PIC16C66-04E/SO - 4MHz 8-Bit OTP MCU 14KB Flash 28-SOIC
MPN: PIC16C66-04E/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.32 | $9.32 |
| 10 | $8.45 | $84.50 |
| 100 | $7.38 | $738.00 |
| 500 | $6.51 | $3,255.00 |
| 1,000 | $5.72 | $5,720.00 |
PIC16C66-04E/SO Overview
An 8-bit microcontroller (MCU) is a small computer-on-a-chip that integrates a CPU, non-volatile program memory, working RAM, programmable I/O, and on-chip peripherals into a single device. The 8-bit PIC family uses a RISC-style Harvard architecture that executes one instruction per cycle (except branches, which take two), giving deterministic throughput at low clock rates. PIC16C66 sits in the mid-range PIC16 family hierarchy: PIC10/12/14/16 -> 8-bit PIC MCU -> microcontroller -> embedded IC -> semiconductor. These devices are typically used as dedicated control processors in cost-sensitive, low-power embedded designs.
Key features include 35 single-word instructions, 8-level hardware stack, four interrupt sources, power-on reset (POR), brown-out reset (BOR), watchdog timer (WDT), in-circuit serial programming (ICSP) capability, and a wide operating voltage range with commercial, industrial, and extended temperature grades. The PIC16C66-04E suffix denotes the 4 MHz speed grade and the "E" extended temperature range (-40C to +125C). The "-04E" speed-grade suffix indicates a 4 MHz maximum oscillator frequency; the same silicon is offered at -10 (10 MHz) and -20 (20 MHz) speed grades for higher-throughput designs.
Architecturally, the PIC16C66 uses an enhanced mid-range core with a 14-bit instruction word that gives more compact code than the baseline PIC16C5X (12-bit) family. It includes the Capture/Compare/PWM (CCP) module, an 8-channel 8-bit ADC, two analog comparators, and 256 bytes of EEPROM data storage in addition to the 368-byte RAM. These integrated peripherals eliminate the need for external ADC, comparator, and EEPROM chips in typical embedded applications.
Typical applications include industrial control, instrumentation, motor control, sensor interfacing, automotive body and chassis subsystems, white goods and appliance controls, and low-power remote or battery-backed sensor nodes. When designing with this device, allocate one of the two I/O ports (PORTA/PORTB) for analog functions if the ADC is used, since analog pins default to digital input and must be explicitly configured. Note that the "C" suffix denotes the OTP (EPROM) program-memory variant - for in-application re-programmability, consider the flash-based PIC16F66 in the same 28-SOIC footprint.
Drop-in alternatives for PIC16C66-04E/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 PIC16C66-04E/SO (same form factor and footprint) — differing in Timers, Package, Program Memory Type, Mounting Type, Program Memory Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C66-10/SO
✅ Drop-In✓ In Stock
$6.93 / Unit
View Datasheet →PIC16C66-20/SO
✅ Drop-In✓ In Stock
$5.45 / Unit
View Datasheet →PIC16C66T-04/SO
✅ Drop-In✓ In Stock
$5.5 / Unit
View Datasheet →PIC16C66-04I/SO
✅ Drop-In✓ In Stock
$5.1 / Unit
View Datasheet →PIC16F876-04I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16F66-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C66-04E/SO Maximum Ratings & Electrical Characteristics
| Manufacturer | Microchip Technology |
| Product Family | PIC16C6X (PIC® 16C) |
| Core | 8-bit PIC RISC |
| Program Memory Type | OTP (EPROM) |
