PIC16C55AT-20/SO - 8-bit 20MHz OTP MCU 768B | Microchip
MPN: PIC16C55AT-20/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.1 | $2.10 |
| 10 | $1.95 | $19.50 |
| 100 | $1.78 | $178.00 |
| 500 | $1.62 | $810.00 |
| 1,000 | $1.45 | $1,450.00 |
PIC16C55AT-20/SO Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU, memory (RAM/ROM/Flash/OTP), and peripherals on one die, designed to execute embedded control tasks in a wide range of products. The PIC16C5X series sits in the MCU taxonomy as an 8-bit RISC MCU, beneath 16-bit PIC24 and 32-bit PIC32 architectures, and is widely used in cost-sensitive and legacy industrial/commercial control applications where deterministic 12-bit wide instruction execution offers 2:1 code compression over competing 8-bit MCUs.
Key features include 24 bytes of RAM, 20 general-purpose I/O pins, a 4.0 oscillator configuration supporting XT/RC/LP/HS modes, a single 8-bit timer/counter, and a watchdog timer for reliable unattended operation. The 'T' suffix denotes tape-and-reel packaging, '-20' specifies 20 MHz maximum operating frequency, and the industrial/commercial temperature range supports 4.5V to 5.5V operation.
The PIC16C5X core uses a 12-bit instruction word with a two-stage pipeline, allowing most instructions to execute in a single 200 ns instruction cycle at 20 MHz. The OTP program memory is programmed once and cannot be erased, making the device suitable for volume production but not for prototyping. Per Microchip compatibility documentation, the PIC16C55A shares the same 28-pin pinout as the PIC16C54, PIC16C54A, PIC16C54C, PIC16C55, PIC16C56, PIC16C57, PIC16C58 and PIC16C554/558 devices, enabling PCB reuse across memory-size variants.
Typical applications include appliance control, automotive body modules, security panels, remote sensors, lighting controllers, and low-cost industrial automation. The 20 I/O pins are sufficient to drive LED indicators, scan keypads, and interface to relays or triac-driven loads directly or via transistors.
When designing with this MCU, ensure your compiler/toolchain targets the PIC16C5X architecture (e.g., MPLAB XC8 in baseline mode) and that the OTP programming step is integrated into your manufacturing flow. Watchdog timer enable is recommended for any system that may experience ESD, brownout, or supply transients that could halt the CPU.
This page synthesizes distributor pricing, drop-in alternatives, application guidance, and design notes not aggregated on any single manufacturer or distributor page.
Drop-in alternatives for PIC16C55AT-20/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 PIC16C55AT-20/SO (same form factor and footprint) — differing in Package, Program Memory Type, Program Memory Size, Timers, RoHS Status.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C55A-20/SO
✅ Drop-In✓ In Stock
$2.9 / Unit
View Datasheet →PIC16C56A-20/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C558-20/SO
✅ Drop-In✓ In Stock
$2.05 / Unit
View Datasheet →PIC16C554T-20/SO
✅ Drop-In✓ In Stock
$1.82 / Unit
View Datasheet →PIC16F57-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C54A-20/SO
✅ Drop-In✓ In Stock
$1.4 / Unit
View Datasheet →PIC16C55AT-20/SO Maximum Ratings & Electrical Characteristics
| Core | PIC 16C (8-bit RISC) |
| Series | PIC16C5X |
| Program Memory Type | OTP (One-Time-Programmable) |
| Program Memory Size | 768 B (512 x 12) |
| RAM Size | 24 B |
| Maximum CPU Frequency | 20 MHz |
| Instruction Cycle | 200 ns (at 20 MHz) |
| Instruction Word Width | 12 bits |
| I/O Pins | 20 |
| Timers | 1 x 8-bit |
| Watchdog Timer | Yes |
| Supply Voltage | 4.5 V to 5.5 V |
| Operating Temperature | 0C to +70C (Commercial) |
| Oscillator Modes | XT, RC, LP, HS |
| Package | 28-SOIC (7.50 mm width, 0.295 in) |
| Package Code | SOP (Gull-wing) |
| Pin Count | 28 |
| Mounting Type | Surface Mount |
PIC16C55AT-20/SO Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O; analog input on some variants |
| Pin 2 | RA3 — Bidirectional I/O |
| Pin 3 | RTCC — RTCC timer/counter I/O pin (also digital I/O) |
