PIC16C66-20I/SO - 8-Bit 20MHz OTP MCU 14KB | Microchip
MPN: PIC16C66-20I/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.77 | $9.77 |
| 10 | $9.12 | $91.20 |
| 100 | $8.04 | $804.00 |
| 500 | $7.18 | $3,590.00 |
| 1,000 | $6.42 | $6,420.00 |
PIC16C66-20I/SO Overview
What is a PIC16C microcontroller? The PIC16C family is a classic mid-range 8-bit RISC microcontroller platform from Microchip, characterized by 35 single-word instructions, single-cycle execution (except program branches), Harvard architecture with separate program and data buses, and a wide operating voltage range. The OTP (One-Time Programmable) variant stores firmware in EPROM cells, providing one-time field programming through an external programmer such as the MPLAB PM3 - this makes PIC16C parts particularly suited for production runs where cost is critical but the firmware is finalized.
Key features include DC to 20 MHz clock input, 200 ns instruction cycle, 8 channels of 8-bit ADC, two 8-bit timers plus one 16-bit timer, USART with 9-bit address masking, 8-level deep hardware stack, and on-chip watchdog timer with its own RC oscillator. The brown-out reset and power-on reset circuits protect against unstable supply conditions.
The PIC16C66 uses a 14-bit instruction word Harvard architecture with separate code and data paths, enabling single-cycle instruction execution for most opcodes. The integrated analog and digital peripherals share I/O pins through programmable multiplexers, and interrupts are vectored with priority support. Industrial-grade -40C to +85C operating range and OTP program memory make this device best for cost-optimized production runs.
Typical applications include industrial control systems, motor control, sensor interface nodes, embedded instrumentation, simple HMI panels, and white-goods appliances. The wide peripheral set allows designers to consolidate multiple discrete functions onto a single MCU.
When designing with the PIC16C66, ensure programmer compatibility before committing to OTP for new designs - many modern designs prefer PIC16F flash variants for in-circuit reprogrammability. The pin-compatible PIC16F876 offers 14KB flash memory and is recommended for new development.
This page synthesizes distributor pricing, drop-in compatible alternatives from the same Microchip PIC16C family, and practical design guidance not found in the standalone datasheet.
Drop-in alternatives for PIC16C66-20I/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 PIC16C66-20I/SO (same form factor and footprint) — differing in Package, ADC, Timers, Family, Program Memory Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C66-04I/SO
✅ Drop-In✓ In Stock
$5.1 / Unit
View Datasheet →PIC16C662-04I/P
✅ Drop-In✓ In Stock
$5.07 / Unit
View Datasheet →PIC16C66-20I/SO Maximum Ratings & Electrical Characteristics
| Manufacturer | Microchip Technology |
| Series | PIC 16C |
| Core Processor | PIC |
| Core Size | 8-Bit |
| Maximum Clock Frequency | 20 MHz |
| Instruction Cycle | 200 ns |
| Program Memory Size | 14 KB (8K x 14) OTP |
| RAM Size | 368 B |
| Number of I/O Pins | 22 |
| ADC | 8-channel, 8-bit |
| Timers | 2 x 8-bit, 1 x 16-bit |
| Communication Interfaces | USART, MSSP (SPI/I2C) |
| Package | 28-SOIC (0.295 inch / 7.50 mm body width) |
| Mounting Type | Surface Mount |
| Operating Temperature Range | -40C to +85C (Industrial) |
| Operating Voltage Range | 3.0 V to 5.5 V |
| Program Memory Type | OTP (One-Time Programmable EPROM) |
| Watchdog Timer | Yes, with dedicated RC oscillator |
| Brown-out Reset / Power-on Reset | Yes |
| RoHS Status | Compliant |
PIC16C66-20I/SO Pin Configuration
| Pin 1 | MCLR/VPP — Master Clear (reset) input / programming voltage |
| Pin 2 | RA0/AN0 — Port A bit 0 / ADC channel 0 |
| Pin 3 | RA1/AN1 — Port A bit 1 / ADC channel 1 |
| Pin 4 | RA2/AN2 — Port A bit 2 / ADC channel 2 |
| Pin 5 | RA3/AN3/VREF — Port A bit 3 / ADC channel 3 / voltage reference |
| Pin 6 | RA4/T0CKI — Port A bit 4 / Timer 0 clock input |
| Pin 7 | RA5/AN4/SS — Port A bit 5 / ADC channel 4 / SPI slave select |
| Pin 8 | OSC1/CLKIN — Oscillator input / external clock in |
| Pin 9 | OSC2/CLKOUT — Oscillator output / clock out |
| Pin 10 | RC0/T1OSO/T1CKI — Port C bit 0 / Timer 1 oscillator out / clock in |
| Pin 11 | RC1/T1OSI/CCP2 — Port C bit 1 / Timer 1 oscillator in / CCP2 |
| Pin 12 | RC2/CCP1 — Port C bit 2 / Capture/Compare/PWM 1 |
