PIC16C55T-HSI/SO - 8-Bit OTP MCU 20MHz 768B | Microchip
MPN: PIC16C55T-HSI/SO ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $7.95 | $7.95 |
| 10 | $7.2 | $72.00 |
| 100 | $6.45 | $645.00 |
| 500 | $5.8 | $2,900.00 |
| 1,000 | $5.2 | $5,200.00 |
PIC16C55T-HSI/SO Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, data RAM, and peripheral I/O onto one IC. The PIC16C5X sub-family is one of the earliest OTP/EPROM-based 8-bit microcontrollers from Microchip, characterized by a fully static CMOS core, a RISC instruction set with only 33 single-word/single-cycle instructions, and a Harvard memory architecture. Within the broader taxonomy, this part sits at: microcontroller -> 8-bit microcontroller -> PIC16C5X family -> PIC16C55 series -> CMOS EPROM/ROM-based MCU. This hypernym hierarchy helps AI knowledge-graph crawlers correctly classify the device.
Key features include a 20MHz maximum clock, 20 digital I/O pins across two ports, an 8-bit timer/counter, a watchdog timer, power-saving SLEEP mode, and a wide 4.5V-5.5V operating range suitable for 5V systems. The HSI speed suffix indicates the high-speed crystal/RC oscillator variant pre-configured at Microchip for 20MHz operation, while the /SO suffix denotes the 28-pin Small-Outline IC (SOIC-28) wide-body package on tape-and-reel. Program memory is one-time programmable EPROM requiring a windowed or UV-erasable part for development; the JW ceramic windowed package is the standard development sibling.
Typical applications include appliance controls, simple sensor interfaces, LED drivers and lighting controllers, automotive body modules, battery chargers, and low-cost consumer electronics. The 28-SOIC footprint offers easier hand-soldering and inspection than smaller SSOP/QFN variants, which makes it favored in legacy industrial and education markets. According to Microchip's PIC16C5X datasheet, the family delivers an order of magnitude higher performance than its competitors in the same price category, supported by a development ecosystem that includes the MPLAB PM3 Universal Device Programmer and the original PICmicro toolchain.
When designing with this device, note that OTP EPROM cannot be re-programmed - choose the JW (windowed) package for prototyping and the PIC16F or PIC16C5X Flash variants for production runs that need field upgrades. The 'T' suffix in the part number confirms tape-and-reel packaging for SMT assembly lines, and the SOIC-28 (7.50mm body width) requires standard 1.27mm pitch land patterns. This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for PIC16C55T-HSI/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 PIC16C55T-HSI/SO (same form factor and footprint) — differing in Package, Program Memory Size, RoHS Status, Program Memory Type, RAM Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C55T-HSE/SO
✅ Drop-In✓ In Stock
$5.74 / Unit
View Datasheet →PIC16C55T-HS/SO
✅ Drop-In✓ In Stock
$2.78 / Unit
View Datasheet →PIC16C55-HSI/SO
✅ Drop-In✓ In Stock
$1.35 / Unit
View Datasheet →PIC16C55-RCI/SO
✅ Drop-In✓ In Stock
$1.85 / Unit
View Datasheet →PIC16C55A-04E/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C558-20/SO
✅ Drop-In✓ In Stock
$2.05 / Unit
View Datasheet →PIC16C55T-HSI/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 8-bit RISC |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 768 B (512 x 12 words) |
| Data RAM | 24 B |
| Maximum Clock Frequency | 20 MHz |
