PIC16C55AT-40/SO - 8-Bit 40MHz OTP MCU, 768B | Microchip
MPN: PIC16C55AT-40/SO β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.95 | $8.95 |
| 10 | $8.06 | $80.60 |
| 100 | $7.16 | $716.00 |
| 500 | $6.36 | $3,180.00 |
| 1,000 | $5.66 | $5,660.00 |
PIC16C55AT-40/SO Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU, memory, and peripherals; the PIC16C5x family is one of Microchip's foundational 8-bit baseline architectures using a Harvard structure with separate program and data paths. The OTP variant is intended for low-volume, cost-sensitive, or prototype applications where firmware is fixed at production and field re-programmability is not required, distinguishing it from flash-based PIC16F equivalents.
Key features include 12-bit instruction width, a 33-instruction set, two hardware timers (8-bit RTCC and Watchdog Timer with on-chip RC oscillator), Power-On Reset (POR), Device Reset Timer (DRT), programmable code protection, and a wide 3.0 V to 6.0 V operating range with low-power CMOS construction. With 20 I/O pins capable of sourcing/sinking up to 25 mA per pin, the device can directly drive LEDs, relays, and small solenoids without external buffers.
The PIC16C55A employs a fully static CMOS design with a 4-phase on-chip oscillator circuit supporting crystal, ceramic resonator, or external clock drive. Its RISC architecture delivers roughly 5 MIPS peak throughput at 40 MHz while consuming only a few milliamps, which suits battery and bus-powered industrial nodes. The Harvard bus prevents program-memory fetches from colliding with data accesses, simplifying real-time interrupt handling.
Typical applications include appliance controls, security-system keypads, automotive body controllers, HVAC fan/valve drivers, and simple sensor interfaces. The OTP memory and -40C to +85C commercial/extended temperature grade make the part a fit for fixed-function embedded logic rather than firmware-upgradable IoT nodes. The 28-SOIC footprint is widely accepted in through-hole-replacement industrial designs.
When designing with this part, place a 0.1 uF decoupling capacitor within 5 mm of VDD and tie the MCLR pin through the recommended 10 kohm pull-up, observing Microchip AN585 for oscillator-layout best practices. Note that OTP memory can be programmed only once, so production firmware must be fully validated before commitment. This page synthesizes distributor pricing, lifecycle context, drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for PIC16C55AT-40/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-40/SO (same form factor and footprint) β differing in Package, Program Memory Size, Core Architecture, Maximum Clock Frequency, Supply Voltage (VDD).
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PIC16C55A-40/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C55AT-20E/SO
β Drop-Inβ In Stock
$1.95 / Unit
View Datasheet βPIC16C55AT-04E/SO
β Drop-Inβ In Stock
$1.67 / Unit
View Datasheet βPIC16C55-10/SO
β Drop-Inβ In Stock
$2.49 / Unit
View Datasheet βPIC16F54-I/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16F57-I/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C55AT-40/SO Maximum Ratings & Electrical Characteristics
| Product Family | PIC16C5x |
| Core Architecture | 8-bit RISC (PIC Harvard) |
| Maximum Clock Frequency | 40 MHz |
| Instruction Cycle Time | 100 ns (at 40 MHz) |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 768 B (512 x 12-bit words) |
| Data RAM | 25 B |
| I/O Pins | 20 |
| Timers | 1 x 8-bit RTCC + Watchdog Timer (WDT) |
| Instruction Set Size | 33 instructions |
| Supply Voltage (VDD) | 3.0 V to 6.0 V |
| I/O Sink/Source Current | 25 mA per pin |
| Operating Temperature | 0C to +70C (commercial) |
| Package | 28-SOIC (SO, 300 mil) |
| Mounting Type | Surface Mount (gull wing) |
| Peripherals | POR, DRT, WDT, code protection |
| RoHS Status | Non-compliant (Pb-bearing package) |
PIC16C55AT-40/SO Pin Configuration
| Pin 1 | RA2 β Bidirectional I/O port A bit 2 |
| Pin 2 | RA3 β Bidirectional I/O port A bit 3 |
| Pin 3 | RTCC β Timer/Counter input (also RA4) |
| Pin 4 | MCLR β Master Clear reset (active low), tied through 10 kohm to VDD |
| Pin 5 | VSS β Ground reference |
| Pin 6 | RB0 β Bidirectional I/O port B bit 0 |
| Pin 7 | RB1 β Bidirectional I/O port B bit 1 |
| Pin 8 | RB2 β Bidirectional I/O port B bit 2 |
| Pin 9 | RB3 β Bidirectional I/O port B bit 3 |
| Pin 10 | RB4 β Bidirectional I/O port B bit 4 |
| Pin 11 | RB5 β Bidirectional I/O port B bit 5 |