| Program Memory Size | 14 KB (8K x 14 words) |
| RAM | 368 bytes |
| EEPROM | 256 bytes |
| Maximum Clock Frequency | 4 MHz |
| Instruction Cycle | 1 cycle (4 clock periods) |
| Supply Voltage Range | 4.0 V to 5.5 V (extended to 6.0 V per datasheet) |
| Operating Temperature Range | -40 C to +125 C (Extended, "E") |
| I/O Pins | 22 |
| Number of Pins | 28 |
| Package | 28-SOIC (0.295", 7.50 mm width) |
| Mounting Type | Surface Mount |
| Communication Interfaces | I2C, SPI, UART/USART |
| Peripherals | Brown-out Detect/Reset, POR, PWM, WDT |
| ADC | 8-bit, 8-channel |
| Timers | 16-bit x 1 + 8-bit x 1 + Watchdog |
| Instruction Set | 35 single-word instructions |
| Hardware Stack | 8 levels |
PIC16C66-04E/SO Pin Configuration
| Pin 1 | MCLR/VPP — Master clear (reset) input / programming voltage input |
| Pin 2 | RA0/AN0 — PORTA bit 0 / analog input 0 |
| Pin 3 | RA1/AN1 — PORTA bit 1 / analog input 1 |
| Pin 4 | RA2/AN2 — PORTA bit 2 / analog input 2 |
| Pin 5 | RA3/AN3/VREF — PORTA bit 3 / analog input 3 / ADC reference |
| Pin 6 | RA4/T0CKI — PORTA bit 4 / Timer0 clock input |
| Pin 7 | RA5/AN4/SS — PORTA bit 5 / analog input 4 / SSP slave select |
| Pin 8 | OSC1/CLKIN — Oscillator crystal input / external clock input |
| Pin 9 | OSC2/CLKOUT — Oscillator crystal output / clock output |
| Pin 10 | RC0/T1OSO/T1CKI — PORTC bit 0 / Timer1 oscillator output / Timer1 clock input |
| Pin 11 | RC1/T1OSI/CCP2 — PORTC bit 1 / Timer1 oscillator input / CCP2 |
| Pin 12 | RC2/CCP1 — PORTC bit 2 / CCP1 (PWM/capture/compare) |
| Pin 13 | RC3/SCK/SCL — PORTC bit 3 / SSP clock (SPI SCK or I2C SCL) |
| Pin 14 | RC4/SDI/SDA — PORTC bit 4 / SSP data in (SPI SDI) / I2C data (SDA) |
| Pin 15 | RC5/SDO — PORTC bit 5 / SSP data out (SPI SDO) |
| Pin 16 | RC6/TX/CK — PORTC bit 6 / USART TX / USART clock |
| Pin 17 | RC7/RX/DT — PORTC bit 7 / USART RX / USART data |
| Pin 18 | RB0/INT — PORTB bit 0 / external interrupt |
| Pin 19 | RB1 — PORTB bit 1 |
| Pin 20 | RB2 — PORTB bit 2 |
| Pin 21 | RB3/PGM — PORTB bit 3 / low-voltage programming |
| Pin 22 | RB4 — PORTB bit 4 |
| Pin 23 | RB5 — PORTB bit 5 |
| Pin 24 | RB6/PGC — PORTB bit 6 / ICSP clock |
| Pin 25 | RB7/PGD — PORTB bit 7 / ICSP data |
| Pin 26 | VSS — Ground reference |
| Pin 27 | VDD — Positive supply voltage |
| Pin 28 | NC — Not connected (per datasheet) |
Typical Applications
PIC16C66-04E/SO is suitable for 6 applications: Industrial Control Systems, White Goods and Appliance Controllers, Automotive Body and Chassis Modules, Sensor Interface and Data Acquisition, Motor Control (Stepper, DC, BLDC), User Interface / Display Controllers.
Industrial Control Systems
The PIC16C66-04E/SO is well suited to industrial control applications such as PLC I/O expanders, sensor signal conditioning front-ends, and discrete process controllers. Its 22 digital I/O pins comfortably handle multiple sensor inputs and actuator outputs, while the integrated 8-channel 8-bit ADC reads analog process variables directly without external converter chips. The 4 MHz instruction rate at 5V provides approximately 1 MIPS throughput, more than enough for slow closed-loop control loops at 10-100 ms update rates. Brown-out reset and watchdog timer protect against industrial power-supply transients and firmware lockups, while the extended -40C to +125C temperature grade ensures reliable operation in unheated enclosures or near motors.
