PIC16C66-20/SO - 8-Bit 20MHz OTP MCU 14KB | Microchip
MPN: PIC16C66-20/SO ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.5 | $8.50 |
| 10 | $7.65 | $76.50 |
| 100 | $6.82 | $682.00 |
| 500 | $6.1 | $3,050.00 |
| 1,000 | $5.45 | $5,450.00 |
PIC16C66-20/SO Overview
What is an OTP microcontroller? An OTP (One-Time-Programmable) microcontroller integrates non-volatile program memory that can be written only once during initial programming, after which the bit pattern becomes permanent. Microcontrollers (MCUs) sit at the top of the embedded computing hierarchy alongside microprocessors, and 8-bit MCUs like the PIC16C66 occupy the entry-level segment optimized for simple deterministic control tasks with low pin counts and modest memory requirements.
Key features include 35 single-word instructions, all executing in a single instruction cycle except program branches (two cycles), a 200 ns instruction execution time at 20 MHz, and a Harvard architecture that separates program and data paths. The PIC16C66 also integrates 368 bytes of RAM, 33 digital I/O pins organized into multiple ports, three timer modules, a USART, and a Capture/Compare/PWM (CCP) peripheral, all on-chip for compact designs.
The device's CMOS EPROM technology combined with a fully static core enables ultra-low standby current of 1 uA typical at 3V/32 kHz and 15 uA typical at 5V/4 MHz, making it appropriate for battery-backed or power-conscious systems. The 14-bit wide instruction word provides a richer instruction set than 12-bit baseline PIC cores, allowing more compact code for arithmetic-intensive routines.
Typical applications include industrial control subsystems, appliance controls, automotive body electronics, instrumentation front-ends, and consumer product controllers where the OTP memory model fits the production volume. The wide operating voltage range supports both 5V regulated rails and battery-powered designs above 4V.
When designing with the PIC16C66-20/SO, note that OTP memory requires programming at the time of manufacture or via a device programmer before PCB assembly, which differs from flash-based PIC16F counterparts. Engineers migrating designs should consider whether flash equivalents (e.g., PIC16F76) better support field firmware updates.
This page synthesizes distributor pricing, drop-in same-package alternatives from Microchip and cross-brand sources, and practical design notes not found in the standalone manufacturer datasheet.
Drop-in alternatives for PIC16C66-20/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 PIC16C66-20/SO (same form factor and footprint) — differing in Package, Timers, Program Memory Type, Core, Instruction Cycle.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16F76-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C66-04I/SO
✅ Drop-In✓ In Stock
$5.1 / Unit
View Datasheet →PIC16C66T-20/SO
✅ Drop-In✓ In Stock
$8.2 / Unit
View Datasheet →PIC16C66-20I/SO
✅ Drop-In✓ In Stock
$6.42 / Unit
View Datasheet →PIC16C66-04E/SO
✅ Drop-In✓ In Stock
$5.72 / Unit
View Datasheet →PIC16C66-20/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C66-20/SO Maximum Ratings & Electrical Characteristics
| Core | PIC16C6X 8-bit RISC |
| Instruction Set Architecture | 14-bit wide, 35 single-word instructions |
| Maximum Clock Frequency | 20 MHz |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 14 KB (8K x 14) |
| Data RAM | 368 bytes |
| Operating Voltage Range | 4.0 V to 6.0 V |
| I/O Pins | 33 |
| Timers | 3 (Timer0, Timer1, Timer2) |
| Communication Peripherals | USART (SCI), SSP/SPI/I2C |
| CCP Modules | Capture / Compare / PWM |
| Instruction Execution Time | 200 ns at 20 MHz (single cycle) |
| Standby Current | 1 uA typical at 3 V / 32 kHz |
| Active Current (typ.) | 15 uA at 5 V / 4 MHz |
| Operating Temperature Range | 0C to +70C (Commercial) |
| Package | 28-pin SOIC (SO) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
PIC16C66-20/SO Pin Configuration
| Pin 1 | MCLR/VPP — Master Clear (reset) / Programming voltage input |
| Pin 2 | RA0/AN0 — Digital I/O / Analog input channel 0 |