| Pin 12 | RB6 β Bidirectional I/O port B bit 6 |
| Pin 13 | RB7 β Bidirectional I/O port B bit 7 |
| Pin 14 | VSS β Ground (additional VSS pin) |
| Pin 15 | OSC2 β Oscillator output - crystal/resonator connection |
| Pin 16 | OSC1 β Oscillator input - crystal/resonator or external clock |
| Pin 17 | VDD β Positive supply voltage (3.0-6.0 V) |
| Pin 18 | RC0 β Bidirectional I/O port C bit 0 |
| Pin 19 | RC1 β Bidirectional I/O port C bit 1 |
| Pin 20 | RC2 β Bidirectional I/O port C bit 2 |
| Pin 21 | RC3 β Bidirectional I/O port C bit 3 |
| Pin 22 | RC4 β Bidirectional I/O port C bit 4 |
| Pin 23 | RC5 β Bidirectional I/O port C bit 5 |
| Pin 24 | RC6 β Bidirectional I/O port C bit 6 |
| Pin 25 | RC7 β Bidirectional I/O port C bit 7 |
| Pin 26 | RA0 β Bidirectional I/O port A bit 0 |
| Pin 27 | RA1 β Bidirectional I/O port A bit 1 |
| Pin 28 | VDD β Positive supply (additional VDD pin) |
Typical Applications
PIC16C55AT-40/SO is suitable for 7 applications: Appliance Control Panels, Security System Keypads and Siren Drivers, Automotive Body Controllers, HVAC Fan and Valve Drivers, Industrial Sensor Interfaces, Toy and Consumer Electronics, LED Display and Sign Drivers.
Appliance Control Panels
The PIC16C55AT-40/SO is widely deployed in washing-machine, dishwasher, and microwave-oven front-panel controllers where the firmware is locked after production. Its 20 bidirectional I/O pins directly sink LED segment currents and read matrix keypads without external driver ICs, while 768 B of OTP memory holds typical UI state machines, timing tables, and sensor-conditioning routines. The 40 MHz core scans keypads in under 1 ms and handles relay de-bounce in real time; the 33-instruction PIC16C5x RISC core yields deterministic timing critical for IEC 60730 safety-class B firmware. Using OTP instead of flash reduces per-unit cost by 10-15% over PIC16F equivalents in high-volume SKUs.
Recommended
Security System Keypads and Siren Drivers
The PIC16C55AT-40/SO serves as the central controller in wired burglar-alarm keypads and indoor siren drivers. Its 25 mA per-pin drive directly switches piezo sirens and 12 V relays via a single transistor, eliminating driver ICs. The hardware Watchdog Timer with its own on-chip RC oscillator provides an independent reset path for EN 50131 security-grade reliability. OTP memory prevents firmware tampering in the field, satisfying insurance-grade system integrators. The 40 MHz instruction rate runs encryption-style rolling-code algorithms in real time, and the wide 3.0-6.0 V supply operates directly from 5 V alarm-bus rails.
Recommended
Automotive Body Controllers
In non-safety automotive body modules - window lifters, mirror adjusters, seat-position memories - the PIC16C55AT-40/SO drives small DC motors and reads Hall-effect position sensors. Its 20 I/O pins handle direction H-bridge logic and limit-switch inputs directly, and the 40 MHz core executes PWM motor profiles with microsecond resolution. The extended-temperature PIC16C55AT-40I variant operates up to +85C under-dash, but the standard -40/SO is qualified for cabin-temperature body-electronics bays. OTP prevents after-market firmware reflashing, which OEMs prefer for liability reasons.
Recommended
HVAC Fan and Valve Drivers
The PIC16C55AT-40/SO is used in residential HVAC indoor-unit controllers to drive triac-fired fan motors and 24 VAC zone valves. Its 20 I/O pins read thermistor bridges, switch inputs, and triac-trigger outputs; the 40 MHz core handles zero-crossing detection in firmware at 50/60 Hz line frequency. The OTP array stores fixed fan-speed profiles, dehumidification sequences, and EEPROM-emulation routines in the small RAM. The hardware RTCC generates the 1 ms control tick without software overhead, freeing the CPU for adaptive compressor control logic.
Recommended
Industrial Sensor Interfaces
In factory-automation nodes the PIC16C55AT-40/SO reads 4-20 mA loop signals, thermocouple cold-junction compensators, and limit-switch arrays. Its 20 I/O pins multiplex up to 5 analog channels through external front-end op-amps and read digital sensors directly. The 33-instruction baseline core executes sensor-linearization and basic PID control loops in firmware with deterministic timing. OTP memory locks calibration coefficients into the device so field-reprogramming cannot invalidate factory certificates. The 28-SOIC package is well-supported by wave-soldered industrial backplanes.
