PIC16C55A-20/SO - 8-Bit 20MHz OTP MCU 768B 28-SOIC | Microchip
MPN: PIC16C55A-20/SO ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.54 | $4.54 |
| 10 | $4.1 | $41.00 |
| 100 | $3.65 | $365.00 |
| 500 | $3.25 | $1,625.00 |
| 1,000 | $2.9 | $2,900.00 |
PIC16C55A-20/SO Overview
An 8-bit microcontroller (MCU) is a single-chip computer built around an 8-bit data path and a Harvard or modified-Harvard architecture. Within the broader hierarchy, MCUs sit inside the microcontrollers category, which itself belongs to integrated circuits, semiconductor devices, and finally electronic components. The PIC16C5X family specifically represents Microchip's lowest-cost OTP/EPROM-based controllers targeted at high-volume, cost-sensitive embedded designs where re-programmability is not required after deployment.
Key features include an 8-bit timer/counter (TMR0) with programmable prescaler, two-level hardware stack, support for direct, indirect and relative addressing modes, and a wide 2.0V to 6.0V operating voltage range. The fully static CMOS design allows the clock to be stopped without losing register contents, and the RISC architecture achieves 2:1 code compression versus typical 8-bit CISC competitors in the same price class.
On the technical depth side, the PIC16C55A-20/SO implements a two-stage pipeline, executes one instruction per clock cycle (except branches), and offers seven or eight special-function hardware registers mapped into its data memory. The 20 MHz oscillator version provides approximately 5 MIPS throughput, which is ample for appliance control, simple sensor interfaces, and low-cost user-interface glue logic.
Typical applications include consumer appliance controllers, LED display drivers, low-end remote controls, battery chargers, security keypads, and educational/hobbyist platforms. Because the program memory is OTP, designers must commit firmware before final assembly, making the part best suited to mature, stable code bases.
When designing with this device, allocate sufficient decoupling (0.1 uF ceramic near VDD) and respect the 20 MHz maximum oscillator limit with appropriate crystal loading capacitance. The 28-SOIC package supports hand-soldering but is also fully compatible with automated pick-and-place assembly for production runs.
This page consolidates current distributor pricing, same-package drop-in alternatives from the Microchip PIC16C5X family and cross-brand equivalents, application design notes, and a parameter comparison table not available on any single manufacturer or distributor page.
Drop-in alternatives for PIC16C55A-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 PIC16C55A-20/SO (same form factor and footprint) — differing in Core Architecture, Program Memory Size, Operating Temperature Range, Package, RAM Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C558-20/SO
✅ Drop-In✓ In Stock
$2.05 / Unit
View Datasheet →PIC16C554-20/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C55-10/SO
✅ Drop-In✓ In Stock
$2.49 / Unit
View Datasheet →PIC16C55A-20I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C558-04I/SO
✅ Drop-In✓ In Stock
$3.11 / Unit
View Datasheet →PIC16C554-04/SO
✅ Drop-In✓ In Stock
$1.62 / Unit
View Datasheet →PIC16C55A-20/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit RISC (PIC16C5X family) |
| Program Memory Type | OTP (One-Time Programmable) EPROM |
| Program Memory Size | 768 B (512 x 12 words) |
| RAM Size | 24 B |
| Maximum CPU Frequency | 20 MHz |
| Instruction Set Width | 12-bit wide instructions |
| Data Path Width | 8-bit |
| I/O Pins | 20 |
| Timers | 1 x 8-bit (TMR0) with prescaler |
| Hardware Stack | 2-level |
| Addressing Modes | Direct, Indirect, Relative |
| Supply Voltage Range | 3.0 V to 5.5 V (operating range varies by speed grade) |
| Operating Temperature Range | 0 C to +70 C (commercial, SO package) |
| Package | 28-pin SOIC (SO) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
PIC16C55A-20/SO Pin Configuration
| Pin 1 | MCLR/VPP — Master Clear (reset) input / programming voltage input |
| Pin 2 | RA0 — PORTA bit 0 (digital I/O) |
| Pin 3 | RA1 — PORTA bit 1 (digital I/O) |
| Pin 4 | RA2 — PORTA bit 2 (digital I/O) |
| Pin 5 | RA3 — PORTA bit 3 (digital I/O) |
| Pin 6 | OSC1 — Oscillator input / external clock input |
| Pin 7 | OSC2 — Oscillator output (crystal/RC mode) |
| Pin 8 | VSS — Ground reference |
| Pin 9 | RB0 — PORTB bit 0 (digital I/O) |
| Pin 10 | RB1 — PORTB bit 1 (digital I/O) |
| Pin 11 | RB2 — PORTB bit 2 (digital I/O) |
| Pin 12 | RB3 — PORTB bit 3 (digital I/O) |
