PIC16C55-XT/SS - 8-bit OTP MCU, 768B, 4MHz, 28-SSOP | Microchip
MPN: PIC16C55-XT/SS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.1227 | $4.12 |
| 10 | $3.71 | $37.10 |
| 100 | $3.3 | $330.00 |
| 500 | $2.86 | $1,430.00 |
| 1,000 | $2.42 | $2,420.00 |
PIC16C55-XT/SS Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, RAM, program memory, and I/O peripherals on one die. The PIC16C5X family from Microchip Technology belongs to the baseline 8-bit RISC MCU category, which sits within the broader taxonomy of microcontroller -> embedded processor -> semiconductor IC. These devices are designed for cost-sensitive, deterministic real-time control tasks where predictable instruction timing, low power consumption, and small package footprint matter more than raw compute throughput.
Key features include a two-level deep hardware stack, 12-bit-wide instruction words with 2:1 code compression versus typical 8-bit CISC architectures, direct/indirect/relative addressing modes, and an 8-bit real-time clock/counter (TMR0). The XT oscillator suffix specifies a standard crystal/resonator frequency range, and the SSOP suffix designates the 0.209-inch (5.30 mm) wide Shrink Small Outline Package. Wide operating voltage and industrial temperature range make this device appropriate for consumer, appliance, and industrial subsystems.
Typical applications include appliance controllers, simple sensor interfaces, LED driving, battery chargers, remote controls, and low-end automotive body electronics. The PIC16C55-XT/SS is commonly designed in where a baseline PIC16C5X instruction set, on-chip oscillator support, and small-form-factor SSOP are needed for cost-optimized production runs.
When designing with this device, ensure the OTP memory is programmed before final PCB assembly because OTP cannot be erased after programming. Use Microchip's MPLAB PM3 Universal Device Programmer or equivalent production-grade programmer. Verify the crystal load capacitor values against the chosen XT-mode resonator specification, and budget board space for the decoupling network near VDD.
This page synthesizes distributor pricing from DigiKey, Mouser, LCSC, and Octopart, plus drop-in alternatives from the Microchip baseline PIC16C5X family and pin-compatible PIC16F successors, alongside practical design notes not consolidated on any single manufacturer page.
Drop-in alternatives for PIC16C55-XT/SS — 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 PIC16C55-XT/SS (same form factor and footprint) — differing in Package, Program Memory Size, Program Memory Type, RAM Size, Instruction Set.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C55A-20I/SS
✅ Drop-In✓ In Stock
$1.04 / Unit
View Datasheet →PIC16C55A-04E/SS
✅ Drop-In✓ In Stock
$2.05 / Unit
View Datasheet →PIC16F57-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C55T-XT/SS
✅ Drop-In✓ In Stock
$2.64 / Unit
View Datasheet →PIC16C55-XT/SS Maximum Ratings & Electrical Characteristics
| Core | 8-bit PIC16C5X baseline RISC |
| Program Memory Type | OTP (One-Time-Programmable) EPROM |
| Program Memory Size | 768 bytes (512 x 12 words) |
| RAM Size | 24 bytes |
| Maximum CPU Speed | 4 MHz (4 MIPS) |
| Number of I/O Pins | 20 |
| Timers | 1 x 8-bit (TMR0) |
| Oscillator Type | XT (external crystal/resonator) |
| Instruction Width | 12-bit |
| Data Bus Width | 8-bit |
| Stack Depth | 2-level hardware |
| Addressing Modes | Direct, Indirect, Relative |
| Package | 28-SSOP (0.209", 5.30 mm width) |
| Mounting Type | Surface Mount |
| Lead-Free / RoHS | Yes (compliant per Microchip product page) |
PIC16C55-XT/SS Pin Configuration
| Pin 1 | RA2 — PORTA bit 2 (digital I/O) |
| Pin 2 | RA3 — PORTA bit 3 (digital I/O) |
| Pin 3 | RA4/T0CKI — PORTA bit 4 / TMR0 clock input |
| Pin 4 | MCLR — Master Clear (reset, active low) |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0 — PORTB bit 0 (digital I/O) |
| Pin 7 | RB1 — PORTB bit 1 (digital I/O) |
| Pin 8 | RB2 — PORTB bit 2 (digital I/O) |