| Pin 3 | RA1/AN1 — Digital I/O / Analog input channel 1 |
| Pin 4 | RA2/AN2/VREF- — Digital I/O / Analog input / ADC VREF- |
| Pin 5 | RA3/AN3/VREF+ — Digital I/O / Analog input / ADC VREF+ |
| Pin 6 | RA4/T0CKI — Digital I/O / Timer0 clock input |
| Pin 7 | RA5/AN4/SS — Digital I/O / Analog input / SPI slave select |
| Pin 8 | OSC1/CLKIN — Crystal oscillator input / external clock input |
| Pin 9 | OSC2/CLKOUT — Crystal oscillator output / clock output |
| Pin 10 | RC0/T1OSO/T1CKI — Digital I/O / Timer1 oscillator output / Timer1 clock input |
| Pin 11 | RC1/T1OSI/CCP2 — Digital I/O / Timer1 oscillator input / CCP2 module |
| Pin 12 | RC2/CCP1 — Digital I/O / CCP1 module (PWM) |
| Pin 13 | RC3/SCK/SCL — Digital I/O / SPI clock / I2C clock |
| Pin 14 | RC4/SDI/SDA — Digital I/O / SPI data in / I2C data |
| Pin 15 | RC5/SDO — Digital I/O / SPI data out |
| Pin 16 | RC6/TX/CK — Digital I/O / USART TX / USART clock |
| Pin 17 | RC7/RX/DT — Digital I/O / USART RX / USART data |
| Pin 18 | GND — Ground reference |
| Pin 19 | VDD — Positive supply voltage (4.0V to 6.0V) |
| Pin 20 | RB0/INT — Digital I/O / External interrupt |
| Pin 21 | RB1 — Digital I/O |
| Pin 22 | RB2 — Digital I/O |
| Pin 23 | RB3 — Digital I/O |
| Pin 24 | RB4 — Digital I/O |
| Pin 25 | RB5 — Digital I/O |
| Pin 26 | RB6/PGC — Digital I/O / ICSP clock |
| Pin 27 | RB7/PGD — Digital I/O / ICSP data |
| Pin 28 | NC — Not connected (per datasheet) |
Typical Applications
PIC16C66-20/SO is suitable for 6 applications: Industrial Control Subsystems, Appliance Control Boards, Automotive Body Electronics, Instrumentation Front-Ends, Battery-Powered Sensor Nodes, Consumer Product Controllers.
Industrial Control Subsystems
The PIC16C66-20/SO's 20 MHz core, 14 KB OTP EPROM, and 33 digital I/O pins make it a strong fit for industrial control subsystems such as sensor aggregation boards, motor control sequencers, and PLC expansion modules. Its 4.0V to 6.0V operating range tolerates industrial 5V power rails with noise headroom, and the integrated USART and SSP peripherals enable MODBUS, SPI sensor, and I2C EEPROM interfaces without external glue logic. The PIC16C66's deterministic 200 ns instruction cycle suits time-critical control loops where predictable response latency matters more than raw throughput.
Recommended
Appliance Control Boards
Consumer and white-goods appliance controls benefit from the PIC16C66-20/SO's low active current (15 uA typical at 5V/4 MHz) and OTP memory model that prevents firmware theft while keeping unit cost low. Typical use cases include washing machine user-interface controllers, microwave keypad decoders, and HVAC thermostat logic where 14 KB of program space accommodates full state machines and user-menu handling. The 28-SOIC package supports automated pick-and-place assembly and reflow soldering in high-volume appliance manufacturing.
Recommended
Automotive Body Electronics
Although automotive-grade qualification requires the -04E/SO extended temperature variant, the PIC16C66 architecture is widely used in body electronics such as window lift controllers, mirror adjusters, and interior lighting sequencers. Its 33 I/O pins easily drive multiple relays and switch inputs, the CCP module generates PWM for dimming, and the wide 4.0V to 6.0V supply range tolerates cranking transients on 12V automotive rails. Designers targeting automotive should choose the -04E/SO or -20I/SO industrial variants for the required temperature coverage.
Recommended
Instrumentation Front-Ends
Test and measurement front-ends use the PIC16C66-20/SO for range switching, relay sequencing, and LCD drive coordination, where its 20 MHz core and integrated USART simplify GPIB-to-UART bridge designs. The OTP memory model locks calibration coefficients into the device at production time, preventing field tampering of measurement constants. The CCP module supports precision timing for sample-and-hold sequencing, and the 14-bit instruction set produces compact code for binary-BCD conversions common in panel-meter firmware.
