PIC18F2550-I/SO - 8-bit 48MHz USB MCU 32KB Flash 28-SOIC | Microchip
MPN: PIC18F2550-I/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.4 | $6.40 |
| 10 | $5.85 | $58.50 |
| 100 | $5.2 | $520.00 |
| 500 | $4.65 | $2,325.00 |
| 1,000 | $4.1 | $4,100.00 |
PIC18F2550-I/SO Overview
An 8-bit microcontroller is a single-chip computer that integrates a CPU, program memory, data RAM, peripherals, and I/O on one silicon die. Microcontrollers belong to the broader class of embedded processors and are the foundation of microcomputer systems used in everything from USB peripherals to industrial controllers. The PIC18F family in particular is a high-performance 8-bit architecture with hardware multiply, nanoWatt power management, and C-compiler friendly instruction set, sitting between PIC16 (baseline) and dsPIC (16-bit DSP) families in Microchip's portfolio.
Key features of the PIC18F2550-I/SO include the Full-Speed USB 2.0 transceiver (no external components required for USB connectivity), three serial ports (USB, I2C/SPI up to 10 Mbit/s, and an LIN-capable EUSART), a 10-bit ADC with up to 13 channels, two PWM modules with Capture/Compare, and nanoWatt power-saving modes. The 28-SOIC (Wide SO, 7.5 mm body) package provides robust through-hole-style wave soldering while remaining surface-mount, with a typical 25 programmable I/O pins for off-chip connectivity.
The PIC18F2550 architecture uses a 16-bit-wide instruction word Flash and a Harvard bus with hardware multiplier, achieving 8-bit throughput that competes with low-end ARM Cortex-M0 parts on cost while providing the deterministic single-cycle I/O that the PIC architecture is famous for. The integrated SIE (Serial Interface Engine) handles USB framing in hardware, freeing the core from bit-banging USB and enabling reliable Full-Speed device classes (CDC, vendor, HID, MIDI) without external PHY chips.
Typical applications include USB HID peripherals (custom keyboards, mice, joysticks, game controllers), USB-to-UART bridges, MIDI adapters, low-cost data loggers with USB connectivity, PICkit-style programmers, educational development boards, industrial sensor interfaces with USB diagnostics, and hobbyist/maker projects that need plug-and-play USB on a single chip. The wide SO-28 footprint is breadboard-friendly through an SOIC-to-DIP adapter.
When designing with this device, remember that the integrated USB requires the 48 MHz PLL to be enabled, which constrains the oscillator configuration; many designs use a 20 MHz crystal with the 96 MHz PLL/2 setting. Ensure adequate bulk decoupling (100 nF + 4.7 uF) on VDD and place the D+/D- traces as a 90-ohm differential pair per USB 2.0 specification.
This page synthesizes distributor pricing, pin-compatible drop-in alternatives (including same-package PIC18F2450, PIC18F2553, PIC18F14K50, PIC18F13K50, PIC18F24K50, PIC18F25K50, and PIC18F26K50 considerations where pinout permits), and practical design notes not found in the standalone manufacturer datasheet.
