PIC16C66-20/SP - 8-Bit 20MHz OTP MCU 14KB | Microchip
MPN: PIC16C66-20/SP ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $7.2 | $7.20 |
| 10 | $6.48 | $64.80 |
| 100 | $5.76 | $576.00 |
| 500 | $5.18 | $2,590.00 |
| 1,000 | $4.61 | $4,610.00 |
PIC16C66-20/SP Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU, RAM, non-volatile program memory, and peripherals such as timers, ADC, and I/O ports. Within the broader semiconductor taxonomy, an MCU sits under microcontrollers -> embedded processors -> digital ICs -> semiconductors. The PIC16C66 specifically belongs to the mid-range 8-bit PIC family, characterized by a Harvard RISC architecture with separate program and data buses, 14-bit-wide instruction words, and a 200 ns instruction execution time at 20 MHz.
Key differentiating features of the PIC16C66-20/SP include 22 digital I/O pins, three timer modules (Timer0, Timer1, Timer2), a USART for serial communication, a 10-bit multi-channel ADC, and a capture/compare/PWM (CCP) module. The wide operating voltage range (commonly 4.0 V to 6.0 V for the PIC16C6x series, with 4.0-5.5 V cited in some sources) and low-power CMOS design (typical 15 µA at 5 V/4 MHz, 1 µA at 3 V/32 kHz) make it suitable for both line-powered and battery-backed applications.
Architecturally, the PIC16C66 uses a fully static CMOS core with EPROM/OTP program memory, allowing field programmability via standard PIC programmers such as the MPLAB PM3. The OTP nature means each device can be programmed once and is intended for production runs where code stability has been validated; for prototyping or low-volume builds, windowed ceramic or UV-erasable variants are preferred.
Typical applications include industrial control systems, appliance controllers, automotive subsystems (non-safety-critical), instrumentation front-ends, sensor signal conditioning, and general-purpose embedded logic replacement. The 22 I/O count and 14 KB code capacity are well matched to mid-complexity control firmware.
A key design consideration with the PIC16C66-20/SP is its OTP memory constraint: firmware must be fully validated before production programming. Designers often prototype on a flash-based PIC16F equivalent (e.g., PIC16F76 in the same 28-pin SPDIP) and migrate to the OTP 'C' variant only after code is frozen to reduce per-unit cost in volume production.
Drop-in alternatives for PIC16C66-20/SP — 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/SP (same form factor and footprint) — differing in Package, Operating Temperature, Mounting Type, RAM, Timers.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16F76-I/SP
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C66-04I/SP
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C65B-20I/P
✅ Drop-In✓ In Stock
$5.42 / Unit
View Datasheet →PIC16C66-04E/SP
✅ Drop-In✓ In Stock
$5.24 / Unit
View Datasheet →PIC16C66-04I/SO
✅ Drop-In✓ In Stock
$5.1 / Unit
View Datasheet →PIC16C66-20/SP Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC RISC (Harvard) |
| Instruction Set | 35 single-word instructions |
| Maximum Clock Frequency | 20 MHz |
| Instruction Execution Time | 200 ns at 20 MHz |
| Program Memory Type | OTP (One-Time Programmable) EPROM |
| Program Memory Size | 14 KB (8K x 14) |
| RAM | 368 bytes |
| Data EEPROM | Not present on PIC16C66 |
| I/O Pins | 22 |
| Timers | 3 (Timer0, Timer1, Timer2) |
| ADC | 8-channel, 8-bit (per family datasheet) |
| Communication Peripherals | USART (SCI/SPI) |
| Capture/Compare/PWM | 1 CCP module |
| Interrupts | Yes (multiple sources) |
| Supply Voltage Range | 4.0 V to 5.5 V |
| Operating Temperature Range | 0C to +70C (Commercial) |
| Package | 28-pin SPDIP (Skinny Plastic DIP), through-hole |
| Mounting Type | Through-Hole (DIP) |
| Lead-Free / RoHS | Lead-free finish available; RoHS compliance depends on date code |
| MSL Level | Not applicable (through-hole package) |
PIC16C66-20/SP Pin Configuration
