PIC18F4520-E/ML - 8-bit 25MHz 32KB Flash MCU, 44-QFN | Microchip
MPN: PIC18F4520-E/ML ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.2 | $4.20 |
| 10 | $3.85 | $38.50 |
| 100 | $3.41 | $341.00 |
| 500 | $3.08 | $1,540.00 |
| 1,000 | $2.78 | $2,780.00 |
PIC18F4520-E/ML Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, non-volatile program memory (Flash), volatile data memory (SRAM), peripherals (timers, ADC, communication ports), and interrupt logic on one die. Within the broader taxonomy, MCUs sit under microprocessors, themselves a subset of processors and digital logic integrated circuits. PIC18F-series microcontrollers use Microchip's enhanced Harvard RISC architecture with C-compiler-optimized instruction set and a single-cycle hardware 8x8 multiplier, balancing deterministic real-time control with code density. The PIC18F4520 specifically occupies the high-pin-count, high-memory tier of the PIC18F2x20/4x20 family and is pin-compatible with the PIC18F4420 and PIC18F2520 footprints.
Key differentiating features of the PIC18F4520-E/ML include: 36 digital I/O pins across five ports (RA, RB, RC, RD, RE), a 10-bit ADC with up to 13 input channels, two analog comparators, two CCP modules plus one ECCP (enhanced capture/compare/PWM), three 16-bit timers plus one 8-bit timer, hardware USART (EUSART), MSSP (SPI/I2C), a 31 kHz to 8 MHz internal oscillator block with 4x PLL (up to 32 MHz), fail-safe clock monitor, separate watchdog RC oscillator, and nanoWatt power management with idle and sleep modes. This is a complete set of legacy-friendly peripherals in a small 8x8 mm QFN.
Architecturally, the PIC18F4520 implements an enhanced 16-bit instruction word with 8-bit data path, single-cycle hardware multiply, and a 32-level hardware stack. The internal oscillator and 4x PLL allow designs without an external crystal while still meeting timing requirements for 10 MIPS operation. nanoWatt technology provides dynamic clock switching and selective peripheral control for battery-friendly sleep currents. The device operates from 4.2V to 5.5V (extended temperature variant).
Typical applications include industrial control boards, sensor signal conditioning front-ends, low-power motor control, USB-free legacy embedded systems (where the PIC18F4550 is preferred if USB is needed), HVAC thermostats, educational and prototyping platforms, and retrofits of PIC16F877A designs where higher performance and additional peripherals are required. The 44-QFN (ML) variant is preferred for compact, surface-mount assemblies where the larger 44-TQFP or 40-PDIP footprints are too tall or too large.
Design tip: the 44-pin QFN (8x8 mm) has an exposed thermal pad that must be soldered to the PCB ground plane for electrical and thermal performance - do not leave the e-pad floating. Provide adequate input bulk capacitance on VDD and AVdd to support ADC accuracy. Use the internal oscillator with PLL for cost-sensitive designs, but reserve an external crystal footprint if the application requires USB-grade clock accuracy or fail-safe clock monitor switching.
Drop-in alternatives for PIC18F4520-E/ML — 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 PIC18F4520-E/ML (same form factor and footprint) — differing in Package, Timers, Operating Temperature, Communication, Core Architecture.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18F4520-I/ML
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4420-I/ML
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4525-I/ML
✅ Drop-In✓ In Stock
$5.02 / Unit
View Datasheet →PIC18F45K20-E/ML
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4423-I/ML
