PIC16C55A-20I/SS - 8-Bit 20MHz 768B OTP MCU SSOP-28 | Microchip
MPN: PIC16C55A-20I/SS â End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.65 | $1.65 |
| 10 | $1.48 | $14.80 |
| 100 | $1.32 | $132.00 |
| 500 | $1.18 | $590.00 |
| 1,000 | $1.04 | $1,040.00 |
PIC16C55A-20I/SS Overview
An 8-bit microcontroller is a single-chip computer that integrates a CPU, program memory, working RAM, and peripheral I/O on one die. The PIC16C5X family implements a RISC Harvard architecture with 12-bit-wide instructions and an 8-bit-wide data path, achieving approximately 2:1 code compression over other 8-bit MCUs in its class. Within the broader microcontroller hierarchy, the PIC16C55A belongs to the mid-range 8-bit category, positioned between baseline PIC10/12/16 devices and 16-bit PIC24/dsPIC families. OTP program memory allows one-time factory or field programming using a device programmer such as the MPLAB PM3, making the part cost-optimized for high-volume fixed-function products.
Key features of the PIC16C55A-20I/SS include a 20MHz maximum operating frequency, 24-byte general-purpose RAM, 20 bidirectional I/O pins, one 8-bit real-time clock/counter (TMR0), Power-On Reset (POR), Watchdog Timer (WDT), and a two-level hardware stack supporting direct, indirect, and relative addressing modes. Seven or eight special-function hardware registers manage peripheral control. The 28-pin SSOP package provides compact surface-mount integration at approximately 5.3mm body width, well-suited for space-constrained designs.
The PIC16C55A uses a RISC architecture executing most instructions in a single cycle, with a 12-bit instruction word and 33 single-word instructions. This compact instruction set yields high code density, reducing total program memory requirements and overall system cost. The two-level hardware stack limits call depth to two levels, which constrains interrupt-driven or deeply nested subroutine architectures but is adequate for simple sequential control loops.
Typical applications include appliance control, industrial sensor interfaces, simple motor drivers, LED controllers, consumer electronics, automotive subsystems (non-safety), battery chargers, and any cost-sensitive embedded system where the OTP memory model fits the production volume profile. The industrial temperature grade extends applicability to factory automation, HVAC controls, and outdoor equipment.
When designing with this device, plan for the two-level hardware stack limitation, the OTP memory programming workflow (which requires a device programmer and cannot be re-flashed in-circuit), and the legacy lifecycle status. For new designs, evaluate Flash-based PIC16F5X equivalents that provide in-circuit programmability and longer-term supply assurance.
Drop-in alternatives for PIC16C55A-20I/SS â 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-20I/SS (same form factor and footprint) â differing in Package, Program Memory Size, Watchdog Timer, Mounting Type, Program Memory Type.
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No drop-in alternatives available for this product.
Request AlternativesPIC16C55A-20I/SS Maximum Ratings & Electrical Characteristics
| Series | PIC 16C |
| Core Processor | PIC |
| Core Size | 8-Bit |
| Maximum Clock Frequency | 20 MHz |
| Program Memory Size | 768 B (512 x 12) OTP |
| Program Memory Type | OTP (One-Time Programmable) |
| RAM Size | 24 B |
| Number of I/O | 20 |
| Number of Timers/Counters | 1 (8-bit TMR0) |
| Supply Voltage Range | 3 V to 5.5 V |
| Operating Temperature Range | -40C to +85C (Industrial) |
| Package | 28-SSOP (5.30 mm) |
| Mounting Type | Surface Mount |
| MSL Level | 1 |
| RoHS Status | Non-Compliant (legacy OTP part, contains Pb) |
| Lifecycle Status | Not Recommended for new designs |
| Architecture | RISC Harvard, 12-bit instruction word |
PIC16C55A-20I/SS Pin Configuration
| Pin 1 | RA2 â Bidirectional I/O port A bit 2 |
| Pin 2 | RA3 â Bidirectional I/O port A bit 3 |
| Pin 3 | RC0 â Bidirectional I/O port C bit 0 |
| Pin 4 | RC1 â Bidirectional I/O port C bit 1 |
| Pin 5 | RC2 â Bidirectional I/O port C bit 2 |
| Pin 6 | RC3 â Bidirectional I/O port C bit 3 |
| Pin 7 | RB0 â Bidirectional I/O port B bit 0 |
| Pin 8 | RB1 â Bidirectional I/O port B bit 1 |
| Pin 9 | RB2 â Bidirectional I/O port B bit 2 |
| Pin 10 | RB3 â Bidirectional I/O port B bit 3 |
| Pin 11 | VSS â Ground reference |
| Pin 12 | RB4 â Bidirectional I/O port B bit 4 |
| Pin 13 | RB5 â Bidirectional I/O port B bit 5 |
| Pin 14 | RB6 â Bidirectional I/O port B bit 6 / ICSP clock |
| Pin 15 | RB7 â Bidirectional I/O port B bit 7 / ICSP data |
| Pin 16 | VDD â Positive supply voltage (+3V to +5.5V) |
| Pin 17 | RC4 â Bidirectional I/O port C bit 4 |
| Pin 18 | RC5 â Bidirectional I/O port C bit 5 |
| Pin 19 | RC6 â Bidirectional I/O port C bit 6 |
| Pin 20 | RC7 â Bidirectional I/O port C bit 7 |
| Pin 21 | RA0 â Bidirectional I/O port A bit 0 |
| Pin 22 | RA1 â Bidirectional I/O port A bit 1 |
| Pin 23 | RA4 â Bidirectional I/O port A bit 4 / T0CKI Timer0 clock input (open-drain) |
| Pin 24 | RA5 â Bidirectional I/O port A bit 5 |
| Pin 25 | MCLR/VPP â Master Clear reset input / OTP programming voltage |
| Pin 26 | OSC2 â Oscillator crystal output |
| Pin 27 | OSC1 â Oscillator crystal input / external clock input |
| Pin 28 | NC â Not connected (per datasheet, pin reserved) |
Typical Applications
PIC16C55A-20I/SS is suitable for 7 applications: White Goods Appliance Control, Industrial Sensor Interface Modules, LED Display and Sign Controllers, Simple Motor and Solenoid Controllers, Consumer Electronics Remote Controls, Battery Chargers and Power Management, HVAC and Building Automation.
