin 6 | RA4/T0CKI/C1OUT — Digital I/O RA4 / Timer0 clock / Comparator1 output |
| Pin 7 | RA5/AN4/SS/C2OUT — Digital I/O RA5 / AN4 / SPI slave select / Comparator2 output |
| Pin 8 | VSS — Ground |
| Pin 9 | OSC1/CLKI/RA7 — Crystal oscillator input / external clock in / RA7 |
| Pin 10 | OSC2/CLKO/RA6 — Crystal oscillator output / clock out / RA6 |
| Pin 11 | RC0/T1OSO/T13CKI — Digital I/O RC0 / Timer1 oscillator output / Timer1 clock |
| Pin 12 | RC1/T1OSI/CCP2 — Digital I/O RC1 / Timer1 oscillator input / CCP2 |
| Pin 13 | RC2/CCP1 — Digital I/O RC2 / Capture Compare PWM1 |
| Pin 14 | RC3/SCK/SCL — Digital I/O RC3 / SPI clock / I2C clock |
| Pin 15 | RC4/SDI/SDA — Digital I/O RC4 / SPI data in / I2C data |
| Pin 16 | RC5/SDO — Digital I/O RC5 / SPI data out |
| Pin 17 | RC6/TX/CK — Digital I/O RC6 / EUSART TX / EUSART clock |
| Pin 18 | RC7/RX/DT — Digital I/O RC7 / EUSART RX / EUSART data |
| Pin 19 | VSS — Ground |
| Pin 20 | VDD — Positive supply 4.2-5.5V |
| Pin 21 | RB0/AN12/INT0 — Digital I/O RB0 / AN12 / external interrupt 0 |
| Pin 22 | RB1/AN10/INT1 — Digital I/O RB1 / AN10 / external interrupt 1 |
| Pin 23 | RB2/AN8 — Digital I/O RB2 / AN8 |
| Pin 24 | RB3/AN9/CCP2 — Digital I/O RB3 / AN9 / CCP2 |
| Pin 25 | RB4/AN11 — Digital I/O RB4 / AN11 |
| Pin 26 | RB5/AN13 — Digital I/O RB5 / AN13 |
| Pin 27 | RB6/PGC — Digital I/O RB6 / ICSP clock |
| Pin 28 | RB7/PGD — Digital I/O RB7 / ICSP data |
| Pin 29 | VSS — Ground |
| Pin 30 | VDD — Positive supply 4.2-5.5V |
| Pin 31 | VSS — Ground |
| Pin 32 | RD0 — Digital I/O RD0 |
| Pin 33 | RD1 — Digital I/O RD1 |
| Pin 34 | RD2 — Digital I/O RD2 |
| Pin 35 | RD3 — Digital I/O RD3 |
| Pin 36 | RD4 — Digital I/O RD4 |
| Pin 37 | RD5 — Digital I/O RD5 |
| Pin 38 | RD6 — Digital I/O RD6 |
| Pin 39 | RD7 — Digital I/O RD7 |
| Pin 40 | VSS — Ground |
| Pin 41 | VDD — Positive supply 4.2-5.5V |
| Pin 42 | VSS — Ground |
| Pin 43 | RE0/RD — Digital I/O RE0 / parallel slave port read |
| Pin 44 | RE1/WR — Digital I/O RE1 / parallel slave port write |
| Pin EP | EP (Exposed Pad) — Must be soldered to ground plane for thermal dissipation |
Typical Applications
PIC18F4221-I/ML is suitable for 6 applications: Industrial Sensor Interface, Appliance Control Panel, HVAC Fan Controller, Low-End Consumer Embedded Device, Automotive Body Module (Non-Safety), USB-Less Embedded Control.