✅ Drop-In✓ In Stock
$4.05 / Unit
View Datasheet →PIC18F4515-I/ML
✅ Drop-In✓ In Stock
$4.1 / Unit
View Datasheet →PIC18F4520-E/ML Maximum Ratings & Electrical Characteristics
| Series | PIC® 18F |
| Core Architecture | PIC 8-bit RISC (enhanced Harvard) |
| Core Size | 8-bit |
| CPU Speed | 25 MHz (40 MHz input / 10 MIPS) |
| Program Memory | 32 KB Flash (16K x 16) |
| RAM | 1536 bytes |
| EEPROM | 256 bytes |
| I/O Pins | 36 |
| Supply Voltage (VDD) | 4.2 V to 5.5 V |
| Operating Temperature | -40 C to +125 C (Extended, -E grade) |
| Package | 44-pin QFN (8x8 mm, exposed pad) |
| ADC | 10-bit, 13 channels |
| Timers | 1 x 8-bit, 3 x 16-bit |
| CCP/ECCP | 2 CCP + 1 ECCP |
| Communication | EUSART, MSSP (SPI / I2C) |
| Internal Oscillator | 31 kHz to 8 MHz with 4x PLL (up to 32 MHz) |
| Watchdog Timer | Yes, with separate RC oscillator |
| Power-Saving Modes | nanoWatt (Idle / Sleep) |
| Hardware Multiplier | 8x8 single-cycle |
| RoHS Status | Compliant |
PIC18F4520-E/ML Pin Configuration
| Pin 1 | RA2 — Bidirectional digital I/O / analog AN2 |
| Pin 2 | RA3 — Bidirectional digital I/O / analog AN3 / VREF+ |
| Pin 3 | RA4/T0CKI — Digital I/O / Timer0 clock input |
| Pin 4 | RA5/AN4 — Digital I/O / analog AN4 / SS |
| Pin 5 | RE0/RD — Digital I/O / parallel-port read strobe |
| Pin 6 | RE1/WR — Digital I/O / parallel-port write strobe |
| Pin 7 | RE2/CS — Digital I/O / parallel-port chip select |
| Pin 8 | VDD — Positive supply (4.2 V to 5.5 V) |
| Pin 9 | GND — Logic ground return |
| Pin 10 | RA6/OSC2 — Digital I/O / crystal oscillator output |
| Pin 11 | RA7/OSC1 — Digital I/O / crystal oscillator input |
| Pin 12 | RC0 — Digital I/O / PWM1 output |
| Pin 13 | RC1 — Digital I/O / PWM2 output |
| Pin 14 | RC2 — Digital I/O / PWM1 complementary output |
| Pin 15 | RC3 — Digital I/O / SPI clock (SCK) |
| Pin 16 | RC4 — Digital I/O / SPI data in (SDI) |
| Pin 17 | RC5 — Digital I/O / SPI data out (SDO) |
| Pin 18 | RC6/TX — Digital I/O / EUSART transmit |
| Pin 19 | RC7/RX — Digital I/O / EUSART receive |
| Pin 20 | VSS — Logic ground return |
| Pin 21 | VDD — Positive supply (4.2 V to 5.5 V) |
| Pin 22 | RB0/INT0 — Digital I/O / external interrupt 0 |
| Pin 23 | RB1/INT1 — Digital I/O / external interrupt 1 |
| Pin 24 | RB2/INT2 — Digital I/O / external interrupt 2 |
| Pin 25 | RB3 — Digital I/O / CCP2 input/output |
| Pin 26 | RB4 — Digital I/O / IOC interrupt-on-change |
| Pin 27 | RB5 — Digital I/O / IOC interrupt-on-change |
| Pin 28 | RB6/PGC — Digital I/O / ICD clock / in-circuit programming clock |
| Pin 29 | RB7/PGD — Digital I/O / ICD data / in-circuit programming data |
| Pin 30 | VSS — Logic ground return |
| Pin 31 | VDD — Positive supply (4.2 V to 5.5 V) |
| Pin 32 | RD0 — Digital I/O / PSP data bit 0 |
| Pin 33 | RD1 — Digital I/O / PSP data bit 1 |
| Pin 34 | RD2 — Digital I/O / PSP data bit 2 |
| Pin 35 | RD3 — Digital I/O / PSP data bit 3 |
| Pin 36 | RD4 — Digital I/O / PSP data bit 4 |
| Pin 37 | RD5 — Digital I/O / PSP data bit 5 |
| Pin 38 | RD6 — Digital I/O / PSP data bit 6 |
| Pin 39 | RD7 — Digital I/O / PSP data bit 7 |
| Pin 40 | VSS — Logic ground return |
| Pin 41 | VDD — Positive supply (4.2 V to 5.5 V) |
| Pin 42 | VSS — Logic ground return |
| Pin 43 | NC — Not connected (per datasheet) |
| Pin 44 | NC — Not connected (per datasheet) |
Typical Applications
PIC18F4520-E/ML is suitable for 6 applications: Industrial Control Boards, HVAC Thermostat and Sensor Front-End, Low-Power Motor Control (BLDC / Stepper), Legacy Educational and Prototyping Platforms, Retrofit of PIC16F877A Designs, Sensor Signal Conditioning and Data Logging.
