PIC16LC55AT-04/SS - 4MHz 768B OTP 8-bit MCU 28-SSOP | Microchip
MPN: PIC16LC55AT-04/SS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.95 | $2.95 |
| 10 | $2.66 | $26.60 |
| 100 | $2.37 | $237.00 |
| 500 | $2.12 | $1,060.00 |
| 1,000 | $1.89 | $1,890.00 |
PIC16LC55AT-04/SS Overview
An 8-bit microcontroller is a single-chip computer that integrates a CPU, program memory, data RAM, and peripheral interfaces on one die. It belongs to the broader category of microcontrollers (MCU) -> embedded microcontrollers -> 8-bit MCUs -> CMOS RISC microcontrollers -> semiconductor ICs. The PIC16C5X family specifically uses a Harvard RISC architecture with only 33 single-word single-cycle instructions, making code density high and execution deterministic — a key reason these MCUs dominated low-cost embedded designs from the mid-1990s onward.
Key features include 768 bytes of OTP EPROM (12-bit word width), 25 bytes of general-purpose RAM, 12 bidirectional I/O pins, a watchdog timer with on-chip RC oscillator, a power-on reset circuit, and an 8-bit real-time timer/counter (RTCC). The "LC" prefix indicates a low-power CMOS variant with an extended supply voltage range of 3 V to 6.25 V, allowing operation from two AA cells or 5 V rails. The "04" speed suffix specifies 4 MHz maximum oscillator frequency.
Architecturally, the device uses a 12-bit instruction word with a 2-stage pipeline, so most instructions execute in a single 250 ns clock cycle at 4 MHz. The OTP memory is programmed via Microchip's ICSP (In-Circuit Serial Programming) protocol, eliminating the need for a separate programmer socket. An 8-bit prescaler extends the RTCC and watchdog timing, and the internal RC oscillator provides a low-cost clock option without external crystals.
Typical applications include consumer appliances, low-end toys and educational devices, simple sensor interfaces, battery-powered remote controls, and white-goods controllers. The wide 3 V to 6.25 V supply range also makes the part a fit for 5 V industrial control boards and automotive accessory modules (where the /I industrial or /E extended temperature grade is required instead).
A key design consideration is that the OTP memory can be programmed only once; for prototyping or field-updatable firmware, choose the PIC16F55 or PIC16CR55 sibling that uses Flash or ROM instead. Also note that this part is built on a legacy 16C5X core — modern designs should consider PIC16F1xxx or PIC16F1xxxx families for active migration paths.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for PIC16LC55AT-04/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 PIC16LC55AT-04/SS (same form factor and footprint) — differing in Package, Timers, Core Architecture, Data RAM, I/O Pins.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C55A-04/SS
✅ Drop-In✓ In Stock
$2.25 / Unit
View Datasheet →PIC16LC55A-04I/SS
✅ Drop-In✓ In Stock
$1.18 / Unit
View Datasheet →PIC16LC55AT-04I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16F55-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC558T-04/SO
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$2.65 / Unit
View Datasheet →PIC16LC55AT-04/SS Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit RISC (PIC16C5X Harvard) |
| Instruction Set | 33 single-word instructions |
| CPU Speed | 4 MHz (250 ns instruction cycle) |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 768 B (512 x 12 bits) |
| Data RAM | 25 B |
| I/O Pins | 12 |
| Timers | 1 x 8-bit RTCC + WDT with on-chip RC |
| Supply Voltage Range | 3 V to 6.25 V (LC low-power) |
| Package | 28-SSOP (0.209 inch / 5.30 mm body) |
| Mounting Type | Surface Mount |
| Temperature Grade | Commercial (PIC16LC55A-04/SS) |
| Oscillator Options | External RC / Crystal / Internal RC |
| Programming Method | ICSP (In-Circuit Serial Programming) |
| RoHS Status | Compliant per Microchip product page |
PIC16LC55AT-04/SS Pin Configuration
| Pin 1 | RA0 — Bidirectional I/O port A bit 0 |
| Pin 2 | RA1 — Bidirectional I/O port A bit 1 |
| Pin 3 | RA2 — Bidirectional I/O port A bit 2 |
| Pin 4 | RA3 — Bidirectional I/O port A bit 3 |
| Pin 5 | RB0 — Bidirectional I/O port B bit 0 / ICSP data |
| Pin 6 | RB1 — Bidirectional I/O port B bit 1 |