Recommended
White Goods and Appliance Controllers
Washing machines, dishwashers, microwave ovens, and HVAC controls are classic PIC16C66-04E/SO applications because OTP EPROM provides the lowest per-unit cost at high volume and the firmware is locked once the design is qualified. The CCP/PWM module drives TRIACs or IGBTs for motor speed and heating-element control, while the USART interfaces to LED/VFD display drivers and the SSP links to EEPROM for user-setting memory. Power-on reset and brown-out reset ensure clean startup after mains interruptions, a critical reliability requirement for white goods.
Recommended
Automotive Body and Chassis Modules
Automotive body controllers, seat-position memory modules, mirror adjusters, and simple instrument clusters use the PIC16C66-04E/SO in its extended-temperature grade. The 22 I/O pins handle switch scanning, LED driving, and motor H-bridge control, while the ADC reads potentiometer positions for seat/mirror memory. The USART interfaces to other ECUs over LIN or K-Line transceivers, and the SSP connects to dashboard display drivers. Note that AEC-Q100 qualification is required for safety-relevant modules - for those applications choose the Q1/Q-graded equivalent.
Recommended
Sensor Interface and Data Acquisition
Portable data loggers, environmental monitors, and remote sensor nodes leverage the PIC16C66-04E/SO's integrated 8-channel 8-bit ADC and 22 digital I/O for multi-sensor reading without external glue logic. The PIC's low-power sleep modes combined with its 4 MHz operation enable battery-powered designs running from 2x AA cells with a boost converter. The 256-byte on-chip EEPROM stores calibration constants and logging parameters without external memory, while the USART or SSP uploads data to a host controller or radio module.
Recommended
Motor Control (Stepper, DC, BLDC)
Small stepper, brushed DC, and low-power BLDC motors in consumer pumps, fans, and small appliances are well served by the PIC16C66-04E/SO's PWM and timer resources. The CCP/PWM module generates variable duty-cycle drive signals to MOSFET gate drivers, while the 16-bit timer captures Hall-sensor feedback for closed-loop commutation. The 4 MHz clock at 5V is sufficient for low-RPM applications with PWM frequencies in the low kHz range, and brown-out reset protects the motor from low-voltage stalls that could damage windings.
Recommended
User Interface / Display Controllers
Front-panel controllers for test equipment, audio amplifiers, and industrial HMIs use the PIC16C66-04E/SO to scan keypads, drive LED or VFD displays, and communicate with the main system processor via SPI, I2C, or UART. The 22 I/O pins handle a 4x4 matrix keypad plus a multiplexed 7-segment or 14-segment display, with the USART serving as a debug or service port. Extended temperature rating allows deployment inside equipment enclosures that may run warm.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C66-04E/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C66-10/SO | PIC16C66-20/SO | PIC16F876-04I/SO | PIC16F66-I/SO |
|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-SOIC (0.295", 7.50 mm) | 28-SOIC (0.295", 7.50 mm) - same | 28-SOIC (0.295", 7.50 mm) - same | 28-SOIC (0.295", 7.50 mm) - same | 28-SOIC (0.295", 7.50 mm) - same |
| Maximum Clock Frequency | 4 MHz | 10 MHz (+150%) | 20 MHz (+400%) | 4 MHz (same) | 20 MHz (+400%) |
| Program Memory Type | OTP EPROM (14 KB) | OTP EPROM (14 KB) - same | OTP EPROM (14 KB) - same | Flash (14 KB) - re-programmable | Flash - re-programmable |
| RAM | 368 bytes | 368 bytes | 368 bytes | 368 bytes | 368 bytes |
