PIC16C66T-04E/SO - 8-Bit 4MHz 14KB OTP MCU, 28-SOIC | Microchip
MPN: PIC16C66T-04E/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $11.5 | $11.50 |
| 10 | $10.35 | $103.50 |
| 100 | $9.2 | $920.00 |
| 500 | $8.05 | $4,025.00 |
| 1,000 | $7.2 | $7,200.00 |
PIC16C66T-04E/SO Overview
A PIC microcontroller is a Harvard-architecture, RISC-based 8-bit device that executes one instruction per cycle (except program branches, which take two), giving deterministic timing and very low interrupt latency. The PIC16C6X sub-family in particular introduced an enhanced instruction set, 14-bit wide instruction word, 8-level hardware stack, and on-chip peripherals such as capture/compare/PWM and an analog comparator. These MCUs sit within the broader power-management/embedded-control hierarchy: microcontroller -> embedded processor -> digital IC -> semiconductor, and are programmed in C or assembly through Microchip's MPLAB X toolchain.
Key features of the PIC16C66T-04E/SO include a 33 I/O pin count (22 strong I/O plus supporting pins), a wide 4.5 V to 5.5 V supply range, automotive temperature grade ('E' suffix indicates -40 °C to +125 °C extended), 200 ns single-cycle instruction time at 20 MHz, and CMOS low-power operation. It is also built on Microchip's mature OTP process, which trades in-system reprogrammability for very low per-unit cost in volume production runs.
The on-chip peripheral set includes three timers, a USART, a synchronous serial port (SSP) supporting SPI and I²C, an 8-bit analog-to-digital converter with up to 8 channels, and a capture/compare/PWM module. This integration lets one PIC16C66 replace a discrete MCU plus several support ICs, simplifying PCB layout and BOM cost.
Typical applications include industrial control logic boards, automotive body and chassis ECUs, appliance motor control, and legacy embedded subsystems designed before flash-based PICs (PIC16F family) became standard. Its OTP memory makes it especially suited for high-volume, code-stable products where firmware never needs field updates.
Designers should note that the '04' speed grade is 4 MHz (versus the '10' and '20' variants that scale to 20 MHz) and the 'E' temperature grade is the -40 °C to +125 °C extended range, not the -40 °C to +85 °C industrial range (which would be 'I').
This page consolidates distributor pricing, pin-compatible drop-in alternatives in the PIC16C66 family, and design notes distilled from the manufacturer datasheet and Microchip cross-reference database - information not aggregated on any single distributor product page.
Drop-in alternatives for PIC16C66T-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 PIC16C66T-04E/SO (same form factor and footprint) — differing in Core Architecture, Family, Number of I/O Pins, Operating Temperature, Package Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C66-04E/SO
✅ Drop-In✓ In Stock
$5.72 / Unit
View Datasheet →PIC16C66T-04/SO
✅ Drop-In✓ In Stock
$5.5 / Unit
View Datasheet →PIC16C66T-04I/SO
✅ Drop-In✓ In Stock
$3.7 / Unit
View Datasheet →PIC16C66-04/SO
✅ Drop-In✓ In Stock
$2.65 / Unit
View Datasheet →PIC16C66-04I/SO
✅ Drop-In✓ In Stock
$5.1 / Unit
View Datasheet →PIC16C642T-04E/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C66T-04E/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC RISC (Harvard) |
| Family | PIC® 16C Series, PIC16C66 sub-family |
| Program Memory Type | OTP (One-Time Programmable) |
| Program Memory Size | 14 KB (8K x 14 words) |
| Data RAM | 368 bytes |
| Maximum Clock Speed | 4 MHz (04 speed grade) |
| Instruction Cycle Time | 200 ns at 20 MHz equivalent clock |
| Supply Voltage (Vdd) | 4.5 V to 5.5 V |
| Number of I/O Pins | 22 strong I/O (33 I/O ports total) |
| Package Type | 28-SOIC (7.50 mm width, wide-body) |
| Temperature Grade | Extended (E): -40 °C to +125 °C |
| Process Technology | CMOS |
| Mounting Type | Surface Mount |
PIC16C66T-04E/SO Pin Configuration
| Pin 1 | MCLR — Master Clear (Reset) input, active low |
| 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 / Timer 0 clock input (open-drain) |
| Pin 7 | RA5/SS/AN4 — PORTA bit 5 / Slave Select for SSP / Analog input 4 |
| Pin 8 | Vss — Ground reference |
| Pin 9 | OSC1/CLKIN — Oscillator crystal input / external clock in |
| Pin 10 | OSC2/CLKOUT — Oscillator crystal output / clock out (Fosc/4) |
| Pin 11 | RC0/T1OSO/T1CKI — PORTC bit 0 / Timer 1 oscillator output / Timer 1 clock input |
| Pin 12 | RC1/T1OSI/CCP2 — PORTC bit 1 / Timer 1 oscillator input / CCP2 I/O |
| Pin 13 | RC2/CCP1 — PORTC bit 2 / Capture Compare PWM 1 |
| Pin 14 | RC3/SCK/SCL — PORTC bit 3 / SSP clock (SPI SCK / I2C SCL) |
| Pin 15 | RC4/SDI/SDA — PORTC bit 4 / SSP data in (SPI SDI / I2C SDA) |
| Pin 16 | RC5/SDO — PORTC bit 5 / SSP data out (SPI SDO) |
| Pin 17 | RC6/TX/CK — PORTC bit 6 / USART TX / USART clock |
| Pin 18 | RC7/RX/DT — PORTC bit 7 / USART RX / USART data |
| Pin 19 | Vss — Ground reference (second Vss pin) |
| Pin 20 | Vdd — Positive supply (4.5 V to 5.5 V) |
| Pin 21 | RB0/INT — PORTB bit 0 / External interrupt input |
| 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
PIC16C66T-04E/SO is suitable for 7 applications: Industrial Control Logic Boards, Automotive Body and Chassis ECUs, Appliance Motor Control, Legacy Embedded Subsystem Replacement, Instrumentation Front Panels, Consumer White Goods Control Boards, Industrial Sensor Signal Conditioning.
