PIC16C55AT-20E/SS - 8-Bit OTP MCU, 768B, 20MHz, 28-SSOP | Microchip
MPN: PIC16C55AT-20E/SS ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.6 | $3.60 |
| 10 | $3.24 | $32.40 |
| 100 | $2.89 | $289.00 |
| 500 | $2.59 | $1,295.00 |
| 1,000 | $2.31 | $2,310.00 |
PIC16C55AT-20E/SS Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, working RAM, and peripheral set into one IC. The PIC16C5X family belongs to the 8-bit MCU hierarchy (8-bit -> CISC/RISC MCU -> microcontroller -> embedded controller -> semiconductor IC). These devices target cost-sensitive, deterministic control tasks where a full 16- or 32-bit MCU would be overkill.
Key features include 20 I/O pins, an instruction set optimized for code density (12-bit wide instructions giving roughly 2:1 compression over competing 8-bit MCUs), and a fully static CMOS core that supports operation down to DC. The OTP (One-Time Programmable) program memory allows factory or low-volume programming at low unit cost.
Technically, the device uses a Harvard architecture with separate program and data buses. Its 20 MHz oscillator produces a 200 ns instruction cycle, and the wide-instruction design means each opcode carries both operation and operand in one fetch, yielding high throughput per MHz. Brown-out and power-on reset plus WDT give it tolerance to harsh industrial supply environments.
Typical applications include appliance controls, simple sensor interfaces, LED driver sequencers, and low-cost consumer white goods where deterministic response and minimum external components matter more than raw MIPS.
When designing, ensure the EPROM programming window (if used for windowed parts) is covered with opaque tape, and verify timing budgets against the 200 ns instruction cycle. This page synthesizes distributor stock, parametric drop-in alternatives, and practical SSOP layout notes beyond the bare Microchip datasheet.
Drop-in alternatives for PIC16C55AT-20E/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 PIC16C55AT-20E/SS (same form factor and footprint) — differing in Program Memory Size, Package, Program Memory Type, Mounting Type, Core Architecture.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C55A-20E/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C55AT-04E/SS
✅ Drop-In✓ In Stock
$2.12 / Unit
View Datasheet →PIC16C55A-20I/SS
✅ Drop-In✓ In Stock
$1.04 / Unit
View Datasheet →PIC16C55AT-04/SS
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →PIC16C558-20E/SS
✅ Drop-In✓ In Stock
$2.53 / Unit
View Datasheet →PIC16C554-20E/SS
✅ Drop-In✓ In Stock
$1.95 / Unit
View Datasheet →PIC16C54CT-20E/SS
✅ Drop-In✓ In Stock
$1.89 / Unit
View Datasheet →PIC16C55AT-20E/SS Maximum Ratings & Electrical Characteristics
| Core | PIC 8-bit (Harvard architecture) |
| Family | PIC16C5X (PIC16C55A) |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 768 bytes (512 x 12 bits) |
| RAM Size | 25 x 8 bytes |
| Maximum Clock Frequency | 20 MHz |
| Instruction Cycle | 200 ns (at 20 MHz) |
| Supply Voltage | 5 V nominal |
| I/O Pins | 20 |
| Peripherals | POR (Power-On Reset), WDT (Watchdog Timer) |
| Package | 28-SSOP (5.30 mm body width) |
| Mounting Type | Surface Mount |
| Operating Temperature Range | Extended -40C to +125C (E suffix) |
| Instruction Width | 12 bits |
| RoHS Status | Compliant |
| Lifecycle | Obsolete (per distributor listing) |
PIC16C55AT-20E/SS Pin Configuration
| Pin 1 | RA2 — Port A bit 2 (digital I/O) |
| Pin 2 | RA3 — Port A bit 3 (digital I/O) |
