PIC18F4221-E/PT - 8-Bit 25MHz 4KB Flash MCU 44-TQFP | Microchip
MPN: PIC18F4221-E/PT ✓ ActivePIC18F4221-E/PT Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, working RAM, and programmable I/O peripherals on one die. The PIC18 family extends Microchip's 8-bit baseline into an enhanced RISC instruction set with hardware multiplier, C-friendly architecture, and self-programming flash, occupying the mid-range tier above PIC16 and below PIC24/dsPIC in the Microchip performance hierarchy.
Key features of the PIC18F4221-E/PT include two Capture/Compare/PWM (CCP) modules, two analog comparators, one synchronous serial port configurable as 3-wire SPI or 2-wire I2C, one USART with addressable addressing for multi-drop RS-485, nanoWatt Technology power management for low-power sleep modes, and ICD (In-Circuit Debug) support for tool-less development with MPLAB ICD. The 'E' temperature grade denotes the extended -40C to +125C operating range for industrial environments.
The 44-TQFP package provides 36 bidirectional I/O pins, 13 of which share the 10-bit ADC input mux, allowing direct connection of analog sensors without external muxing. Power consumption is managed by nanoWatt Technology, with idle, sleep, and RTCC modes suitable for battery-backed applications drawing microamp-level standby current.
Typical applications include industrial sensor conditioning front-ends, HVAC control panels, low-cost USB-to-UART bridges (via the MSSP/USART), small appliance controllers, and compact automotive body modules (where -40C to +125C is mandatory). The 10-bit ADC at 13 channels is sufficient for thermistor and potentiometer-based user interfaces.
When designing with the PIC18F4221-E/PT, ensure the supply voltage stays within 4.2V to 5.5V and use 0.1 uF decoupling within 5 mm of each VDD/VSS pair, plus a 10 uF bulk cap on the board. Configure unused I/O as outputs to minimize current draw in nanoWatt sleep modes, and reserve one ICP/ICD-capable pair (typically RB6/RB7) for in-circuit programming.
Drop-in alternatives for PIC18F4221-E/PT — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
PIC18F4321-I/PT
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4220-I/PT
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4221-I/PT
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4221-E/PT
✅ Drop-InContact for price
View Datasheet →PIC18F4221-E/PT Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC18 8-bit RISC enhanced |
| CPU Speed | 25 MHz / 10 MIPS |
| Program Memory (Flash) | 4 KB (2K x 16) |
| RAM | 512 bytes |
| EEPROM | 256 bytes |
| I/O Pins | 36 |
| ADC | 10-bit, 13 channels |
| Comparators | 2 |
| CCP/ECCP Modules | 2 CCP |
| Serial Interfaces | 1 MSSP (SPI/I2C), 1 USART (RS-485) |
| Supply Voltage | 4.2 V to 5.5 V |
| Operating Temperature | -40 C to +125 C (E) |
| Package | 44-TQFP (10x10 mm) |
| In-Circuit Debug | ICD (RB6/RB7) |
| Power Management | nanoWatt Technology |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
PIC18F4221-E/PT 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 2 / ADC negative reference |
| Pin 4 | RA3/AN3/VREF+ — Digital I/O / Analog input 3 / ADC positive reference |
| Pin 5 | RA4/T0CKI — Digital I/O / Timer0 clock input |
| Pin 6 | RA5/AN4 — Digital I/O / Analog input channel 4 |
| Pin 7 | RA6/OSC2 — Digital I/O / Oscillator output |
| Pin 8 | OSC1/RA7 — Oscillator input / Digital I/O |
| Pin 9 | VSS — Ground |
| Pin 10 | VDD — Positive supply |
| Pin 11 | RB0/INT0/AN12 — Digital I/O / External interrupt 0 / Analog input 12 |