Drop-in alternatives for PIC18F2550-I/SO — 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 PIC18F2550-I/SO (same form factor and footprint) — differing in Package, Timers, ADC, Program Memory (Flash), Serial Interfaces.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18F2553-I/SO
✅ Drop-In✓ In Stock
$5.55 / Unit
View Datasheet →PIC18F2455-I/SO
✅ Drop-In✓ In Stock
$6.4 / Unit
View Datasheet →PIC18F2550T-I/SO
✅ Drop-In✓ In Stock
$4.83 / Unit
View Datasheet →PIC18F2550-I/SP
✅ Drop-In✓ In Stock
$4.1 / Unit
View Datasheet →PIC18F2550-E/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F24K50-I/SO
✅ Drop-In✓ In Stock
$2.05 / Unit
View Datasheet →PIC18F2550-I/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 8-bit (Harvard, enhanced mid-range) |
| Program Memory (Flash) | 32 KB (16K x 16 words) |
| Data RAM | 2 KB |
| Data EEPROM | 256 bytes |
| Maximum CPU Frequency | 48 MHz (12 MIPS) |
| Supply Voltage (VDD) | 4.2 V to 5.5 V |
| I/O Pins | 25 programmable (PortA/B/C, multiplexed) |
| USB Controller | Full-Speed USB 2.0 (12 Mbit/s) with on-chip SIE and transceiver |
| ADC | 10-bit, up to 13 input channels |
| PWM Outputs | 2 CCP modules (10-bit PWM resolution) |
| Serial Interfaces | USB 2.0 FS, I2C, SPI up to 10 Mbit/s, EUSART (LIN-capable) |
| Timers | 4 (Timer0/1/2/3) 8/16-bit |
| Operating Temperature | -40 C to +85 C (industrial, -I suffix) |
| Package | 28-pin SOIC (Wide, 7.5 mm body) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
| Lead-Free | Yes |
PIC18F2550-I/SO Pin Configuration
| Pin 1 | /MCLR — Master Clear (reset) input, active low; tied to VDD through 10k resistor for normal operation |
| Pin 2 | RA0/AN0 — Digital I/O / analog input channel 0 |
| Pin 3 | RA1/AN1 — Digital I/O / analog input channel 1 |
| Pin 4 | RA2/AN2/VREF- — Digital I/O / analog input channel 2 / ADC VREF- |
| Pin 5 | RA3/AN3/VREF+ — Digital I/O / analog input channel 3 / ADC VREF+ |
| Pin 6 | RA4/T0CKI — Digital I/O / Timer0 clock input |
| Pin 7 | RA5/AN4/SS — Digital I/O / analog input channel 4 / SPI slave select |
| Pin 8 | VSS — Ground reference |
| Pin 9 | OSC1/CLKI — Crystal oscillator input or external clock input (typically 20 MHz crystal) |
| Pin 10 | OSC2/CLKO — Crystal oscillator output / clock output |
| Pin 11 | VDD — Positive supply voltage (4.2 V to 5.5 V) |
| Pin 12 | VSS — Ground reference |
| Pin 13 | RB0/AN12/INT0 — Digital I/O / analog input channel 12 / external interrupt 0 |
| Pin 14 | RB1/AN10/INT1 — Digital I/O / analog input channel 10 / external interrupt 1 |
| Pin 15 | RB2/AN8 — Digital I/O / analog input channel 8 |
| Pin 16 | RB3/AN9/CCP2 — Digital I/O / analog input channel 9 / CCP2 PWM output |
| Pin 17 | RB4/AN11 — Digital I/O / analog input channel 11 |
| Pin 18 | RB5/AN13 — Digital I/O / analog input channel 13 |
| Pin 19 | RB6/PGC — Digital I/O / ICSP clock (programming clock input) |
| Pin 20 | RB7/PGD — Digital I/O / ICSP data (programming data line) |
| Pin 21 | RC0 — Digital I/O |
| Pin 22 | RC1 — Digital I/O |
| Pin 23 | RC2/CCP1 — Digital I/O / CCP1 PWM output |
| Pin 24 | RC4/D- — Digital I/O / USB Full-Speed D- line |
| Pin 25 | RC5/D+ — Digital I/O / USB Full-Speed D+ line (FS pull-up enabled here) |
| Pin 26 | RC6/TX/CK — Digital I/O / EUSART asynchronous transmit / synchronous clock |
| Pin 27 | RC7/RX/DT — Digital I/O / EUSART asynchronous receive / synchronous data |
| Pin 28 | VUSB — Internal USB 3.3 V regulator output; connect to VDD via 220 nF capacitor |
Typical Applications
PIC18F2550-I/SO is suitable for 7 applications: USB HID Peripherals (Keyboard/Mouse/Joystick), USB-to-UART / CDC Virtual COM Port Bridge, MIDI Adapter and USB-MIDI Controllers, Low-Cost USB Data Logger, PICkit-Compatible Programmer / Debugger, Educational Development Boards, Industrial Sensor Interface with USB Diagnostics.
