PIC18F4221T-I/ML - 8-bit PIC MCU 4KB Flash 40MHz 44-QFN | Microchip
MPN: PIC18F4221T-I/ML ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.2 | $4.20 |
| 10 | $3.78 | $37.80 |
| 100 | $3.36 | $336.00 |
| 500 | $2.95 | $1,475.00 |
| 1,000 | $2.55 | $2,550.00 |
PIC18F4221T-I/ML Overview
An 8-bit microcontroller is a programmable system-on-a-chip that combines a CPU core, memory, and peripherals on a single silicon die. PIC microcontrollers (Programmable Intelligent Controllers) use a Harvard RISC architecture with only 77 single-word instructions, making them easy to program while delivering deterministic real-time performance. PIC18F family parts sit in the mid-range tier of the PIC portfolio, above baseline PIC16 and below PIC24/dsPIC, and are widely deployed in consumer, industrial, and automotive subsystems.
Key features of the PIC18F4221 include 10 MIPS throughput, self-programmable Flash, an internal oscillator block, and a 10-bit ADC with up to 13 channels. It also supports multiple communication interfaces - I2C, SPI, and UART/USART - enabling easy integration with sensors, displays, and wireless modules. The integrated nanoWatt power management reduces quiescent current in sleep modes.
The device uses Microchip's enhanced PIC18 architecture with a 16-bit wide instruction word and an 8-bit data path, providing code density comparable to 16-bit cores while preserving 8-bit pricing. The 44-QFN package exposes up to 36 I/O pins and supports in-circuit serial programming (ICSP) plus in-circuit debugging via two pins, allowing field firmware updates and on-board debug without removing the MCU.
Typical applications include industrial control systems, sensor interface modules, small appliance controls, automotive body electronics, and low-cost consumer devices. The combination of low power, ample peripherals, and the PIC18 instruction set makes it a strong fit for cost-sensitive embedded designs.
When designing with this part, plan for proper decoupling (100 nF on VDD close to each VDD pin plus a bulk 10 uF), use the internal RC oscillator when crystal accuracy is not critical, and leverage the nanoWatt sleep modes for battery-powered applications. Always reference the Microchip PIC18F4221 datasheet (DS39631) for errata and AC/DC timing.
This page synthesizes distributor pricing, parametric alternatives, and practical design notes not found in the manufacturer datasheet alone, giving engineers a single decision-ready reference.
Drop-in alternatives for PIC18F4221T-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 PIC18F4221T-I/ML (same form factor and footprint) — differing in ADC, Package, Core Architecture, Timers, I/O Pins.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18F4221-I/ML
✅ Drop-In✓ In Stock
$3.5 / Unit
View Datasheet →PIC18F4220T-I/ML
✅ Drop-In✓ In Stock
$3.64 / Unit
View Datasheet →PIC18F4221T-I/PT
✅ Drop-In✓ In Stock
$1.82 / Unit
View Datasheet →PIC18F4321T-I/ML
✅ Drop-In✓ In Stock
$4.1 / Unit
View Datasheet →PIC18F4421T-I/ML
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4520T-I/ML
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4221T-I/ML Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC18 (8-bit, Harvard RISC) |
| Instruction Set | 77 single-word instructions |
| Max CPU Speed | 40 MHz (10 MIPS) |
| Program Memory (Flash) | 4 KB (2K x 16) |
| Data RAM | 512 bytes |
| Data EEPROM | 256 bytes |
| I/O Pins | Up to 36 |
| ADC | 10-bit, up to 13 channels |
| Communication Interfaces | I2C, SPI, UART/USART |
| Timers | Multiple 8-bit and 16-bit timers |
| Package | 44-pin QFN (8x8 mm) |
| Mounting Type | Surface Mount |
| Operating Temperature | -40C to +85C (Industrial) |
| Supply Voltage | 2.0 V to 5.5 V |
| ICSP / ICD | Yes (In-Circuit Serial Programming and Debug) |
| RoHS Status | Compliant |
| Lead-Free | Yes |
PIC18F4221T-I/ML Pin Configuration
| Pin 1 | RA0/AN0 — Digital I/O / Analog input channel 0 |
| Pin 2 | RA1/AN1 — Digital I/O / Analog input channel 1 |
| Pin 3 | RA2/AN2/VREF- — Digital I/O / Analog input / ADC VREF- |
| Pin 4 | RA3/AN3/VREF+ — Digital I/O / Analog input / ADC VREF+ |
| Pin 5 | RA4/T0CKI — Digital I/O / Timer0 clock input |
| Pin 6 | RA5/AN4/SS — Digital I/O / Analog input / SPI slave select |
| Pin 7 | RA6 — Digital I/O / oscillator pin |
| Pin 8 | OSC1/CLKI/RA7 — Crystal oscillator input / external clock in |
