PIC16C55AT-04E/SO - 8-Bit 4MHz OTP MCU 28-SOIC | Microchip
MPN: PIC16C55AT-04E/SO β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.65 | $2.65 |
| 10 | $2.38 | $23.80 |
| 100 | $2.12 | $212.00 |
| 500 | $1.89 | $945.00 |
| 1,000 | $1.67 | $1,670.00 |
PIC16C55AT-04E/SO Overview
An 8-bit OTP microcontroller is a single-chip computer built around an 8-bit data path with non-volatile program memory that can be written exactly once via EPROM programming. In the system hierarchy, OTP MCUs sit below flash-based MCUs (re-programmable) and above mask-ROM MCUs (factory-programmed), within the broader category of microcontrollers, embedded controllers, and finally semiconductors. The PIC16C5X family pioneered Microchip's baseline RISC architecture with 12-bit wide instructions yielding 2:1 code compression versus 8-bit competitors.
Key features include 20 digital I/O pins, a hardware timer/counter, watchdog timer, power-on reset, brown-out detection, and low-power SLEEP mode. The fully static CMOS design eliminates the need for a continuous clock and supports DC operation down to zero frequency, allowing the device to wake from interrupts for ultra-low standby power. The 12-bit instruction set is highly orthogonal, reducing development time and code density.
The device employs a Harvard architecture with separate program and data buses, single-cycle instructions (except program branches which take two), and a four-stage pipeline. The 4 MHz clock with 250 ns instruction cycle delivers up to 4 MIPS throughput, sufficient for sensor reading, simple actuator control, and user-interface tasks in cost-sensitive embedded products.
Typical applications include industrial control, consumer electronics, automotive body and convenience subsystems, and white-goods appliance controllers. The 28-SOIC footprint is well suited for hand-soldered prototypes as well as high-volume pick-and-place production.
When designing, allocate one port pin to MCLR, leave adequate decoupling on VDD/VSS, and verify timing budgets using worst-case 4 MHz oscillator tolerance. The 'E' suffix denotes the extended temperature grade (-40 C to +125 C), required for automotive and industrial environments.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for PIC16C55AT-04E/SO β 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 PIC16C55AT-04E/SO (same form factor and footprint) β differing in Package, Program Memory Size, Core Architecture, Maximum Clock Frequency, Operating Temperature.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PIC16F54-I/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16F57-I/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C55AT-04/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C55AT-40/SO
β Drop-Inβ In Stock
$5.66 / Unit
View Datasheet βPIC16C55A-04E/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C554-04E/SO
β Drop-Inβ In Stock
$2.1 / Unit
View Datasheet βPIC16C558-04/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C55AT-04E/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC RISC |
| Family | PIC16C5X |
| Maximum Clock Frequency | 4 MHz |
| Instruction Cycle | 250 ns |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 768 B (512 x 12) |
| RAM Size | 25 B |
| I/O Pins | 20 |
| Timers | 1 x 8-bit |
| Watchdog Timer | Yes |
| Supply Voltage (VDD) | 3.0 V to 5.5 V |
| Operating Temperature | -40 C to +125 C (Extended 'E' grade) |
| Package | 28-SOIC (0.295", 7.50 mm width) |
| Mounting Type | Surface Mount |
| MSL Level | 1 |
| RoHS Status | Compliant |
| Data EEPROM | None |
PIC16C55AT-04E/SO Pin Configuration
| Pin 1 | RA2 β PORTA bit 2 (bidirectional I/O) |
| Pin 2 | RA3 β PORTA bit 3 (bidirectional I/O) |
| Pin 3 | RA4/T0CKI β PORTA bit 4 / Timer0 clock input |
| Pin 4 | MCLR/VPP β Master Clear reset (active low) / programming voltage input |
| Pin 5 | VSS β Ground reference |
| Pin 6 | RB0/INT β PORTB bit 0 / external interrupt input |
| Pin 7 | RB1 β PORTB bit 1 (bidirectional I/O) |
| Pin 8 | RB2 β PORTB bit 2 (bidirectional I/O) |
| Pin 9 | RB3 β PORTB bit 3 (bidirectional I/O) |
| Pin 10 | RB4 β PORTB bit 4 (bidirectional I/O) |
| Pin 11 | RB5 β PORTB bit 5 (bidirectional I/O) |
| Pin 12 | RB6 β PORTB bit 6 (bidirectional I/O) |
| Pin 13 | RB7 β PORTB bit 7 (bidirectional I/O) |
| Pin 14 | VSS β Ground reference |
| Pin 15 | OSC1/CLKIN β Oscillator crystal input / external clock input |
| Pin 16 | OSC2/CLKOUT β Oscillator crystal output / clock output |
| Pin 17 | RC0 β PORTC bit 0 (bidirectional I/O) |
| Pin 18 | RC1 β PORTC bit 1 (bidirectional I/O) |
| Pin 19 | RC2 β PORTC bit 2 (bidirectional I/O) |
| Pin 20 | RC3 β PORTC bit 3 (bidirectional I/O) |
| Pin 21 | RC4 β PORTC bit 4 (bidirectional I/O) |
| Pin 22 | RC5 β PORTC bit 5 (bidirectional I/O) |
| Pin 23 | RC6 β PORTC bit 6 (bidirectional I/O) |
| Pin 24 | RC7 β PORTC bit 7 (bidirectional I/O) |
| Pin 25 | RA0 β PORTA bit 0 (bidirectional I/O) |
| Pin 26 | RA1 β PORTA bit 1 (bidirectional I/O) |
| Pin 27 | VDD β Positive supply voltage |
| Pin 28 | NC β Not connected (per datasheet, reserved) |
Typical Applications
PIC16C55AT-04E/SO is suitable for 6 applications: Industrial Control Modules, Consumer Appliance Controllers, Automotive Body and Convenience Subsystems, Sensor Interface and Signal Conditioning, Hobby Electronics and Education Kits, Smart Lighting and LED Driver Modules.