USB HID Peripherals (Keyboard/Mouse/Joystick)
The PIC18F2550's integrated Full-Speed USB 2.0 SIE and 32 KB Flash make it ideal for USB HID class devices. The hardware SIE handles framing, CRC, and packet ID filtering so the core spends most cycles on application logic rather than USB protocol state. With 12 MIPS throughput and 2 KB RAM, the device comfortably implements HID boot or report protocols plus matrix scanning, debounce, and LED control. Typical reference designs include 4x4 to 8x8 matrix keypads, custom gaming controllers, and HID-streamed sensor peripherals, all without external USB PHY. The on-chip 3.3 V regulator and internal 96 MHz PLL eliminate external USB components, reducing BOM cost and PCB area. Developers can use the Microchip USB Framework (HID/CDC/Vendor) which provides turnkey firmware for HID class enumeration on Windows, Linux, and macOS hosts.
Recommended
USB-to-UART / CDC Virtual COM Port Bridge
The PIC18F2550's USB SIE plus hardware EUSART create a clean single-chip CDC class bridge, replacing the legacy FTDI FT232R with an integrated solution that costs less and supports field firmware updates via USB. Operating at 12 MIPS, the device handles USB endpoint buffering, line-coding CDC requests, and up to 1 Mbaud UART streams without CPU stress. The 2 KB RAM is sufficient for 64-byte USB packet buffering plus UART FIFOs, and the 32 KB Flash hosts the CDC stack with room for vendor commands. Typical applications include industrial RS-232 replacement, debug console bridges for embedded Linux systems, and ISP programming adapters for legacy targets. The CDC stack is available in the Microchip MLA (Microchip Libraries for Applications) and runs unmodified on the related PIC18F4550 for higher pin-count variants.
Recommended
MIDI Adapter and USB-MIDI Controllers
USB-MIDI class devices benefit from the PIC18F2550's deterministic USB timing and low interrupt latency, both critical for jitter-free musical performance. The MIDI 1.0 class uses USB bulk transfers at Full Speed, and the 12 MIPS core handles MIDI event parsing, FIFO management, and UART-style MIDI DIN I/O without packet loss. The 32 KB Flash accommodates USB-MIDI class descriptors, button-matrix scanning, encoder handling, and patch storage in EEPROM. Typical builds include 8-16 channel MIDI controllers with rotary encoders, MIDI-to-CV converters for analog synthesizers, and DIY surface controllers. The wide industrial temperature grade supports stage and touring use. Reference firmware from open-source projects like the MIDIbox community demonstrates full multi-port USB-MIDI on this chip.
Recommended
Low-Cost USB Data Logger
With 32 KB Flash, 2 KB RAM, 256 bytes EEPROM, and a 10-bit 13-channel ADC, the PIC18F2550-I/SO is a strong fit for USB-attached data loggers that sample slow signals (temperature, voltage, current) and stream logs to a host PC. The integrated USB provides direct host connectivity for real-time streaming or post-hoc bulk download, eliminating removable storage costs. The PIC18F2550's nanoWatt sleep modes (down to <1 uA standby with RTCC) support battery-powered field loggers that wake on timer or interrupt to take samples. The 4.2 V-5.5 V supply matches USB bus power directly without additional regulators. Designs typically pair the PIC18F2550 with SPI FRAM or external EEPROM for bulk storage while using internal ADC for direct sensor interfaces.