| Pin 1 | MCLR/VPP — Master Clear (Reset) input / Programming voltage |
| Pin 2 | RA0/AN0 — PORTA bit 0 / Analog input 0 |
| Pin 3 | RA1/AN1 — PORTA bit 1 / Analog input 1 |
| Pin 4 | RA2/AN2/CVREF — PORTA bit 2 / Analog input 2 / Comparator Voltage Reference |
| Pin 5 | RA3/AN3/VREF — PORTA bit 3 / Analog input 3 / ADC Voltage Reference |
| Pin 6 | RA4/T0CKI — PORTA bit 4 / Timer0 clock input |
| Pin 7 | RA5/AN4/SS — PORTA bit 5 / Analog input 4 / SPI Slave Select |
| Pin 8 | VSS — Ground reference |
| Pin 9 | OSC1/CLKIN — Oscillator crystal input / External clock input |
| Pin 10 | OSC2/CLKOUT — Oscillator crystal output / Clock output (Fosc/4) |
| Pin 11 | RC0 — PORTC bit 0 |
| Pin 12 | RC1 — PORTC bit 1 |
| Pin 13 | RC2 — PORTC bit 2 |
| Pin 14 | RC3 — PORTC bit 3 |
| Pin 15 | RC4 — PORTC bit 4 |
| Pin 16 | RC5 — PORTC bit 5 |
| Pin 17 | RC6/TX/CK — PORTC bit 6 / USART TX / SPI clock |
| Pin 18 | RC7/RX/DT — PORTC bit 7 / USART RX / SPI data |
| Pin 19 | VSS — Ground reference |
| Pin 20 | VDD — Positive supply voltage (4.0 V to 5.5 V) |
| Pin 21 | RB0/INT — PORTB bit 0 / External interrupt |
| Pin 22 | RB1 — PORTB bit 1 |
| Pin 23 | RB2 — PORTB bit 2 |
| Pin 24 | RB3 — PORTB bit 3 |
| Pin 25 | RB4 — PORTB bit 4 |
| Pin 26 | RB5 — PORTB bit 5 |
| Pin 27 | RB6 — PORTB bit 6 |
| Pin 28 | RB7 — PORTB bit 7 |
Typical Applications
PIC16C66-20/SP is suitable for 7 applications: Industrial Control Systems, Appliance Motor Control, HVAC Sensor Front-Ends, Automotive Body Electronics (Non-Safety), Instrumentation and Data Loggers, Consumer Electronics Embedded Logic, Security and Access Control Panels.
Industrial Control Systems
The PIC16C66-20/SP fits industrial control panels thanks to its 22 digital I/O, USART for Modbus RTU or RS-232 host links, and 8-channel 8-bit ADC for analog sensor inputs (temperature, pressure, current). At 20 MHz with 200 ns instruction cycle, deterministic loop times under 100 µs support real-time PLC-style logic. The OTP program memory suits high-volume panels where firmware is locked. Industrial designers benefit from Microchip's proven PIC16C6x reliability in 24/7 operation and wide toolchain support (MPLAB X, XC8 compiler).
Recommended
Appliance Motor Control
Appliance designs use the PIC16C66-20/SP for low-cost brushed-DC or universal-motor PWM control, leveraging its Timer2/CCP module to generate variable duty-cycle drive signals. The 20 MHz clock allows PWM frequencies above 20 kHz (above audible range), reducing acoustic noise in washing machines, fans, and small kitchen appliances. With 368 B RAM and 14 KB code space, firmware can implement soft-start, current limiting, and tacho feedback loops. The 28-pin SPDIP package is well-suited to through-hole PCB assemblies typical in appliance main boards.
Recommended
HVAC Sensor Front-Ends
The PIC16C66-20/SP serves as the digital front-end in HVAC thermostats and air-handler controllers, reading multiple analog temperature/humidity sensors through its 8-channel ADC and driving triac outputs via opto-isolated I/O. Its low-power CMOS design (15 µA typical at 5 V/4 MHz) supports battery-backed thermostats. OTP memory avoids field reprogramming concerns, and the 22 I/O easily accommodates keypads, LCD displays, and relay drivers. The PIC16C6x interrupt architecture efficiently wakes the MCU on sensor edges to extend battery life.
Recommended
Automotive Body Electronics (Non-Safety)
Non-safety automotive subsystems such as interior lighting, seat controllers, and accessory modules leverage the PIC16C66-20/SP for its robust CMOS design and automotive-grade temperature variants in the same PIC16C6x family. The 22 I/O drive LEDs and small relays; USART interfaces with body control modules; and the 8-bit ADC monitors battery voltage and current shunts. Designers should select the PIC16C66-20I/SP industrial-temperature variant for under-hood or cabin-mounted applications where temperatures can exceed 70°C.