White Goods Appliance Control
The PIC16C55A-20I/SS suits washer, dryer, dishwasher, and microwave control boards where the program logic is fully fixed at manufacturing time. The 768-byte OTP memory (512 x 12 instructions) accommodates typical appliance state machines (wash cycles, timer logic, sensor fusion) with substantial code-density headroom thanks to the 12-bit RISC instruction set achieving roughly 2:1 compression over other 8-bit MCUs. The 20 digital I/O lines directly interface relays, triac drivers, keypad matrices, and LED/LCD segments. The industrial -40C to +85C temperature grade handles the thermal environment inside appliance housings. The two-level hardware stack is adequate for sequential appliance control programs that do not require deep subroutine nesting or interrupt-driven preemptive multitasking.
Recommended
Industrial Sensor Interface Modules
The PIC16C55A-20I/SS works in dedicated sensor-to-serial converter modules that read one analog or digital sensor, apply linearization, and output a calibrated 4-20mA, 0-10V, or UART stream. With 20 I/O pins, the chip handles 8-channel analog mux scanning via a CD4051, drives an RS-485 transceiver such as MAX485, and operates from a regulated 5V supply. The 20MHz clock supports 9600 to 57600 baud UART rates easily. The 768-byte OTP memory holds calibration tables for common sensor types (thermocouple linearization, RTD curves). Industrial-grade -40C to +85C operation covers factory floor conditions. The 28-SSOP surface-mount package is preferred for DIN-rail module designs where mechanical height constraints exist.
Recommended
LED Display and Sign Controllers
The PIC16C55A-20I/SS drives standalone LED message boards, scrolling text displays, and small RGB pixel arrays in cost-sensitive consumer and commercial signage. The 20 I/O lines multiplex directly into a 7-segment plus RGB matrix without external logic. The 20MHz clock multiplexes LED refresh at 100+ Hz, eliminating visible flicker. The OTP program memory locks in static display sequences once qualified, removing any field-tampering risk. The industrial temperature grade handles outdoor sign enclosures in summer and winter. The 28-SSOP package provides the small form factor needed for embedded signage controllers. For battery-powered portable signs, the 5V low-power CMOS process keeps quiescent current low.
Recommended
Simple Motor and Solenoid Controllers
The PIC16C55A-20I/SS controls DC brushed motors, stepper motors (unipolar), and solenoids in HVAC dampers, vending machines, and small appliances. The 20MHz clock provides sufficient PWM resolution (Timer0 in software) for basic speed control of small DC fans and pump motors. The 20 I/O lines drive H-bridge ICs such as L293D or directly sink solenoid coils via flyback diodes. The 768-byte OTP holds lookup tables for soft-start ramps and stall-recovery routines. Industrial temperature rating handles HVAC plenum environments. The 28-SSOP package fits inside the motor housing PCB. The PIC16C5X two-level hardware stack is adequate for sequential motor control state machines without complex interrupt prioritization.
Recommended
Consumer Electronics Remote Controls
The PIC16C55A-20I/SS serves in IR/RF remote controls, toy controllers, and battery-powered consumer handheld devices. The 20 I/O lines scan 4x5 key matrices directly. The 20MHz clock generates precise 38kHz or 40kHz carrier frequencies for IR transmission using Timer0 PWM. The 3V to 5.5V supply range supports both 3V lithium coin cells and 4.5V from three AAA cells. The 768-byte OTP memory stores button debounce, code translation, and pairing tables. The CMOS low-power design extends battery life. The 28-SSOP package is small enough for slim remote housings. The PIC16C5X architecture is well-suited to simple sequential scan-and-transmit logic with minimal interrupt complexity.