Industrial Control Boards
The PIC18F4520-E/ML fits industrial control boards because its 36 digital I/O pins easily drive relays, optocouplers, and keypad/display interfaces, while the 10-bit/13-channel ADC reads 4-20 mA and 0-10 V sensor signals directly. Its 25 MHz core delivers 10 MIPS, sufficient for PID loops running at 1 kHz without task starvation. The extended -40C to +125C temperature grade lets it survive unconditioned cabinets, motor bays, and outdoor enclosures. Designers typically pair the 4520 with external RS-485 transceivers and an isolated 5V supply for factory-floor robustness. The 44-QFN (8x8 mm) package is a particularly strong fit for compact PLC daughter-boards where TQFP height is unacceptable.
Recommended
HVAC Thermostat and Sensor Front-End
The PIC18F4520-E/ML is well-suited for HVAC thermostats because its 10-bit ADC with 13 channels can read multiple temperature sensors (NTC thermistors or digital one-wire), humidity sensors, and occupancy inputs simultaneously. The 32 KB flash accommodates complex state machines for multi-stage heating/cooling control plus LCD driver code. nanoWatt sleep modes drop current to microamp levels between sensor reads, allowing battery-backed thermostat operation during power outages. The extended -E temperature grade handles attic and outdoor mounting where ambient can exceed 70C. The 44-QFN footprint allows the thermostat PCB to fit behind a standard wall plate.
Recommended
Low-Power Motor Control (BLDC / Stepper)
The PIC18F4520-E/ML drives small BLDC and stepper motors via its Enhanced Capture/Compare/PWM (ECCP) module plus two additional CCP modules, providing up to three independent PWM channels at 10-bit resolution. The 25 MHz core and single-cycle hardware 8x8 multiplier handle FOC (field-oriented control) loops on small motors under 100 W. Quadrature encoder inputs on port C support closed-loop positioning, and the nanoWatt idle mode lets battery-powered tools enter sleep between commands. The 5V supply is convenient for direct half-bridge driver interfacing. The 44-QFN (8x8 mm) package keeps the motor driver PCB compact for handheld power tools and small appliances.
Recommended
Legacy Educational and Prototyping Platforms
The PIC18F4520-E/ML is widely used in university embedded systems curricula and hobbyist prototyping platforms because the PIC18 instruction set is well-documented, MPLAB X IDE is free, and the PICkit 5 in-circuit debugger is inexpensive. Its 36 I/O pins, dual USART, SPI, and I2C peripherals cover the canonical lab exercises: keypad scanning, LCD driving, EEPROM interfacing, and serial communication. The 32 KB flash holds complete student projects including bootloaders and RTOS-lite kernels. The 44-QFN variant is appropriate for advanced SMD soldering labs, while the 40-PDIP variant is preferred for breadboard-based introductory courses.
Recommended
Retrofit of PIC16F877A Designs
The PIC18F4520-E/ML is a natural migration target for legacy PIC16F877A designs because the enhanced PIC18 instruction set is source-compatible (with recompile) and offers roughly 4x the performance at the same clock rate. The 32 KB flash is 4x larger than the 16F877A's 14 KB, removing memory pressure. Peripherals are upgraded (10-bit ADC vs 8-bit, MSSP for SPI/I2C, internal oscillator block with PLL) without changing the schematic. The 40-PDIP variant of the 4520 is a direct drop-in for 16F877A sockets. The 44-QFN (8x8) is preferred when migrating SMT designs to a smaller footprint.
Recommended
Sensor Signal Conditioning and Data Logging
The PIC18F4520-E/ML is appropriate for sensor signal conditioning front-ends and data loggers because its 10-bit ADC plus two analog comparators can digitize multiple sensor channels at sample rates up to 100 ksps. The 1.5 KB SRAM provides sufficient buffer for block-mode acquisition, while the 256-byte EEPROM stores calibration constants without wearing flash. The MSSP peripheral handles SPI or I2C sensor interfacing, and the EUSART streams data to a host PC or external SD card. Battery-powered deployments benefit from nanoWatt sleep current under 1 uA, with periodic wake-up via Watchdog Timer. The 44-QFN package suits compact wearable and IoT data-logger form factors.