| Pin 4 | MCLR — Master clear reset (active low); programming voltage input |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0 — Bidirectional I/O; external interrupt |
| Pin 7 | RB1 — Bidirectional I/O |
| Pin 8 | RB2 — Bidirectional I/O |
| Pin 9 | RB3 — Bidirectional I/O |
| Pin 10 | RB4 — Bidirectional I/O |
| Pin 11 | RB5 — Bidirectional I/O |
| Pin 12 | RB6 — Bidirectional I/O |
| Pin 13 | RB7 — Bidirectional I/O |
| Pin 14 | VDD — Positive supply (4.5 V to 5.5 V) |
| Pin 15 | OSC2 — Oscillator output (crystal/RC) |
| Pin 16 | OSC1 — Oscillator input (crystal/RC/external clock) |
| Pin 17 | RA0 — Bidirectional I/O |
| Pin 18 | RA1 — Bidirectional I/O |
| Pin 19 | RA4 — Bidirectional I/O (open-drain on some variants) |
| Pin 20 | RA5 — Bidirectional I/O |
| Pin 21 | RA6 — Bidirectional I/O |
| Pin 22 | RA7 — Bidirectional I/O |
| Pin 23 | RB0 — Bidirectional I/O (second port B bank on 28-pin) |
| Pin 24 | RB1 — Bidirectional I/O |
| Pin 25 | RB2 — Bidirectional I/O |
| Pin 26 | RB3 — Bidirectional I/O |
| Pin 27 | RB4 — Bidirectional I/O |
| Pin 28 | RB5 — Bidirectional I/O |
Typical Applications
PIC16C55AT-20/SO is suitable for 6 applications: Home Appliance Control, Security Keypad Panels, Automotive Body Electronics (Non-Safety), Remote Sensor / IoT Edge Node, LED Lighting Controllers, Industrial Control Logic Replacement.
Home Appliance Control
The PIC16C55AT-20/SO fits white-goods and small-appliance controllers because its 768 B of OTP memory and 20 MHz core can run fixed-cycle state machines for washers, microwaves, and toaster ovens without external program storage. Twenty I/O pins drive relay coils, triac gates, and seven-segment LED indicators directly, while the on-chip watchdog timer recovers the CPU from line-voltage transients common on appliance mains. The 28-SOIC wide-body package offers 0.295-inch (7.5 mm) gull-wing leads that survive wave-solder and hot-air rework on thick appliance PCBs. Designers pair this MCU with the MOC3021 triac driver and the 1N4007 rectifier in reference designs; the 4.5-5.5 V supply aligns with standard 5 V regulator rails from a bridge-rectified transformer.
Recommended
Security Keypad Panels
The PIC16C55AT-20/SO is well-suited to alarm keypads and access-control panels where a fixed code set and a small number of zones must be scanned deterministically. Its 12-bit instruction word and 200 ns cycle time allow real-time debounce of a 4x4 matrix keypad without CPU stalls, and the 20 I/O pins easily accommodate zone inputs, siren drivers, and LED status indicators. OTP memory prevents firmware tampering or extraction, an important security feature. The watchdog timer guards against ESD-induced CPU lockup at the panel's metal enclosure, and the commercial 0C to 70C range covers indoor installations.
Recommended
Automotive Body Electronics (Non-Safety)
For non-safety automotive body modules such as interior lighting controllers, mirror adjusters, and seat-position memories, the PIC16C55AT-20/SO provides a cost-effective 8-bit compute core qualified to commercial temperature grades. Its 20 I/O pins drive LED arrays and small DC motors through H-bridge drivers, and the 20 MHz core executes PWM duty-cycle updates with adequate resolution. For under-hood or AEC-Q100 required positions, the industrial-temperature PIC16C55AT-20I/SO variant is preferred, sharing the same 28-SOIC pinout.
Recommended
Remote Sensor / IoT Edge Node
The PIC16C55AT-20/SO powers simple IoT edge nodes and remote sensor interfaces that periodically read an analog or digital sensor, format a short message, and trigger a low-power RF transmitter. Its 24-byte RAM and 768-byte OTP store tight driver loops for SPI or UART peripherals, and the 8-bit timer sets wake/sleep cadences when paired with an external RTC or watchdog-driven polling scheme. Combined with an RFM69 or LoRa transceiver and a 5V regulator, the PIC16C55AT-20/SO forms a sub-$5 bill-of-materials wireless sensor node for agricultural, environmental, and asset-tracking deployments.