| Pin 9 | RB3 — PORTB bit 3 (digital I/O) |
| Pin 10 | RB4 — PORTB bit 4 (digital I/O) |
| Pin 11 | RB5 — PORTB bit 5 (digital I/O) |
| Pin 12 | RB6 — PORTB bit 6 (digital I/O) |
| Pin 13 | RB7 — PORTB bit 7 (digital I/O) |
| Pin 14 | VSS — Ground reference |
| Pin 15 | OSC2 — Oscillator output (XT crystal) |
| Pin 16 | OSC1 — Oscillator input (XT crystal) |
| Pin 17 | RC0 — PORTC bit 0 (digital I/O) |
| Pin 18 | RC1 — PORTC bit 1 (digital I/O) |
| Pin 19 | RC2 — PORTC bit 2 (digital I/O) |
| Pin 20 | RC3 — PORTC bit 3 (digital I/O) |
| Pin 21 | RC4 — PORTC bit 4 (digital I/O) |
| Pin 22 | RC5 — PORTC bit 5 (digital I/O) |
| Pin 23 | RC6 — PORTC bit 6 (digital I/O) |
| Pin 24 | RC7 — PORTC bit 7 (digital I/O) |
| Pin 25 | VSS — Ground reference |
| Pin 26 | RA0 — PORTA bit 0 (digital I/O) |
| Pin 27 | RA1 — PORTA bit 1 (digital I/O) |
| Pin 28 | VDD — Positive supply voltage |
Typical Applications
PIC16C55-XT/SS is suitable for 7 applications: Appliance Control Boards, Remote Controls and IR Transmitters, LED Lighting and Sign Drivers, Battery Chargers and Power Management, Simple Sensor Interfaces, Industrial Timing and Sequencing Relays, Automotive Body Electronics (Legacy).
Appliance Control Boards
The PIC16C55-XT/SS fits appliance control boards (washing machines, dishwashers, microwave ovens) because its 20 GPIO pins can directly drive relays, triacs, LEDs, and 7-segment displays without external logic. The 768-byte OTP memory is sufficient for fixed sequence-control firmware (wash cycles, timed heating, motor direction), while the 4 MHz / 4 MIPS performance meets the real-time interrupt deadlines typical of appliance safety interlocks. Compared with Flash MCUs, the OTP variant reduces unit cost at high production volumes where code is finalized and stable.
Recommended
Remote Controls and IR Transmitters
The PIC16C55-XT/SS is well matched to IR remote controls because its TMR0 timer generates accurate carrier frequencies (typically 36-40 kHz) and its 20 GPIO pins can scan 4x4 or 5x5 key matrices with minimal external components. The 768-byte OTP memory stores 32-64 command codes, while the 24-byte RAM supports key-debounce state. The XT oscillator and 28-SSOP package allow a compact 2-AAA battery-powered PCB. Estimated: at 3V supply with 4 MHz oscillator, the device draws roughly 2 mA active, enabling 100+ hour battery life in typical remote usage.
Recommended
LED Lighting and Sign Drivers
The PIC16C55-XT/SS drives LED lighting controllers, decorative sign chasers, and channel letter modules by sequencing GPIO outputs to switch MOSFETs or constant-current drivers. Its 8-bit TMR0 sets chase rates from milliseconds to minutes, and the 20 I/O pins can control up to 20 individual LED segments or PWM channels via bit-banging. Compared with dedicated LED driver ICs, the PIC16C55-XT/SS offers flexible firmware-controlled patterns at lower BOM cost for high-volume sign and architectural lighting.
Recommended
Battery Chargers and Power Management
The PIC16C55-XT/SS implements basic battery charger controllers for NiCd/NiMH packs and SLA batteries by monitoring voltage dividers on its GPIO pins and switching charge MOSFETs. The 768-byte OTP holds CC/CV charge profiles, safety timers, and temperature foldback logic, while TMR0 sets the PWM charge duty cycle via bit-banging. The 4 MHz speed is sufficient for sub-1 kHz charge control loops. Compared with dedicated charger ASICs, the PIC16C55-XT/SS enables firmware-adjustable chemistries at minimal incremental cost.
Recommended
Simple Sensor Interfaces
The PIC16C55-XT/SS interfaces to digital-output sensors such as DHT11/DHT22 temperature/humidity, HC-SR04 ultrasonic, and simple thermistor-based circuits by reading GPIO inputs and driving indicator LEDs. While lacking an internal ADC, the device can use an external ADC IC (e.g., MCP3002) over bit-banged SPI. The 768-byte OTP is sufficient for lookup-table linearization, and the 28-SSOP package fits in compact sensor hub designs.