| Pin 13 | RB4 — PORTB bit 4 (digital I/O) |
| Pin 14 | RB5 — PORTB bit 5 (digital I/O) |
| Pin 15 | RB6 — PORTB bit 6 (digital I/O) |
| Pin 16 | RB7 — PORTB bit 7 (digital I/O) |
| Pin 17 | VSS — Ground reference |
| Pin 18 | VDD — Positive supply voltage |
| Pin 19 | RC0 — PORTC bit 0 (digital I/O) |
| Pin 20 | RC1 — PORTC bit 1 (digital I/O) |
| Pin 21 | RC2 — PORTC bit 2 (digital I/O) |
| Pin 22 | RC3 — PORTC bit 3 (digital I/O) |
| Pin 23 | RC4 — PORTC bit 4 (digital I/O) |
| Pin 24 | RC5 — PORTC bit 5 (digital I/O) |
| Pin 25 | RC6 — PORTC bit 6 (digital I/O) |
| Pin 26 | RC7 — PORTC bit 7 (digital I/O / TMR0 clock input) |
| Pin 27 | VDD — Positive supply voltage |
| Pin 28 | VSS — Ground reference |
Typical Applications
PIC16C55A-20/SO is suitable for 6 applications: Consumer Appliance Control, LED Display Drivers, Remote Control Transmitters, Battery Chargers (Simple CC/CV Profiles), Security Keypads and Access Panels, Educational and Hobbyist Platforms.
Consumer Appliance Control
The PIC16C55A-20/SO fits consumer appliance controllers (toasters, coffee makers, washing-machine sub-modules) because it offers a minimal 8-bit RISC core with 20 I/O pins to drive relays, triacs, keypads, and seven-segment displays. Its 768-byte OTP program memory holds well-tested, mature appliance firmware; the 20 MHz clock delivers 5 MIPS throughput, enough to multiplex displays while scanning inputs within a 10 ms refresh window. The 28-SOIC package assembles cleanly on automated lines. Compared with newer PIC16F parts, the PIC16C55A-20/SO costs less per unit, which matters for sub-USD 30 appliance BOMs where Microchip's NRND status is acceptable on a stable production run.
Recommended
LED Display Drivers
The PIC16C55A-20/SO works well as a low-cost LED display driver controller in scoreboards, channel signs, and instrument readouts. Its 20 I/O pins can directly multiplex an 8-digit seven-segment display with row/column scanning, while the 8-bit TMR0 with prescaler generates accurate multiplex refresh intervals. The 5 MIPS throughput at 20 MHz executes the scan loop plus per-segment brightness correction in tens of microseconds. The OTP program memory locks the display font and animation pattern at production. Compared to off-the-shelf LED driver ICs, the PIC16C55A-20/SO gives designers full control over custom fonts, brightness curves, and communication protocols.
Recommended
Remote Control Transmitters
The PIC16C55A-20/SO suits low-end IR/RF remote controls for TVs, fans, and industrial cranes because it combines 8-bit RISC performance with 24-byte RAM and 20 I/O pins in a compact 28-SOIC footprint. At 20 MHz, the core can bit-bang a 38 kHz carrier for IR transmission while simultaneously scanning a 4x4 keypad matrix. OTP memory ensures the remote's key map and protocol cannot be reprogrammed by end users, raising production security. The fully static CMOS design lets the device enter sleep mode between button presses, extending battery life. Compared to dedicated encoder ICs like the PT2262, the PIC16C55A-20/SO allows custom protocols and learning remote functionality.
Recommended
Battery Chargers (Simple CC/CV Profiles)
The PIC16C55A-20/SO is a candidate controller for simple constant-current/constant-voltage (CC/CV) chargers used in cordless phones, power tools, and small Li-ion packs. Its 20 I/O pins can drive MOSFET gates, read shunt voltages via the integrated comparator (where present in family variants), and manage LED status indication. The 5 MIPS throughput at 20 MHz closes a PWM current-control loop in well under 100 microseconds. OTP memory locks the charge profile at production. Compared to dedicated charger ICs like the MCP73831, the PIC16C55A-20/SO gives designers flexibility to implement custom charge algorithms for non-standard cell chemistries.
Recommended
Security Keypads and Access Panels
The PIC16C55A-20/SO is well suited to security keypads, access control panels, and alarm annunciators where its 20 I/O pins directly drive a 4x4 matrix keypad plus status LEDs and a piezo buzzer without external logic. The 5 MIPS throughput at 20 MHz debounces inputs and verifies PIN codes in real time, while OTP memory prevents end-user firmware tampering. The 28-SOIC package supports automated assembly in OEM panel production. Compared with PIC16F flash parts, the PIC16C55A-20/SO offers a lower unit cost for high-volume security products, though Microchip's NRND notice means designers should plan a migration path to PIC16F equivalent.