| Pin 9 | OSC2/CLKO/RA6 — Crystal oscillator output |
| Pin 10 | VSS — Ground reference |
| Pin 11 | VDD — Positive supply (2.0 V to 5.5 V) |
| Pin 12 | RB0/INT0 — Digital I/O / External interrupt 0 |
| Pin 13 | RB1/INT1 — Digital I/O / External interrupt 1 |
| Pin 14 | RB2/INT2 — Digital I/O / External interrupt 2 |
| Pin 15 | RB3/INT3 — Digital I/O / External interrupt 3 |
| Pin 16 | RB4 — Digital I/O / interrupt-on-change |
| Pin 17 | RB5 — Digital I/O / interrupt-on-change |
| Pin 18 | RB6/PGC — Digital I/O / ICSP clock |
| Pin 19 | RB7/PGD — Digital I/O / ICSP data |
| Pin 20 | VSS — Ground reference |
| Pin 21 | VDD — Positive supply (2.0 V to 5.5 V) |
| Pin 22 | RC0/T1OSO — Digital I/O / Timer1 oscillator output |
| Pin 23 | RC1/T1OSI — Digital I/O / Timer1 oscillator input |
| Pin 24 | RC2/CCP1 — Digital I/O / Capture/Compare/PWM 1 |
| Pin 25 | RC3/SCL — Digital I/O / I2C clock |
| Pin 26 | RC4/SDA — Digital I/O / I2C data |
| Pin 27 | RC5 — Digital I/O |
| Pin 28 | RC6/TX/CK — Digital I/O / UART TX / USART clock |
| Pin 29 | RC7/RX/DT — Digital I/O / UART RX / USART data |
| Pin 30 | VSS — Ground reference |
| Pin 31 | VDD — Positive supply (2.0 V to 5.5 V) |
| Pin 32 | RD0 — Digital I/O / Parallel port bit 0 |
| Pin 33 | RD1 — Digital I/O / Parallel port bit 1 |
| Pin 34 | RD2 — Digital I/O / Parallel port bit 2 |
| Pin 35 | RD3 — Digital I/O / Parallel port bit 3 |
| Pin 36 | RD4 — Digital I/O / Parallel port bit 4 |
| Pin 37 | RD5 — Digital I/O / Parallel port bit 5 |
| Pin 38 | RD6 — Digital I/O / Parallel port bit 6 |
| Pin 39 | RD7 — Digital I/O / Parallel port bit 7 |
| Pin 40 | VSS — Ground reference |
| Pin 41 | VDD — Positive supply (2.0 V to 5.5 V) |
| Pin 42 | RE0/RD — Digital I/O / Parallel port read control |
| Pin 43 | RE1/WR — Digital I/O / Parallel port write control |
| Pin 44 | RE2/CS — Digital I/O / Parallel port chip select |
Typical Applications
PIC18F4221T-I/ML is suitable for 7 applications: Industrial Sensor Interface Module, Small Appliance Control Board, Automotive Body Electronics, IoT Edge Sensor Node, HMI Keypad and LCD Front Panel, Battery Charging Controller, Educational Trainer Board.
Industrial Sensor Interface Module
The PIC18F4221T-I/ML fits industrial sensor interfaces because it integrates a 10-bit ADC with up to 13 channels, I2C/SPI/UART peripherals for digital sensors, and runs at 10 MIPS for real-time filtering. Its 4 KB Flash stores small protocol stacks, while 512 B RAM is ample for buffer and state. The -40C to +85C industrial temperature rating covers factory environments, and the 44-QFN 8x8 mm footprint fits compact DIN-rail sensor boards. Pair it with a 4-20 mA current loop driver and an RS-485 transceiver for a complete analog front end.
Recommended
Small Appliance Control Board
Household appliances like coffee machines, washing machines, and induction cooktops benefit from the PIC18F4221T-I/ML's 36 I/O pins for keypad, LED, relay, and triac control. Its 40 MHz speed runs PID loops for temperature regulation at 100 Hz update rates. The 256-byte EEPROM stores user preferences (brew strength, cycle count) across power cycles. nanoWatt sleep modes drop quiescent current below 1 uA in standby, helping meet energy-star idle targets. The 44-QFN package enables compact PCB designs that fit behind control panels.
Recommended
Automotive Body Electronics
Body control modules for seat position, mirror adjustment, and interior lighting use the PIC18F4221T-I/ML for its CAN-equivalent UART communication to other ECUs and its PWM-capable I/O for motor drive. Although not AEC-Q100 qualified at the 4221 variant, the industrial temperature range handles most cabin environments. The wide 2.0 V to 5.5 V supply tolerates 12 V battery transients after regulator conditioning. Use it for non-safety functions like window lift control or ambient lighting color mixing.
Recommended
IoT Edge Sensor Node
For low-power IoT edge sensors (temperature, humidity, occupancy), the PIC18F4221T-I/ML handles sensor polling, local averaging, and packet formatting before forwarding to a paired radio module. Its nanoWatt sleep draws less than 1 uA, enabling multi-year battery life on 2x AA cells for sensors reporting every 5 minutes. The I2C and SPI peripherals connect directly to digital sensors like the SHT30 or BME280. A UART link bridges to a Wi-Fi or LoRa module for backhaul.
