PIC16LC66-04I/SO - 8-bit 4MHz 14KB OTP MCU 28-SOIC | Microchip
MPN: PIC16LC66-04I/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.36 | $4.36 |
| 10 | $3.92 | $39.20 |
| 100 | $3.49 | $349.00 |
| 500 | $3.1 | $1,550.00 |
| 1,000 | $2.78 | $2,780.00 |
PIC16LC66-04I/SO Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, program memory (ROM/OTP/Flash), data memory (RAM), and programmable I/O peripherals. Within the broader semiconductor taxonomy, the PIC16LC66-04I/SO sits in the microcontroller hierarchy: microcontroller -> embedded controller -> integrated circuit -> semiconductor. The 'LC' suffix denotes the low-voltage CMOS variant of the PIC16C66 family, optimized for battery-powered and low-power embedded designs where 5V rails are not available.
Key differentiating features include three timer/counter blocks (8-bit Timer0 with prescaler, 16-bit Timer1 with prescaler and external crystal/clock sleep-mode increment capability, and 8-bit Timer2), a synchronous/asynchronous serial port (USART), an 8-bit parallel slave port, and an on-chip 8-bit ADC with multiple input channels. The integrated watchdog timer and programmable code protection enhance field reliability for unattended industrial nodes.
The RISC architecture delivers deterministic execution, predictable interrupt latency, and low interrupt latency - a critical requirement for real-time control loops. The Harvard bus separates instruction and data paths so the next instruction can be prefetched while the current instruction executes data operations, sustaining near-1 MIPS/MHz throughput.
Typical applications include industrial control subsystems, motor control peripheral boards, sensor signal conditioning front-ends, low-power instrumentation, remote sensor nodes, and embedded user-interface controllers. The wide 2.5V to 6.0V operating range simplifies battery-backed and 3.3V/5V mixed-rail designs without level shifting.
Design consideration: when migrating legacy designs to this part, note that OTP memory is one-time programmable and cannot be erased - prototype code should be validated on a windowed CERDIP (JW) variant, then committed to the SOIC OTP for production. Always confirm the part is still active on Microchip's product page before committing to new designs, as PIC16C OTP parts are mature and may approach end-of-life.
This page synthesizes distributor pricing, same-package drop-in alternatives, and practical design notes not found in the standalone manufacturer datasheet - intended as a decision-support complement to the official Microchip PIC16C66 datasheet for engineers selecting or sourcing this legacy MCU.
Drop-in alternatives for PIC16LC66-04I/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 PIC16LC66-04I/SO (same form factor and footprint) — differing in Program Memory Size, Mounting Type, Program Memory Type, RAM Size, ADC.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC66-04/SO
✅ Drop-In✓ In Stock
$2.4 / Unit
View Datasheet →PIC16LC66-04I/SP
✅ Drop-In✓ In Stock
$3.65 / Unit
View Datasheet →PIC16F76-I/SO
✅ Drop-In✓ In Stock
$2.9 / Unit
View Datasheet →PIC16F876A-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC66-04I/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 16C, 8-bit RISC |
| Program Memory Size | 14 KB (8K x 14) OTP |
| RAM Size | 368 bytes (368 x 8) |
| Maximum Clock Frequency | 4 MHz |
| Operating Supply Voltage | 2.5 V to 6.0 V |
| Number of I/O Pins | 22 |
| Package | 28-pin SOIC (SO) |
| Mounting Type | Surface Mount |
| Operating Temperature Range | -40 C to +85 C (Industrial) |
| Instruction Set | 35 single-word instructions |
| Instruction Cycle Time | 1 cycle (branches 2 cycles) |
| ADC | 8-bit, multi-channel on-chip |
| Timers | Timer0 (8-bit), Timer1 (16-bit), Timer2 (8-bit) |
| Communication | USART (SCI), 8-bit Parallel Slave Port |
| Watchdog Timer | Yes, on-chip |
| ROM/Program Type | OTP (One-Time Programmable) |
| RoHS Status | Compliant |
PIC16LC66-04I/SO Pin Configuration
| Pin 1 | RA0/AN0 — Port A bit 0 / analog input 0 |
| Pin 2 | RA1/AN1 — Port A bit 1 / analog input 1 |
| Pin 3 | RA2/AN2 — Port A bit 2 / analog input 2 |
| Pin 4 | RA3/AN3/VREF — Port A bit 3 / analog input 3 / voltage reference |
| Pin 5 | RA4/T0CKI — Port A bit 4 / Timer0 clock input |
| Pin 6 | RA5/AN4/SS — Port A bit 5 / analog input 4 / slave select |
| Pin 7 | OSC1/CLKIN — Oscillator crystal input / external clock input |
| Pin 8 | OSC2/CLKOUT — Oscillator crystal output / clock output |