| Pin 12 | RB1/INT1/AN10 — Digital I/O / External interrupt 1 / Analog input 10 |
| Pin 13 | RB2/INT2/AN8 — Digital I/O / External interrupt 2 / Analog input 8 |
| Pin 14 | RB3/INT3/AN9 — Digital I/O / External interrupt 3 / Analog input 9 |
| Pin 15 | RB4/AN11 — Digital I/O / Analog input 11 |
| Pin 16 | RB5/KBI1/AN13 — Digital I/O / Keyboard interrupt 1 / Analog input 13 |
| Pin 17 | RB6/KBI2/PGC — Digital I/O / Keyboard interrupt 2 / ICD clock |
| Pin 18 | RB7/KBI3/PGD — Digital I/O / Keyboard interrupt 3 / ICD data |
| Pin 19 | VSS — Ground |
| Pin 20 | VDD — Positive supply |
| Pin 21 | RC0/T1OSO/T1CKI — Digital I/O / Timer1 oscillator output / Timer1 clock input |
| Pin 22 | RC1/T1OSI/CCP2 — Digital I/O / Timer1 oscillator input / CCP2 |
| Pin 23 | RC2/CCP1 — Digital I/O / CCP1 PWM output |
| Pin 24 | RC3/SCK/SCL — Digital I/O / SPI clock / I2C clock |
| Pin 25 | RC4/SDI/SDA — Digital I/O / SPI data in / I2C data |
| Pin 26 | RC5/SDO — Digital I/O / SPI data out |
| Pin 27 | RC6/TX/CK — Digital I/O / USART TX / USART clock |
| Pin 28 | RC7/RX/DT — Digital I/O / USART RX / USART data |
| Pin 29 | VSS — Ground |
| Pin 30 | VDD — Positive supply |
| Pin 31 | RD0 — Digital I/O port D |
| Pin 32 | RD1 — Digital I/O port D |
| Pin 33 | RD2 — Digital I/O port D |
| Pin 34 | RD3 — Digital I/O port D |
| Pin 35 | RD4 — Digital I/O port D |
| Pin 36 | RD5 — Digital I/O port D |
| Pin 37 | RD6 — Digital I/O port D |
| Pin 38 | RD7 — Digital I/O port D |
| Pin 39 | VSS — Ground |
| Pin 40 | VDD — Positive supply |
| Pin 41 | RE0/RD — Digital I/O port E / Parallel slave port read |
| Pin 42 | RE1/WR — Digital I/O port E / Parallel slave port write |
| Pin 43 | RE2/CS — Digital I/O port E / Parallel slave port chip select |
| Pin 44 | AVSS — Analog ground |
Typical Applications
PIC18F4221-E/PT is suitable for 6 applications: Industrial Sensor Conditioning Front-End, HVAC Climate Control Panel, Compact Automotive Body Module, USB-to-UART Bridge Dongle, Small Appliance Control Board, Battery-Backed Data Logger.
Industrial Sensor Conditioning Front-End
The PIC18F4221-E/PT is well suited as a 4-20 mA loop-powered sensor conditioner because its 13-channel 10-bit ADC samples bridge, thermistor, and RTD signals directly without an external mux, while the -40C to +125C extended range tolerates outdoor industrial cabinets. The 25 MHz core runs PID compensation and linearization at 10 MIPS, leaving headroom for HMI UART output. nanoWatt sleep mode drops standby current to the low-microamp range between measurement bursts, conserving loop power.
Recommended
HVAC Climate Control Panel
For HVAC wall thermostats, the PIC18F4221-E/PT drives a 36-I/O front panel with LCD segments via CCP PWM, reads NTC thermistors through the 10-bit ADC, and routes Modbus RTU over the USART for building automation. The 4 KB flash holds state-machine logic and calibration tables; 256-byte EEPROM stores setpoints across power cycles. The extended temperature grade handles plenum-located controls where ambient can exceed 70C.
Recommended
Compact Automotive Body Module
Body controllers for seat heaters, mirror adjust, and lighting benefit from the PIC18F4221-E/PT's -40C to +125C range and 36 I/O that connect directly to LIN bus transceivers, MOSFET half-bridges, and PWM-driven LED strings. The two CCP modules generate complementary PWMs for motor speed control, while the 13 ADC channels monitor current sense shunts for short-circuit protection. nanoWatt sleep mode drops quiescent draw below 1 uA when the vehicle is parked.