Recommended
LED Lighting Controllers
The PIC16C55AT-20/SO drives RGB and addressable-LED strip controllers in architectural and stage lighting fixtures. With 20 I/O pins and a 20 MHz instruction rate, the MCU generates WS2812 / SK6812 timing patterns in software bit-bang, supporting strings of 100+ LEDs at 30 Hz refresh without DMA. The OTP memory holds color-effect tables and DMX-512 address logic. The 28-SOIC package fits inside small controller enclosures and supports the +70C ambient typical of enclosed LED drivers.
Recommended
Industrial Control Logic Replacement
Designers retrofitting legacy PLC I/O cards and custom industrial relay-logic panels use the PIC16C55AT-20/SO as a one-chip replacement for multi-IC discrete logic. Its 20 I/O pins replace dozens of 74HC-series gates, the on-chip timer generates sequencing pulses, and the watchdog timer resets the controller if the relay rack loses power transiently. The 28-SOIC package and 4.5-5.5 V supply slot directly into existing 5 V industrial backplanes, while the OTP memory locks the application code to prevent unauthorized field modifications.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55AT-20/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55A-20/SO | PIC16C56A-20/SO | PIC16C558-20/SO | PIC16F57-I/SO |
|---|---|---|---|---|---|
| Package | 28-SOIC (7.50 mm) | 28-SOIC (7.50 mm) - same | 28-SOIC (7.50 mm) - same | 28-SOIC (7.50 mm) - same | 28-SOIC (7.50 mm) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Memory Type | OTP (768 B / 512 x 12) | OTP (768 B / 512 x 12) | OTP (1 K x 12) | EPROM (2 KB) | Flash (2 KB) |
| Maximum CPU Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| RAM Size | 24 B | 24 B | 24 B | 72 B | 72 B |
| I/O Pins | 20 | 20 | 20 | 20 | 20 |
| In-Circuit Re-programmable | No (OTP) | No (OTP) | No (OTP) | No (EPROM window-less) | Yes (Flash) |
| Unit Price (qty 1) | USD 2.10 | USD 2.10 (tube) | USD 2.20 | USD 3.50 | USD 1.95 |
Key Differentiators
- Tape-and-reel packaging variant of PIC16C55A-20/SO silicon (vs PIC16C55A-20/SO)
- Larger code memory than the lower-end PIC16C54A-20/SO (vs PIC16C54A-20/SO)
- More I/O and a real timer than the PIC16C54/55 base parts (vs PIC16C54A-20/SO)
Design Notes
The PIC16C55AT-20/SO operates from a single 4.5 V to 5.5 V supply. Place a 100 nF decoupling capacitor as close as practical to the VDD pin (pin 14) and a bulk 10 uF tantalum or aluminum electrolytic capacitor on the same supply rail to suppress the inrush current drawn when the OTP programming algorithm pulses the MCLR pin. The VSS pin (pin 5) should be tied to a low-impedance ground plane; a star-ground topology is preferred when the design shares a PCB with relay or triac drivers.
OTP memory cannot be erased; engineers used to flash-based PIC16F MCUs must build a debug harness around a PIC16C55A-20/JW or PIC16F57-I/SO during firmware development, then commit the final code image to OTP for production. Pull MCLR high through a 10 kohm resistor to VDD; do not leave it floating. Failure to disable the watchdog timer (WDTE fuse) during initial bring-up can mask a perfectly functioning firmware as a continuously-reset device.
The 28-SOIC wide-body (0.295 in) footprint follows JEDEC MS-013 dimensional standards. Reserve at least 6 mm of copper pour under the device for thermal relief; at 20 MHz the PIC16C55AT-20/SO dissipates under 100 mW but the wide-body SOIC's larger copper tab aids board warpage control during reflow. Keep crystal traces on OSC1/OSC2 (pins 15/16) short and guard them with a ground ring to reduce EMI injection into the rest of the PCB.
Route the RTCC pin (pin 3) and any external-interrupt RB0 (pin 6) traces away from the OSC1/OSC2 oscillator traces and away from relay-driver outputs to avoid coupling noise into the timekeeping or interrupt logic. If the design drives off-board connectors, place 100 ohm series resistors on the connector-side of the trace to limit ESD current; the PIC16C5X I/O pins are not 5 V tolerant above VDD and cannot withstand much over-voltage.
Compliance Information
RoHS/REACH/lead-free status not explicitly stated in the verified web data; consult Microchip product compliance documentation directly. The device is commercial temperature grade (0C to +70C) and is not AEC-Q100 qualified; for industrial or automotive use, select the PIC16C55AT-20I/SO (-40C to +85C) variant.
