PIC18F2550-I/SP - 8-Bit USB MCU, 32KB Flash, 28-SPDIP | Microchip
MPN: PIC18F2550-I/SP ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.95 | $6.95 |
| 10 | $6.1 | $61.00 |
| 100 | $5.25 | $525.00 |
| 500 | $4.65 | $2,325.00 |
| 1,000 | $4.1 | $4,100.00 |
PIC18F2550-I/SP Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, program memory (Flash/ROM), data memory (RAM), and peripherals onto one silicon die. Within the embedded-system taxonomy, an MCU sits under the broader category of microcomputer -> embedded processor -> microcontroller, and serves as the active decision-making element in everything from USB peripherals to industrial controllers. The PIC18 family is Microchip's mid-range 8-bit architecture, positioned above the baseline PIC10/12/16 families and below the PIC24/dsPIC33 16-bit families, offering an enhanced instruction set, C-compiler-friendly architecture, and rich peripheral integration.
Key features include 32KB self-programmable Flash (16K x 16 words), 256 bytes of EEPROM data memory, full-speed USB 2.0 device/host/OTG transceiver with internal pull-up resistors, nanoWatt power-saving modes that drop quiescent current below 1 microamp in sleep, and an operating voltage range of 4.2 V to 5.5 V. The ICSP (In-Circuit Serial Programming) interface enables in-field firmware updates without removing the device from the board.
The architecture uses a 16-bit-wide Flash program memory bus and an 8-bit data path, with hardware multiplier supporting single-cycle 8x8 multiply. The integrated USB SIE handles bus protocol, automatically managing packet framing, CRC-5/CRC-16, and endpoint FIFOs, so application code operates on simple buffer reads/writes rather than bit-banging NRZI signaling.
Typical applications include USB-to-UART bridges, HID-class input devices such as keyboards and custom game controllers, low-cost USB sensors, and educational/hobbyist development platforms like the open-source Pinguino and various PIC-based USB IO boards. The combination of through-hole SPDIP packaging and legacy-friendly toolchain (MPLAB X, XC8 compiler) makes it especially popular in educational labs and retrofits of legacy designs.
When designing with this part, ensure the USB VBUS line is routed through the on-chip 3.3V regulator with adequate bulk capacitance, and respect the 5.5V absolute maximum to avoid latch-up. Firmware should enable the USB PLL only after the 48 MHz lock is established to prevent out-of-spec bus signaling. This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found on DigiKey or Mouser product pages alone.
Drop-in alternatives for PIC18F2550-I/SP — 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/SP (same form factor and footprint) — differing in Package, Timers, Serial Interfaces, ADC, Operating Temperature.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18F2553-I/SP
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F2455-I/SP
✅ Drop-In✓ In Stock
$4.65 / Unit
View Datasheet →PIC18F2520-I/SP
✅ Drop-In✓ In Stock
$3.33 / Unit
View Datasheet →PIC18F2420-I/SP
✅ Drop-In✓ In Stock
$5.22 / Unit
View Datasheet →PIC18F2480-I/SP
✅ Drop-In✓ In Stock
$4.1 / Unit
View Datasheet →PIC18F2550-I/SP Maximum Ratings & Electrical Characteristics
| Family | PIC18 |
| Core | 8-bit PIC18 enhanced Harvard |
| Program Memory | 32 KB Flash (16K x 16 words) |
| Data SRAM | 2048 bytes |
| Data EEPROM | 256 bytes |
| Maximum CPU Frequency | 48 MHz (12 MIPS) |
| Supply Voltage | 4.2 V to 5.5 V |
| I/O Pins | 25 |
| Package | 28-pin SPDIP (300 mil) |
| Mounting Type | Through-Hole |
| USB | USB 2.0 Full-Speed Device/Host/OTG, 12 Mbit/s |
| ADC | 10-bit, up to 13 channels |
| Timers | 2x 8-bit + 2x 16-bit |
