PIC12C508A-04/SM - 8-Bit 4MHz OTP MCU, 8-SOIJ | Microchip
MPN: PIC12C508A-04/SM ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.85 | $1.85 |
| 10 | $1.66 | $16.60 |
| 100 | $1.48 | $148.00 |
| 500 | $1.32 | $660.00 |
| 1,000 | $1.18 | $1,180.00 |
PIC12C508A-04/SM Overview
What is an 8-bit OTP microcontroller? An 8-bit microcontroller is a single-chip computer that processes data in 8-bit chunks and is the workhorse of cost-sensitive embedded control. OTP (One-Time-Programmable) memory can be written exactly once, which lowers die cost versus Flash and suits high-volume, fixed-function products. Within the hierarchy: microcontroller -> embedded controller -> semiconductor, the PIC12C5xx family sits at the small-footprint, low-pin-count tier aimed at replacing discrete logic and small electromechanical timers.
Key differentiating features include: (1) only 33 single-word, single-cycle instructions, enabling extremely compact code; (2) 8-bit timer/counter (TMR0) with 8-bit prescaler; (3) internal 4 MHz RC oscillator option eliminating the external crystal in many designs; (4) watchdog timer with on-chip RC oscillator for reliable reset behavior; and (5) in-circuit serial programming (ICSP) capability even on the 8-pin package. Each instruction executes in 1 microsecond at 4 MHz, yielding roughly 1 MIPS performance.
Architecturally, the PIC12C508A uses a Harvard-style RISC core with separate program and data buses, an 8-level deep hardware stack, and a 2-level instruction pipeline. This is sufficient for state machines, simple sensor conditioning, and logic-replacement tasks, but it is not designed for USB, Ethernet, or display interfaces. The CMOS process gives very low power consumption (typically < 2 mA active, < 1 uA standby), enabling battery-friendly designs.
Typical applications include appliance timers, fan/HVAC controls, security-system keypads, IR remote-control transmitters, battery chargers for low-end consumer goods, automotive body controllers (when paired with the I-grade variant), and small consumer toys. The wide operating voltage range makes it suitable for both 3.3 V and 5 V rails, and the SOIJ package is friendly to wave-solder and reflow profiles.
When designing in this part, pay attention to the OTP-only nature: code must be 100 percent verified before programming, since there is no way to re-flash a defective unit. Always budget the GP3/MCLR shared-pin behaviour and ensure adequate decoupling on VDD (0.1 uF) close to the package. OTP programming reduces unit cost versus Flash in volume production, but increases development risk for prototypes.
This page synthesizes distributor stock levels, drop-in same-package alternatives from the PIC12C5xx/12F5xx family, and practical PCB design notes that go beyond the information found in the standalone manufacturer datasheet.
Drop-in alternatives for PIC12C508A-04/SM — 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 PIC12C508A-04/SM (same form factor and footprint) — differing in Program Memory Size, Package, Timers, Operating Temperature Range, Program Memory Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC12C509A-04/SM
✅ Drop-In✓ In Stock
$0.99 / Unit
View Datasheet →PIC12C508A-04I/SM
✅ Drop-In✓ In Stock
$1.05 / Unit
View Datasheet →PIC12F508-I/SN
✅ Drop-In✓ In Stock
$0.31 / Unit
View Datasheet →PIC12C508A-04/SM Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 8-bit RISC (Harvard) |
| Instruction Set Width | 12-bit |
| Number of Instructions | 33 single-word instructions |
| Program Memory Type | OTP (One-Time-Programmable) |
| Program Memory Size | 768 bytes (512 x 12 words) |
| RAM | 25 bytes |
| EEPROM | None |
| Maximum CPU Frequency | 4 MHz |
| Instruction Cycle Time | 1 us at 4 MHz |
| I/O Pins | 6 (GPIO) |
| Timers | 1 x 8-bit (TMR0) with 8-bit prescaler |
| Watchdog Timer | Yes, with dedicated on-chip RC oscillator |
| Operating Voltage (VDD) | 3.0 V to 5.5 V |
| Operating Temperature | 0 C to +70 C (commercial) |
| Package | 8-SOIJ (208 mil) |
| Mounting Type | Surface Mount |
| In-Circuit Programming | ICSP supported |
| Oscillator Options | External RC, external crystal/ceramic, or internal 4 MHz RC |
| RoHS Status | Compliant |
| Pin Count | 8 |
PIC12C508A-04/SM Pin Configuration
| Pin 1 | VDD — Positive power supply (3.0 V to 5.5 V) |
| Pin 2 | OSC1/GP5 — Oscillator input or general-purpose I/O bit 5 |
| Pin 3 | OSC2/GP4 — Oscillator output or general-purpose I/O bit 4 |
| Pin 4 | VSS — Ground reference |
| Pin 5 | GP0 — General-purpose I/O bit 0 / ICSP data |
| Pin 6 | GP1 — General-purpose I/O bit 1 / ICSP clock |
| Pin 7 | GP2/T0CKI — General-purpose I/O bit 2 / Timer 0 clock input |
| Pin 8 | GP3/MCLR — General-purpose I/O bit 3 / master clear reset |
Typical Applications
PIC12C508A-04/SM is suitable for 7 applications: Appliance Timer / Delay Module, IR Remote Control Transmitter, Small Battery Charger / Power Controller, Automotive Body Electronics (Under-Hood Submodules), Industrial Sensor Signal Conditioning, Smart Home IoT Edge Node (Simple Devices), Security Keypad / Access Control.