Recommended
Battery Chargers and Power Management
The PIC16C55A-20I/SS implements lead-acid, NiMH, and Li-ion charge controllers in the 100-500 mA range where the OTP memory locks in charge algorithms for safety certification. The 20MHz clock supports accurate ADC-free charge voltage/current monitoring via comparator thresholds. The 20 I/O lines drive MOSFET switches, status LEDs, and fault relays. The industrial temperature range handles under-hood automotive and outdoor solar applications. The 28-SSOP package fits compact charger modules. The 768-byte OTP memory holds multi-stage charge profiles (bulk/absorption/float) with temperature compensation tables. The PIC16C5X deterministic execution provides the predictable timing needed for safety-critical battery control algorithms.
Recommended
HVAC and Building Automation
The PIC16C55A-20I/SS controls thermostats, damper actuators, and zone valves in residential and light commercial HVAC systems. The 20 I/O lines interface thermistor inputs (via resistor divider), relay outputs for compressor/fan control, and LCD segment displays for setpoint indication. The 20MHz clock drives 1-Wire or I2C sensor polling with deterministic timing. The 768-byte OTP memory holds PID coefficients for temperature control loops. The industrial -40C to +85C range covers plenum and outdoor equipment installations. The 28-SSOP surface-mount package suits modern slim thermostat designs. The PIC16C5X RISC architecture provides the predictable, jitter-free execution needed for control loop stability.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55A-20I/SS â comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55A-20I/SP | PIC16C55A-20I/P | PIC16C558-20I/SS | PIC16C554-20I/SS |
|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-SSOP | 28-SPDIP (different footprint, drop-in only in same SSOP layout) | 28-PDIP | 28-SSOP - same | 28-SSOP - same |
| Program Memory | 768 B (512 x 12) OTP | 768 B (512 x 12) OTP - same | 2K x 14 OTP | 1K x 14 OTP | |
| Maximum Clock Frequency | 20 MHz | 20 MHz | 4 MHz | 20 MHz | 20 MHz |
| RAM Size | 24 B | 24 B | 72 B | 80 B | |
| I/O Pins | 20 | 20 | 20 | 20 | |
| Operating Temperature | -40C to +85C (Industrial) | -40C to +85C (Industrial) | 0C to +70C (Commercial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) |
| Memory Type | OTP (One-Time Programmable) | OTP | OTP | OTP | |
| Lifecycle Status | NRND | NRND | NRND | NRND |
Key Differentiators
- Same SSOP-28 footprint as PIC16C558 but smaller 768B OTP (vs PIC16C558-20I/SS)
- Higher 20MHz clock than 4MHz variants (vs PIC16C55A-04E/SS)
- PIC16C5X legacy architecture vs Flash-based PIC16F5X (vs PIC16F57-I/SS)
Design Notes
OTP memory can be programmed only ONCE. There is no in-circuit reprogramming and no in-circuit reprogramming pathway. Develop all firmware on a PIC16F57-I/SS Flash prototype board first (same 28-SSOP footprint, same instruction set), validate timing and I/O behavior, then commit the final code to OTP parts via MPLAB PM3. Always keep a few blank PIC16C55A-20I/SS parts in reserve for engineering rework, because a programming error or Vpp timing glitch on OTP parts bricks them permanently.
Decouple VDD (pin 16) and VSS (pin 11) with 100 nF ceramic capacitors placed within 5mm of the supply pins. For battery-powered or sleep-mode designs, add a 10 uF bulk capacitor on VDD to handle inrush from relay or LED loads. The PIC16C5X CMOS process draws under 2 mA at 5V/20MHz active and under 1 uA in sleep, so power supply design can be very simple - a 78L05 regulator or direct 3xAA cells with a 100 nF cap are typically adequate.
The 28-SSOP (Shrink Small Outline Package, 5.30 mm body width, 0.65 mm pitch) requires careful PCB layout: keep traces between SSOP pads short and use a ground plane beneath the IC to reduce EMI. The exposed die paddle (if present on this package variant) should be soldered to a copper pad tied to VSS for thermal dissipation. The MCLR/VPP pin (pin 25) requires a 10 kohm pull-up to VDD plus a 100 nF cap to ground; this prevents spurious resets during OTP programming voltage transitions.
When using an external crystal on OSC1 (pin 27) and OSC2 (pin 26), place the crystal within 10mm of the IC pins and route the traces over a continuous ground plane. Add 22 pF load capacitors from each crystal pin to ground as specified in the PIC16C5X datasheet. For designs in noisy environments (motor control, relay switching), add a 100 ohm series resistor on OSC2 to dampen harmonics. If using the internal RC oscillator instead, leave OSC1 as a digital I/O but disable the crystal driver in the configuration word.
Compliance Information
Legacy OTP part. RoHS non-compliant due to Pb-containing die attach; use PIC16F57-I/SS or other Flash PIC16F5X parts for RoHS-compliant new designs. Not AEC-Q100 qualified.