Industrial Sensor Interface
The PIC18F4221-I/ML's 13-channel 10-bit ADC and nanoWatt Technology make it well-suited for industrial sensor aggregation boards that sample multiple analog transducers in parallel. The 36 digital I/O lines handle discrete inputs (limit switches, optocouplers) and outputs (relay drivers, indicator LEDs) without external multiplexing. The 4.2-5.5V supply range accommodates industrial 5V rails, and the 40 MHz CPU executes sensor-fusion algorithms at sub-millisecond cadence. Compared to newer PIC18F46K22, it costs less but offers only 4 KB Flash, so reserve it for fixed-function sensor nodes rather than configurable platforms. The 44-QFN package is preferred over TQFP for compact sensor pods where vibration tolerance matters.
Recommended
Appliance Control Panel
Consumer appliance front-panel controllers fit PIC18F4221-I/ML well because the part combines a 10-bit ADC for keypad or potentiometer inputs, two CCP/PWM channels for buzzer or backlight dimming, and the MSSP for I2C keypad expansion. The nanoWatt idle/sleep modes cut quiescent current in standby below typical appliance standby budgets, helping meet Energy Star requirements. The 44-QFN's small footprint (8x8 mm) suits behind-glass panel modules, and the industrial -40 to +85 C range survives refrigerator or oven-door environments. Use the 256-byte EEPROM for user-setting persistence across power cycles. Firmware fits comfortably in 4 KB Flash for keypad scan, display driver, and simple state machines.
Recommended
HVAC Fan Controller
HVAC fan and blower controllers benefit from the PIC18F4221-I/ML's two CCP/PWM channels for motor speed control and 13 ADC channels for monitoring temperature sensors, current shunt, and tach feedback. The 40 MHz core handles sensor-fusion logic and PI control loops at 10 kHz update rates while leaving headroom for user-interface processing. nanoWatt Technology's Sleep and Idle modes reduce standby draw when the system is off but still sensing. The 4 KB Flash is sufficient for a closed-loop fan controller with NTC thermistor linearization and ramp-up/ramp-down profiles. Industrial temperature range covers unconditioned attic or basement installations where ambient can swing -20 to +70 C.
Recommended
Low-End Consumer Embedded Device
General-purpose consumer products like battery chargers, electronic toys, and small home appliances can use PIC18F4221-I/ML as a low-cost general-purpose controller. The PIC18 Harvard architecture provides deterministic interrupt latency for time-sensitive tasks like button debouncing and LED multiplexing, while the C-friendly instruction set supports portable firmware development under MPLAB X and XC8. 4 KB Flash holds small to medium-scale logic; for >8 KB applications, use the same-footprint PIC18F4321. The 44-QFN 8x8 mm footprint shrinks the design to a footprint smaller than a thumbnail, leaving room for the user-interface and battery compartment.
Recommended
Automotive Body Module (Non-Safety)
For non-safety automotive body electronics such as interior lighting, seat controllers, or window switches, PIC18F4221-I/ML provides adequate compute and ADC resources. The industrial -40 to +85 C temperature range covers cabin and trunk environments. The MSSP supports SPI/I2C communication with body-control transceivers, and the EUSART provides LIN-bus capability for low-speed body networks. Note: For under-hood or safety-critical automotive use, choose PIC18F46K22 or PIC18F25K80 (AEC-Q100 qualified) instead - the PIC18F4221 is not AEC-Q100 qualified. The 44-QFN package suits PCB-down automotive designs with limited board area.
Recommended
USB-Less Embedded Control
Embedded designs that don't need USB but require reliable 8-bit processing can use PIC18F4221-I/ML as a low-cost main controller. Its MSSP provides SPI for sensors and flash storage, and EUSART for RS-232/RS-485 networking with simple ASCII or Modbus ASCII protocols. 512 bytes of SRAM supports short message buffers for sensor data logging, while 4 KB Flash holds the control firmware. The internal RC oscillator option eliminates external clock components, reducing BOM cost. For designs that may later add USB, upgrade to PIC18F2550 or PIC18F4550 which add USB 2.0 full-speed peripherals in 28 or 40-pin packages.