| Pin 13 | RC3/SCK/SCL — Port C bit 3 / SPI clock / I2C clock |
| Pin 14 | RC4/SDI/SDA — Port C bit 4 / SPI data in / I2C data |
| Pin 15 | RC5/SDO — Port C bit 5 / SPI data out |
| Pin 16 | RC6/TX/CK — Port C bit 6 / USART TX / clock |
| Pin 17 | RC7/RX/DT — Port C bit 7 / USART RX / data |
| Pin 18 | RB0/INT — Port B bit 0 / external interrupt |
| Pin 19 | RB1 — Port B bit 1 |
| Pin 20 | RB2 — Port B bit 2 |
| Pin 21 | RB3 — Port B bit 3 |
| Pin 22 | RB4 — Port B bit 4 |
| Pin 23 | RB5 — Port B bit 5 |
| Pin 24 | RB6/PGC — Port B bit 6 / ICSP clock |
| Pin 25 | RB7/PGD — Port B bit 7 / ICSP data |
| Pin 26 | VSS — Ground |
| Pin 27 | VDD — Positive supply (3.0 V to 5.5 V) |
| Pin 28 | RE2/CS — Port E bit 2 / Chip Select (analog or digital) |
Typical Applications
PIC16C66-20I/SO is suitable for 6 applications: Industrial Control Systems, Sensor Interface Nodes, Motor Control (BLDC and Stepper), Embedded Instrumentation, White Goods and Appliances, Simple HMI Panels.
Industrial Control Systems
The PIC16C66-20I/SO fits industrial control systems where its 22 I/O lines, 14 KB OTP program memory, and -40C to +85C industrial operating range meet factory automation requirements. Its 8-channel 8-bit ADC reads analog sensors such as temperature probes, pressure transducers, and 4-20 mA loop inputs after external signal conditioning. The MSSP module supports I2C sensor expansion to EEPROM or external ADC, while the USART provides RS-232 or RS-485 connectivity to supervisory controllers. The 20 MHz clock and 200 ns instruction cycle handle PID loops at moderate update rates (1-5 kHz) for motor speed control and process variable regulation. Brown-out reset and watchdog timer protect against industrial supply disturbances. The 28-SOIC package withstands standard SMT reflow profiles, and the industrial temperature grade ensures reliable operation near motors and power electronics.
Recommended
Sensor Interface Nodes
The PIC16C66-20I/SO serves as a sensor interface node in distributed measurement systems, where its integrated 8-bit ADC samples 8 analog channels and forwards digital readings through the USART. For simple temperature, humidity, and pressure sensor hubs, the 368-byte RAM buffers calibration coefficients and recent readings, while 14 KB OTP stores the conversion routines. The 20 MHz clock supports averaging algorithms and digital filtering without throughput penalty. I2C via MSSP reads additional digital sensors like accelerometers or ambient light sensors on a shared bus. The 3.0-5.5 V supply range allows direct battery operation or 5 V rail powering. Industrial temperature grade suits outdoor enclosures and HVAC duct installations. The 28-SOIC package provides mechanical robustness for vibration-prone mounting in machine cabinets.
Recommended
Motor Control (BLDC and Stepper)
The PIC16C66-20I/SO controls small brushless DC and stepper motors using its 16-bit timer for PWM generation and the capture/compare/PWM peripheral for precise phase timing. The 20 MHz instruction rate supports commutation loops up to 50 kHz for motors up to several hundred watts. Its 22 I/O lines drive gate driver enable signals, sense motor current via the ADC, and read Hall-effect sensor feedback for rotor position. The 28-SOIC package suits integration on motor control PCBs alongside gate drivers and FET bridges. The industrial temperature grade handles under-hood automotive auxiliary pumps or appliance motor enclosures. For higher-current applications the MCU pairs with external gate drivers such as the IR2104 to drive MOSFET half-bridges.
Recommended
Embedded Instrumentation
The PIC16C66-20I/SO integrates measurement and user-interface functions in portable test instruments where its USART streams data to a host PC and the MSSP drives an I2C LCD display. The 8-channel ADC reads measurement inputs from sensors or external signal conditioning circuits, and 368 bytes of RAM store measurement buffers and conversion tables. The 14 KB OTP program memory holds instrument calibration routines, lookup tables, and serial command interpreters. The 28-SOIC compact body fits hand-held enclosures while leaving room for batteries and connectors. Industrial temperature rating supports field use in varied environments, and the brown-out reset prevents corruption during battery swaps. The 5 V operating range suits USB-powered instruments and bench-top supplies.
