PIC18LF2321-I/SO - 8KB Flash 8-bit MCU 40MHz SOIC-28 | Microchip
MPN: PIC18LF2321-I/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.62 | $4.62 |
| 10 | $4.16 | $41.60 |
| 100 | $3.49 | $349.00 |
| 500 | $3.05 | $1,525.00 |
| 1,000 | $2.68 | $2,680.00 |
| 3,000 | $2.4 | $7,200.00 |
PIC18LF2321-I/SO Overview
What is a microcontroller? A microcontroller (MCU) is a single-chip computer that combines a CPU core, program memory (Flash/ROM), working memory (RAM), and on-chip peripherals such as timers, ADC, communication interfaces, and I/O ports. Within the broader semiconductor taxonomy, an MCU sits inside the embedded IC category, below the hypernym integrated circuit (IC). Microchip's PIC18 family adds enhanced 16-bit instruction width and a hardware multiplier to the legacy PIC16 8-bit core, doubling throughput while preserving upward code compatibility from PIC16C5X, PIC12CXXX, PIC16CXX and PIC17CXX designs.
Key features include ten MIPS peak performance at 40 MHz, 77 single-word instructions, a 16-bit instruction word, hardware multiplier (8x8 in one cycle), ICD/ICSP in-circuit debugging and programming, 256 bytes of EEPROM data storage, 10-bit ADC, USART, MSSP (SPI/I2C), Capture/Compare/PWM modules, and nanoWatt XLP sleep modes. The 28-pin wide SOIC provides ease of hand-soldering and breadboard-friendly development while the LF voltage range (down to 2.0 V) supports two-AA cell, single Li-ion, or USB-powered designs.
Architecture-wise the PIC18LF2321 uses a Harvard RISC core with separate program and data buses, 32 levels of hardware stack, and a vectored interrupt controller supporting both legacy and prioritized interrupt modes. The flash program memory supports self-programming under firmware control, enabling bootloaders and field-upgradable devices.
Typical applications include consumer appliances, sensor conditioning front-ends, low-power remote controls, HVAC controls, USB-to-UART bridges, low-end digital photo frames, industrial sensor nodes, and small appliances with LED/LCD user interfaces. The PIC18F2321 (non-LF) version is also drop-in compatible, enabling easy migration to 5 V-only designs.
Design consideration: when migrating firmware from PIC16 to PIC18, port the configuration bits and review the interrupt priority scheme; PIC18 adds a two-level priority mode that must be enabled before use.
This page synthesizes distributor pricing, drop-in pin-compatible alternatives, and practical design notes not found in the manufacturer datasheet to speed your sourcing decision.
Drop-in alternatives for PIC18LF2321-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 PIC18LF2321-I/SO (same form factor and footprint) — differing in Package, ADC, Communication, Core Architecture, Operating Temperature.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18LF2321-I/SP
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18LF2321-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F2321-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18LF2320-I/SO
✅ Drop-In✓ In Stock
$3.31 / Unit
View Datasheet →PIC18LF2221-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18LF2421-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18LF2321-I/SO Maximum Ratings & Electrical Characteristics
| Family | PIC18LF23xx |
| Core | PIC 8-bit RISC |
| Instruction Set | 77 single-word instructions, 16-bit instruction width |
| Program Memory | 8 KB Flash (4K x 16) |
| SRAM | 512 bytes |
| EEPROM | 256 bytes |
| Maximum CPU Speed | 40 MHz (10 MIPS) |
| Supply Voltage (Vdd) | 2.0 V to 5.5 V |
| I/O Pins | 25 |
| ADC | 10-bit, 9 channels |
| Timers | 4 (Timer0/1/2/3) |
| Communication | EUSART, MSSP (SPI / I2C) |
| Capture/Compare/PWM | 1 ECCP + 2 CCP |
| Package | 28-pin SOIC (7.50 mm body width) |
| Mounting Type | Surface Mount |
| Operating Temperature | -40 C to +85 C (Industrial) |
| Lead-Free / RoHS | Yes, RoHS compliant |
| MSL Level | 1 (unlimited floor life) |
| On-Chip Debug | ICSP / ICD support |
| Power-Saving Mode | nanoWatt XLP (multiple sleep modes) |
PIC18LF2321-I/SO Pin Configuration
| Pin 1 | RA0/AN0 — Digital I/O / Analog input 0 |
| Pin 2 | RA1/AN1 — Digital I/O / Analog input 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/SS — Digital I/O / Analog input 4 / SPI slave select |
| Pin 7 | RA6/OSC2 — Digital I/O / Oscillator output |
| Pin 8 | RA7/OSC1 — Digital I/O / Oscillator input |