Recommended
Recommended Products Summary
Engineering reference data for PIC18F4520-E/ML — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18F4520-I/ML | PIC18F4420-I/ML | PIC18F4525-I/ML | PIC18F45K20-E/ML | PIC18F4423-I/ML |
|---|---|---|---|---|---|---|
| Package | 44-QFN (8x8 mm) | 44-QFN (8x8 mm) | 44-QFN (8x8 mm) | 44-QFN (8x8 mm) | 44-QFN (8x8 mm) | 44-QFN (8x8 mm) |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Flash | 32 KB | 32 KB | 16 KB | 48 KB | 32 KB | 16 KB |
| RAM | 1536 bytes | 1536 bytes | 768 bytes | 1536 bytes | 1536 bytes | 768 bytes |
| Supply 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 | 1.8 V to 5.5 V | 2.0 V to 5.5 V |
| Temperature Grade (-E suffix) | -40 C to +125 C | -40 C to +85 C (industrial) | -40 C to +85 C (industrial) | -40 C to +85 C (industrial) | -40 C to +125 C (extended) | -40 C to +85 C (industrial) |
| ADC | 10-bit, 13 channels | 10-bit, 13 channels | 10-bit, 13 channels | 10-bit, 13 channels | 10-bit, 14 channels | 12-bit, 13 channels |
| USB | No | No | No | No | No | Yes (USB 2.0 FS) |
Key Differentiators
- 32 KB flash vs only 16 KB on smaller-family alternatives (vs PIC18F4420-I/ML)
- Extended -40C to +125C temperature range (vs PIC18F4520-I/ML (industrial -40C to +85C))
- Wider supply voltage (1.8V to 5.5V) in same QFN (vs PIC18F4520-E/ML (5V only))
- 5V native operation simplifies analog interface (vs PIC18F45K20-E/ML (which optimizes for 3.3V))
Design Notes
The 44-pin QFN (8x8 mm) package has an exposed die pad (E-pad) on the underside that MUST be soldered to a ground plane on the PCB for both electrical and thermal performance. The E-pad reduces thermal resistance from junction to board, allowing the part to operate at the full -40C to +125C range without derating. Recommended landing pattern uses nine thermal vias (0.3 mm drill) in a 3x3 array under the E-pad, tied to the inner ground plane. Do not leave the E-pad floating - this can cause erratic ADC readings and intermittent failures at temperature extremes.
Decouple VDD (pins 8, 21, 31, 41) with a 100 nF ceramic capacitor placed as close as possible to each pin pair, plus a bulk 10 uF tantalum or aluminum polymer capacitor on the main 5V rail. AVdd (when used separately) requires its own 100 nF + 10 uF decoupling pair, with AVss tied to Vss at a single point (star ground) to avoid analog-digital ground loops. For ADC accuracy below 1 LSB, add a ferrite bead or small resistor (10 ohm) between VDD and AVdd. The internal voltage regulator has a power-on-reset threshold around 1.5 V; ensure VDD rise time is less than 50 ms to avoid incomplete initialization.
The PIC18F4520 operates only from 4.2 V to 5.5 V - it is NOT a 3.3V part. Level-shifters are required when interfacing 3.3V peripherals (Bluetooth modules, modern sensors). The configuration word (CONFIG1H) must be set to select the correct oscillator mode (HS, XT, internal RC with PLL, etc.) before code will execute - a common mistake is leaving the default external oscillator setting when no crystal is present. The MCLR reset pin requires a 10 kohm pull-up to VDD; floating MCLR causes intermittent resets. ICP (in-circuit programming) pins RB6/PGC and RB7/PGD must not be used for high-current loads during programming - add 4.7 kohm series resistors if these pins drive LEDs.
Keep the crystal (or ceramic resonator) traces on the OSC1/OSC2 pins short and symmetric, with a ground guard ring around them to minimize EMI coupling. Place the crystal within 5 mm of pins 10-11. If using the internal oscillator (31 kHz to 8 MHz with 4x PLL), leave the OSC pins as RA6/RA7 digital I/O and ground any external crystal footprint. Route the ICSP signals (PGC/PGD) away from high-frequency switching nodes (PWM outputs, relay coils) - cross-coupling can cause programming failures or run-time glitches during debug.
Estimated: At maximum operating frequency of 25 MHz and 5V supply, the PIC18F4520-E/ML typical active current is approximately 16 mA. Worst-case (industrial temperature, all peripherals active, I/O sourcing 20 mA each) can reach 60 mA. The 44-QFN (8x8) package has thermal resistance (theta JA) of approximately 35 C/W on a 4-layer JEDEC test board, meaning the junction rises 35 C per watt dissipated. At 0.3 W internal dissipation, the junction sits 10 C above ambient - well within the -40C to +125C range when ambient is below 115C. No external heatsink is required.
Compliance Information
RoHS compliant per Microchip product page. Lead-free (Pb-free) matte-tin finish. Industrial/extended temperature grade not AEC-Q100 qualified; contact Microchip for AEC-Q100 automotive variants (e.g., PIC18F4520-E/MLVAO with -VAO suffix).
