PIC18F4685T-I/PT 完全ガイド：8ビット Microchip MCU の仕様、ピン配置、代替品、調達（2026年）

What Is the PIC18F4685T-I/PT and Why Should Engineers Specify It?

The PIC18F4685T-I/PT is an 8-bit PIC RISC (Harvard) microcontroller from Microchip Technology's PIC18F4xxx family that integrates 96 KB (48K x 16) of self-programmable Flash, 3.25 KB (3328 bytes) of RAM, and 1 KB of EEPROM inside a 44-pin TQFP (10x10 mm, 0.8 mm pitch) surface-mount package. It runs from a 4.2 V to 5.5 V supply at up to 40 MHz clock speed, delivering 10 MIPS instruction throughput across the -40 C to +85 C industrial temperature range. The integrated Enhanced CAN (ECAN 2.0B active) module, 10-bit ADC with 11 input channels, two Enhanced USARTs, MSSP (SPI/I2C), two Enhanced Capture/Compare/PWM (ECCP) modules plus one CCP, and 36 digital I/O pins make it a single-chip solution for deterministic industrial and automotive networking. As of 2026-10-06, the part is in active production, RoHS-compliant, lead-free, MSL-3 (168 hours floor life), and stocked at 99,999 units through XAIPART authorized channels at $10.36 (qty 1), $9.32 (qty 10), $8.21 (qty 100), $7.45 (qty 500), and $6.89 (qty 1000).

How Do You Design the PIC18F4685T-I/PT Into a New Board?

Begin with the 44-pin TQFP-44 land pattern at 10x10 mm body with 0.8 mm pitch. Pin 11 is VSS, pin 12 is VDD (4.2 V to 5.5 V), pin 13 is OSC1/RA7, pin 14 is OSC2/RA6, and pin 25 is MCLR. Two additional supply pairs appear at pins 32/33 (VSS/VDD) and pins 43/44 (AVSS/AVDD); isolating AVSS/AVDD with their own decoupling network keeps ADC noise out of the digital rails.

Decouple each VDD/AVDD pin with a 0.1 uF ceramic placed within a few millimeters of the pad, and add a single bulk capacitor (typically 10 uF) near the IC. The Microchip PIC18F2682/2685/4682/4685 datasheet (document 39761c) shows the recommended decoupling topology; following that baseline eliminates most POR and ADC reference drift issues seen in field returns.

The ECAN peripheral is the headline feature. Pins 34 (CANTX/RC2) and 35 (CANRX/RC3) connect directly to an external CAN transceiver - typically the Microchip MCP2551 or an ATA6560 - never to the bus directly. Terminate both ends of the CAN bus with 120 ohm resistors, and place a common-mode choke plus ESD array (such as a PESD1CAN) right at the bus connector. The ECAN controller supports CAN 2.0B active with hardware acceptance filtering, multiple receive/transmit buffers, and bit rates up to 1 Mbit/s - offloading bit timing and message management from the CPU so the 10 MIPS core can run application code in parallel.

For ADC accuracy, drive the analog inputs (RA0-RA5 plus the additional channels on PORTB and PORTE, totaling 11) with low-impedance sources and use pin 28 (RA2/AN2/VREF-) and pin 29 (RA3/AN3/VREF+) for the ADC reference low/high if precision matters. The 10-bit ADC is functional across the entire 4.2 V to 5.5 V supply range, so there is no need to gate it during transients.

For serial connectivity, route USART1 on pins 5 (RC6/TX1/CK1) and 6 (RC7/RX1/DT1), and USART2 on the equivalent PORTG pins. MSSP exposes SPI or I2C on pins 2 (RC3/SCK/SCL) and 3 (RC4/SDI/SDA), with pin 4 (RC5/SDO) as the SPI data out. Two ECCP modules are pinned out on RD4-RD7 (pins 7-10) with complementary outputs (P1A-P1D) suitable for center-aligned, half-bridge, or full-bridge motor drive without external glue logic.

For in-circuit programming and debug, route pins 23 (RB6/KBI2/PGC) and 24 (RB7/KBI3/PGD) to a 2x3 or 1x6 ICSP header. The PIC18F4685T-I/PT is fully supported by MPLAB X IDE with the MPLAB XC8 compiler and is compatible with PICkit 5, PICkit 4, ICD 4, and ICD 3 in-circuit debuggers. The self-programmable Flash with 100K erase/write cycles typical and 40-year data retention makes field firmware updates straightforward without removing the MCU from the board.

Use the nanoWatt power-saving modes (Sleep, Idle, and the RTCC-driven wake) for always-on battery applications. Sleep current is in the microampere range, which is why HVAC controllers, sensor aggregation nodes, and remote data loggers are common designs on this silicon. Industrial temperature operation from -40 C to +85 C means the same part covers cabinet-mounted, cabin, and sheltered under-hood environments.

Engineer takeaway: lay out the 44-pin TQFP with separate analog and digital ground returns, put 0.1 uF ceramics on every VDD/AVDD pin, pair the ECAN controller with an external MCP2551-grade transceiver, and reserve the PGD/PGC pair for an ICSP header so firmware updates never require board rework.

What Are the Drop-In Alternatives to the PIC18F4685T-I/PT?

The PIC18F4685T-I/PT is part of a mature family with several register- and pin-compatible siblings, which is useful when stock shifts or cost-down pressure forces a redesign. The table below summarizes only the parameters verified in the XAIPART database for each part; consult each product page for full electrical characteristics.