Appliance Timer / Delay Module
The PIC12C508A-04/SM is a strong fit for low-cost appliance timer modules (washing-machine delay boards, microwave relays, fan run-on timers). Its 1 us instruction cycle at 4 MHz gives the timing resolution needed for sub-second delays, while the 768-byte OTP holds a state machine plus interrupt service routine. The 8-SOIJ package keeps the PCB compact enough to fit inside appliance enclosures, and the 3.0 V to 5.5 V range matches common 5 V relay-driver rails. Designers typically run TMR0 with the internal 4 MHz RC and use GP2 to drive a triac/relay, eliminating the external crystal.
Recommended
IR Remote Control Transmitter
Consumer IR remote controls are a canonical PIC12C508A-04/SM application. The 6 GPIO pins handle a 3 x 4 keypad matrix, the carrier oscillator (typically 38 kHz via TMR0 PWM), and an LED driver. OTP memory keeps the unit cost below the Flash threshold at >100k annual volume, and the 1 MIPS performance easily generates NEC or RC5 carrier modulation. The 3.0 V operating voltage matches two AAA cells. Use the same SOIJ-8 footprint across model variants to reuse the PCB.
Recommended
Small Battery Charger / Power Controller
For low-end NiMH single-cell chargers and USB-powered sensor modules, the PIC12C508A-04/SM offers enough MIPS to run a CC/CV charge algorithm while drawing < 1 uA in standby. The 8-SOIJ package allows the entire control circuit to occupy < 50 mm^2 of PCB, and the wide 3.0 V to 5.5 V supply range accepts both 1-cell Li-ion (with boost) and 2-cell alkaline inputs. OTP programming removes the risk of accidental firmware overwrite in the field.
Recommended
Automotive Body Electronics (Under-Hood Submodules)
While the commercial-grade PIC12C508A-04/SM tops out at 70 C, the underlying die supports industrial (-40 C to +85 C) variants like PIC12C508A-04I/SM used in seat-controller submodules, mirror-adjust logic, and interior lighting sequencers. The 8-SOIJ footprint tolerates automotive thermal cycling, and the wide supply range handles 12 V battery transients when paired with a 5 V LDO such as the MCP1700. Engineers value the deterministic 1 us instruction cycle for timing-critical body-control tasks.
Recommended
Industrial Sensor Signal Conditioning
Industrial sensor front-ends (limit switches, photoelectric sensors, proximity detectors) often need a tiny MCU for de-bouncing, hysteresis, and Modbus-style pulse encoding. The PIC12C508A-04/SM handles the timing logic with 1 us resolution while staying inside the 8-SOIJ footprint for M12 connector-style housings. The internal 4 MHz RC oscillator removes the external crystal, saving board space and BOM cost in high-volume industrial automation deployments.
Recommended
Smart Home IoT Edge Node (Simple Devices)
For ultra-low-cost smart-home edge nodes that only need to toggle a relay or read a contact closure (door sensors, water-leak detectors), the PIC12C508A-04/SM provides just enough compute in an 8-SOIJ package. The OTP memory locks the firmware to prevent field tampering, and the < 1 uA standby current enables multi-year battery life on a coin cell. The 3.0 V minimum supply works directly from a CR2032 with no boost regulator.
