PIC16C55A-04I/SO - 8-Bit OTP MCU, 4MHz, 768B | Microchip
MPN: PIC16C55A-04I/SO β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.255 | $3.26 |
| 10 | $2.93 | $29.30 |
| 100 | $2.61 | $261.00 |
| 500 | $2.29 | $1,145.00 |
| 1,000 | $2.05 | $2,050.00 |
PIC16C55A-04I/SO Overview
An OTP microcontroller (One-Time-Programmable MCU) is a microcontroller whose program memory is implemented as one-time-writable EPROM rather than flash. OTP MCUs occupy the middle ground between mask-ROM parts (lowest cost at high volume, but cannot be programmed in the field) and flash-based MCUs (re-programmable, higher cost per bit). OTP is widely used in cost-sensitive, high-volume consumer and industrial products where the firmware is finalized before production and field updates are not required. Within the broader taxonomy, PIC16C55A is a microcontroller -> 8-bit MCU -> RISC MCU -> CMOS MCU -> semiconductor.
Key specifications include 12-bit wide instructions for 2:1 code compression versus other 8-bit MCUs, direct/indirect/relative addressing modes, 33 instruction set, and compatibility with the PIC16C5X baseline. The device runs from 3.0V to 6.0V, supports in-circuit serial programming (ICSP) via the PICmicro mid-range family convention, and is well-suited for high-volume embedded designs that have moved beyond prototyping. Its 4 MHz clock delivers up to 1 MIPS of throughput, sufficient for simple control loops and user-interface tasks.
Architecturally, the PIC16C55A employs a Harvard-style RISC core with separate program and data buses, allowing instruction fetch and operand read to occur in a single cycle except for branches. The OTP array is organized as 512 x 12, and the data memory is structured as 24 general-purpose registers plus special-function registers mapped into a common file. Reset is provided by power-on, MCLR, and watchdog expiry, with brown-out detection unavailable on this baseline part.
Typical applications include appliance control (washing machines, microwave user-interface boards), battery chargers, LED drivers, simple sensor signal conditioning, low-end remote controls, and replacement of discrete logic. Designers choose this part when absolute lowest unit cost matters more than field re-programmability and the code footprint fits within 768 bytes.
For new designs, prefer PIC16F54 (flash, pin-compatible drop-in upgrade) or PIC16C558 (more memory, same 28-SOIC footprint). Designers should note that this part is in Microchip's NRND lifecycle - order lifetime-buy quantities if your product must ship beyond the last-time-buy cutoff.
This page synthesizes distributor pricing, pin-compatible PIC16C5X alternatives, and practical migration guidance to PIC16F54 flash parts not found in any single datasheet or distributor listing.
Drop-in alternatives for PIC16C55A-04I/SO β 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-04I/SO (same form factor and footprint) β differing in Program Memory Size, Program Memory Type, Operating Temperature Range, Timers, Mounting Type.
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Request AlternativesPIC16C55A-04I/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit RISC Harvard |
| Instruction Set Width | 12-bit |
| Program Memory Type | OTP EPROM (one-time programmable) |
| Program Memory Size | 768 bytes (512 x 12) |
| Data RAM | 24 bytes |
| Maximum Clock Frequency | 4 MHz |
| Throughput | 1 MIPS (1 instruction per clock cycle) |
| Operating Voltage Range | 3.0 V to 6.0 V |
| I/O Pins | 20 |
| Timers | 1 x 8-bit (TMR0 with watchdog) |
| Hardware Stack | 2-level |
| Operating Temperature Range | -40 C to +85 C (industrial, -I suffix) |
| Package | 28-SOIC (7.50 mm body width, SO) |
| Mounting Type | Surface Mount |
| ICSP Programming | Supported (PICmicro baseline convention) |
| Brown-Out Reset | Not available on baseline PIC16C5X |
| Instruction Set | 33 instructions |
PIC16C55A-04I/SO Pin Configuration
| Pin 1 | RA2 β Bidirectional I/O port A bit 2 |
| Pin 2 | RA3 β Bidirectional I/O port A bit 3 |
| Pin 3 | RA4/T0CKI β Bidirectional I/O port A bit 4 / Timer0 clock input |
| Pin 4 | MCLR/VPP β Master Clear (reset) input / programming voltage |
| Pin 5 | VSS β Ground reference |
| Pin 6 | RB0/INT β Bidirectional I/O port B bit 0 / external interrupt |
| Pin 7 | RB1 β Bidirectional I/O port B bit 1 |
| Pin 8 | RB2 β Bidirectional I/O port B bit 2 |
| Pin 9 | RB3 β Bidirectional I/O port B bit 3 |
| Pin 10 | RB4 β Bidirectional I/O port B bit 4 |
| Pin 11 | RB5 β Bidirectional I/O port B bit 5 |
| Pin 12 | RB6 β Bidirectional I/O port B bit 6 |
| Pin 13 | RB7 β Bidirectional I/O port B bit 7 |
| Pin 14 | VSS β Ground reference |
| Pin 15 | OSC1/CLKIN β Crystal oscillator input / external clock input |
| Pin 16 | OSC2/CLKOUT β Crystal oscillator output / clock output |
| Pin 17 | RC0 β Bidirectional I/O port C bit 0 |
| Pin 18 | RC1 β Bidirectional I/O port C bit 1 |
| Pin 19 | RC2 β Bidirectional I/O port C bit 2 |
| Pin 20 | RC3 β Bidirectional I/O port C bit 3 |
| Pin 21 | RC4 β Bidirectional I/O port C bit 4 |
| Pin 22 | RC5 β Bidirectional I/O port C bit 5 |
| Pin 23 | RC6 β Bidirectional I/O port C bit 6 |
| Pin 24 | RC7 β Bidirectional I/O port C bit 7 |
| Pin 25 | RA0 β Bidirectional I/O port A bit 0 |
| Pin 26 | RA1 β Bidirectional I/O port A bit 1 |
| Pin 27 | VDD β Positive supply voltage (3.0 V to 6.0 V) |
| Pin 28 | VDD β Positive supply voltage (3.0 V to 6.0 V, second pin) |
Typical Applications
PIC16C55A-04I/SO is suitable for 7 applications: Home Appliance Control Boards, Battery Chargers and Power Tools, LED Lighting Drivers and Controllers, Remote Controls and IR Transmitters, Simple Sensor Signal Conditioning, Replacement of Discrete Logic (Glue Logic Replacement), Automotive Aftermarket Accessories.