Recommended
Instrumentation and Data Loggers
Portable data loggers for field instrumentation use the PIC16C66-20/SP to sample sensors at programmable intervals, buffer readings in 368 B RAM, and dump captured records over USART to a host PC or SD card interface. The 14 KB OTP program memory stores compression algorithms and protocol stacks. At 20 MHz, the ADC can be sequenced at rates exceeding 50 ksamples/s aggregate across multiple channels, supporting vibration, strain, and environmental logging.
Recommended
Consumer Electronics Embedded Logic
Consumer products like remote controls, toy electronics, and small appliances use the PIC16C66-20/SP as a cost-down replacement for discrete logic, with USART enabling firmware updates via bootloader in some configurations and 22 I/O supporting keypads, displays, and IR receivers. The PIC16C6x instruction set's 35 single-word instructions keeps firmware small (typically under 8 KB), allowing cost-effective OTP programming. The wide 4.0-5.5 V supply range directly accommodates 4-cell battery or 5 V USB-powered designs.
Recommended
Security and Access Control Panels
Security alarm panels and access controllers use the PIC16C66-20/SP for keypad scanning, zone monitoring (via ADC or digital inputs), and relay/siren driver outputs. The 22 I/O accommodate up to 8 zones plus 4-wire keypad plus siren and dialer interfaces; the USART drives a PSTN dialer or GSM modem for off-premises notification. OTP memory prevents field tampering with firmware, a security-positive attribute. The PIC16C6x watchdog timer ensures the panel recovers from ESD or power-line transients.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C66-20/SP — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16F76-I/SP | PIC16C66-04I/SP | PIC16C65B-20I/P | PIC16C66-04E/SP | PIC16C66-04I/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-pin SPDIP | 28-pin SPDIP - same | 28-pin SPDIP - same | 28-pin DIP - same | 28-pin SPDIP - same | 28-pin SOIC - surface-mount variant |
| Program Memory Type | OTP EPROM (14 KB) | Flash (14 KB) - reprogrammable | OTP EPROM (14 KB) | OTP EPROM (7 KB) | OTP EPROM (14 KB) | OTP EPROM (14 KB) |
| Program Memory Size | 14 KB (8K x 14) | 14 KB (8K x 14) - same | 14 KB (8K x 14) - same | 7 KB (4K x 14) -50% | 14 KB (8K x 14) - same | 14 KB (8K x 14) - same |
| Maximum Clock Speed | 20 MHz | 20 MHz | 4 MHz -80% | 20 MHz | 4 MHz -80% | 4 MHz -80% |
| RAM | 368 bytes | 368 bytes - same | 368 bytes - same | 192 bytes -48% | 368 bytes - same | 368 bytes - same |
| I/O Pins | 22 | 22 - same | 22 - same | 22 - same | 22 - same | 22 - same |
| Operating Temperature | 0C to +70C (Commercial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +125C (Extended) | -40C to +85C (Industrial) |
Key Differentiators
- Industry-standard 28-pin SPDIP PIC16C6x pinout (vs ATmega48PA-PU)
- 14 KB OTP EPROM at 20 MHz for cost-optimized production (vs PIC16F76-I/SP)
- Triple timer architecture with CCP module (vs PIC16C65B-20I/P)
Design Notes
The PIC16C66-20/SP uses OTP EPROM and cannot be reprogrammed once written. Validate firmware completely on a flash-equipped prototype part (PIC16F76-I/SP, same 28-pin SPDIP) before committing to OTP programming in production. Programming errors on OTP parts are irreversible and require chip replacement.
Decouple VDD (pin 20) with a 100 nF ceramic capacitor placed within 5 mm of the pin, plus a 10 µF bulk capacitor on the supply rail. The PIC16C6x core can produce brief switching spikes on VDD when I/O banks toggle; inadequate decoupling causes code runaway or ADC inaccuracy. Place VSS (pin 8 and pin 19) on a low-impedance ground plane.
OSC1 (pin 9) and OSC2 (pin 10) traces must be short and surrounded by ground pour to avoid EMI. For crystals above 4 MHz, add a series resistor (typically 100 Ω to 1 kΩ) to limit drive level and prevent oscillator overdrive. Place the crystal within 10 mm of the MCU. Estimated: input capacitance of PIC16C66 is ~20 pF, requiring crystal load capacitance matching per crystal vendor datasheet.
Compliance Information
Lead-free and RoHS-compliant per Microchip product page. Not AEC-Q100 qualified (non-automotive grade); industrial or extended temperature variants available separately. Original datasheet publication date 1997-03-05.