| Pin 9 | Vss — Ground |
| Pin 10 | Vdd — Positive supply voltage (2.0-5.5V) |
| Pin 11 | RB0/INT0 — Digital I/O / External interrupt 0 |
| Pin 12 | RB1/INT1 — Digital I/O / External interrupt 1 |
| Pin 13 | RB2/INT2 — Digital I/O / External interrupt 2 |
| Pin 14 | RB3/CCP2 — Digital I/O / CCP2 output |
| Pin 15 | RB4 — Digital I/O / interrupt-on-change |
| Pin 16 | RB5 — Digital I/O / interrupt-on-change / I2C SDA on PIC18LF24/25xx (not 23xx) |
| Pin 17 | RB6/PGC — Digital I/O / ICSP clock / ICD clock |
| Pin 18 | RB7/PGD — Digital I/O / ICSP data / ICD data |
| Pin 19 | Vss — Ground |
| Pin 20 | Vdd — Positive supply voltage (2.0-5.5V) |
| Pin 21 | RC0/T1OSO — Digital I/O / Timer1 oscillator output |
| Pin 22 | RC1/T1OSI — Digital I/O / Timer1 oscillator input |
| Pin 23 | RC2/CCP1 — Digital I/O / CCP1 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 / EUSART TX / clock |
| Pin 28 | RC7/RX/DT — Digital I/O / EUSART RX / data |
Typical Applications
PIC18LF2321-I/SO is suitable for 6 applications: Consumer Appliance Control Board, Battery-Powered Sensor Node, USB-to-UART Bridge Dongle, HVAC Thermostat Controller, Industrial Sensor Signal Conditioner, LED Display Driver Board.
Consumer Appliance Control Board
Why PIC18LF2321-I/SO fits: The PIC18LF2321's 10 MIPS performance, 25 I/O pins, and 2.0-5.5V wide supply range let a single chip drive relays, read keypad inputs, and pulse LED indicators in toasters, microwaves, and washing machines without a second IC. How it is used + performance consideration: One ECCP+PWM module drives a buzzer or triac at line frequency while a 10-bit ADC reads thermistor and water-level sensors; firmware fits inside 8 KB flash with self-programming left for future options. Estimated standby current in nanoWatt sleep drops to roughly 100 nA, preserving energy-star compliance on line-powered units.
Recommended
Battery-Powered Sensor Node
Why PIC18LF2321-I/SO fits: The LF 2.0-5.5V supply window supports two AA cells (3.0V nominal) down to a near-end cutoff of 2.0V, extracting every joule from the battery. nanoWatt XLP sleep modes drop quiescent current to roughly 100 nA. How it is used + performance consideration: A 10-bit ADC samples a thermistor every 30 seconds; EUSART wakes up only to transmit. The 28-SOIC and 25 I/O leave room for an SPI sensor interface (MSSP) and a low-battery indicator LED while the 8 KB flash holds a small RTOS and 256-byte EEPROM stores calibration constants.
Recommended
USB-to-UART Bridge Dongle
Why PIC18LF2321-I/SO fits: The integrated EUSART and MSSP peripherals provide asynchronous serial plus optional SPI, and the LF variant tolerates USB 5V VBUS through the SOIC's wide voltage range. 25 I/O pins are ample for status LEDs and RTS/CTS handshake lines. How it is used + performance consideration: Firmware implements a CDC class on the EUSART at 115200 bps with full 8 KB flash budget; the 10-bit ADC is repurposed as a VBUS voltage monitor. For designs needing native USB, PIC18LF14K50 or PIC18LF13K50 are better alternatives since this device lacks a USB peripheral.
Recommended
HVAC Thermostat Controller
Why PIC18LF2321-I/SO fits: The 9-channel 10-bit ADC reads room temperature, setpoint, humidity, and indoor air-quality sensors simultaneously, while 4 timers drive a 7-day schedule and PWM output drives a triac for fan/valve control. How it is used + performance consideration: Firmware runs a PID loop at 1 Hz; the 8 KB flash holds a small menu engine for the LCD interface. Industrial -40 C to +85 C temperature rating (the -I suffix) handles attic and basement installation, and the wide SOIC allows hand rework during prototyping.
Recommended
Industrial Sensor Signal Conditioner
Why PIC18LF2321-I/SO fits: The 10-bit ADC samples 4-20 mA loop inputs through a 250 ohm shunt while the EUSART streams processed values to a host PLC over RS-485 (with external transceiver). Industrial temperature grade (-40 C to +85 C) and the wide 2.0-5.5V supply tolerate plant-power environments. How it is used + performance consideration: Four timers generate precise acquisition intervals and PWM pulse widths; the MSSP SPI port interfaces to a separate ADC for high-precision applications. Estimated: with a 25 MHz CPU clock and ECCP running PWM, current draw is about 8 mA active, dropping to nanoWatt sleep between samples.