Industrial Control Modules
The PIC16C55AT-04E/SO's 4 MHz RISC core, 20 digital I/O pins, and -40 C to +125 C extended temperature grade make it well suited to industrial control modules such as relay drivers, sensor aggregators, and small PLC I/O expanders. Its 768 B OTP program memory accommodates typical ladder-logic-style state machines, while the hardware watchdog timer protects against firmware lockup in unattended factory installations. The 28-SOIC wide-body package with 7.50 mm body width provides robust solder joints that withstand vibration in motor control cabinets. With 25 B of RAM and an 8-bit timer, the MCU can debounce mechanical switches, time pulse-width modulated outputs, and run simple PID loops for temperature or pressure regulation at modest cost. The fully static CMOS design allows the core to halt during long idle periods, saving power in duty-cycled sensor nodes.
Recommended
Consumer Appliance Controllers
White-goods appliance controllers - washing machines, microwave ovens, dishwashers, and small kitchen appliances - frequently use the PIC16C55AT-04E/SO because of its low unit cost, OTP memory security (firmware cannot be copied via flash readout), and compact 28-SOIC footprint. The MCU drives 7-segment displays, scans keypad matrices, and switches triac-controlled loads via optoisolators. Its 250 ns instruction cycle delivers deterministic response times for safety-critical lockout sequences. With 20 I/O pins, the device handles up to four 7-segment digits plus key matrix scanning plus a half-dozen actuator signals in a single chip, eliminating the cost of an external I/O expander. The extended temperature grade supports oven-adjacent mounting where ambient can exceed 70 C during operation.
Recommended
Automotive Body and Convenience Subsystems
The PIC16C55AT-04E/SO has historically been designed into automotive body controllers for seat adjustment, mirror positioning, interior lighting, and window lift subsystems where its -40 C to +125 C grade handles under-dash thermal stress. The OTP memory is considered a feature in this segment because anti-cloning prevents aftermarket ECU duplication. The 4 MHz core is sufficient for slow mechanical actuator sequencing, while the 20 I/O pins drive H-bridge enable signals, sense limit switches, and PWM seat motors. However, because the part is obsolete, automotive designers should migrate new platforms to PIC16F57-I/SO or PIC16F1823-I/SO which offer AEC-Q100 qualification and active lifecycle support from Microchip. The 28-SOIC footprint remains the standard for these subsystems, easing PCB redesign.
Recommended
Sensor Interface and Signal Conditioning
For cost-sensitive sensor interface modules such as thermistor readers, optical interrupters, and simple 4-20 mA loop replacements, the PIC16C55AT-04E/SO delivers adequate performance with a bill-of-materials cost under $3. The 8-bit ADC-free architecture (this part has no integrated ADC) suits designs where an external delta-sigma or SAR converter handles the analog front-end, while the PIC16C55AT-04E/SO executes linearization, calibration, and HART or Modbus framing. Its 25 B RAM accommodates modest packet buffers, and the 768 B OTP holds lookup tables and protocol stacks. The fully static core allows event-driven operation with the device waking from sleep on PORTB interrupts, achieving standby current under 1 uA for battery-powered wireless sensor nodes.
Recommended
Hobby Electronics and Education Kits
The PIC16C55AT-04E/SO appears in legacy PIC programmer training kits, university embedded systems courses, and hobbyist robotics controllers because of its simple RISC instruction set, deterministic timing, and extensive tutorial ecosystem built around the PIC16C5X family. The 28-SOIC breakout board footprint is breadboard-friendly with a 0.1" SOIC-to-DIP adapter, and the OTP EPROM can be programmed with low-cost PICSTART or PROMATE II programmers. Students learn fundamentals including polled I/O, timer-driven scheduling, interrupt handling, and watchdog supervision. For active curricula, instructors prefer PIC16F54-I/SO because students can re-flash the device without UV erasure. The PIC16C55AT-04E/SO remains useful as a study reference for understanding OTP-era microcontroller architecture.