| Pin 7 | RB2 — Bidirectional I/O port B bit 2 |
| Pin 8 | RB3 — Bidirectional I/O port B bit 3 |
| Pin 9 | RB4 — Bidirectional I/O port B bit 4 |
| Pin 10 | RB5 — Bidirectional I/O port B bit 5 |
| Pin 11 | RB6 — Bidirectional I/O port B bit 6 / ICSP clock |
| Pin 12 | RB7 — Bidirectional I/O port B bit 7 |
| Pin 13 | RC0 — Bidirectional I/O port C bit 0 |
| Pin 14 | VSS — Ground reference |
| Pin 15 | RC1 — Bidirectional I/O port C bit 1 |
| Pin 16 | RC2 — Bidirectional I/O port C bit 2 |
| Pin 17 | RC3 — Bidirectional I/O port C bit 3 |
| Pin 18 | RC4 — Bidirectional I/O port C bit 4 |
| Pin 19 | RC5 — Bidirectional I/O port C bit 5 |
| Pin 20 | RC6 — Bidirectional I/O port C bit 6 |
| Pin 21 | RC7 — Bidirectional I/O port C bit 7 |
| Pin 22 | OSC1 — Oscillator input / external clock |
| Pin 23 | OSC2 — Oscillator output (crystal mode) |
| Pin 24 | VDD — Positive supply (3.0 V to 6.25 V) |
| Pin 25 | MCLR/VPP — Master clear reset (active low) / programming voltage |
| Pin 26 | T0CKI — Timer0 clock input |
| Pin 27 | RTCC — Real-time clock/counter output |
| Pin 28 | NC — Not connected (per datasheet) |
Typical Applications
PIC16LC55AT-04/SS is suitable for 7 applications: Consumer Appliance Controllers, Battery-Powered Remote Controls, Educational and Toy Electronics, Industrial Sensor Interfaces, Automotive Accessory Modules, White-Goods User Interface Boards, Simple Sensor Hubs.
Consumer Appliance Controllers
The PIC16LC55AT-04/SS fits consumer appliance controllers — washing-machine keypads, microwave user interfaces, low-end air-conditioner remotes — because its 12 I/O lines directly drive 7-segment displays, matrix keypads, and triac-trigger optos without external glue logic. The 4 MHz CPU executes scan loops in well under 1 ms, and the 3.0-6.25 V LC supply tolerates rectified 5 V rails without an LDO. The 768 B OTP holds typical user-interface firmware; the part is cost-optimized for high-volume SKUs where per-unit MCU pricing is paramount.
Recommended
Battery-Powered Remote Controls
The PIC16LC55AT-04/SS is well-suited for battery-powered remote controls (TV, set-top, garage-door, key-fob) because its 3.0-6.25 V LC supply operates directly from two AA cells, and the PIC16C5X core's sleep current is in the microamp range when the WDT-driven wakeup is used. The 4 MHz CPU wakes instantly for IR carrier generation (typically 38 kHz), and 12 I/O drive IR LEDs, keypad matrix, and indicator LEDs without external logic. The 768 B OTP fits standard remote-control firmware with multiple device codes.
Recommended
Educational and Toy Electronics
The PIC16LC55AT-04/SS is a canonical educational and toy-electronics MCU because the PIC16C5X instruction set is small (33 instructions), the OTP cost is minimal at high volume, and Microchip's free MPLAB X IDE with MPASM/XC8 toolchain supports the part out of the box. Hobbyists use it for blinking-LED trainers, line-following robots, and simple talking toys. The 28-SSOP package is breadboard-friendly via SSOP-to-DIP adapters, and 768 B OTP is enough for animated sequences and basic sensor feedback loops.
Recommended
Industrial Sensor Interfaces
The PIC16LC55AT-04/SS handles industrial sensor interface modules (limit switches, photoelectric sensors, proximity probes) because its 12 I/O lines are split across ports sufficient for sensor input, alarm output, and serial communication. The 3.0-6.25 V supply rails run from a regulated 24 V industrial bus via a small LDO. The /I industrial-grade variant (PIC16LC55AT-04I/SS) covers -40C to +85C. The 4 MHz CPU bit-bangs Modbus RTU or simple UART protocols at 9600 baud with minimal firmware overhead.
Recommended
Automotive Accessory Modules
The PIC16LC55AT-04/SS /I variant fits automotive accessory modules (interior lighting controllers, seat-heater keypads, generic body controllers) because its 3.0-6.25 V LC supply tolerates 12 V battery transients when paired with a TVS diode and bulk capacitor. The industrial -40C to +85C temperature grade covers cabin environments, and the 12 I/O drive LEDs, switches, and LIN-bus transceivers. Note that AEC-Q100 qualification is NOT held by this part; for safety-critical modules, migrate to PIC16F1xxx AEC-Q100 grades.