Recommended
White Goods and Appliances
The PIC16C66-20I/SO powers washing machines, dishwashers, and microwave ovens where its integrated peripherals replace multiple discrete timers and counters. The 22 I/O lines drive relays, triac optocouplers, LED indicators, and keypads for user interface. The 8-bit ADC reads water level sensors, thermistors for temperature control, and motor current feedback. The 20 MHz clock runs the appliance state machine, timing routines, and PWM output for motor speed control. OTP program memory locks firmware at production to prevent unauthorized modification. The 28-SOIC package is hand-solderable for prototype builds and mass-producible via standard SMT lines. The -40C to +85C industrial range covers the appliance operating envelope including under-counter and unheated garage installations.
Recommended
Simple HMI Panels
The PIC16C66-20I/SO drives simple human-machine interface panels with 4x4 keypads, 7-segment LED displays, and rotary encoders via its 22 I/O lines. The MSSP module interfaces to SPI-driven character LCDs or LED driver ICs for extended visual output, while the USART connects to a host controller for command and status exchange. The 14 KB OTP memory stores menu structures, debounce routines, and display font tables. The 8-channel ADC reads backlight brightness sensors and analog knob positions. The 20 MHz instruction cycle supports rapid key scanning and display refresh without flicker. The 28-SOIC package keeps the panel PCB compact, and the industrial temperature grade ensures reliable operation in factory and vehicle dashboards.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C66-20I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C66-04I/SO | PIC16C662-04I/P |
|---|---|---|---|
| Package | 28-SOIC | 28-SOIC (same) | 28-SOIC (same) |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology |
| Maximum Clock Frequency | 20 MHz | 4 MHz (-80%) | 4 MHz (-80%) |
| Program Memory Type | 14 KB OTP | 14 KB OTP (same) | 14 KB OTP (same) |
| RAM Size | 368 B | 368 B (same) | 176 B (-52%) |
| I/O Pins | 22 | 22 (same) | 22 (same) |
| ADC | 8-ch, 8-bit | 8-ch, 8-bit (same) | 8-ch, 8-bit (same) |
| LCD Driver | No | No | Yes (up to 4 commons) |
| Unit Price (qty 1) | $9.77 | $8.30 (approx, -15%) | $9.50 (approx, similar) |
Key Differentiators
- 20 MHz maximum clock vs 4 MHz in same-package PIC16C66-04 variant (vs PIC16C66-04I/SO)
- Industrial temperature range -40C to +85C vs commercial-grade 0C to +70C (vs PIC16C66-20/SO)
- Compact 28-SOIC vs 40-pin DIP alternative (vs PIC16C66-20/P)
Design Notes
The PIC16C66-20I/SO operates from 3.0 V to 5.5 V with a brown-out reset voltage of approximately 4.0 V (factory-set). Place a 100 nF decoupling capacitor within 5 mm of VDD (pin 27) and a 10 uF bulk capacitor on the supply rail. Estimated: total quiescent current draw at 20 MHz with all peripherals off is approximately 2 mA typical; with ADC and USART active, expect 5-8 mA. Plan supply design accordingly - USB or 5 V linear regulator sources provide adequate current for industrial designs.
Keep the crystal or resonator within 10 mm of OSC1 (pin 8) and OSC2 (pin 9). Provide a ground guard ring around the oscillator components to reduce EMI coupling into adjacent analog inputs. The MCLR/VPP pin (pin 1) requires a 10 kohm pull-up to VDD; do not leave it floating. For ICSP programming, expose the PGC (RB6, pin 24) and PGD (RB7, pin 25) pins to a header or test pad - they are dual-purpose with port B and cannot be repurposed without losing in-circuit programming access.
The PIC16C66 contains OTP EPROM, so firmware bugs cannot be fixed after programming. Estimated: prototype with the PIC16F76-I/SO (pin-compatible flash variant) first, then convert to the PIC16C66-20I/SO for production. Configuration bits must be set during programming to select oscillator mode, watchdog enable, and code protection; verify with the MPLAB PM3 before committing the lot. Do not exceed the maximum source/sink current of 25 mA per pin or 200 mA per port.
Compliance Information
RoHS and REACH compliant per Microchip product page; lead-free finish confirmed. Not AEC-Q100 qualified - PIC16C family is not designed for automotive safety-critical use cases.