Recommended
LED Display Driver Board
Why PIC18LF2321-I/SO fits: With three PWM-capable outputs (ECCP + 2 CCP) and a 10 MIPS core, the PIC18LF2321 can drive RGB LED strings at refresh rates above 100 Hz with anti-flicker dithering. The 256-byte EEPROM stores user color profiles; 25 I/O pins directly drive Charlieplex LED matrices without additional driver ICs. How it is used + performance consideration: Firmware fits in 8 KB flash with a small WS2812-like bit-banged protocol on a single MSSP/SPI line. For larger LED arrays, the PIC18LF2522 (32 KB) or PIC18F46K22 are better fits.
Recommended
Recommended Products Summary
Engineering reference data for PIC18LF2321-I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18LF2321-I/SP | PIC18LF2321-I/SS | PIC18F2321-I/SO | PIC18LF2320-I/SO | PIC18LF2221-I/SO | PIC18LF2421-I/SO |
|---|---|---|---|---|---|---|---|
| Package | 28-pin SOIC (7.50 mm) | 28-pin SPDIP (NOT SOIC footprint) | 28-pin SSOP (NOT SOIC footprint) | 28-pin SOIC (7.50 mm) - same | 28-pin SOIC (7.50 mm) - same | 28-pin SOIC (7.50 mm) - same | 28-pin SOIC (7.50 mm) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Program Memory | 8 KB (4K x 16) | 8 KB | 8 KB | 8 KB | 4 KB | 4 KB | 16 KB |
| SRAM | 512 bytes | 512 bytes | 512 bytes | 512 bytes | 512 bytes | 512 bytes | 1024 bytes |
| Supply Voltage (Vdd) | 2.0 V to 5.5 V | 2.0 V to 5.5 V | 2.0 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 |
| Max CPU Speed | 40 MHz (10 MIPS) | 40 MHz | 40 MHz | 40 MHz | 40 MHz | 40 MHz | 40 MHz |
| I/O Pins | 25 | 25 | 25 | 25 | 25 | 25 | 25 |
| ADC | 10-bit, 9 channels | 10-bit, 9 ch | 10-bit, 9 ch | 10-bit, 9 ch | 10-bit, 9 ch | 10-bit, 9 ch | 10-bit, 9 ch |
| EEPROM | 256 bytes | 256 bytes | 256 bytes | 256 bytes | 256 bytes | 256 bytes | 256 bytes |
| Operating Temperature | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C |
Key Differentiators
- Wide 2.0-5.5 V supply range (vs PIC18F2321-I/SO)
- 8 KB flash versus 4 KB (vs PIC18LF2221-I/SO)
- On-chip 10-bit ADC with 9 channels (vs External ADC + PIC18LF2320)
Design Notes
Use the LF variant's 2.0 V Vdd minimum to power the PIC18LF2321 from two AA cells that droop below 2.7 V. Disable modules in firmware before sleep: clear ADCON0.ADON, disable comparators, and switch unused I/O to output low. nanoWatt XLP sleep current drops to roughly 100 nA per Microchip datasheet, extending battery life by orders of magnitude over active mode.
The 28-pin SOIC dissipates up to roughly 800 mW at 40 MHz with all peripherals active; in a typical 25 C ambient and natural convection the SOIC package easily handles this load without a heatsink. For sealed enclosures or above +60 C ambient, derate to 70 percent of peripherals enabled. The industrial -I temperature grade already covers -40 C to +85 C ambient operation per Microchip datasheet.
Place a 100 nF decoupling capacitor within 5 mm of each Vdd pin (there are two Vdd pins on the 28-SOIC). Add a 10 uF bulk cap near the MCU and route the MCLR pin through a 10 kohm pull-up and a 100 nF cap to ground for a hardware-reset button. Keep the 28-SOIC SOIC footprint's pad-to-pad pitch at 1.27 mm per JEDEC MS-013 to ensure hand-rework friendliness.
Route the quartz crystal traces (OSC1/OSC2 or RA6/RA7) within 10 mm of the MCU and shield them with a ground guard ring. For high-speed SPI signals (>10 MHz) match the trace length and keep series resistance under 50 ohm. Use the MSSP module's slew-rate control bits if your bus exceeds 1 MHz to reduce EMI per Microchip PIC18 datasheet recommendations.
Do not exceed 5.5 V on Vdd or 5.5 V on any I/O pin - the PIC18LF2321 lacks internal clamping on most pins. When migrating firmware from PIC16 to PIC18, ensure the configuration bits are set properly: disable watchdog unless needed, select HS or XT oscillator mode correctly, and configure the brown-out reset voltage to 4.0 V or 2.5 V per your supply. Failing to configure the LF vs F voltage range will produce undefined behavior below 4.2 V on PIC18F2321 (non-LF) parts.
Compliance Information
RoHS compliant per Microchip product page and distributor listings. Industrial temperature grade -40 C to +85 C. Not AEC-Q100 qualified (use PIC18FxxKxx with Q suffix for automotive).
