PIC16F631-I/SO - 20MHz 8-Bit Flash MCU, 1.75KB | Microchip
MPN: PIC16F631-I/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.16 | $2.16 |
| 10 | $1.94 | $19.40 |
| 100 | $1.66 | $166.00 |
| 500 | $1.45 | $725.00 |
| 1,000 | $1.28 | $1,280.00 |
PIC16F631-I/SO Overview
A microcontroller (MCU) is a single-chip computer containing a CPU core, program and data memory, I/O peripherals, and timers on one integrated circuit. The PIC16F631 belongs to the low pin-count (20-pin) subset of Microchip's mid-range x14 architecture, standardizing on 35 instructions, an 8-level hardware stack, and a wide 2.0-5.5 V operating voltage range that makes it well suited to both 3.3 V and 5 V designs.
Key features include 18 I/O pins capable of driving LEDs directly, an internal oscillator selectable from 31 kHz to 8 MHz via OSCCAL calibration, a 10-bit ADC with up to 12 channels depending on package, dual comparators, an enhanced PWM/capture/compare module, and an onboard EEPROM data memory block. The nanoWatt technology provides multiple power-managed modes (RUN, IDLE, SLEEP) that drop quiescent current into the microamp range for battery-powered applications.
Typical applications include small appliance control, sensor signal conditioning, LED driver sequencing, battery chargers, remote-control transmitters, and industrial logic replacement. With its broad operating voltage and on-chip EEPROM for nonvolatile parameter storage, the PIC16F631 is frequently chosen as a cost-optimized glue logic replacement in place of discrete analog components.
A core consideration when designing with this MCU is that it does NOT have a hardware UART; designers needing asynchronous serial must implement a software bit-banged UART, which constrains it versus PIC16F88x or PIC16F1xxx family members. Programming is performed via In-Circuit Serial Programming (ICSP) through the ICSPCLK/ICSPDAT pins, requiring two signal lines plus VPP/MCLR/VSS during programming.
Drop-in alternatives for PIC16F631-I/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 PIC16F631-I/SO (same form factor and footprint) — differing in Operating Temperature, Package, ADC, Timers, I/O Pins.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16F631-E/SO
✅ Drop-In✓ In Stock
$0.5927 / Unit
View Datasheet →PIC16F690-I/SO
✅ Drop-In✓ In Stock
$1.62 / Unit
View Datasheet →PIC16F631-I/SO Maximum Ratings & Electrical Characteristics
| Product Family | PIC16F |
| Core Architecture | PIC Mid-Range (8-bit, x14, 35 instructions, 8-level hardware stack) |
| CPU Speed (max) | 20 MHz |
| Program Memory | 1.75 KB (1K x 14) Flash |
| Data EEPROM | 128 bytes |
| Data RAM | 64 bytes |
| I/O Pins | 18 |
| Supply Voltage | 2.0 V to 5.5 V (per family datasheet) |
| Operating Temperature | -40C to +85C (industrial, "I" grade) |
| ADC | 10-bit, 12 channels |
| Comparators | 2 |
| PWM / CCP Modules | Enhanced CCP (1 channel) |
| Timers | Timer0 (8-bit), Timer1 (16-bit), Timer2 (8-bit) |
| Internal Oscillator | 31 kHz to 8 MHz (OSCCAL, factory calibrated) |
| UART / USART | No hardware UART |
| Package | 20-pin SOIC (SOIC-20, 300-mil) |
| Mounting Type | Surface Mount |
| MSL Level | 1 |
| RoHS Status | Compliant |
| Programming Method | ICSP (In-Circuit Serial Programming) via ICSPCLK/ICSPDAT |
| Technology | nanoWatt (RUN/IDLE/SLEEP modes) |
PIC16F631-I/SO Pin Configuration
| Pin 1 | RA2/AN2/T0CKI — PORTA bit 2 / Analog input 2 / Timer0 clock input |
| Pin 2 | RA3/AN3/C1OUT — PORTA bit 3 / Analog input 3 / Comparator 1 output |
| Pin 3 | RA4/AN4/T1G — PORTA bit 4 / Analog input 4 / Timer1 gate |
| Pin 4 | RA5/MCLR/VPP — PORTA bit 5 / Master Clear (reset) / Programming voltage |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB4/AN10/SDI/SDA — PORTB bit 4 / Analog input 10 / SPI data in / I2C data |
