PIC16C66T-20I/SO - 8-Bit 20MHz MCU 14KB OTP 28-SOIC | Microchip
MPN: PIC16C66T-20I/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $12.45 | $12.45 |
| 10 | $11.2 | $112.00 |
| 100 | $9.95 | $995.00 |
| 500 | $8.5 | $4,250.00 |
| 1,000 | $7.25 | $7,250.00 |
PIC16C66T-20I/SO Overview
A microcontroller (MCU) is a single-chip computer containing a CPU core, program memory, working RAM, and programmable I/O peripherals. The PIC16C66 belongs to Microchip's mid-range PIC family, which uses a Harvard RISC architecture with 35 single-word instructions and a 14-bit program word. In the broader taxonomy, MCUs sit within semiconductors -> microcontrollers -> 8-bit microcontrollers -> PIC16CXX family -> PIC16C6X sub-family. Most instructions execute in a single 200 ns instruction cycle at 20 MHz, while program branches take two cycles, yielding deterministic timing suitable for embedded control.
Key features of the PIC16C66T-20I/SO include three timer/counter modules (Timer0, Timer1, and Timer2), a 5-channel 8-bit ADC, an analog comparator, a capture/compare/PWM (CCP) module, and a watchdog timer with its own on-chip RC oscillator. The device operates from 4.5V to 5.5V, has 22 I/O lines capable of sinking up to 25 mA for direct LED drive, and supports in-circuit serial programming (ICSP) through RB6/RB7.
The PIC16C66 architecture combines a RISC CPU with a unified 14-bit instruction word, allowing efficient code density and predictable interrupt latency. Its OTP program memory is programmed once at production and cannot be erased, making the part ideal for mature, high-volume, cost-sensitive products where firmware is frozen. Per Microchip's pin and code compatibility chart, the PIC16C66 is pin-compatible with other members of the PIC16C6X family in the 28-pin SPDIP/SOIC package.
Typical applications include industrial control subsystems, appliance controllers, sensor interfaces, automotive body electronics (non-safety), instrumentation front-ends, and consumer device main boards. Industrial automation is a strong fit thanks to the 22 strong I/O lines, three serial interfaces, and -40C to +85C operating range.
When designing with this part, ensure that in-circuit programming lines (RB6/RB7) are accessible and that decoupling is placed within a few millimetres of VDD. Choose the PIC16F66 instead if you need Flash memory and in-field reprogrammability; the PIC16C66 OTP is final.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes for the PIC16C66T-20I/SO not found in the manufacturer datasheet alone.
Drop-in alternatives for PIC16C66T-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 PIC16C66T-20I/SO (same form factor and footprint) — differing in Package, ADC, Family, Watchdog Timer, Timers.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C66-20I/SO
✅ Drop-In✓ In Stock
$6.42 / Unit
View Datasheet →PIC16C66T-20/SO
✅ Drop-In✓ In Stock
$8.2 / Unit
View Datasheet →PIC16C66T-10/SO
✅ Drop-In✓ In Stock
$5.2 / Unit
View Datasheet →PIC16C66T-10E/SO
✅ Drop-In✓ In Stock
$5.8 / Unit
View Datasheet →PIC16C66-04I/SO
✅ Drop-In✓ In Stock
$5.1 / Unit
View Datasheet →PIC16F877A-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C66T-20I/SO Maximum Ratings & Electrical Characteristics
| Manufacturer | Microchip Technology |
| Series | PIC16C6X |
| Family | PIC® 16C |
| Core Processor | 8-bit RISC PIC |
| Core Size | 8-Bit |
| Maximum Clock Speed | 20 MHz |
| Instruction Cycle Time | 200 ns (single-cycle) |
| Program Memory Type | OTP (One-Time Programmable) EPROM |
| Program Memory Size | 14 KB (8K x 14 words) |
| RAM Size | 368 bytes |
| Number of I/O Pins | 22 |
| Supply Voltage Range | 4.5 V to 5.5 V |
| Operating Temperature Range | -40C to +85C (Industrial) |
| Package | 28-pin SOIC (SO), 7.50 mm body width |
| Mounting Type | Surface Mount |