Recommended
Security Keypad / Access Control
Security keypads and small access-control panels benefit from the PIC12C508A-04/SM's 6 GPIO driving a 3 x 4 matrix without external decoding logic. OTP programming protects the PIN-verification firmware from being read back, raising tamper resistance versus Flash parts. The 8-SOIJ package supports slim wall-mount enclosures, and 1 MIPS performance runs the debounce, code-hashing, and lock-relay control loops in real time.
Recommended
Recommended Products Summary
Engineering reference data for PIC12C508A-04/SM — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC12C509A-04/SM | PIC12C508A-04I/SM | PIC12F508-I/SN |
|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 8-SOIJ (208 mil) | 8-SOIJ - same | 8-SOIJ - same | 8-SOIJ - same |
| Program Memory | 768 B OTP (512 x 12) | 1.5 KB OTP (1024 x 12) | 768 B OTP (512 x 12) | 768 B Flash |
| Memory Type | OTP | OTP | OTP | Flash (reprogrammable) |
| RAM | 25 B | 41 B | 25 B | 25 B |
| CPU Speed | 4 MHz / 1 MIPS | 4 MHz / 1 MIPS | 4 MHz / 1 MIPS | 4 MHz / 1 MIPS |
| I/O Pins | 6 | 6 | 6 | 6 |
| Operating Temperature | 0 C to +70 C | 0 C to +70 C | -40 C to +85 C (industrial) | -40 C to +85 C (industrial) |
| Operating Voltage | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 2.0 V to 5.5 V |
Key Differentiators
- Smallest-footprint Microchip 8-bit MCU with built-in 4 MHz RC oscillator (vs PIC12C509A-04/SM)
- Industrial temperature option available in the same SOIJ-8 footprint (vs PIC12C508A-04I/SM)
- Direct Flash upgrade path with no PCB rework (vs PIC12F508-I/SN)
Design Notes
Place a 0.1 uF ceramic decoupling capacitor within 5 mm of the VDD pin (pin 1) on the PIC12C508A-04/SM. For designs that drive relays or triacs, add a bulk 10 uF tantalum or aluminum polymer cap on the same 5 V rail. The internal 4 MHz RC oscillator draws approximately 1 mA active and < 1 uA standby; budget quiescent supply current accordingly for battery-powered designs. Reset behaviour on VDD brownout is not guaranteed below 2.5 V - consider an external MCP100 or equivalent voltage supervisor if the application rides through slow power-down events.
The 8-SOIJ package has a 208 mil body width, which fits standard SOIC-8 footprint but with a J-leaded profile that protrudes slightly higher (about 1.75 mm). When laying out the PCB, leave at least 1.5 mm clearance between the package outline and adjacent components to avoid wave-solder shadowing. For reflow soldering, follow JEDEC J-STD-020 with peak temperature of 250 C for lead-free assembly. The exposed pads under the SOIJ are not present (unlike QFN); thermal dissipation is primarily through the 8 leads, so avoid routing high current through adjacent ground returns that could lift the package during thermal cycling.
Three pitfalls are common on PIC12C508A-04/SM designs. (1) GP3 is shared with MCLR - do NOT drive this pin as an output without configuring it as such, or the device will continuously reset. (2) Because the part uses OTP memory, there is no way to recover from a programming error - always verify hex code on a Flash-equivalent (PIC12F508) prototype first. (3) The internal 4 MHz RC oscillator drifts +/- 1 percent over temperature and voltage, which is fine for timing loops but NOT for UART or IR carrier generation that requires precise baud rate; in those cases select the crystal oscillator configuration via the configuration word and add a 4 MHz external resonator with 22 pF loading caps.
The PIC12C508A-04/SM GPIO pins can source/sink up to 25 mA per pin (100 mA total package), but each transition couples a small ground bounce onto VSS. Keep sensitive analog traces (if any) away from GP0/GP1 ICSP lines and route them on a different layer. Use a star-ground topology with the MCU as the central node when interfacing to relays, to keep digital return currents from disturbing the oscillator reference. The ICSP pins (GP0 data, GP1 clock) should each have a series 100 ohm resistor near the MCU to damp ringing during in-circuit programming.
Compliance Information
RoHS compliant per Microchip product page and DigiKey catalog entry. Lead-free SOIJ-8 packaging. Not AEC-Q100 qualified - for AEC-Q100 automotive designs use the PIC12F508-E/SN industrial variant or a newer PIC16xxx family member.