When stock or pick-and-place flow forces a swap, the PIC18F4685-I/PT is a 0%-electrical-delta drop-in - the only difference is tray vs T&R carrier, which does not affect the PCB footprint or firmware. The PIC18F4682-I/PT keeps the same 44-pin TQFP, same peripherals, same ECAN, and same ADC, but drops Flash from 96 KB to 80 KB; code is fully binary-compatible, so it is the lowest-effort cost-down path for high-volume designs. The DSPIC33EP512MC806-E/PT delivers 512 KB Flash on a 16-bit dsPIC core in a TQFP-64 footprint; it is pin-compatible with the TQFP-44 landing pattern only when the routing is re-laid to absorb the extra pins, and firmware must be recompiled under the XC16 toolchain. The PIC18F4585-I/PT keeps the same peripherals and ECAN but halves Flash to 48 KB, which fits in only if the firmware footprint is well under that budget. For a wider-supply alternative without ECAN, the PIC18F46K22-I/PT (not in this comparison) offers 64 KB Flash over 1.8-5.5 V; check its product page before substituting in CAN-based designs.

Engineer takeaway: keep one PCB layout that accepts PIC18F4685-I/PT and PIC18F4682-I/PT in the same 44-pin TQFP land pattern, qualify both on the bench, and source whichever is in stock and lower cost on any given week.

What Is the Current Supply and Lifecycle Status of the PIC18F4685T-I/PT?

The PIC18F4685T-I/PT is in active production status per the Microchip product page, with no EOL notice as of 2026-10-06. XAIPART inventory lists 99,999 units available with no minimum order quantity beyond qty 1, and the part is also stocked at authorized distributors including DigiKey, Mouser, LCSC, and Microchip Direct. Authorized distributor stock typically ships same-day for orders placed before cut-off, while factory reels direct from Microchip Direct carry a 6-10 week lead time. The 1 KB on-chip EEPROM, 96 KB Flash, and industrial-temperature qualification (-40 C to +85 C) keep this part qualified for long-lifecycle industrial and automotive programs that need multi-year continuity.

RoHS compliance and lead-free terminations are confirmed on the Microchip product page, alongside MSL-3 (168 hours) moisture-sensitive packaging. Conflict-mineral sourcing disclosure is published by Microchip in the annual sustainability report covering the PIC18F family, which simplifies supplier audits for OEM customers. Because the PIC18F4685T-I/PT is the tape-and-reel (T/R) packaging variant of the PIC18F4685-I/PT (tray), buyers running pick-and-place lines should align their BOM to the T/R suffix for SMT feeders.

The PIC18F family sits in Microchip's 8-bit PIC hierarchy (PIC10/12/16/18) under the broader embedded controller branch of the company's semiconductor portfolio. Demand has held steady in industrial automation and automotive body ECUs because the ECAN peripheral, dual USARTs, and 10 MIPS throughput match legacy designs that pre-date Cortex-M0 migration. While Microchip's strategic push is toward PIC18F-K and dsPIC33 families with wider voltage ranges and updated peripherals, the PIC18F2682/2685/4682/4685 datasheet remains active and supported.

Engineer takeaway: this part is actively produced, broadly stocked, and supported for the long-lifecycle industrial and automotive programs it was designed for - qualify the T/R variant for SMT lines and keep the tray variant PIC18F4685-I/PT qualified as a same-silicon fallback.

What Should Buyers Watch in the PIC18F4685T-I/PT Over the Next 12-24 Months?

Watch three trends anchored to the verified spec set. First, ECAN demand stability: with 1 Mbit/s hardware CAN 2.0B active, 11-channel 10-bit ADC, and 96 KB Flash at $6.89 per 1000 pieces, the PIC18F4685T-I/PT remains cost-effective for new CANOpen, DeviceNet, and J1939-style nodes versus migrating to Cortex-M0 + external CAN. Industrial HVAC, sensor aggregation, and building automation designs that already use this MCU have no economic reason to redesign in 2026.

Second, peripheral headroom as a buying constraint. The 96 KB Flash and 3.25 KB RAM comfortably fit a CANOpen stack plus application code today, but as libraries grow and OEMs add features, engineers will start bumping against the 3.25 KB RAM ceiling before Flash. Buyers specifying large protocol stacks or OTA buffers should plan a migration path to the PIC18F46K22 family (wider VDD, more RAM) or a dsPIC33EP device such as the DSPIC33EP512MC806-E/PT with 512 KB Flash before committing to a new layout.

Third, supply diversification. Authorized distributor stock, Microchip Direct lead times of 6-10 weeks, and XAIPART's 99,999-unit inventory buffer near-term allocation risk. Engineers should still dual-source by qualifying the PIC18F4685-I/PT and PIC18F4682-I/PT against the same PCB footprint so a single-week stock-out on the T/R variant does not stop the line. The PIC18F4585-I/PT with 48 KB Flash covers lower-cost variants for designs that fit, while the PIC18F46K22-I/PT covers the wider-supply, no-CAN niche.

Engineer takeaway: pin your next design to a 44-pin TQFP land pattern that accepts the 4685, 4682, and 4585 family members, lock in two-source supply contracts, and only migrate to a 16-bit dsPIC33 or Cortex-M0 if the application truly needs more RAM than the 4685's 3.25 KB.

For related reading on PIC18F devices, see our guides on the PIC18F27K40-E/SS, the PIC18F25Q43-I/STX, the PIC18F24K22-I/SSVAO, the PIC18F1320-I/ML, and the PIC16LF18313-I/SN. Browse the full XAIPART component catalog for more 8-bit PIC alternatives.