| Pin 7 | RB5/AN11/RX — PORTB bit 5 / Analog input 11 / software UART RX (no hardware UART) |
| Pin 8 | RB6/ICSPCLK/ADC — PORTB bit 6 / ICSP clock / Analog input |
| Pin 9 | RB7/ICSPDAT/TX — PORTB bit 7 / ICSP data / software UART TX |
| Pin 10 | VSS — Ground reference (second pin) |
| Pin 11 | VDD — Positive supply (2.0 V - 5.5 V) |
| Pin 12 | RA6/OSC2/CLKOUT — PORTA bit 6 / Oscillator output / Clock out |
| Pin 13 | RA7/OSC1/CLKIN — PORTA bit 7 / Oscillator input / Clock in |
| Pin 14 | RC0 — PORTC bit 0 |
| Pin 15 | RC1 — PORTC bit 1 |
| Pin 16 | RC2/CCP1 — PORTC bit 2 / Enhanced CCP1 PWM output |
| Pin 17 | RC3 — PORTC bit 3 |
| Pin 18 | RC4/C2OUT — PORTC bit 4 / Comparator 2 output |
| Pin 19 | RC5 — PORTC bit 5 |
| Pin 20 | RC6 — PORTC bit 6 |
Typical Applications
PIC16F631-I/SO is suitable for 6 applications: Small Appliance Control, Sensor Signal Conditioning, LED Driver Sequencing, Battery Charger Controller, Remote Control / IR Transmitter, Industrial Logic Replacement.
Small Appliance Control
The PIC16F631-I/SO fits small-appliance controllers (coffee makers, blenders, air purifiers) because its 20 MHz core and 18 I/O pins can drive relay drivers, triac optos, and keypad scans while the 1.75 KB Flash is sufficient for state-machine firmware. The 2.0-5.5 V supply range accepts unregulated 5 V or rectified 3.3 V rails without LDOs. With 128 B EEPROM for setpoint memory and nanoWatt SLEEP drawing under 1 uA, the MCU also powers standby-only appliances where battery backup preserves clock time during mains outages.
Recommended
Sensor Signal Conditioning
The PIC16F631-I/SO's integrated 10-bit ADC with 12 input channels and two comparators allows direct interface to thermistor, NTC, and voltage-divider sensor networks without external analog front ends. Placed between the sensor bridge and a downstream MCU/display, it pre-digities linearizes, and applies offset calibration using the onboard 128 B EEPROM for stored coefficients. With its 8-level hardware stack and fast interrupt response, the PIC16F631 can run closed-loop sensor control at sub-millisecond rates while consuming under 100 uA/MHz active.
Recommended
LED Driver Sequencing
The PIC16F631-I/SO drives LED matrix or RGB string lighting through its enhanced CCP module and 18 I/O pins, with each PWM cycle running on Timer2 at 20 MHz. Compared to a discrete 555-timer-based sequencing board, the PIC16F631 lets the designer change patterns, brightness curves, and chases in firmware without re-spinning the PCB. The nanoWatt IDLE mode is invoked between pattern updates to keep average quiescent current under 50 uA, extending battery life in portable decorative lighting.
Recommended
Battery Charger Controller
The PIC16F631-I/SO operates as a NiMH or single-cell Li-ion charge controller, using its two comparators for voltage and current thresholds while the ADC monitors battery temperature via an external thermistor. Because the device supports 2.0-5.5 V operation, it can be powered directly from the charger input without a separate LDO. The 128-byte EEPROM stores charge profile parameters and the 10-bit ADC provides accurate termination voltage detection within +/-5 mV - sufficient for small-format consumer battery chargers.
Recommended
Remote Control / IR Transmitter
The PIC16F631-I/SO with its enhanced CCP module generates 38 kHz carrier modulation for IR remote transmitters at sub-mW average draw. Its internal oscillator eliminates the external crystal, saving PCB space and BOM cost - a key differentiator versus 4-bit remote controllers. The 18 I/O lines support a 5x5 keypad matrix or 16 direct command keys with interrupt-on-change wakeup from SLEEP on RB port pins, achieving years of operation from two AAA cells.