| Pin 3 | RA4/T0CKI — Port A bit 4 / Timer0 clock input |
| Pin 4 | MCLR — Master Clear (reset, active low) |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Port B bit 0 / external interrupt |
| Pin 7 | RB1 — Port B bit 1 |
| Pin 8 | RB2 — Port B bit 2 |
| Pin 9 | RB3 — Port B bit 3 |
| Pin 10 | RB4 — Port B bit 4 |
| Pin 11 | RB5 — Port B bit 5 |
| Pin 12 | RB6 — Port B bit 6 |
| Pin 13 | RB7 — Port B bit 7 |
| Pin 14 | VSS — Ground reference |
| Pin 15 | OSC1/CLKIN — Oscillator crystal input / external clock in |
| Pin 16 | OSC2/CLKOUT — Oscillator crystal output / clock out |
| Pin 17 | RC0 — Port C bit 0 |
| Pin 18 | RC1 — Port C bit 1 |
| Pin 19 | RC2 — Port C bit 2 |
| Pin 20 | RC3 — Port C bit 3 |
| Pin 21 | RC4 — Port C bit 4 |
| Pin 22 | RC5 — Port C bit 5 |
| Pin 23 | RC6 — Port C bit 6 |
| Pin 24 | RC7 — Port C bit 7 |
| Pin 25 | VSS — Ground reference |
| Pin 26 | VDD — Positive supply voltage |
| Pin 27 | RA0 — Port A bit 0 |
| Pin 28 | RA1 — Port A bit 1 |
Typical Applications
PIC16C55AT-20E/SS is suitable for 6 applications: Appliance Control Boards, Simple Sensor Interfaces, LED Display Sequencers, Low-Cost Consumer White Goods, Automotive Body Electronics (Legacy), Industrial Timer and Counter Modules.
Appliance Control Boards
The PIC16C55AT-20E/SS fits white-goods control boards such as washing-machine timers, microwave keypads, and dishwasher cycle controllers. Its 768 bytes of OTP memory holds a typical appliance state machine, the 20 MHz clock provides 200 ns instruction cycles for fast relay and triac switching, and the 20 I/O pins drive 7-segment displays, keypads, and indicator LEDs. The extended -40C to +125C temperature grade tolerates the thermal environment inside a sealed appliance. Power-On Reset and Watchdog Timer prevent lock-ups during mains brown-outs, a common failure mode in white goods.
Recommended
Simple Sensor Interfaces
The PIC16C55AT-20E/SS is well suited to read sensors such as thermistors, NTC probes, optical interrupters, and simple switches in industrial sensor-interface modules. With 20 I/O pins and 25 bytes of RAM, the MCU can scan 4-8 sensor channels, debounce inputs, and output a logic-level or PWM signal. Its 20 MHz speed allows 10-bit-equivalent sigma-delta oversampling of low-frequency analog channels when paired with an external RC network. The OTP memory is sufficient for fixed calibration tables used in production.
Recommended
LED Display Sequencers
The PIC16C55AT-20E/SS drives chasing-light, marquee, and decorative LED strips in signage and consumer lighting. Its 20 I/O pins multiplex 8x8 LED matrices or 4-digit 7-segment displays using charlieplexing or direct drive. The 200 ns instruction cycle supports smooth PWM dimming at frequencies above the flicker fusion threshold. OTP memory locks in animation patterns that the manufacturer wants protected from end-user modification. Brown-out reset prevents LED corruption during power dips.
Recommended
Low-Cost Consumer White Goods
The PIC16C55AT-20E/SS targets cost-sensitive consumer products such as remote-control handsets, electronic toys, small kitchen gadgets, and bathroom fixtures. At 768 bytes of OTP, the firmware size matches typical product feature sets. The 28-SSOP package gives a compact 5.30 mm body that fits inside handheld enclosures. The 20 MHz clock supports infrared RC5/RC6 transmit encoding at 36-40 kHz carrier with margin for protocol timing tolerances.