| Pin 9 | RC0/T1OSO/T1CKI — Port C bit 0 / Timer1 oscillator output / Timer1 clock |
| Pin 10 | RC1/T1OSI/CCP2 — Port C bit 1 / Timer1 oscillator input / CCP2 |
| Pin 11 | RC2/CCP1 — Port C bit 2 / Capture/Compare/PWM 1 |
| Pin 12 | RC3/SCK/SCL — Port C bit 3 / SPI clock / I2C clock |
| Pin 13 | RC4/SDI/SDA — Port C bit 4 / SPI data in / I2C data |
| Pin 14 | RC5/SDO — Port C bit 5 / SPI data out |
| Pin 15 | RC6/TX/CK — Port C bit 6 / USART TX / USART clock |
| Pin 16 | RC7/RX/DT — Port C bit 7 / USART RX / USART data |
| Pin 17 | RB7/PGD — Port B bit 7 / ICSP data |
| Pin 18 | RB6/PGC — Port B bit 6 / ICSP clock |
| Pin 19 | RB5 — Port B bit 5 |
| Pin 20 | RB4 — Port B bit 4 |
| Pin 21 | RB3/PGM — Port B bit 3 / LVP programming |
| Pin 22 | RB2 — Port B bit 2 |
| Pin 23 | RB1 — Port B bit 1 |
| Pin 24 | RB0/INT — Port B bit 0 / external interrupt |
| Pin 25 | VSS — Ground |
| Pin 26 | VDD — Positive supply |
| Pin 27 | MCLR/VPP — Master clear reset / programming voltage |
| Pin 28 | RE0/RD/AN — Port E bit 0 / parallel slave port read / analog |
Typical Applications
PIC16LC66-04I/SO is suitable for 6 applications: Industrial Control Subsystems, Sensor Signal Conditioning Front-Ends, Low-Power Instrumentation, Motor Control Peripheral Boards, Embedded User Interface Controllers, Remote Sensor Nodes.
Industrial Control Subsystems
The PIC16LC66-04I/SO is well-suited for industrial control subsystems where moderate program complexity (14 KB OTP) and 22 GPIO pins are sufficient for sensor aggregation and actuator control. Its 2.5V to 6.0V supply range accommodates both 3.3V sensor rails and 5V driver stages directly, eliminating level shifters. The 8-bit ADC on-chip handles analog sensor inputs, while the 16-bit Timer1 with external crystal/clock-in-sleep capability enables precise interval timing even in low-power modes. Industrial-grade -40C to +85C operation ensures field reliability. Pair with external RS-485 transceivers for multi-drop industrial networks.
Recommended
Sensor Signal Conditioning Front-Ends
Use the PIC16LC66-04I/SO as a sensor front-end MCU that digitizes analog signals via its 8-bit ADC, performs linearization, and forwards processed data over the on-chip USART. The 4 MHz clock and deterministic instruction timing support 1-2 kHz sample rates per channel, adequate for thermocouple, strain-gauge, and process-variable conditioning. The wide 2.5V-6.0V supply range simplifies battery-backed designs where the same MCU runs directly from 3.6V lithium packs. The 368-byte RAM is sufficient for circular sample buffers; the 14KB OTP holds calibration tables and lookup routines.
Recommended
Low-Power Instrumentation
The PIC16LC66-04I/SO's low-voltage LC variant draws minimal current at reduced clock rates, making it a strong fit for battery-powered instrumentation such as portable data loggers, handheld meters, and remote sensor pods. Operating down to 2.5V lets the system run directly from two AA alkaline cells without boost converters. Timer1 can be clocked from an external 32.768 kHz crystal during sleep, providing a real-time clock with nanoamp-level sleep current. The OTP memory reduces unit cost versus flash parts in volume production where firmware is frozen.
Recommended
Motor Control Peripheral Boards
Deploy the PIC16LC66-04I/SO as a peripheral controller for stepper or brushed-DC motor driver boards, where its 22 GPIO pins drive H-bridge logic, encoder inputs, and fault-feedback lines. The 8-bit PWM capability (via Timer2) supports commutation and speed control loops, while the USART links to a host controller for command and telemetry. Industrial temperature rating enables under-hood and outdoor installations. The 4 MHz maximum clock is adequate for closed-loop control at typical motor PWM frequencies; pair with dedicated gate drivers for high-current switching.
Recommended
Embedded User Interface Controllers
The PIC16LC66-04I/SO can drive small user-interface subsystems - keypads, LED indicators, character LCDs, and rotary encoders - where its 22 GPIO lines map directly to a typical 4x4 matrix keypad plus LCD data bus. With 14KB OTP, designers can embed keypad scanning debouncing, menu navigation state machines, and simple text rendering. The USART enables command exchange with a host processor or PC interface. Operating from 2.5V to 6.0V makes it compatible with both 3.3V OLED modules and 5V LCDs without level translation.