Recommended
HMI Keypad and LCD Front Panel
Human-machine interface front panels with 4x4 keypads, character LCDs, or LED indicators are well-served by the PIC18F4221T-I/ML. The 36 I/O pins handle matrix keypad scanning (8 pins), a 16x2 character LCD in 4-bit mode (6 pins), and status LEDs (8 pins) with room to spare. The 10 MIPS throughput executes debounce, key mapping, and menu navigation without latency. The compact 44-QFN package is ideal for slimmer front-panel PCBs behind glass overlays.
Recommended
Battery Charging Controller
The PIC18F4221T-I/ML can implement CC/CV charging profiles for lead-acid, NiMH, or Li-ion packs using its ADC to monitor voltage and current. Its PWM peripherals drive a buck or synchronous rectifier topology. The 256-byte EEPROM saves charge profiles for multiple battery chemistries, and nanoWatt sleep preserves battery when the charger is idle. The 2.0 V minimum supply allows operation down to deeply discharged cells for safe recovery charging.
Recommended
Educational Trainer Board
Universities and training centers use the PIC18F4221T-I/ML on development boards to teach embedded programming. The 77-instruction RISC core is easy to learn, ICSP debugging allows step-through code execution, and the 44-QFN provides enough I/O for student-led peripheral expansions. The wide supply range (2.0 V to 5.5 V) lets students experiment with both 3.3 V and 5 V peripherals on the same board. The PIC18 heritage means abundant example code and MPLAB X IDE support.
Recommended
Recommended Products Summary
Engineering reference data for PIC18F4221T-I/ML — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18F4221-I/ML | PIC18F4220T-I/ML | PIC18F4321T-I/ML | PIC18F4421T-I/ML | PIC18F4520T-I/ML |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 44-QFN (8x8 mm) | 44-QFN (8x8 mm) | 44-QFN (8x8 mm) | 44-QFN (8x8 mm) | 44-QFN (8x8 mm) | 44-QFN (8x8 mm) |
| Program Flash | 4 KB | 4 KB | 2 KB | 8 KB | 4 KB | 32 KB |
| Data RAM | 512 B | 512 B | 512 B | 512 B | 768 B | 1536 B |
| Data EEPROM | 256 B | 256 B | 256 B | 256 B | 256 B | 256 B |
| Max CPU Speed | 40 MHz (10 MIPS) | 40 MHz (10 MIPS) | 40 MHz (10 MIPS) | 40 MHz (10 MIPS) | 40 MHz (10 MIPS) | 40 MHz (10 MIPS) |
| I/O Pins | Up to 36 | Up to 36 | Up to 36 | Up to 36 | Up to 36 | Up to 36 |
| ADC | 10-bit, 13 channels | 10-bit, 13 channels | 10-bit, 13 channels | 10-bit, 13 channels | 10-bit, 14 channels | 10-bit, 13 channels |
| Operating Temperature | -40C to +85C (Industrial) | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
| Supply Voltage | 2.0 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 | 2.0 V to 5.5 V | 2.0 V to 5.5 V |
Key Differentiators
- Compact 44-QFN 8x8 mm with industrial temp range (vs PIC18F4520T-I/ML)
- 4 KB Flash is the sweet-spot density (vs PIC18F4220T-I/ML)
- 10 MIPS is fast enough for most control loops (vs PIC18F4221T-I/PT (TQFP-44))
Design Notes
Decouple each VDD pin with a 100 nF ceramic capacitor placed within 5 mm of the pin, plus a single 10 uF bulk capacitor at the IC's main supply entry. The 44-QFN has multiple VDD/VSS pairs (pins 11/10, 21/20, 31/30, 41/40) - all must be connected even if some peripheral blocks are unused. Estimated: VDD rise time should stay below 50 ms for proper POR; adding a 10 kohm pull-up on MCLR ensures clean reset behavior.
Route the ICSP pins RB6/PGC and RB7/PGD away from switching nodes and high-current traces to avoid programming glitches. Place the MCLR pull-up (typically 10 kohm to VDD) close to the pin. The QFN44 thermal pad (pin 45, central pad) MUST be soldered to a ground copper pour for mechanical integrity and thermal dissipation. Use at least 4 thermal vias in the central pad for 0.5 W or higher dissipation cases.
Do not configure RA4 as a digital output while the internal comparator is active - RA4 is an open-drain output and requires a pull-up. The 10-bit ADC requires acquisition time (Tacq) of at least 2.45 us at 5 V with a 10 kohm source impedance - configure ADCON2 properly or readings will be inaccurate. When using the internal RC oscillator, the factory calibration constant in Flash location 0x3FFF (or last word of Flash) must be loaded to OSCCAL at startup for accurate frequency.
I2C lines SCL/SCL (RC3/RC4) require pull-up resistors; 4.7 kohm is typical for 100 kHz, 2.2 kohm for 400 kHz. UART TX/RX lines should be series-terminated with 100 ohm if the cable length exceeds 20 cm to suppress ringing. The ICSP clock (PGC) line should not exceed 30 cm to maintain debug signal integrity.
Compliance Information
RoHS and REACH compliant per Microchip product page. Not AEC-Q100 qualified - choose PIC18F2520/4520 automotive variants (I/PT or -E versions) for automotive designs. Lead-free and halogen-free per Microchip environmental certification.