Recommended
Industrial Logic Replacement
The PIC16F631-I/SO replaces 4-6 discrete CMOS logic ICs (74HC quad gates, latches, and timers) by absorbing glue logic into a single programmable part. Operating at 5 V with industrial -40C to +85C temperature grade, it survives factory floor electrical environments while 18 I/O pins handle fanout for relay coils, optos, and indicator LEDs. The PIC16F631's ICSP interface means factory firmware updates can be pushed through the same 2-pin programming header used at NPI, eliminating separate test fixtures for field rework.
Recommended
Recommended Products Summary
Engineering reference data for PIC16F631-I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16F631-E/SO | PIC16F631-E/SS | PIC16F690-I/SO | PIC16F677-I/P |
|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | SOIC-20 (300-mil) | SOIC-20 (same) | SSOP-20 (different) | SOIC-20 (same) | PDIP-20 (different) |
| Flash Memory | 1.75 KB (1K x 14) | 1.75 KB | 1.75 KB | 8 KB | 8 KB |
| Data RAM | 64 bytes | 64 bytes | 64 bytes | 256 bytes | 256 bytes |
| EEPROM | 128 bytes | 128 bytes | 128 bytes | 256 bytes | 256 bytes |
| Max CPU Speed | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| Operating Voltage | 2.0 V to 5.5 V | 2.0 V to 5.5 V | 2.0 V to 5.5 V | 2.0 V to 5.5 V | 2.0 V to 5.5 V |
| Temperature Grade | Industrial (-40C to +85C) | Extended (-40C to +125C) | Extended (-40C to +125C) | Industrial (-40C to +85C) | Industrial (-40C to +85C) |
| Hardware UART | No (software bit-bang) | No (software bit-bang) | No (software bit-bang) | Yes (EUSART) | Yes (EUSART) |
| Approx Unit Price (qty 1) | $2.16 | ~$2.40 | ~$2.50 | ~$3.10 | ~$3.00 |
Key Differentiators
- Lowest-cost 20-pin PIC mid-range with industrial temperature grade (vs PIC16F690-I/SO)
- Family supports extended temperature variant without silicon change (vs PIC16F631-E/SO)
- Same SOIC-20 footprint as larger-memory siblings (vs PIC16F685-I/SO)
Design Notes
Decouple VDD (pin 11) and VSS (pin 5/10) with a 100 nF X7R ceramic placed within 5 mm of the package and a 10 uF bulk tantalum or aluminum-polymer cap on the supply rail. The PIC16F631-I/SO draws under 1 uA in SLEEP mode but its active current is roughly 100-200 uA/MHz, so the bulk cap prevents supply droop when PWM-driven loads switch near the MCU. If powering from a switching regulator, place an LC pi-filter ahead of the MCU to block ripple injection into the ADC reference.
Keep the ICSP header (ICSPCLK on pin 8 and ICSPDAT on pin 9) accessible on the PCB - they are also general PORTB I/O so do not route them deep inside the board. For SOIC-20 hand assembly, leave 0.3 inch clearance around the part; for production, JEDEC J-STD-020 MSL-1 reflow at peak 250C is acceptable since this part is moisture-insensitive.
Because the PIC16F631 lacks a hardware UART, attempting to use the EUSART library registers will silently fail - designers must implement the software UART on RB7/RB5 (or any free PORTB pin) and accept that one timer is consumed for baud-rate generation. Also note that internal oscillator calibration is per-die and the OSCCAL register must be loaded at startup with the factory value stored in Flash location 0x3FF - skipping this drops accuracy from +/-1% to roughly +/-5% across temperature.
Route the MCLR/VPP pin (pin 5) through a 10 kOhm pull-up to VDD and place a 100 nF cap to VSS for noise immunity - this prevents spurious resets from EMI on long cable harnesses. Keep analog inputs (RA2/RA3/RA4) physically separated on the PCB from digital PORTB switching lines by at least one ground trace or guard ring to preserve ADC accuracy.
Compliance Information
RoHS and REACH compliant per Microchip product page; lead-free Matte Tin finish; MSL-1 rated. Not AEC-Q100 qualified - for automotive choose PIC16F631-E/SO (extended grade) or PIC16F631-I/SS plus a separate Q100-compatible variant.