| Serial Interfaces | USB, I2C, SPI (up to 10 Mbit/s), EUSART (LIN-capable) |
| PWM Outputs | Capture/Compare/PWM modules |
| Operating Temperature | -40 C to +85 C (Industrial, -I suffix) |
| MSL Level | 1 (unlimited) |
| RoHS Status | Compliant |
PIC18F2550-I/SP Pin Configuration
| Pin 1 | MCLR/RE3 — Master Clear (reset) input or digital input only on RE3 |
| Pin 2 | RA0/AN0 — Digital I/O or analog input channel 0 |
| Pin 3 | RA1/AN1 — Digital I/O or analog input channel 1 |
| Pin 4 | RA2/AN2/VREF-/CVREF — Digital I/O, analog input 2, or DAC reference voltage low |
| Pin 5 | RA3/AN3/VREF+ — Digital I/O, analog input 3, or ADC positive reference |
| Pin 6 | RA4/T0CKI/C1OUT — Digital I/O, Timer0 clock input, or Comparator 1 output |
| Pin 7 | RA5/AN4/SS/C2OUT — Digital I/O, analog input 4, SPI slave select, or Comparator 2 output |
| Pin 8 | VSS — Ground reference (0 V) |
| Pin 9 | OSC1/CLKI — Crystal oscillator input or external clock input |
| Pin 10 | OSC2/CLKO — Crystal oscillator output or clock output (Fosc/4) |
| Pin 11 | RC0/T1OSO/T1CKI — Digital I/O, Timer1 oscillator output, or Timer1 clock input |
| Pin 12 | RC1/T1OSI/CCP2 — Digital I/O, Timer1 oscillator input, or Capture/Compare/PWM 2 |
| Pin 13 | RC2/CCP1/P1A — Digital I/O, CCP1 output, or PWM enhanced output |
| Pin 14 | VUSB — Internal 3.3V USB voltage regulator output (decouple with 470 nF + 220 uF to VSS) |
| Pin 15 | RC4/D-/VM — Digital I/O, USB D- data line, or external USB monitor input |
| Pin 16 | RC5/D+/VP — Digital I/O, USB D+ data line, or external USB monitor input |
| Pin 17 | RC6/TX/CK — Digital I/O, EUSART asynchronous transmit, or synchronous clock |
| Pin 18 | RC7/RX/DT — Digital I/O, EUSART asynchronous receive, or synchronous data |
| Pin 19 | VSS — Ground reference (0 V) - second ground pin for noise isolation |
| Pin 20 | VDD — Positive supply voltage (4.2 V to 5.5 V) |
| Pin 21 | RB0/AN12/INT0 — Digital I/O, analog input 12, or external interrupt 0 |
| Pin 22 | RB1/AN10/INT1 — Digital I/O, analog input 10, or external interrupt 1 |
| Pin 23 | RB2/AN8/INT2 — Digital I/O, analog input 8, or external interrupt 2 |
| Pin 24 | RB3/AN9/CCP2 — Digital I/O, analog input 9, or alternate CCP2 output |
| Pin 25 | RB4/AN11/KBI0 — Digital I/O, analog input 11, or interrupt-on-change KBI0 |
| Pin 26 | RB5/KBI1/PGM — Digital I/O, KBI1 interrupt, or ICSP low-voltage programming input |
| Pin 27 | RB6/KBI2/PGC — Digital I/O, KBI2 interrupt, or ICSP clock input |
| Pin 28 | RB7/KBI3/PGD — Digital I/O, KBI3 interrupt, or ICSP data input/output |
Typical Applications
PIC18F2550-I/SP is suitable for 6 applications: USB-to-UART Bridge (CDC Virtual COM Port), USB HID Input Devices (Keyboard, Mouse, Custom HID), Educational Microcontroller Platform (Pinguino, USB IO Boards), Industrial USB Sensor Interface, USB Bootloader / Programmer Host, Legacy Equipment Retrofit & Replacement.
USB-to-UART Bridge (CDC Virtual COM Port)
The PIC18F2550-I/SP is ideal for USB-to-serial bridges because its integrated Full-Speed USB SIE handles all bus protocol automatically and the EUSART peripheral provides an asynchronous UART up to 115.2 kbaud (and higher). Connect the MCU's USB D+/D- pins directly to a USB Type-B or Mini-B receptacle, configure the on-chip 3.3V regulator for USB power, and run Microchip's USB CDC class driver for instant virtual COM port behavior on Windows/Linux/macOS. The 32KB Flash accommodates the USB stack, CDC class driver, and application UART logic, while 2KB RAM is sufficient for endpoint FIFOs and ring buffers. Compared to FTDI FT232 alternatives, the PIC18F2550-I/SP requires no proprietary driver but does require firmware effort.