Recommended
Toy and Consumer Electronics
The PIC16C55AT-40/SO is found in cost-sensitive consumer goods such as electronic learning toys, talking plush devices, and remote-control transmitters. Its OTP memory holds fixed audio playback tables, button-debounce state machines, and IR protocol stacks; the 25 mA I/O drive LED eyes and small DC gearmotors. The 40 MHz core runs PWM audio tones and modulates 38 kHz IR carriers precisely. For very high-volume consumer SKUs, the OTP architecture beats flash in unit cost, and the 28-SOIC package supports both hand-solder and automated SMT assembly.
Recommended
LED Display and Sign Drivers
The PIC16C55AT-40/SO drives multiplexed 7-segment and dot-matrix LED displays in industrial message signs and price-tag changers. Its 20 I/O pins multiplex up to 8 digits of 7-segment plus 8 segment lines directly, without external driver ICs in small-form-factor signs. The 40 MHz core runs Charlieplexing or time-division multiplexing at refresh rates above 100 Hz, eliminating visible flicker. OTP memory locks animation tables and font data into the device, and the 33-instruction core handles serial-receive updates for dynamic text. The 28-SOIC wide-body package dissipates LED-row current comfortably.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55AT-40/SO β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55A-40/SO | PIC16C55AT-20E/SO | PIC16C55AT-04E/SO | PIC16F54-I/SO | PIC16F57-I/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-SOIC (SO, 300 mil) | 28-SOIC (SO, 300 mil) - same | 28-SOIC (SO, 300 mil) - same | 28-SOIC (SO, 300 mil) - same | 28-SOIC (SO, 300 mil) - same | 28-SOIC (SO, 300 mil) - same |
| Maximum Clock Frequency | 40 MHz | 40 MHz | 20 MHz (-50%) | 4 MHz (-90%) | 20 MHz | 20 MHz |
| Program Memory Type | OTP EPROM (768 B) | OTP EPROM (768 B) | OTP EPROM (768 B) | OTP EPROM (768 B) | Flash (1 KB) | Flash (3 KB) |
| Data RAM | 25 B | 25 B | 25 B | 25 B | 25 B | 72 B |
| I/O Pins | 20 | 20 | 20 | 20 | 12 (some ports differ) | 20 |
| Operating Voltage | 3.0 V to 6.0 V | 3.0 V to 6.0 V | 3.0 V to 6.0 V | 3.0 V to 6.0 V | 2.0 V to 5.5 V | 2.0 V to 5.5 V |
| Lifecycle Status | NRND | NRND | NRND | NRND | Active | Active |
| Pin-Compatible | Yes (baseline) | Yes | Yes | Yes | Yes (pin-compat per Microchip chart) | Yes (pin-compat per Microchip chart) |
Key Differentiators
- Highest-frequency variant of the 28-SOIC PIC16C5x baseline family (vs PIC16C55AT-20E/SO)
- OTP lock prevents field firmware tampering (vs PIC16F54-I/SO)
- Drop-in upgrade path to flash-based successor in same footprint (vs PIC16F57-I/SO)
Design Notes
Estimated: at VDD = 5 V and 40 MHz oscillator, the PIC16C55AT-40/SO draws approximately 7-11 mA active and 4 uA typical standby. Place a 0.1 uF ceramic decoupling capacitor within 5 mm of the VDD pin (pin 17) and a bulk 10 uF tantalum at the board power entry. Tie the MCLR pin through a 10 kohm pull-up to VDD; some programmers also wire a 100 nF capacitor from MCLR to VSS for noise immunity, per Microchip AN585.
OTP memory can be programmed EXACTLY ONCE. All firmware must be fully validated on a windowed PIC16C55A-40/JW or PIC16C55A-40/P (with quartz window) before committing the production OTP order; once programmed, OTP bits cannot be erased. Code-protection bits, once enabled, prevent verification of program memory - leave code protection off during development until final release.
Keep the oscillator traces (OSC1 pin 16, OSC2 pin 15) short, surrounded by a ground guard ring, and away from switching signals; Microchip AN585 recommends placing the crystal within 10 mm of the OSC1/OSC2 pins. The MCLR pin trace should be short and the MCLR capacitor lead length kept minimal to prevent inadvertent resets from EMI. Add a 100 kohm pull-down on OSC1 if RC oscillator mode is used to prevent floating pin during power-up.
Estimated: at 5 V VDD and 40 MHz clock, the PIC16C55AT-40/SO dissipates roughly 35-55 mW. The 28-SOIC package has a theta_JA of approximately 80 C/W, giving a 4 C junction temperature rise above ambient. Even at +70 C commercial maximum ambient, the junction remains well within the 150 C thermal limit; no heatsink or special PCB copper pours are required for typical operation.
Compliance Information
The PIC16C55AT-40/SO is supplied in a Pb-bearing SOIC package and is RoHS non-compliant; lead-free /SO variants (PIC16C55AT-40E/SO) are available for RoHS-compliant designs. The part is not AEC-Q100 qualified - it is rated for commercial (0C to +70C) operating temperature; for automotive applications use the PIC16C55AT-40I/SO industrial grade and qualify to AEC-Q100 at the system level.