Recommended
Automotive Body Electronics (Legacy)
The PIC16C55AT-20E/SS has historically served in non-safety automotive body modules such as mirror controllers, seat-position memory switches, and interior lighting timers. Its extended temperature grade meets under-dash thermal requirements. Power-On Reset handles cranking brown-outs and the Watchdog Timer recovers from EMC-induced faults. Note that for new automotive designs, AEC-Q100-qualified PIC16F counterparts from Microchip are required; this OTP part is recommended only for legacy service and aftermarket repairs.
Recommended
Industrial Timer and Counter Modules
The PIC16C55AT-20E/SS implements DIN-rail timer, counter, and pulse-stretcher modules in industrial control cabinets. The Watchdog Timer and Power-On Reset deliver the deterministic recovery required for unattended operation. Its 20 I/O pins accept 24 V signals via external optocouplers or resistor dividers, and drive relay coils or solid-state outputs through drivers. The 768-byte OTP holds canned timing profiles for delay-on-make, delay-on-break, and interval-on operations used in process automation.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55AT-20E/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55A-20E/SS | PIC16C55AT-04E/SS | PIC16C55A-20I/SS | PIC16C558-20E/SS | PIC16C554-20E/SS |
|---|---|---|---|---|---|---|
| Package | 28-SSOP (5.30 mm) | 28-SSOP - same | 28-SSOP - same | 28-SSOP - same | 28-SSOP - same | 28-SSOP - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Core / Architecture | PIC 8-bit Harvard | PIC 8-bit Harvard | PIC 8-bit Harvard | PIC 8-bit Harvard | PIC 8-bit Harvard | PIC 8-bit Harvard |
| Program Memory | 768 B OTP | 768 B OTP | 768 B OTP | 768 B OTP | 2 KB OTP | 896 B OTP |
| Maximum Clock | 20 MHz | 20 MHz | 4 MHz | 20 MHz | 20 MHz | 20 MHz |
| RAM | 25 bytes | 25 bytes | 25 bytes | 25 bytes | 72 bytes | 80 bytes |
| Temperature Grade | Extended -40C to +125C | Extended -40C to +125C | Extended -40C to +125C | Industrial -40C to +85C | Extended -40C to +125C | Extended -40C to +125C |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete |
Key Differentiators
- Tape-and-reel suffix for high-volume SMT lines (vs PIC16C55A-20E/SS)
- Extended -40C to +125C temperature grade (vs PIC16C55A-20I/SS)
- 20 MHz maximum clock for fast control loops (vs PIC16C55AT-04E/SS)
- 20 I/O pins across three ports (vs PIC16C54CT-20E/SS)
Design Notes
The 28-SSOP package has a 0.65 mm pin pitch; route all signals on a 0.20 mm trace width with 0.10 mm clearance to escape the fine-pitch lead frame. Place a 100 nF decoupling capacitor within 3 mm of the VDD pin and a 10 uF bulk capacitor at the board power entry. The MCLR pin requires a 10 kohm pull-up to VDD and, if not used, can be tied directly to VDD. The OSC1/OSC2 pair should be guarded by a ground pour to minimize EMI coupling into adjacent signal traces.
PIC16C5X devices use a 12-bit instruction set that is incompatible with PIC16F and PIC18 instruction sets. When migrating from PIC16C55AT-20E/SS to a flash-based PIC16F54 or PIC16F57, the assembly source or C source must be recompiled against the new architecture; you cannot simply re-flash the binary. Also note that the PIC16C5X lacks a hardware UART, so any serial protocol must be bit-banged in firmware, reserving one or two timer resources.
When designing a long-life industrial product on PIC16C55AT-20E/SS, plan for end-of-life migration now. The part is marked obsolete by major distributors, so allocate PCB space on the carrier board for a daughter-module footprint that can accept either the legacy PIC16C55AT-20E/SS in 28-SSOP or a future PIC16F57-I/SS migration board. Use a common pinout to avoid redesign. The 28-SSOP land pattern is shared across the entire PIC16C5X family, simplifying drop-in retrofits.
Compliance Information
RoHS and lead-free per Microchip product page. Not AEC-Q100 qualified - this is a commercial/industrial OTP part, not automotive-qualified.