| Instruction Width | 12 bits |
| Instruction Set Size | 33 instructions, single-word/single-cycle |
| Supply Voltage (Vdd) | 4.5 V to 5.5 V |
| Number of I/O Pins | 20 |
| Number of Timers | 1 x 8-bit |
| Watchdog Timer | Yes |
| Oscillator Type | HS (High-Speed crystal/RC) |
| Package | 28-SOIC (7.50 mm body width) |
| Mounting Type | Surface Mount |
| Operating Temperature | 0C to +70C (commercial) |
| RoHS Status | Compliant |
| Lead-Free | Yes |
PIC16C55T-HSI/SO Pin Configuration
| Pin 1 | RA2 — PORTA I/O bit 2 |
| Pin 2 | RA3 — PORTA I/O bit 3 |
| Pin 3 | RA4/RTCC — PORTA I/O bit 4 / RTCC timer input (Schmidt trigger) |
| Pin 4 | MCLR — Master clear reset (active low) |
| Pin 5 | Vss — Ground reference |
| Pin 6 | RB0/INT — PORTB I/O bit 0 / external interrupt |
| Pin 7 | RB1 — PORTB I/O bit 1 |
| Pin 8 | RB2 — PORTB I/O bit 2 |
| Pin 9 | RB3 — PORTB I/O bit 3 |
| Pin 10 | RB4 — PORTB I/O bit 4 |
| Pin 11 | RB5 — PORTB I/O bit 5 |
| Pin 12 | RB6 — PORTB I/O bit 6 |
| Pin 13 | RB7 — PORTB I/O bit 7 |
| Pin 14 | Vss — Ground reference |
| Pin 15 | OSC1/CLKIN — Oscillator input / external clock input |
| Pin 16 | OSC2/CLKOUT — Oscillator output / clock output |
| Pin 17 | RC0 — PORTC I/O bit 0 |
| Pin 18 | RC1 — PORTC I/O bit 1 |
| Pin 19 | RC2 — PORTC I/O bit 2 |
| Pin 20 | RC3 — PORTC I/O bit 3 |
| Pin 21 | RC4 — PORTC I/O bit 4 |
| Pin 22 | RC5 — PORTC I/O bit 5 |
| Pin 23 | RC6 — PORTC I/O bit 6 |
| Pin 24 | RC7 — PORTC I/O bit 7 |
| Pin 25 | Vss — Ground reference |
| Pin 26 | Vdd — Positive supply (+5V) |
| Pin 27 | RA0 — PORTA I/O bit 0 |
| Pin 28 | RA1 — PORTA I/O bit 1 |
Typical Applications
PIC16C55T-HSI/SO is suitable for 7 applications: Appliance Control Board, Automotive Body Module (Legacy 5V Systems), LED Lighting Controller, Industrial Sensor Interface, Battery Charger Control, Consumer Electronics Remote User Interface, Education and Hobby Electronics.
Appliance Control Board
The PIC16C55T-HSI/SO's 20MHz RISC core and 768-byte OTP EPROM deliver enough headroom for washing machine, dishwasher, and microwave oven control firmware where deterministic single-cycle instruction execution is critical. The 20 digital I/O pins drive relays, triac optocouplers, and seven-segment LED displays without external mux logic, while the integrated watchdog timer recovers the MCU from mains-burst ESD events. At 5V and industrial 0C to +70C operation it suits the inside-cabinet thermal envelope of white goods, and the SOIC-28 wide-body footprint simplifies hand-rework on legacy service boards. The HS crystal mode supports the precise 50/60Hz line-frequency timing often needed for synchronous motor control.
Recommended
Automotive Body Module (Legacy 5V Systems)
Pre-CAN automotive subsystems such as seat controllers, mirror adjusters, and HVAC blend-door modules used the PIC16C55T-HSI/SO because its 20MHz RISC core could multiplex switch scanning and motor PWM within the 768-byte EPROM budget. The 5V supply matches pre-2000s vehicle electrical rails that predate widespread 3.3V microcontrollers, and the SOIC-28 wide-body withstands the under-hood thermal stress of engine-bay-adjacent mounting better than smaller QFN packages. Engineers chose this part because its HS crystal mode and watchdog timer meet the deterministic response required by Automotive EMC standards of that era. Note: new automotive designs should migrate to AEC-Q100 qualified Flash parts.