Recommended
PICkit-Compatible Programmer / Debugger
The PIC18F2550-I/SO is the historical silicon heart of the open-source PICkit-2 programmer; its integrated USB SIE, robust I/O, and ability to act as an ICSP host made it the de-facto choice for hobby and educational programming tools. Pushed at 48 MHz with the 96 MHz PLL, the device generates accurate ICSP clock and data waveforms and the integrated 5 V-tolerant I/O eliminates level shifters on modern targets. Reference designs include the PICkit-2 clone, the ICD2 clone, and various open-source ICSP programmers distributed as CC-BY or GPL firmware. The 32 KB Flash holds the ICSP host stack with ample room for device-specific protocol extensions. The industrial temperature grade and Microchip longevity program make the part a stable choice for tool builders.
Recommended
Educational Development Boards
The PIC18F2550-I/SO is widely adopted in university curricula and hobbyist training because the SOIC-28 package breaks out easily to breadboards via SOIC-to-DIP adapters, and the USB peripheral gives students a tangible 'plug it in and see the host see it' learning moment. The 12 MIPS performance supports C-based firmware using the free XC8 compiler, and the PIC18 architecture's deterministic I/O timing teaches embedded fundamentals like ISR latency, register-level peripheral control, and Harvard memory separation. Educational kits like the Microchip PICDEM FSUSB bundle this MCU with a USB port, buttons, LEDs, and a potentiometer, providing a self-contained lab platform. The -I industrial temperature range handles classroom lab environments without derating, and the part's long lifecycle protects multi-year curriculum investments.
Recommended
Industrial Sensor Interface with USB Diagnostics
The PIC18F2550's industrial temperature grade (-40C to +85C) and integrated USB SIE make it a strong bridge between factory-floor sensors and PC-based SCADA or diagnostic software. The 10-bit 13-channel ADC reads thermocouples via external amplifiers, RTDs via excitation circuits, and 4-20 mA loops via shunt resistors, while the USB CDC channel streams real-time readings to host software without additional protocol converters. The PIC18F2550-I/SO operates directly from USB bus power at 5 V, simplifying cabinet wiring. The on-chip EUSART supports RS-485 with an external transceiver for legacy Modbus RTU networks, allowing the same firmware to serve both USB diagnostics and fieldbus networks. The 32 KB Flash accommodates custom protocol stacks.
Recommended
Recommended Products Summary
Engineering reference data for PIC18F2550-I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18F2553-I/SO | PIC18F2455-I/SO | PIC18F2550T-I/SO | PIC18F2550-E/SO | PIC18F24K50-I/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-pin SOIC (Wide, 7.5 mm body) | 28-pin SOIC - same | 28-pin SOIC - same | 28-pin SOIC - same | 28-pin SOIC - same | 28-pin SOIC - same |
| Flash Memory | 32 KB | 32 KB (same) | 24 KB (-25%) | 32 KB (same) | 32 KB (same) | 16 KB (-50%) |
| RAM | 2 KB | 2 KB (same) | 2 KB (same) | 2 KB (same) | 2 KB (same) | 2 KB (same) |
| Max CPU Speed | 48 MHz (12 MIPS) | 48 MHz (same) | 48 MHz (same) | 48 MHz (same) | 48 MHz (same) | 48 MHz (same) |
| USB Controller | USB 2.0 Full-Speed (12 Mbit/s), integrated SIE | USB 2.0 FS (same) | USB 2.0 FS (same) | USB 2.0 FS (same) | USB 2.0 FS (same) | USB 2.0 FS (same) |
| ADC Resolution | 10-bit (13 channels) | 12-bit (13 channels) | 10-bit (13 channels) | 10-bit (same) | 10-bit (same) | 10-bit (same) |
| Supply Voltage Range | 4.2 V to 5.5 V | 4.2 V to 5.5 V (same) | 4.2 V to 5.5 V (same) | 4.2 V to 5.5 V (same) | 4.2 V to 5.5 V (same) | 1.8 V to 5.5 V (wider) |