Recommended
USB HID Input Devices (Keyboard, Mouse, Custom HID)
HID-class devices benefit from the PIC18F2550-I/SP's native Full-Speed USB and 32KB Flash budget for HID report descriptors, multi-language keyboard layouts, and boot protocol support. The MCU's 25 I/O pins are ample for matrix-scanned keyboards (up to 8x8 matrix), rotary encoder quadrature inputs, or capacitive touch button arrays. The 48MHz CPU handles 1ms USB polling intervals with substantial headroom for debouncing, NKRO processing, and macro scripting. The integrated USB pull-up resistors eliminate external components, reducing BOM cost for consumer HID products. The 28-SPDIP package supports easy hand-soldering for limited-run or open-source hardware projects.
Recommended
Educational Microcontroller Platform (Pinguino, USB IO Boards)
The PIC18F2550-I/SP is the canonical MCU for the open-source Pinguino Arduino-compatible platform and similar educational development boards because of its 28-SPDIP through-hole package that fits standard breadboards and 0.1-inch protoboards, its integrated USB eliminating external programmer cost, and its mature XC8 C compiler toolchain. Students can program and debug directly over USB using the PICkit 3 or ICD 3, with no external ISP needed. The 32KB Flash supports complex firmware examples including USB, I2C, SPI, ADC, and PWM, while the nanoWatt power-saving modes teach energy-conscious design. The Microchip Academic Program distributes the PIC18F2550 heavily for university embedded courses worldwide.
Recommended
Industrial USB Sensor Interface
Industrial USB sensor interfaces leverage the PIC18F2550-I/SP's 13-channel 10-bit ADC, USB Full-Speed data acquisition capability, and 4.2-5.5V industrial supply range. Connect multiple analog sensors (temperature, pressure, light) to the ADC channels, digitize at up to 100 ksps aggregate, and stream the samples over USB as a custom HID or vendor-class device. The 48MHz CPU enables real-time digital filtering (FIR, moving average) within the MCU before USB transmission, reducing host-side processing. The industrial -40C to +85C temperature grade supports factory-floor and outdoor installations. The SPDIP package is easy to swap during prototyping or field service.
Recommended
USB Bootloader / Programmer Host
The PIC18F2550-I/SP serves as a USB host or device bootloader, enabling field firmware updates on target PIC18 microcontrollers via USB. The MCU implements Microchip's USB HID bootloader protocol, communicating with a host PC application (e.g., Microchip's HID Bootloader utility) to receive new firmware hex files and program them into the target MCU over SPI or UART. The 32KB Flash holds the bootloader, USB stack, and protocol handlers; the 2KB RAM supports large bootloader packets. The same hardware can also act as a PICkit-compatible programmer for production programming. This application is especially valuable for product retrofit and OTA update scenarios.
Recommended
Legacy Equipment Retrofit & Replacement
Retrofitting legacy RS-232 industrial equipment with USB connectivity is a classic PIC18F2550-I/SP application: the MCU bridges an existing DB-9 RS-232 port (via MAX232-style level shifter) to a USB Type-B port, providing modern PC connectivity without redesigning the legacy hardware. The 5V-tolerant EUSART supports standard baud rates from 300 to 115200 (and beyond), while the integrated USB eliminates external transceivers. The 28-SPDIP package is easy to integrate into existing enclosures with point-to-point wiring. This pattern is widely used for retrofitting scientific instruments, CNC controllers, and POS terminals whose original serial ports are incompatible with modern PCs lacking DB-9 connectors.