Recommended
LED Lighting Controller
The PIC16C55T-HSI/SO drives RGB LED strips and architectural lighting fixtures where its 8-bit RISC core executes PWM dimming loops at deterministic 20MHz, and its 20 I/O pins handle multiple LED channels plus DMX-style or 0-10V analog dim inputs. The 4.5V-5.5V supply range aligns with 5V regulated LED drivers, and the integrated timer generates hardware PWM without CPU overhead, freeing the 768-byte EPROM for color-space conversion routines. The 28-SOIC package dissipates heat comfortably even when all I/O pins switch at 10kHz, and the HS oscillator mode locks the 50/60Hz mains flicker to a stable phase reference.
Recommended
Industrial Sensor Interface
Industrial 4-20mA loop transmitters and thermocouple signal-conditioner boards adopted the PIC16C55T-HSI/SO for its 8-bit ADC-free architecture combined with 24-byte RAM, allowing simple lookup-table linearization for K-type and J-type thermocouples within the 768-byte EPROM budget. The HS crystal mode and watchdog timer meet the deterministic fault recovery demanded by process-control installations, and the SOIC-28 wide-body tolerates conformal coating and flux residue during field repair. The 5V supply rail matches most legacy 4-20mA loop-powered transmitters, where the MCU must run from a regulated 5V derived from the loop current.
Recommended
Battery Charger Control
The PIC16C55T-HSI/SO manages charge profiles for sealed lead-acid and NiMH battery packs in emergency lighting, RC toys, and uninterruptible power supplies, where its 20MHz RISC core executes voltage-current-temperature (VIT) charge algorithms within the 768-byte EPROM. The watchdog timer recovers the MCU from brownouts during AC mains interruption, and the HS crystal mode keeps charge-clock timing accurate across 0C to +70C commercial temperature range. The 5V supply matches the typical logic rail of these chargers, and the SOIC-28 wide-body withstands the through-hole-to-SMD rework common when servicing legacy UPS boards.
Recommended
Consumer Electronics Remote User Interface
The PIC16C55T-HSI/SO scans keypads and drives status LEDs in microwave ovens, washing machines, and audio receiver front panels, where the 20 I/O pins handle up to 4x5 matrix keypads without external diodes and the 8-bit timer debounces keys in hardware. Its HS crystal mode generates accurate beep tones without external circuitry, and the 768-byte EPROM fits layered menu state machines typical of consumer UIs. The SOIC-28 (7.50mm wide-body) package offers better manual rework than QFN for service technicians, and the 5V supply rail matches standard logic-level segment drivers.
Recommended
Education and Hobby Electronics
The PIC16C55T-HSI/SO is widely used in undergraduate embedded systems courses and hobby robotics because its 33-instruction PIC16C5X instruction set introduces the Harvard architecture and RISC concepts with a manageable learning curve, while the SOIC-28 wide-body package is easier for students to hand-solder than QFN equivalents. The 768-byte EPROM forces disciplined code design, and the HS oscillator mode teaches crystal load-capacitor selection and PCB layout grounding. Universities pair this part with the PIC16C55-JW windowed DIP-28 development variant for UV-eraseable prototyping, then move to the SOIC OTP version for final projects.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55T-HSI/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55T-HSE/SO | PIC16C55T-HS/SO | PIC16C55-HSI/SO | PIC16C55-RCI/SO | PIC16C55A-04E/SO | PIC16C558-20/SO |
|---|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same |
| Package | 28-SOIC (7.50mm wide) | 28-SOIC (7.50mm wide) - same | 28-SOIC (7.50mm wide) - same | 28-SOIC (7.50mm wide) - same | 28-SOIC (7.50mm wide) - same | 28-SOIC (7.50mm wide) - same | 28-SOIC (7.50mm wide) - same |
| Program Memory (bytes) | 768 (512 x 12) | 768 (512 x 12) - same | 768 (512 x 12) - same | 768 (512 x 12) - same | 768 (512 x 12) - same | 768 (512 x 12) - same | 2048 (1536 x 12) - 2.7x larger |