Recommended
Recommended Products Summary
Engineering reference data for PIC18F4221-I/ML — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18F4220-I/ML | PIC18F4321-I/ML | PIC18F4221-I/PT | PIC18F4420-I/ML | PIC18F46K22-I/ML |
|---|---|---|---|---|---|---|
| Package | 44-QFN (8x8) | 44-QFN (8x8) - same | 44-QFN (8x8) - same | 44-TQFP - different | 44-QFN (8x8) - same | 44-QFN (8x8) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash | 4 KB | 4 KB | 8 KB | 4 KB | 16 KB | 16 KB |
| SRAM | 512 B | 512 B | 768 B | 512 B | 768 B | 3896 B |
| ADC | 10-bit, 13 channels | 10-bit, 10 channels | 10-bit, 13 channels | 10-bit, 13 channels | 10-bit, 13 channels | 12-bit, 28 channels |
| I/O Pins | 36 | 36 | 36 | 36 | 36 | 36 |
| MIPS | 10 MIPS at 40 MHz | 10 MIPS at 40 MHz | 10 MIPS at 40 MHz | 10 MIPS at 40 MHz | 10 MIPS at 40 MHz | 16 MIPS at 64 MHz |
| Supply Voltage | 4.2-5.5 V | 4.2-5.5 V | 4.2-5.5 V | 4.2-5.5 V | 4.2-5.5 V | 1.8-5.5 V (XLP) |
| EEPROM | 256 B | 256 B | 256 B | 256 B | 256 B | 256 B |
Key Differentiators
- More ADC channels than PIC18F4220 (vs PIC18F4220-I/ML)
- Drop-in 8 KB Flash upgrade path (vs PIC18F4321-I/ML)
- Lowest cost in PIC18F42xx 44-QFN family (vs PIC18F4420-I/ML)
Design Notes
The 44-QFN package has an exposed thermal pad that MUST be soldered to a continuous ground copper pour on the PCB to meet the datasheet thermal ratings. Without this thermal path, the junction-to-ambient resistance (theta_JA) rises significantly, potentially causing thermal shutdown under heavy I/O load. Use an array of thermal vias (typically 9 to 16 in a 3x3 or 4x4 grid) under the EP to conduct heat to the bottom-side ground plane or copper pour on inner layers.
Place a 100 nF decoupling capacitor as close as possible to each VDD pin (pins 20, 30, 41) and a single 10 uF bulk capacitor near the IC. The PIC18F4221 has three VDD pins; tying each to its own bypass cap reduces switching noise coupling into analog measurements. For designs using the ADC, also place a 100 nF cap on VREF+ (RA3) and keep analog and digital grounds separated at the IC, joining at a single point at the power-supply ground.
ICSP programming requires dedicated access to MCLR/VPP (pin 1), PGC (RB6/pin 27), and PGD (RB7/pin 28). When designing the PCB, either expose these pins to a programming header or include test points for pogo-pin programming fixtures. MCLR must be pulled up to VDD through a 10 kohm resistor; a 100 nF cap on MCLR improves ESD immunity. Avoid placing capacitors directly on PGC/PGD pins as they can interfere with programming signals.
Configuration bits must be set correctly or the device may not run. Specifically, set FOSC to select the oscillator mode (HS for high-speed crystal, INTIO2 for internal RC), enable the watchdog timer only if your application requires it (otherwise it can cause spurious resets), and disable low-voltage programming (LVP) bit if you are using high-voltage programming on MCLR. Misconfiguration of these bits is the most common cause of bricked PIC18F devices. Always verify configuration bits in MPLAB X before programming.
Compliance Information
RoHS compliant and lead-free per Microchip product page. NOT AEC-Q100 qualified - for safety-related automotive use choose PIC18F25K80 or PIC18F46K22 (AEC-Q100).