Recommended
Educational and Hobbyist Platforms
The PIC16C55A-20/SO has historically been a teaching example for 8-bit RISC microcontroller courses, embedded systems labs, and DIY hobbyist projects. Its 28-SOIC package is breadboard-friendly with a SOIC-to-DIP adapter, and the PIC16C5X architecture exposes only 33 instructions, making it an ideal vehicle for teaching instruction sets, addressing modes, and assembly programming. The 20 MHz speed grade allows real-time demonstrations of timer/counter, GPIO, and interrupt-free polling. Compared with modern PIC16F or ATmega platforms, the PIC16C55A-20/SO is no longer recommended for new designs, but pre-programmed OTP units remain an inexpensive way to teach low-level MCU concepts.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55A-20/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C558-20/SO | PIC16C554-20/SO | PIC16C55-10/SO | PIC16C55A-20I/SO | PIC16C558-04I/SO | PIC16C554-04/SO |
|---|---|---|---|---|---|---|---|
| Package | 28-SOIC | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Maximum Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 10 MHz | 20 MHz | 4 MHz | 4 MHz |
| Program Memory | 768 B (512 x 12 OTP) | 2 KB (EPROM) | 896 B OTP | 768 B (512 x 12 OTP) | 768 B (512 x 12 OTP) | 2 KB (EPROM) | 896 B OTP |
| RAM Size | 24 B | 24 B | 24 B | 24 B | 24 B | 24 B | 24 B |
| I/O Pins | 20 | 20 | 20 | 20 | 20 | 20 | 20 |
| Interrupt Support | No | No | Yes | No | No | No | Yes |
| Operating Temperature | 0 C to +70 C | 0 C to +70 C | 0 C to +70 C | 0 C to +70 C | -40 C to +85 C | -40 C to +85 C | 0 C to +70 C |
| Lifecycle Status | NRND | NRND | NRND | NRND | NRND | NRND | NRND |
Key Differentiators
- Lowest-cost OTP variant with industrial-temp grade available (vs PIC16C558-20/SO)
- No interrupt hardware simplifies deterministic polling code (vs PIC16C554-20/SO)
- Mature 20 MHz PIC16C5X core with broad third-party toolchain support (vs PIC16C55-10/SO)
Design Notes
The PIC16C55A-20/SO operates across a 3.0 V to 5.5 V supply range (per Microchip datasheet DS30453). Place a 100 nF ceramic decoupling capacitor as close as physically possible to the VDD pin (pin 18 and pin 27 share VDD on the 28-SOIC variant). Add a bulk 10 uF tantalum or aluminum electrolytic capacitor at the regulator output feeding the MCU. For battery-powered designs, the PIC16C5X family supports a sleep mode (clock stopped) that drops current consumption to the low microampere range; cycle the oscillator on/off via TMR0 wake-up to extend battery life. The MCLR pin (pin 1) must be tied to VDD through a 10 kohm pull-up to avoid spurious resets; add a 100 nF cap from MCLR to VSS if the supply has slow rise times.
Keep the crystal/oscillator traces short and symmetric. The PIC16C55A-20/SO uses pins 6 (OSC1) and 7 (OSC2) for crystal or ceramic resonator connection; route both traces between the MCU and the crystal with ground guarding on both sides, no vias. For 20 MHz operation, the crystal load capacitance is typically 15-33 pF; refer to the crystal vendor's load-capacitance specification and the PIC16C5X datasheet's oscillator section to choose C1 and C2. Place the crystal within 5 mm of the MCU body to minimize stray capacitance. Avoid routing high-frequency signals (PORTB transitions, oscillator) parallel to analog traces - on the PIC16C5X there is no analog input, but switching noise can couple into adjacent analog circuitry in mixed-signal boards.
Three common pitfalls when designing with the PIC16C55A-20/SO: (1) The PIC16C5X core has NO interrupt hardware - all event handling must be polled. Code written for PIC16F or PIC18 parts will not run correctly if it relies on interrupts. (2) The 768-byte OTP program memory can be programmed only once in the SOIC package; verify your code with a JW (windowed) ceramic prototype before committing to OTP production units. (3) Microchip marks the PIC16C55A as NRND (Not Recommended for new designs) - for new designs, choose the PIC16C558-20/SO or PIC16F84A in the same 28-SOIC footprint to avoid future obsolescence risk. Always double-check that your chosen programmer (e.g., MPLAB PM3, PICkit 3) supports the PIC16C5X OTP family before designing the production programming fixture.
Compliance Information
RoHS compliance confirmed by DigiKey product page 281891 and LCSC listing. AEC-Q100 not applicable - this is a commercial-grade MCU; industrial-temp -20I variants exist for extended temperature applications but are not automotive-qualified.