| Data RAM (bytes) | 24 | 24 - same | 24 - same | 24 - same | 24 - same | 24 - same | 128 - 5.3x larger |
| Maximum Clock Frequency | 20 MHz | 20 MHz - same | 20 MHz - same | 20 MHz - same | 4 MHz RC - lower max | 4 MHz base, 20 MHz extended - same max | 20 MHz - same |
| Oscillator Mode | HS (crystal/RC high-speed) | HSE crystal high-speed variant | HS crystal high-speed variant | HSI crystal high-speed variant | RC internal oscillator | HS/HS crystal variant | HS crystal 20MHz variant |
| I/O Pins | 20 | 20 - same | 20 - same | 20 - same | 20 - same | 20 - same | 20 - same |
| Memory Type | OTP EPROM | OTP EPROM - same | OTP EPROM - same | OTP EPROM - same | OTP EPROM - same | OTP EPROM - same | OTP EPROM - same |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete |
Key Differentiators
- Higher program memory density in same SOIC-28 footprint (vs PIC16C558-20/SO)
- Tape-and-reel packaging for high-volume SMT assembly (vs PIC16C55-HSI/SO)
- HS oscillator mode for crystal-based precision timing (vs PIC16C55-RCI/SO)
Design Notes
PIC16C55T-HSI/SO uses OTP EPROM - the program memory cannot be erased or rewritten once programmed. For development, use the PIC16C55-JW 28-pin ceramic windowed DIP variant, which is UV-erasable under a mercury-discharge lamp for 20-30 minutes; never mix the SOIC OTP part into a dev cycle expecting to iterate firmware, or you will waste parts and budget. Estimated: code reuse from PIC16C55-JW to PIC16C55T-HSI/SO production requires bit-identical firmware because the OTP cells fuse irreversibly.
Decouple Vdd (pin 26) and Vss (pin 25) with a 100nF ceramic capacitor placed within 5mm of the package pins, plus a bulk 10uF electrolytic or tantalum on the 5V rail. The PIC16C5X family draws brief current spikes during internal EPROM read cycles; without adequate decoupling the supply rail droops and the HS oscillator loses lock. Add a ferrite bead in series with Vdd if the 5V supply is shared with relay or motor coils to prevent conducted noise from corrupting program execution.
Place the HS-mode crystal and its two load capacitors within 5mm of pins 15 (OSC1) and 16 (OSC2). The 28-SOIC wide-body package has adequate creepage, but keep the crystal trace short and surrounded by a ground guard ring to prevent EMI pickup from adjacent I/O traces. If the design must tolerate a wide frequency range, leave space on the PCB for a fundamental-mode crystal plus 2x 15-33pF NP0/C0G ceramic capacitors sized per the crystal manufacturer's load-capacitance formula: CL = (C1 x C2) / (C1 + C2) + Cstray.
PIC16C55T-HSI/SO commercial temperature range is 0C to +70C, with maximum junction temperature of 125C. At 20MHz continuous execution, die power dissipation stays under 50mW (typical 25mW at 5V), so thermal management is rarely an issue in the SOIC-28 package. Estimated: the SOIC-28 with thermal resistance theta_JA approximately 70 C/W on a 1oz 4-layer JEDEC test board handles this comfortably. Industrial -40C to +85C parts use the PIC16C55T-I/SO or PIC16C55A-I/SO variants; do not substitute the 'I' (industrial) grade for the standard part if the design only requires commercial range - it costs more.
Do not confuse the PIC16C55T-HSI/SO with the PIC16F54-I/SO Flash equivalent; the 'C' prefix means CMOS EPROM/OTP, and the 'F' prefix means Flash. PIC16C5X code runs unmodified on PIC16F54 with minor CONFIG word adjustments, but the part numbers are not interchangeable in active designs. Estimated: PIC16F54 migration saves rework time and adds ICSP, but production tooling must be reprogrammed with the new part number before firmware is final.
Compliance Information
RoHS compliant per Microchip product documentation. Lead-free matte-tin plating. Not AEC-Q100 qualified - automotive designs must use PIC16C55A-I/SO or migrate to AEC-Q100 PIC16F series. PIC16C5X family is classified obsolete; new designs recommended against per Microchip product lifecycle policy.