Recommended
White-Goods User Interface Boards
The PIC16LC55AT-04/SS is widely deployed in white-goods user interface boards (dishwasher panels, refrigerator displays, oven timers) because the 28-SSOP footprint is compact enough for slim door panels, the 12 I/O drive 7-segment LCD/LED multiplex directly, and the OTP cost-per-unit is below Flash equivalents at million-unit volumes. The 3.0-6.25 V LC supply accepts rectified 5 V or 12 V rails. The 4 MHz CPU handles button debouncing, encoder tracking, and beeper control with substantial firmware headroom.
Recommended
Simple Sensor Hubs
The PIC16LC55AT-04/SS serves as a simple sensor hub in low-cost data loggers, environmental monitors, and HVAC zone controllers because its 4 MHz core reads multiple I/O sensors sequentially, applies moving-average filtering in firmware, and outputs via UART or PWM. The 768 B OTP accommodates 4-5 channels of 10-bit equivalent sensor reading with averaging. The 25 B RAM is tight but workable for circular buffers. For higher-channel-count designs, step up to PIC16F1xxx with 14-bit ADC and DMA.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC55AT-04/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55A-04/SS | PIC16LC55A-04I/SS | PIC16LC55AT-04I/SS | PIC16F55-I/SS | PIC16LC558T-04/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | 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 | 28-SOIC - larger body but pin-compatible |
| Program Memory Type | OTP EPROM (768 B) | Mask ROM (768 B) | OTP EPROM (768 B) | OTP EPROM (768 B) | Flash (re-programmable) | OTP EPROM (768 B) |
| CPU Speed | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| I/O Pins | 12 | 12 | 12 | 12 | 12 | 12 |
| Supply Voltage | 3.0 V to 6.25 V (LC) | 4.5 V to 5.5 V (standard) | 3.0 V to 6.25 V (LC) | 3.0 V to 6.25 V (LC) | 2.0 V to 5.5 V | 3.0 V to 6.25 V (LC) |
| Temperature Grade | Commercial (0C to +70C) | Commercial | Industrial (-40C to +85C) | Industrial (-40C to +85C) | Industrial (-40C to +85C) | Commercial |
Key Differentiators
- OTP EPROM programming for lowest die cost in high volume (vs PIC16F55-I/SS)
- Wide 3.0 V to 6.25 V LC supply range supports battery and 5 V rails (vs PIC16C55A-04/SS)
- Compact 28-SSOP footprint saves PCB area over 28-SOIC (vs PIC16LC558T-04/SO)
Design Notes
Estimated: the PIC16LC55AT-04/SS draws roughly 2 mA active at 4 MHz / 5 V and under 4 uA in SLEEP mode with WDT disabled, per the PIC16C5X family datasheet. Add a 100 nF decoupling capacitor as close as possible to VDD (pin 24), and a 10 uF bulk capacitor on the 5 V rail. For 3 V battery designs, include a 100 kohm pull-up on MCLR (pin 25) and a series resistor on the ICSP clock line (RB6) to prevent leakage paths in sleep.
Route the 28-SSOP footprint with 0.65 mm pitch SOIC-style land patterns; Microchip publishes reference land dimensions in the SSOP package specification. Keep the MCLR/VPP trace short and away from switching nodes to avoid spurious resets. The OSC1/OSC2 pins should be guarded with a ground ring if a crystal is used; for cost-sensitive designs using the internal RC oscillator, leave OSC2 floating or pulled low to avoid stray coupling.
Do not attempt to erase OTP memory — it is One-Time Programmable by definition, so firmware bugs require a new physical part. Verify all firmware on a PIC16F55 Flash prototype before committing to OTP volume. Also note that the 16C5X core has no hardware UART; UART communication must be bit-banged on any I/O pin using the RTCC or a tight instruction loop. Finally, ensure the supply voltage does not exceed 6.25 V even on transient spikes — add a TVS diode if the design sees inductive loads.
Place the ICSP connector (typically a 5-pin header with VPP/VSS/VDD/RB6/RB7) on the same PCB edge as the MCU so production programming is straightforward. If the board is double-sided, route RB6 and RB7 on the top layer directly under the connector pads to minimize stray capacitance during high-speed ICSP. For low-EMI designs, place the crystal within 5 mm of OSC1/OSC2 and surround it with a ground pour stitched with vias every 5 mm.
Compliance Information
RoHS and REACH compliance per Microchip product page. Lead-free and halogen-free per Microchip packaging specifications. AEC-Q100 not held — for automotive safety modules, migrate to PIC16F1xxx AEC-Q100 grades.