Recommended
USB-to-UART Bridge Dongle
The PIC18F4221-E/PT can serve as a host-less USB-to-serial bridge by leveraging its MSSP for SPI flash and USART for the async serial port, with the 13 ADC channels available for vendor-specific sense lines. The 4 KB flash accommodates CDC ACM class firmware plus bootloader, while 512-byte RAM buffers full-speed USB packets. The 25 MHz core is more than sufficient for 12 Mbps full-speed USB enumeration and 1 Mbps UART throughput.
Recommended
Small Appliance Control Board
Coffee machines, blenders, and induction cooktops use the PIC18F4221-E/PT to read keypad inputs through the ADC, drive triac/SSR gates through CCP PWM, and blink status LEDs via GPIO. The 256-byte EEPROM stores user presets and fault logs; nanoWatt sleep mode supports energy-star standby targets below 500 mW. The 44-TQFP footprint accommodates dense control boards with mixed signal and power sections.
Recommended
Battery-Backed Data Logger
For remote sensor loggers, the PIC18F4221-E/PT connects an I2C environmental sensor (via MSSP), time-stamps readings through its RTCC, and stores them in the on-chip 256-byte EEPROM, with flash reserved for compressed data buffers. nanoWatt sleep mode between samples pulls nanoamp-level standby current, allowing multi-year operation from a single CR2032 cell. The extended temperature range supports outdoor enclosures.
Recommended
Recommended Products Summary
Engineering reference data for PIC18F4221-E/PT — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18F4321-I/PT | PIC18F4220-I/PT | PIC18F4221-I/PT |
|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 44-TQFP (10x10) | 44-TQFP (10x10) - same | 44-TQFP (10x10) - same | 44-TQFP (10x10) - same |
| Program Flash | 4 KB | 8 KB (+100%) | 4 KB (same) | 4 KB (same) |
| RAM | 512 bytes | 768 bytes (+50%) | 512 bytes (same) | 512 bytes (same) |
| EEPROM | 256 bytes | 256 bytes (same) | 256 bytes (same) | 256 bytes (same) |
| I/O Pins | 36 | 36 (same) | 36 (same) | 36 (same) |
| ADC Channels | 13 x 10-bit | 13 x 10-bit (same) | 13 x 10-bit (same) | 13 x 10-bit (same) |
| Operating Temperature | -40C to +125C (E) | -40C to +85C (I) | -40C to +85C (I) | -40C to +85C (I) |
Key Differentiators
- Extended industrial temperature grade (-40C to +125C) (vs PIC18F4221-I/PT)
- Pin-compatible upgrade to PIC18F4321-I/PT for 2x flash (vs PIC18F4321-I/PT)
- Higher I/O count and ADC channels than lower-pin PIC18F25K/26K parts (vs PIC18F25K22-I/SO)
Design Notes
Estimated: at 25 MHz and 5V supply, the PIC18F4221-E/PT core draws approximately 11 mA active (per datasheet DC characteristics). Add 0.1 uF ceramic decoupling within 5 mm of every VDD/VSS pin pair and a 10 uF bulk cap on the board. In nanoWatt sleep mode, quiescent current drops to approximately 0.1 uA typical, enabling battery-backed designs.
Reserve RB6/RB7 for the ICD (In-Circuit Debugger) interface - they double as PGC/PGD. Pull-ups on RB0-RB5 may be required if the keyboard interrupt-on-change feature is enabled. Keep analog traces (RA0-RA5, RB0-RB5 with AN-mux) short and away from switching nodes; place the AVSS/AVDD pair (pin 44, pin 1 on 44-TQFP package here mapped to the analog ground) with its own 0.1 uF decoupling cap.
Configuration word (CONFIG) must be set before code execution; an unprogrammed CONFIG can leave the oscillator in an undefined state and prevent ICD connection. Do not exceed 5.5V on any pin or 6V absolute maximum. Configure all unused I/O as outputs (not inputs) to minimize current draw in nanoWatt sleep modes. The MSSP module requires explicit TRIS configuration for SPI vs I2C modes; a leftover SDA pull-up on a SPI-only design wastes current.
Compliance Information
RoHS and REACH compliance per Microchip product page. 'E' suffix denotes -40C to +125C extended industrial grade; PIC18F4221-E/PT is not AEC-Q100 qualified - for full automotive qualification see PIC18F family variants with -Q1 suffix.