Home Appliance Control Boards
The PIC16C55A-04I/SO is widely deployed in home appliances such as washing machines, microwave oven user-interface boards, rice cookers, and dishwasher control panels. Its 768-byte OTP program memory is sufficient to encode state machines for water-level sensing, motor timing, and push-button HMI. The 20 I/O pins drive 7-segment displays, relay coils, and triac interfaces directly. The -I industrial temperature grade handles under-cabinet heat in kitchen environments. Designers appreciate the PIC16C55A's sub-$1 unit cost at high volume, which is critical in appliance markets where BOM cost dominates the bill of materials.
Recommended
Battery Chargers and Power Tools
Battery chargers for cordless drills, vacuum cleaners, and power tools use the PIC16C55A-04I/SO to implement CC/CV charge profiles, temperature monitoring, and LED status displays. The 8-bit TMR0 timer provides PWM for primary-side switching converters, while the 20 I/O lines read cell voltage, current-sense amplifiers, and thermistor inputs. Operating from a rectified mains supply down to 3.0 V, the PIC16C55A tolerates the wide Vin range typical of offline switch-mode chargers. Its 1 MIPS throughput at 4 MHz handles simple charge algorithms without requiring a more powerful MCU.
Recommended
LED Lighting Drivers and Controllers
Low-cost LED drivers and color-mixing controllers use the PIC16C55A-04I/SO to generate PWM dimming signals and chase patterns for decorative lighting. The 4 MHz clock delivers 1 MIPS, allowing 8-bit PWM resolution at refresh rates suitable for LED dimming without visible flicker. The 20 I/O pins drive multiple MOSFET gate drivers for RGBW channels, while the 24-byte RAM stores the current color/animation state. Indoor decorative lighting fixtures benefit from the PIC16C55A's sub-$1 cost and industrial temperature grade for ceiling-mounted installations.
Recommended
Remote Controls and IR Transmitters
Universal remote controls, IR-based toys, and RF transmitter key fobs use the PIC16C55A-04I/SO to encode button presses into NEC, RC5, or Sony SIRC IR protocols. The 24-byte RAM is sufficient for bufferless state machines that emit pre-stored IR patterns directly from OTP. The 8-bit TMR0 generates accurate 38 kHz carrier frequencies without CPU intervention in interrupt-driven designs. Coin-cell powered designs benefit from the wide 3.0 V to 6.0 V operating range and the PIC16C55A's low-power sleep modes.
Recommended
Simple Sensor Signal Conditioning
Low-cost sensor interface boards for HVAC thermistors, soil moisture probes, and industrial limit switches use the PIC16C55A-04I/SO to threshold-detect analog sensor signals and drive relay outputs. The 20 I/O pins read multiple comparator outputs and drive open-drain signaling lines to upstream controllers. The industrial -40 C to +85 C temperature range supports outdoor sensor pods. The OTP memory locks the calibration curve at production, preventing field tampering with safety-critical thresholds.
Recommended
Replacement of Discrete Logic (Glue Logic Replacement)
Designers use the PIC16C55A-04I/SO to replace discrete 74HC-series glue logic on legacy boards, consolidating timing, sequencing, and decoding functions into a single MCU. The 33-instruction PIC16C5X instruction set is easy to learn for engineers transitioning from TTL/CMOS logic, and the 768-byte OTP is enough for substantial state machines. The 28-SOIC footprint is compatible with many older 28-pin PLCC and SOIC logic carriers, easing mechanical refit. Cost-conscious designs benefit from sub-$1 unit pricing at high volume.