| Operating Temperature | -40 C to +85 C (industrial) | -40 C to +85 C (same) | -40 C to +85 C (same) | -40 C to +85 C (same) | -40 C to +125 C (extended) | -40 C to +85 C (same) |
| Approx. Unit Price (qty 1000) | $4.10 | $4.40 (+7%) | $3.90 (-5%) | $4.10 (same) | $4.95 (+21%) | $3.60 (-12%) |
Key Differentiators
- Lowest-cost Microchip MCU with integrated USB 2.0 Full-Speed SIE in 28-pin SOIC (vs PIC18F14K50-I/SO (20-pin))
- Drop-in upgrade path to 12-bit ADC (vs PIC18F2553-I/SO)
- Industrial-temperature USB MCU with 32 KB Flash in 28-SOIC (vs PIC18F4550-I/P (40-pin))
- Extended temperature option for harsh environments (vs PIC18F2550-E/SO)
- Wider supply voltage range on newer K-series (vs PIC18F24K50-I/SO)
Design Notes
USB operation requires the 96 MHz PLL to be active, which forces a specific oscillator configuration. Use a 20 MHz crystal (HS_PLL with OSC1/OSC2) and set the CPUDIV to /2 to get the 48 MHz system clock, or use a 12 MHz crystal with the PLL x8 and CPUDIV /2. According to the PIC18F2455/2550/4455/4550 datasheet, attempting USB without the PLL configured correctly results in enumeration failure and the host will not detect the device. Verify by checking the UCON register's USBEN bit and the OSCCON register's IRCF/PLLEN bits at startup.
The D+ and D- USB lines (RC4 and RC5 on the PIC18F2550) must be routed as a 90-ohm differential pair per USB 2.0 specification. Use controlled impedance (typically 1 oz copper with FR-4, 0.20 mm wide on 0.40 mm spacing for 90 ohms). Keep the pair matched within 0.5 mm length mismatch, route over a continuous ground plane, and place the 27-ohm series termination resistors within 5 mm of the PIC pins. Avoid stubs, vias in the differential pair if possible, and keep clock and switching signals away from the pair.
Place a 100 nF decoupling capacitor as close as possible to every VDD pin, with a 4.7 uF bulk capacitor on the bus. The internal USB 3.3 V regulator (VUSB pin 28) requires a 220 nF decoupling capacitor directly on the pin to ground; this regulator powers the USB transceiver only, not the core. For bus-powered designs, ensure the host's 5 V supply is stable; some hosts deliver as little as 4.4 V under load which is at the PIC18F2550's lower spec limit, so consider a low-dropout external regulator (e.g., MCP1700) if operating near the 4.2 V minimum.
Use a 4-layer PCB with a continuous ground plane for best EMI and signal-integrity performance; a 2-layer board is acceptable for low-speed designs but may cause USB enumeration issues on bus-powered setups with high switching noise. Keep the ICSP clock and data lines (RB6/PGC and RB7/PGD) accessible even if not used in production, so firmware updates are possible without board rework. Place test points on VDD, VSS, and the USB D+/D- lines for oscilloscope-based signal integrity validation.
Estimated: at full USB load and 48 MHz operation, the PIC18F2550-I/SO typically dissipates approximately 50-80 mW of power. With the SOIC-28 package thermal resistance around 60 C/W, the junction temperature rise above ambient is approximately 3-5 C, well within the 125 C absolute maximum. No external heatsink is required. For industrial installations in enclosed housings at 60 C ambient, verify with a thermal probe on the top of the package; if running near 100 C, consider reducing CPU clock to 16 MHz or migrating to the lower-power PIC18F24K50.
Compliance Information
RoHS and REACH compliance per Microchip product page. Industrial temperature grade (-40C to +85C); not AEC-Q100 qualified for automotive under-hood - choose PIC18F2550-E/SO for extended temperature industrial, or contact Microchip for AEC-Q100 qualified PIC18F2550 variants.