Industrial Control Logic Boards
The PIC16C66T-04E/SO is well-suited to industrial control logic boards where deterministic real-time response is more important than raw throughput. Its 4 MIPS throughput, 200 ns single-cycle instruction time, and 8-level hardware stack let it run PID loops, debounce inputs, and drive relays at kHz rates without an RTOS. The PIC16C66's 22 I/O pins accept 5 V CMOS/TTL logic directly from industrial sensors and the extended -40 °C to +125 °C temperature grade (E-suffix) survives factory-floor enclosure conditions. The on-chip 8-channel 8-bit ADC reads 4-20 mA current loop or 0-10 V process signals through external scaling resistors. Typical use is a standalone sequencer for a conveyor or packaging line, replacing discrete TTL/MSI logic with one surface-mount SOIC.
Recommended
Automotive Body and Chassis ECUs
The PIC16C66T-04E/SO is widely deployed in automotive body and chassis ECUs - seat controllers, mirror adjusters, wiper logic, and lighting drivers - where its extended -40 °C to +125 °C temperature grade (E-suffix) handles the cabin-to-engine-bay ambient range. The PIC16C6X core's 200 ns deterministic interrupt latency meets the timing margin requirements for simple PWM motor control and switch debouncing, and the 5 V supply tolerates load-dump transients typical in 12 V automotive power nets. With 14 KB OTP the device holds body-control firmware comfortably (lighting state machines, mirror position memory). Modern designs have migrated to PIC16F or dsPIC33, but the C66 family remains in production for long-life vehicle platforms.
Recommended
Appliance Motor Control
Major appliances (washing machines, dishwashers, refrigerators) historically relied on PIC16C66T-04E/SO for cost-sensitive motor control: the on-chip Capture/Compare/PWM (CCP) module generates brushed-DC or universal-motor PWM at kHz rates, while the 8-bit ADC reads motor current for soft-start and stall detection. The 5 V supply simplifies interface to legacy triac driver optocouplers (MOC3021) and zero-cross detectors. The 14 KB OTP program memory stores state-machine firmware for wash cycles, fault codes, and user interface menus, while 368 bytes of RAM handles run-time variables and EEPROM emulation. The wide-body 28-SOIC package is hand-solderable for low-volume repair depots.
Recommended
Legacy Embedded Subsystem Replacement
Many industrial OEMs still ship products designed around the PIC16C66T-04E/SO in the late 1990s, and the part remains the only legitimate long-term source for repair/replacement of those field-deployed boards. The PIC16C66 is mature, well-documented, and electrically stable across temperature, and Microchip continues limited production runs for lifecycle-support contracts. Designers of new products should choose the flash-based PIC16F876A-I/SO or PIC18F25K22-I/SO instead (lower cost, more features, broader supply); the PIC16C66T-04E/SO serves primarily as a form-fit-function preservation part for legacy designs.
Recommended
Instrumentation Front Panels
The PIC16C66T-04E/SO is found in older laboratory and process instrumentation front panels - multimeters, signal sources, chart recorders - where the USART and synchronous serial port interface to character LCDs, keypads, and isolated RS-485 transceivers. The 5 V supply matches standard alphanumeric LCD modules (HD44780), and the 22 I/O pins directly drive a 4x4 keypad matrix and up to 8 status LEDs with no external decoding. The 14 KB OTP is sufficient to host menu-driven user interfaces, calibration routines, and Modbus RTU slave handlers. The CMOS low-power design lets battery-powered handheld instruments operate for hundreds of hours on a 9 V cell when the MCU spends most of its time in sleep mode.