| Connectivity | I2C (MSSP), SPI, UART/USART |
| ADC | 5-channel x 8-bit |
| Timers | 3 (Timer0, Timer1, Timer2) |
| PWM Modules | 1 (CCP) |
| Analog Comparator | Yes (1) |
| Watchdog Timer | Yes (with own RC oscillator) |
| In-Circuit Programming | ICSP via RB6/RB7 |
| I/O Sink/Source Current | 25 mA per pin |
| RoHS Status | Compliant |
| Packaging Form | Tape & Reel (T suffix) |
PIC16C66T-20I/SO 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/VREF- — PORTA bit 2 / analog input 2 / ADC VREF- |
| Pin 5 | RA3/AN3/VREF+ — PORTA bit 3 / analog input 3 / ADC VREF+ |
| 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 | RE0/RD — PORTE bit 0 / read control (parallel slave port) |
| Pin 9 | OSC1/CLKIN — Oscillator input / external clock input |
| Pin 10 | OSC2/CLKOUT — Oscillator output / clock out |
| Pin 11 | RC0/T1OSO/T1CKI — PORTC bit 0 / Timer1 oscillator output / Timer1 clock |
| Pin 12 | RC1/T1OSI/CCP2 — PORTC bit 1 / Timer1 oscillator input / CCP2 |
| Pin 13 | RC2/CCP1 — PORTC bit 2 / Capture-Compare-PWM 1 |
| Pin 14 | RC3/SCK/SCL — PORTC bit 3 / SPI clock / I2C clock |
| Pin 15 | RC4/SDI/SDA — PORTC bit 4 / SPI data in / I2C data |
| Pin 16 | RC5/SDO — PORTC bit 5 / SPI data out |
| Pin 17 | RC6/TX/CK — PORTC bit 6 / UART TX / UART clock |
| Pin 18 | RC7/RX/DT — PORTC bit 7 / UART RX / UART data |
| Pin 19 | VSS — Ground |
| Pin 20 | VDD — Positive supply (4.5V-5.5V) |
| 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/PGC — PORTB bit 6 / ICSP clock |
| Pin 28 | RB7/PGD — PORTB bit 7 / ICSP data |
Typical Applications
PIC16C66T-20I/SO is suitable for 6 applications: Industrial Control Subsystems, Appliance Controllers, Sensor Interface Front-Ends, Automotive Body Electronics (Non-Safety), Instrumentation and Metering, Consumer Device Main Boards.
Industrial Control Subsystems
The PIC16C66T-20I/SO fits industrial control subsystems where deterministic 8-bit RISC timing and a 5V industrial-grade MCU are required. Its 22 I/O lines each sink 25 mA, enough to drive relays, optocouplers, and indicator LEDs without external buffers. The 14 KB OTP memory holds substantial state machines for conveyor control, pump sequencing, and packaging machinery. Per Microchip's mid-range PIC reference design, the chip's three timers plus a CCP/PWM channel support closed-loop PID at modest sampling rates (about 1 kHz). Operating from -40C to +85C, it tolerates factory-floor temperatures, while ICSP over RB6/RB7 enables end-of-line calibration.
Recommended
Appliance Controllers
In white-goods and appliance controllers the PIC16C66T-20I/SO provides a frozen-firmware MCU core that resists field tampering, because OTP memory cannot be electronically read back. Its 5-channel 8-bit ADC reads thermistor, voltage, and current-sense inputs for motor control, while the CCP/PWM output drives TRIAC or MOSFET gates for heater regulation or universal-motor speed control. UART enables communication with an HMI or display board, and the -40C to +85C industrial grade handles under-cabinet heat. Cost-conscious appliance OEMs value the OTP form factor because shipping programmed parts at scale keeps per-unit cost low.
Recommended
Sensor Interface Front-Ends
The PIC16C66T-20I/SO is well suited to sensor-interface front ends requiring UART or SPI delivery to a host processor. Its 8-bit ADC samples up to five analog channels fast enough for most thermistor, photocell, and strain-gauge signals, and the I2C/SPI/UART trio allows flexible host integration. Running at 20 MHz with 200 ns instruction cycles gives ample headroom for digital filtering and linearization in firmware. The 368-byte RAM is small but enough for moving-average filters and lookup tables, while 14 KB OTP accommodates calibration coefficients. Industrial-grade operation supports outdoor enclosures.