Recommended
Industrial Timing and Sequencing Relays
The PIC16C55-XT/SS serves as a programmable timing relay or sequencer in industrial control cabinets, replacing discrete 555-timer-based designs with firmware-configurable delays, pulse trains, and interlock logic. Its 20 GPIO pins drive relays, contactors, and indicator lamps directly, while TMR0 generates millisecond-to-hour delays with crystal accuracy. The 28-SSOP package supports DIN-rail mounted controller PCBs, and the OTP memory protects proprietary timing profiles from unauthorized firmware extraction.
Recommended
Automotive Body Electronics (Legacy)
The PIC16C55-XT/SS appears in legacy automotive body modules such as interior lighting controllers, mirror adjusters, and seat-position memories where its 20 GPIO pins and 4 MHz performance are sufficient. However, new automotive designs should migrate to AEC-Q100 qualified parts such as PIC16F15344T-I/SS or dsPIC33 family members. The OTP memory requires windowed or production programmers, and Microchip typically discontinues OTP parts in favor of Flash equivalents.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55-XT/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55A-20I/SS | PIC16C55A-04E/SS | PIC16F57-I/SS | PIC16C55T-XT/SS |
|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-SSOP | 28-SSOP - same | 28-SSOP - same | 28-SSOP - same | 28-SSOP - same |
| Program Memory Type | OTP (768 B) | OTP (768 B) | OTP (768 B) | Flash (2 KB) | OTP (768 B) |
| RAM Size | 24 B | 24 B | 24 B | 72 B | 24 B |
| Maximum CPU Speed | 4 MHz (4 MIPS) | 20 MHz (5 MIPS) | 4 MHz (4 MIPS) | 20 MHz (5 MIPS) | 4 MHz (4 MIPS) |
| Number of I/O Pins | 20 | 20 | 20 | 20 | 20 |
| Oscillator Mode | XT | XT/HS/RC/LP | XT/HS/RC/LP | XT/HS/RC/LP/INTOSC | XT |
| Temperature Grade | Commercial | Industrial | Extended | Industrial | Commercial |
| Reprogrammability | No (OTP) | No (OTP) | No (OTP) | Yes (Flash, 1000 cycles) | No (OTP) |
Key Differentiators
- Lowest-cost baseline PIC16C5X with XT oscillator in SSOP-28 (vs PIC16F57-I/SS)
- Industry-standard baseline RISC core with 2:1 code compression (vs PIC16C55A-20I/SS)
- 28-SSOP surface-mount package for compact designs (vs PIC16C55-XT/P (PDIP-28))
Design Notes
Estimated: at VDD=5V and 4 MHz oscillator, the PIC16C55-XT/SS draws approximately 2 mA active and 5 uA standby. Place a 100 nF ceramic decoupling capacitor within 5 mm of VDD (pin 28) and VSS (pin 25 or 14), plus a 10 uF bulk capacitor near the regulator output. For battery applications, route MCLR (pin 4) through a 10 kohm pull-up to VDD to avoid spurious resets during power-down. The PIC16C55A variant reduces active current by ~30% compared with the legacy PIC16C55.
The 28-SSOP package has 0.65 mm pitch leads - use a fine-pitch PCB process (0.4 mm drill, 0.2 mm trace clearance) for the land pattern. Route the XT crystal traces (OSC1/OSC2, pins 16-15) as short as possible (under 10 mm) with a ground guard ring to minimize EMI. Place the crystal load capacitors (typically 15-33 pF for XT mode) immediately adjacent to the crystal, with the ground side connected to a quiet ground plane (not the noisy digital return).
The PIC16C55 uses One-Time-Programmable (OTP) memory - once programmed, it cannot be erased. Always validate firmware on a windowed PIC16C55/JW or a Flash equivalent (PIC16F57) before committing to OTP programming for production. Do not confuse the XT oscillator mode with HS (high-speed, 4-20 MHz) or LP (low-power, 32-768 kHz) - using the wrong mode prevents startup. Also note that PIC16C5X parts have only a 2-level hardware stack, which limits subroutine nesting to 2 deep - plan interrupt and main code flow accordingly.
When migrating between PIC16C55-XT/SS (SSOP-28) and PIC16C55-XT/P (PDIP-28), the SSOP-28 land pattern is required because the lead pitch differs (0.65 mm SSOP vs 2.54 mm PDIP). Do not attempt to use a PDIP footprint on an SSOP part - this will short adjacent pins. Conversely, the SSOP-28 and PIC16C55A-20I/SS share identical SSOP-28 footprints, allowing direct drop-in replacement.
Compliance Information
RoHS and lead-free compliance per Microchip product page; AEC-Q100 not qualified - for new automotive designs choose AEC-Q100 graded PIC16F15344T-I/SS or dsPIC33 family members.