Recommended
Consumer White Goods Control Boards
Coffee machines, microwave ovens, rice cookers, and air purifiers built in the 2000s frequently used the PIC16C66T-04E/SO as the single-chip controller: reading membrane keypads, driving 7-segment LED displays, switching triacs for heaters, and modulating fans via the CCP/PWM module. Its OTP memory keeps BOM cost low (no programming infrastructure needed for end-of-line), and its CMOS operation pulls only a few mA active, well within wall-adapter power budgets. Extended temperature grade is a bonus for kitchen environments where ambient can reach 50-60 °C. Retrofit and aftermarket repair boards continue to source this part for the installed base.
Recommended
Industrial Sensor Signal Conditioning
In distributed sensor networks, the PIC16C66T-04E/SO acts as a smart sensor node: reading strain gauges, thermistors, or pressure transducers through the 8-bit ADC, linearizing the result in firmware, and outputting either a 4-20 mA current loop or a digital RS-485 Modbus stream via the USART. The PIC16C66's 22 I/O and CCP modules drive a local status LED and energize an alarm relay when out-of-range conditions occur. Industrial temperature grade (E-suffix -40 to +125 °C) supports deployment in unheated outdoor enclosures or near motor housings. For new designs requiring 16-bit ADC resolution, the PIC24F or dsPIC33 family is preferred, but the C66 remains adequate for sub-1% accuracy instrumentation.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C66T-04E/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C66-04E/SO | PIC16C66T-04/SO | PIC16C66T-04I/SO | PIC16C66-04I/SO | PIC16C642T-04E/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-SOIC (7.50 mm wide-body) | 28-SOIC (same) | 28-SOIC (same) | 28-SOIC (same) | 28-SOIC (same) | 28-SOIC (same) |
| Core | 8-bit PIC16C6X RISC | 8-bit PIC16C6X RISC | 8-bit PIC16C6X RISC | 8-bit PIC16C6X RISC | 8-bit PIC16C6X RISC | 8-bit PIC16C6X RISC (smaller peripheral set) |
| Program Memory | 14 KB OTP | 14 KB OTP | 14 KB OTP | 14 KB OTP | 14 KB OTP | 7 KB OTP (-50 %) |
| RAM | 368 bytes | 368 bytes | 368 bytes | 368 bytes | 368 bytes | 256 bytes (-30 %) |
| Maximum Clock | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| Supply Voltage | 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 | 4.5 V to 5.5 V |
| Temperature Grade | Extended -40 °C to +125 °C | Extended -40 °C to +125 °C | Commercial 0 °C to +70 °C | Industrial -40 °C to +85 °C | Industrial -40 °C to +85 °C | Extended -40 °C to +125 °C |
Key Differentiators
- Extended -40 °C to +125 °C temperature range supports automotive and industrial deployment (vs PIC16C66T-04/SO)
- Tape-and-reel packaging ('T' suffix) supports high-volume automated SMD assembly (vs PIC16C66-04E/SO)
- 22 strong I/O with independent direction control and pull-ups on PORTB (vs PIC16C642T-04E/SO)
Design Notes
Estimated: The PIC16C66T-04E/SO draws 2-5 mA active at 4 MHz and 5 V supply, dropping to <5 μA in sleep mode (per PIC16C6X family datasheet, watch-dog timer disabled). For battery-backed designs, add a decoupling 100 nF ceramic + 10 μF tantalum bulk on Vdd (pin 20), placed within 5 mm of the package. MCLR (pin 1) requires a 10 kΩ pull-up to Vdd - do NOT leave it floating, as the device can intermittently reset. Brown-out detection is not internally programmable on the PIC16C6X family; add an external voltage supervisor (MCP100 or equivalent) if 5 V rails are unstable.
Route OSC1/OSC2 traces as a short differential pair with a ground guard ring when using a crystal oscillator, and keep high-frequency digital lines (RC3 SCK, RC4 SDI) at least 3 mm from analog inputs (RA0-RA3) to prevent digital noise coupling into ADC readings. Per Microchip's PIC16C6X hardware design checklist, the ADC VREF+ pin (RA3) should be bypassed with 100 nF ceramic; VREF- (RA2) must be tied to ground for 8-bit operation. ICSP programming pins (RB6/RB7) need no isolation resistors in production but should be reserved in the layout for programming access.
Critical: PIC16C66 OTP memory is One-Time Programmable - once code is written, it cannot be erased or rewritten. Plan firmware versioning and pre-production testing carefully; a single code bug means scrapping the MCU (or in-circuit emulation on a windowed PIC16C66JW). Also note that the PIC16C66 uses 14-bit instruction words and requires MPLAB X IDE with the XC8 compiler for development; legacy HI-TECH PICC compilers should not be used. Final: the device is not recommended for new designs - migrate to PIC16F876A-I/SO (flash-based, pin-compatible superset for most code but NOT pin-to-pin) for new projects.
Compliance Information
Verified web data does not include explicit RoHS, REACH, lead-free, halogen-free, or AEC-Q100 status for PIC16C66T-04E/SO. The PIC16C66 family generally predates widespread RoHS compliance; many E-grade parts are Pb-free but verification with the supplier is required. AEC-Q100 is not_applicable because Microchip does not market this part with automotive certification - the E-temperature grade is extended industrial, not auto-qualified.