Recommended
Smart Lighting and LED Driver Modules
Architectural lighting controllers, signage dimmers, and decorative LED strips commonly integrate the PIC16C55AT-04E/SO as the timing brain for PWM generation across multiple channels. The 8-bit timer combined with software PWM routines supports 8-12 channels of 8-bit PWM resolution at 4 MHz, sufficient for mood lighting and color-mixing applications. The 20 I/O pins drive MOSFET gates for high-current LED strings while monitoring temperature sensors and pushbutton inputs. The OTP memory secures vendor-specific color calibration tables and animation sequences against reverse engineering. The wide 3.0-5.5 V supply range accommodates both 3.3 V logic-level designs and 5 V analog front-ends, simplifying the power tree. The 28-SOIC wide-body package handles the thermal load of nearby linear regulators.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55AT-04E/SO β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16F54-I/SO | PIC16F57-I/SO | PIC16C55AT-04/SO | PIC16C554-04E/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 | 20 MHz | 20 MHz | 4 MHz | 4 MHz |
| Program Memory | 768 B OTP | 768 B Flash | 2 KB Flash | 768 B OTP | 768 B OTP |
| RAM Size | 25 B | 25 B | 72 B | 25 B | 80 B |
| I/O Pins | 20 | 20 | 20 | 20 | 20 |
| Operating Temperature | -40 C to +125 C (E grade) | -40 C to +85 C (I grade) | -40 C to +85 C (I grade) | 0 C to +70 C (commercial) | -40 C to +125 C (E grade) |
| Lifecycle Status | Obsolete | Active | Active | Obsolete | Obsolete |
| Memory Type | OTP EPROM | Flash (re-programmable) | Flash (re-programmable) | OTP EPROM | OTP EPROM |
Key Differentiators
- Extended temperature grade available with E suffix (vs PIC16C55AT-04/SO)
- OTP memory security vs flash re-programmability trade-off (vs PIC16F54-I/SO)
- Mature PIC16C5X pinout heritage (vs PIC16F716-I/SO)
Design Notes
Estimated: At VDD = 5 V, 4 MHz active current is approximately 2 mA and sleep current drops to under 1 uA. Place a 100 nF ceramic decoupling capacitor within 5 mm of the VDD pin (pin 27) with a short trace to the adjacent VSS pin (pin 28 in this package variant or pin 14). For battery-powered designs, leverage SLEEP mode aggressively - the fully static core halts the clock entirely and preserves RAM/registers, allowing wake-on-interrupt operation with multi-year battery life from a single CR2032 cell. Estimated values assume typical silicon; verify against the datasheet's Figure 8-9 (DC characteristic curves) before committing to a power budget.
OTP memory can be programmed only once - any firmware bug discovered after programming bricks the device. Always program production units only after a complete engineering validation cycle on windowed (PIC16C55/JW) or flash (PIC16F54-I/SO) equivalents. MCLR (pin 4) must be tied to VDD through a 10 kohm pull-up resistor for normal operation; leaving it floating causes intermittent resets. The OSC1/OSC2 pins require a properly loaded crystal or ceramic resonator - capacitance values depend on the specific part number and stray PCB capacitance, so consult the resonator manufacturer's datasheet for the correct load capacitor selection.
The 28-SOIC wide-body package has 1.27 mm pin pitch and 7.50 mm body width - design the PCB land pattern per IPC-7351 SOIC-28W with 0.65 mm pad width and 2.0 mm pad length to ensure reliable solder joints. Route the oscillator traces (OSC1/OSC2, pins 15-16) with short, symmetric traces and guard them from switching signals. Place a ground pour under and around the MCU to reduce EMI susceptibility. The MCLR trace should be short and protected from capacitive coupling that could cause spurious resets; adding a 100 nF capacitor from MCLR to ground improves noise immunity.
PORTB pins 0-7 on this device have no analog or PWM capability - all I/O is purely digital CMOS with TTL-level input thresholds. Drive long cables or relay coils through external protection circuits (TVS diodes, RC snubbers, schmitt-trigger buffers). When using RB0/INT as the external interrupt source, ensure the input pulse is longer than the oscillator period (250 ns at 4 MHz) and debounced in software if driven by a mechanical switch. The internal weak pull-ups on PORTB (where available) are typically 50-100 kohm - too weak for reliable switch pull-up, so add external 10 kohm resistors.
Compliance Information
RoHS and lead-free per Microchip product page; not AEC-Q100 qualified (use PIC16F54-E/SO or PIC16F57-E/SO for automotive-grade replacements). Halogen-free status not confirmed in distributor data.