Recommended
Automotive Body Electronics (Non-Safety)
The PIC16C66T-20I/SO appears in non-safety automotive body electronics such as HVAC blend-door controllers, mirror adjusters, and seat-position modules. The 22 strong I/O lines interface directly with H-bridge drivers and lamp loads, while UART or LIN-like bit-banged comms connect to the body controller. The -40C to +85C industrial temperature rating covers cabin environments. Because the part is OTP, code is finalized at production - appropriate for high-volume, long-lifecycle vehicle programs where firmware is frozen. For safety-critical functions such as airbags or ABS, use an AEC-Q100-qualified MCU instead.
Recommended
Instrumentation and Metering
The PIC16C66T-20I/SO drives low-cost digital panel meters, handheld multimeters, and process-loop indicators. Its 8-bit ADC combined with averaging firmware gives usable 10-11 bit effective resolution for current/voltage display, and the 22 I/O lines drive multiplexed LCD segments via external CD4056 or HT1621 drivers. The single CCP/PWM channel can synthesize a 4-20 mA loop output. UART reports data to a host PLC or logging PC. Industrial-grade -40C to +85C operation supports outdoor or factory-cabinet installations.
Recommended
Consumer Device Main Boards
The PIC16C66T-20I/SO serves as the main controller on consumer devices such as washing-machine sub-boards, dishwasher UI panels, and microwave oven controllers. Its 14 KB OTP stores the entire user interface state machine and timing logic. The 5-channel ADC monitors keypad, weight sensor (for washing machines), and humidity sensor. UART communicates with the display board, while the PWM channel drives a buzzer for audible feedback. Because the part is OTP and tape-and-reel packaged, it is optimized for high-volume SMT assembly lines where per-unit cost matters.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C66T-20I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C66-20I/SO | PIC16C66T-20/SO | PIC16C66T-10/SO | PIC16C66-04I/SO | PIC16F877A-I/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-SOIC | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same |
| Program Memory Type | OTP (14 KB) | OTP (14 KB) | OTP (14 KB) | OTP (14 KB) | OTP (14 KB) | Flash (14 KB) |
| Maximum Clock Speed | 20 MHz | 20 MHz | 20 MHz | 10 MHz | 4 MHz | 20 MHz |
| RAM Size | 368 bytes | 368 bytes | 368 bytes | 368 bytes | 368 bytes | 368 bytes |
| Number of I/O Pins | 22 | 22 | 22 | 22 | 22 | 33 |
| Operating Temperature Range | -40C to +85C (Industrial) | -40C to +85C | 0C to +70C | 0C to +70C | -40C to +85C | -40C to +85C |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 2.0 V to 5.5 V |
Key Differentiators
- Largest OTP memory in the 28-pin PIC16C6X family (vs PIC16C63T-20I/SO)
- Industrial -40C to +85C temperature range (vs PIC16C66T-20/SO)
- 22 high-current I/O pins with 25 mA sink/source (vs PIC16C642T-20E/SO)
Design Notes
Decouple VDD (pin 20) with a 100 nF ceramic capacitor placed within 5 mm of the pin, and add a bulk 10 uF tantalum or aluminium electrolytic near the chip. The PIC16C66 draws up to about 30 mA at 20 MHz in active mode; in standby (sleep) the current drops to microamps, useful for battery-backed instrumentation.
Place the quartz crystal or resonator within a few millimetres of OSC1 and OSC2 (pins 9-10) and route the traces symmetrically. Keep high-speed switching lines (CCP1, SPI SCK) away from the oscillator traces to avoid frequency pulling. MCLR/VPP (pin 1) needs a 10 kohm pull-up to VDD unless the in-circuit debugger drives it; add a 100 nF decoupling directly on MCLR when ICSP is in use.
Do not exceed VDD of 5.5V; OTP devices have no on-chip regulator. Brown-out is enabled by default after programming but must be configured in the configuration word or the MCU may run erratically at low battery. RB6/RB7 serve as ICSP lines: ensure both are accessible at the programming header. Avoid leaving the watchdog timer enabled without a CLRWDT in the main loop, or the MCU will reset unexpectedly.
The PIC16C66's ADC has a recommended source impedance below 10 kohm for full 8-bit accuracy at the highest conversion rate; if your sensor is higher impedance, buffer it with an op-amp or add a 100 nF cap at the ADC pin. The analog reference inputs (RA2/VREF-, RA3/VREF+) must be bypassed with 100 nF each if used in non-default VDD-referenced mode.
Compliance Information
RoHS compliant per Microchip product page. Not AEC-Q100 qualified; not designed for automotive safety applications. Lead-free matte-tin finish.