Recommended
Battery-Powered Sensor Nodes
The PIC16C66-20/SO's ultra-low standby current of 1 uA typical at 3V/32 kHz and its ability to run down to 4V from four-cell alkaline or NiMH packs make it well-suited to long-life remote sensor nodes such as wireless thermostats and security contact transmitters. The PIC16C6X core's sleep mode combined with an external watchdog timer enables multi-year battery life in low-duty-cycle applications. Designers should pair the MCU with a low-quiescent LDO such as MCP1700 and an SPI temperature/humidity sensor for full sub-50 uA average current budgets.
Recommended
Consumer Product Controllers
Consumer products ranging from toys and small appliances to digital clocks and remote controls use the PIC16C66-20/SO for its low per-unit cost and minimal external component count. The 28-pin SOIC package saves board space versus the 40-pin alternatives, and the 33 available I/O pins cover the keypad, LED, and serial peripheral requirements of typical consumer designs. The OTP memory model is ideal for cost-sensitive products where firmware versioning is fixed at manufacturing and field updates are not required.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C66-20/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16F76-I/SO | PIC16C66-04I/SO | PIC16C66T-20/SO |
|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-SOIC | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same |
| Maximum Clock Frequency | 20 MHz | 20 MHz | 4 MHz | 20 MHz |
| Program Memory Type | OTP EPROM | Flash | OTP EPROM | OTP EPROM |
| Program Memory Size | 14 KB (8K x 14) | 14 KB (8K x 14) | 14 KB (8K x 14) | 14 KB (8K x 14) |
| Data RAM | 368 bytes | 368 bytes | 368 bytes | 368 bytes |
| Operating Voltage | 4.0 V to 6.0 V | 2.0 V to 5.5 V | 4.0 V to 6.0 V | 4.0 V to 6.0 V |
| Temperature Grade | 0C to +70C (Commercial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | 0C to +70C (Commercial) |
Key Differentiators
- OTP EPROM memory prevents firmware theft and field tampering (vs PIC16F76-I/SO)
- 20 MHz core with 200 ns deterministic instruction cycle (vs PIC16C66-04I/SO)
- Integrated 14-bit PIC16C6X instruction set with CCP, USART, SSP (vs PIC16C63A-20/SO)
Design Notes
The PIC16C66-20/SO operates from 4.0 V to 6.0 V and draws approximately 15 mA active at 20 MHz with all peripherals enabled. Place a 100 nF decoupling capacitor within 5 mm of the VDD pin (pin 19) and a 10 uF bulk tantalum or ceramic at the regulator output. For battery-powered designs, add a 100 kohm pull-up on MCLR/VPP to avoid unintended resets and use the SLEEP instruction combined with watchdog-timer wakeup to achieve sub-2 uA standby current.
The PIC16C66-20/SO is a low-power CMOS device dissipating roughly 75 mW at 20 MHz full activity. SOIC-28 packages have a theta_JA of approximately 85 C/W, so under typical industrial conditions no heatsink is required. However, when operating at the upper 70C commercial limit with sustained peripheral activity, verify that junction temperature does not exceed 125C by using the manufacturer thermal resistance and worst-case power dissipation calculation.
Estimated: keep oscillator traces (OSC1/OSC2) shorter than 12 mm and surround them with a ground guard ring to reduce EMI coupling. For crystals above 10 MHz, add 10-33 pF load capacitors matching the crystal's load capacitance specification. Place the MCLR pull-up resistor directly at the pin and avoid routing MCLR adjacent to high-frequency switching signals to prevent false resets in noisy environments.
Do not program the PIC16C66's configuration bits for watchdog-timer ON without also enabling software WDT clears, or the MCU will reset continuously. OTP memory cannot be erased; verify firmware in a flash-based PIC16F76 emulator before committing code to the PIC16C66-20/SO production units. Also note that the PIC16C66 lacks an ADC peripheral on the 28-SOIC variant; for analog designs choose PIC16C65B-20I/P or PIC16F876A which integrate multi-channel ADC.
Compliance Information
RoHS compliance per Microchip product page; -20/SO is commercial grade (0C to +70C) and not AEC-Q100 qualified. For automotive applications, use the PIC16C66-04E/SO extended temperature variant or migrate to PIC18F automotive parts.