Recommended
Automotive Aftermarket Accessories
Aftermarket automotive accessories such as alarm systems, remote starters, and LED accent lighting use the PIC16C55A-04I/SO as a cost-optimized controller when automotive-grade qualification is not required. The industrial -40 C to +85 C temperature range covers cabin environments, and the 4 MHz clock delivers timing accuracy for alarm arming delays. For under-hood or AEC-Q100-mandated applications, designers should select PIC16F54-I/SO or a true automotive-grade MCU such as PIC16F15323. The 28-SOIC package fits standard automotive PCB form factors.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55A-04I/SO β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C558-04I/SO | PIC16C554-04I/SO | PIC16F54-I/SO | PIC16LC55A-04I/SO | PIC16C55A-04E/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-SOIC (SO) | 28-SOIC (SO) - same | 28-SOIC (SO) - same | 28-SOIC (SO) - same | 28-SOIC (SO) - same | 28-SOIC (SO) - same |
| Program Memory | 768 B (512 x 12) OTP | 1,536 B (1,024 x 12) OTP | 896 B (512 x 14) OTP | 896 B (512 x 14) Flash | 768 B (512 x 12) OTP | 768 B (512 x 12) OTP |
| Maximum Clock | 4 MHz | 4 MHz | 4 MHz | 20 MHz | 4 MHz | 4 MHz |
| Operating Voltage | 3.0 V to 6.0 V | 3.0 V to 6.0 V | 3.0 V to 6.0 V | 2.0 V to 6.0 V | 2.0 V to 6.0 V | 3.0 V to 6.0 V |
| I/O Pins | 20 | 20 | 20 | 12 | 20 | 20 |
| Memory Type | OTP EPROM | OTP EPROM | OTP EPROM | Flash (reprogrammable) | OTP EPROM | OTP EPROM |
| Temperature Grade | -40 C to +85 C (industrial) | -40 C to +85 C (industrial) | -40 C to +85 C (industrial) | -40 C to +85 C (industrial) | -40 C to +85 C (industrial) | -40 C to +125 C (extended) |
| Lifecycle Status | NRND | NRND | NRND | Active (recommended replacement) | NRND | NRND |
Key Differentiators
- Flash-based pin-compatible upgrade available (vs PIC16F54-I/SO)
- Doubled program memory at same package (vs PIC16C558-04I/SO)
- Lower voltage operation for battery-powered designs (vs PIC16LC55A-04I/SO)
Design Notes
The PIC16C55A-04I/SO requires a stable VDD between 3.0 V and 6.0 V with a decoupling capacitor placed within 5 mm of the VDD pin (pin 27 or 28). Use a 100 nF X7R ceramic plus a 10 uF electrolytic bulk capacitor; the EPROM program-cell read voltage is rail-referenced, so noisy supplies below 3.0 V can cause instruction-fetch errors. Brown-out reset is not implemented on the baseline PIC16C5X family, so an external supervisor such as MCP100 is required for safety-critical designs that must detect undervoltage events. Estimate: at 4 MHz / 5 V / all I/O static, ICC is ~2 mA; with 20 mA I/O drive, total ICC peaks ~25 mA.
PIC16C55A OTP memory cannot be re-programmed in-circuit except via windowed ceramic packages (PIC16C55A-JW); the plastic SOIC and PDIP packages are one-time-programmable only. Engineers building prototype boards that will be re-flashed during firmware development must use PIC16F54-I/SO (flash, ICSP-reprogrammable) or a windowed JW package on the dev board. Do not design production boards around JW packages - they are costly, fragile, and intended for development only. Always verify the MCLR pull-up resistor (typically 10 kohm to VDD) is present, or the part will fail to start after power-up.
Place a 100 nF decoupling capacitor on each VDD pin (27 and 28 are both VDD on the 28-SOIC), with traces shorter than 5 mm and a ground return via directly beneath the cap pad. Keep the OSC1/OSC2 traces short and surrounded by ground pour to reduce EMI pickup. The MCLR pin (pin 4) needs a 10 kohm pull-up to VDD and a 100 nF cap to ground for noise immunity; without this, EMI on long cables can trigger spurious resets. For RC oscillator configurations, place the timing resistor and capacitor adjacent to OSC1 to minimize stray capacitance that would shift the clock frequency.
The 28-SOIC (SO) package has a theta_JA of approximately 70 C/W on a 2-layer JEDEC test board per Microchip's package thermal data. At 5 V VDD with 20 mA total I/O drive and 4 MHz clock, typical power dissipation is 25-50 mW, well below thermal limits. Estimate: even at +85 C ambient, junction temperature stays below 90 C with 50 mW dissipation. No heatsink required for any normal application; however, ensure the PCB copper pour under the exposed SOIC pad (if present) is solder-mask-defined to avoid floating pad issues.
Compliance Information
RoHS, REACH, lead-free, and halogen-free status not stated in the verified web data - all set to 'unknown' rather than assumed. AEC-Q100 not qualified; this is an industrial-grade (-40 C to +85 C) baseline PIC16C5X part. Microchip conflict-minerals statement: compliant.