Recommended
Recommended Products Summary
Engineering reference data for PIC18F2550-I/SP — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18F2553-I/SP | PIC18F2455-I/SP | PIC18F2550-I/SO | PIC18F2520-I/SP | PIC18F2420-I/SP | PIC18F2480-I/SP |
|---|---|---|---|---|---|---|---|
| Package | 28-SPDIP (SP) | 28-SPDIP (SP) - same | 28-SPDIP (SP) - same | 28-SOIC (SO) - same die, surface mount | 28-SPDIP (SP) - same | 28-SPDIP (SP) - same | 28-SPDIP (SP) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Memory | 32 KB Flash | 32 KB Flash | 24 KB Flash (-25%) | 32 KB Flash | 32 KB Flash | 16 KB Flash (-50%) | 16 KB Flash (-50%) |
| Data SRAM | 2048 bytes | 2048 bytes | 2048 bytes | 2048 bytes | 1536 bytes (-25%) | 768 bytes (-62%) | 768 bytes (-62%) |
| Maximum CPU Frequency | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 40 MHz (-17%) | 40 MHz (-17%) | 40 MHz (-17%) |
| USB Peripheral | USB 2.0 Full-Speed 12 Mbit/s | USB 2.0 Full-Speed | USB 2.0 Full-Speed | USB 2.0 Full-Speed | No USB | No USB | No USB (CAN instead) |
| ADC Resolution | 10-bit (13 channels) | 12-bit (12 channels) | 10-bit (13 channels) | 10-bit (13 channels) | 10-bit (8 channels) | 10-bit (8 channels) | 10-bit (8 channels) |
| Operating Voltage | 4.2 V to 5.5 V | 4.2 V to 5.5 V | 4.2 V to 5.5 V | 4.2 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 |
| I/O Pins | 25 | 25 | 25 | 25 | 23 | 23 | 22 |
Key Differentiators
- Integrated Full-Speed USB with on-chip pull-up resistors (vs PIC18F2520-I/SP)
- Higher ADC resolution available in drop-in sibling (vs PIC18F2553-I/SP)
- Lower voltage operation available in alternative families (vs PIC18F24K50)
Design Notes
The PIC18F2550's internal USB voltage regulator on the VUSB pin (pin 14) requires a 220 uF low-ESR capacitor and a 470 nF ceramic capacitor to VSS for stability, as specified in the Microchip datasheet. The internal regulator outputs 3.3V to power the USB transceiver's pull-up resistor and D+/D- drivers, and must not be loaded externally. VDD should be decoupled with a 100 nF ceramic + 10 uF bulk capacitor placed within 10 mm of the package. For battery-powered applications, route VUSB to VDD through a diode to allow the internal regulator to operate from the USB bus while the rest of the board runs from battery.
For USB Full-Speed compliance, the D+ (pin 16) and D- (pin 15) traces must be routed as a 90-ohm differential pair with matched length (within 2 mm) and no stubs. Keep the pair adjacent to a continuous ground plane and avoid routing near switching signals or crystal traces. Place the USB connector within 25 mm of the MCU pins; the on-chip pull-up resistors eliminate external 1.5K resistors to D+ only in device mode. Keep crystal traces (OSC1/OSC2, pins 9-10) short and symmetric, with the load capacitors placed within 5 mm of the MCU pins to minimize parasitic capacitance and EMI.
Do not enable the USB module until the 48 MHz PLL has stabilized (check the PLL lock status bit in the OSCTUNE register), or the USB SIE will transmit at the wrong baud and fail USB compliance certification. The CONFIG1L register must be configured for HS-PLL clock mode (HS oscillator with PLL enabled) before USB attach. Forgetting to configure the CONFIG registers correctly is the #1 cause of 'dead' PIC18F2550 USB designs. Always use the #pragma config directives in your XC8 source or set fuses via MPLAB X to specify FOSC, PLLEN, and USBDIV correctly for your crystal frequency.
Estimated: The PIC18F2550 in 28-SPDIP package typically dissipates <100 mW in normal operation, so thermal management is rarely a concern. At maximum CPU load (48 MHz, all peripherals active, USB transmitting) the device may dissipate up to 250 mW, but the SPDIP package's theta_JA of ~70 C/W keeps junction rise below 20 C above ambient. For industrial deployments with sustained USB activity at +85 C ambient, consider the PIC18F4550-I/P variant in 40-pin DIP which has slightly better thermal characteristics. No external heatsink is required for any standard application.
Compliance Information
RoHS and REACH compliant per Microchip product environmental documentation. Lead-free and halogen-free per modern revision date codes. Not AEC-Q100 qualified - the -I suffix denotes industrial temperature grade only (-40C to +85C), not automotive. For automotive applications, consider AEC-Q100 qualified PIC18F variants in the K-series families.