Recommended
Remote Sensor Nodes
The PIC16LC66-04I/SO serves as a low-cost controller for remote sensor nodes (utility metering, agricultural monitoring, environmental telemetry) where cost per node dominates the BOM and firmware is finalized. Its 2.5V minimum supply lets the node run from primary lithium thionyl-chloride cells with no boost converter. The on-chip 8-bit ADC, three timers, and USART cover typical sensor-pod I/O. OTP memory prevents field firmware tampering - a benefit for metering infrastructure. Industrial temperature rating supports outdoor enclosures. Pair with low-power radios for wireless mesh networks.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC66-04I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC66-04/SO | PIC16LC66-04I/SP | PIC16F76-I/SO | PIC16F876A-I/SO |
|---|---|---|---|---|---|
| Package | 28-SOIC (SO) | 28-SOIC (SO) - same | 28-SPDIP (SP) - through-hole | 28-SOIC (SO) - same | 28-SOIC (SO) - same |
| Brand | Microchip Technology | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same |
| Program Memory | 14 KB OTP | 14 KB OTP | 14 KB OTP | 14 KB Flash (reprogrammable) | 14 KB Flash + ICD |
| RAM Size | 368 bytes | 368 bytes | 368 bytes | 368 bytes | 368 bytes |
| Max Clock Frequency | 4 MHz | 4 MHz | 4 MHz | 20 MHz (faster) | 20 MHz (faster) |
| Supply Voltage | 2.5 V to 6.0 V | 2.5 V to 6.0 V | 2.5 V to 6.0 V | 2.0 V to 5.5 V | 2.0 V to 5.5 V |
| I/O Pins | 22 | 22 | 22 | 22 | 22 |
| Operating Temperature | -40 C to +85 C (Industrial) | 0 C to +70 C (Commercial) | -40 C to +85 C (Industrial) | -40 C to +85 C (Industrial) | -40 C to +85 C (Industrial) |
Key Differentiators
- Wide low-voltage supply range enables direct battery operation (vs PIC16C66-04/P (standard voltage variant))
- Industrial temperature grade for field deployment (vs PIC16LC66-04/SO (commercial temperature))
- Surface-mount 28-SOIC package for compact designs (vs PIC16LC66-04I/SP (28-SPDIP through-hole))
Design Notes
The PIC16LC66-04I/SO's wide 2.5V to 6.0V supply range lets the MCU run directly from 3.3V or 5V rails without a regulator. Place a 0.1 uF decoupling capacitor within 5 mm of the VDD pin (pin 26) and an additional 10 uF bulk capacitor near the supply entry point. For battery-powered designs, the LC variant's low-voltage operation enables direct connection to two AA alkaline cells (nominally 3.0V). Brown-out reset should be enabled in configuration bits to prevent undefined behavior during voltage dips below 2.5V.
OTP (One-Time-Programmable) memory cannot be erased after programming - a programming error bricks the device. Always validate firmware on a windowed CERDIP (JW) variant or a flash-based PIC16F76-I/SO before committing to OTP production parts. Also note the I-suffix denotes industrial temperature grade (-40C to +85C); the non-I PIC16LC66-04/SO is commercial (0C to +70C) and will malfunction outside that range. Verify your application's worst-case ambient before selecting the suffix.
For the 28-SOIC package, follow standard SOIC PCB layout practices: route the ICSP pins (RB6/PGC and RB7/PGD) with short, parallel traces to a 6-pin ICSP header for in-system programming access. Place the decoupling capacitor (0.1 uF ceramic) immediately adjacent to VDD pin 26, with the ground return via the shortest path to the VSS pin 25 plane. Keep the MCLR/VPP pin pulled high through a 10 kohm resistor, with a 100 nF cap to ground for noise immunity, unless external reset control is needed.
The PIC16LC66-04I/SO's parallel slave port (PSP) pins (RE0/RD/AN, RC0-RC7) share functionality with general-purpose I/O. When PSP is enabled, avoid using these pins for time-critical GPIO; instead, allocate dedicated I/O for interrupt sources and Timer inputs. The 8-bit ADC shares analog input pins with Port A and Port E; configure ADCON1 to enable only the channels in use, leaving unused channels tied to a defined voltage (GND or VDD) to minimize input leakage.
Compliance Information
RoHS compliant per Microchip product page. Not AEC-Q100 qualified - this is a general-purpose MCU, not automotive-grade. Lead-free reflow profile JEDEC J-STD-020 compatible.