| I/O Pins | 22 | 22 | 22 | 22 | 22 |
| Temperature Range | -40C to +125C (Extended) | depends on suffix (commercial/industrial/extended) | depends on suffix (commercial/industrial/extended) | -40C to +85C (Industrial) | -40C to +85C (Industrial) |
| ADC Resolution | 8-bit, 8-channel | 8-bit, 8-channel | 8-bit, 8-channel | 10-bit, 8-channel | 10-bit, 8-channel |
| Communication Interfaces | I2C, SPI, UART/USART | I2C, SPI, UART/USART | I2C, SPI, UART/USART | I2C, SPI, UART/USART | I2C, SPI, UART/USART |
| Field Reprogrammable | No (OTP) | No (OTP) | No (OTP) | Yes (Flash, ICSP) | Yes (Flash, ICSP) |
Key Differentiators
- Lowest-cost 28-SOIC 14KB 8-bit PIC with extended temperature grade (vs PIC16F876-04I/SO)
- Extended -40C to +125C operating temperature (vs PIC16C66-10/SO)
- Mature PIC16C6X peripheral set with proven long-term availability (vs PIC16C66-20/SO)
- Drop-in pin compatibility with modern flash-based PIC16F66 family (vs PIC16F66-I/SO)
Design Notes
Decouple VDD (pin 27) with a 100 nF ceramic capacitor placed within 5 mm of the pin and a bulk 10 uF tantalum or aluminum capacitor on the same 5 V rail. The PIC16C66 has a wide supply range (4.0 V to 6.0 V) but the ADC accuracy is only specified at 5 V +/- 10%; if you run on a 3.3 V rail the analog readings must be re-characterized. For brown-out-reset operation, ensure VDD rises monotonically above the BOR threshold (~4.0 V) within the device's start-up time window, otherwise the part may enter an indeterminate state.
Route the oscillator traces (OSC1 pin 8, OSC2 pin 9) symmetrically with the crystal as close as possible to the MCU and guard them with a ground ring. Place MCLR (pin 1) decoupling (typically 10-100 nF to VDD via the pull-up resistor) directly at the pin, not at the connector. Keep analog traces (RA0-RA5) short and away from digital switching signals (especially RC2 PWM output, pin 12) to preserve ADC accuracy. Provide a solid ground plane under the entire 28-SOIC footprint for thermal dissipation and EMI suppression.
The "-04" speed grade suffix denotes a 4 MHz maximum oscillator; using a 10 MHz or 20 MHz crystal will cause the chip to behave erratically or fail to start the oscillator. The PORTA analog pins (RA0-RA5) default to ANALOG input on reset and must be explicitly configured as digital I/O by clearing the corresponding bits in the ADCON1 register before being used for digital signals. The PIC16C66 has only 22 digital I/O despite being in a 28-pin package - the missing 6 pins are VDD, VSS, MCLR, OSC1, OSC2, and one no-connect, do not assume all 28 pins are general-purpose I/O.
Estimated: At 4 MHz clock and 5 V supply, the PIC16C66 typical operating current is approximately 2-5 mA active and 1 uA typical sleep (per datasheet). For a typical SOIC-28 design with theta-JA around 80 C/W, this 10-25 mW dissipation produces a junction temperature rise of only 1-2 C above ambient - thermal management is generally not required. However, in high-ambient environments (>85 C) ensure the extended-temperature ("E") grade variant is used, and consider airflow if the part is mounted near a heat source.
Compliance Information
RoHS and lead-free status not explicitly stated in the verified web data; the standard industrial PIC16C66 family is generally available in both lead and lead-free versions depending on date code. AEC-Q100 is not_applicable for the standard -04E/SO; automotive safety-relevant designs should select an AEC-Q100-qualified variant. The Microchip PIC16C66 family is covered by Microchip's standard conflict-minerals compliance program.
