PIC16F84AT-04I/SO - 4MHz 8-bit Flash MCU, 1.75KB | Microchip
MPN: PIC16F84AT-04I/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.74 | $3.74 |
| 10 | $3.39 | $33.90 |
| 100 | $2.95 | $295.00 |
| 500 | $2.64 | $1,320.00 |
| 1,000 | $2.38 | $2,380.00 |
PIC16F84AT-04I/SO Overview
An 8-bit microcontroller (MCU) is a single-chip computer integrating a CPU, memory (Flash program + RAM + EEPROM), and peripherals on one die. The PIC16F8X family sits inside the mid-range PIC16CXX series of low-cost, high-performance, fully-static CMOS RISC microcontrollers. Hierarchy: 8-bit MCU -> microcontroller -> embedded IC -> semiconductor. The 'T' suffix denotes tape-and-reel packaging, '04' indicates the 4 MHz speed grade, 'I' specifies the industrial temperature range (-40C to +85C), and 'SO' is the 18-pin SOIC package designation.
Key features include a 14-bit instruction word with only 35 single-word instructions, 200 ns instruction cycle at 4 MHz (most instructions are single-cycle), an 8-level hardware stack, and 15 special-function hardware registers. The device integrates an EEPROM with 1 million erase/write cycles endurance and 40-year data retention, a watchdog timer with on-chip RC oscillator, power-on reset, power-saving Sleep mode, and an in-circuit serial programming (ICSP) interface for field upgrades without removing the part.
Architecturally, the PIC16F84A uses a Harvard RISC core with separate program and data buses, giving deterministic instruction timing. The 4 MHz oscillator drives a 4-stage pipeline-free core that executes one instruction per instruction cycle (except branches which are 2-cycle). Compared to CISC architectures, this RISC approach yields higher code density per MHz and predictable interrupt latency. The integrated EEPROM allows parameter storage without external serial memory.
Typical applications include industrial control systems, low-power remote sensors, smart-card readers, small appliance controls, hobbyist projects and educational prototyping, and battery-powered embedded systems where Sleep mode current is critical. The 13 I/O pins can directly drive LEDs, sense switches, or bit-bang serial protocols like UART and I2C in software.
When designing, note that 4 MHz is the rated maximum at 5V VDD; operation above this frequency requires the -20 speed grade. Also reserve one I/O pin for ICSP if you intend in-field firmware updates, or plan for ISP header access during production.
Drop-in alternatives for PIC16F84AT-04I/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 PIC16F84AT-04I/SO (same form factor and footprint) — differing in Package, Core Architecture, I/O Pins, Timers, Instruction Execution Time.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16F84A-04I/SO
✅ Drop-In✓ In Stock
$3.59 / Unit
View Datasheet →PIC16F84A-20I/SO
✅ Drop-In✓ In Stock
$2.2 / Unit
View Datasheet →PIC16F84A-20/SO
✅ Drop-In✓ In Stock
$1.78 / Unit
View Datasheet →PIC16F84A-04/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16F84A-04E/SO
✅ Drop-In✓ In Stock
$2.45 / Unit
View Datasheet →PIC16F84A-20E/SO
✅ Drop-In✓ In Stock
$2.63 / Unit
View Datasheet →PIC16F84AT-04I/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC RISC (Harvard) |
| Program Memory | 1.75 KB Flash (1K x 14 instructions) |
| RAM | 68 bytes |
| EEPROM | 64 bytes |
| Maximum Clock Frequency | 4 MHz |
| Instruction Cycle | 200 ns at 4 MHz |
| I/O Pins | 13 |
| Supply Voltage (VDD) | 4.0 V to 5.5 V |
| Operating Temperature | -40 C to +85 C (Industrial) |
| Package | 18-pin SOIC (SO, 0.300 inch body) |
| Mounting Type | Surface Mount |
| Timers | 1 x 8-bit (TMR0) |
| Hardware Stack Depth | 8 levels |
| Watchdog Timer | Yes (with on-chip RC oscillator) |
| In-Circuit Programming | ICSP (2-wire serial) |
| Power-on Reset | Yes |
| RoHS Status | Compliant |
| Speed Grade | 04 (4 MHz) |
PIC16F84AT-04I/SO Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O port A bit 2 |
| Pin 2 | RA3 — Bidirectional I/O port A bit 3 |
| Pin 3 | RA4/T0CKI — Bidirectional I/O port A bit 4 / Timer0 clock input |
| Pin 4 | MCLR — Master clear (reset) input, active low |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Bidirectional I/O port B bit 0 / external interrupt |
| Pin 7 | RB1 — Bidirectional I/O port B bit 1 |
| Pin 8 | RB2 — Bidirectional I/O port B bit 2 |
| Pin 9 | RB3 — Bidirectional I/O port B bit 3 |
| Pin 10 | RB4 — Bidirectional I/O port B bit 4 |
| Pin 11 | RB5 — Bidirectional I/O port B bit 5 |
| Pin 12 | RB6/PGC — Bidirectional I/O port B bit 6 / ICSP clock |
| Pin 13 | RB7/PGD — Bidirectional I/O port B bit 7 / ICSP data |
| Pin 14 | VDD — Positive supply voltage (4.0 V to 5.5 V) |
| Pin 15 | OSC1/RA7 — Crystal oscillator input / port A bit 7 |
| Pin 16 | OSC2/RA6 — Crystal oscillator output / port A bit 6 |
| Pin 17 | RA0 — Bidirectional I/O port A bit 0 |
| Pin 18 | RA1 — Bidirectional I/O port A bit 1 |
Typical Applications
PIC16F84AT-04I/SO is suitable for 7 applications: Industrial Control Logic Replacement, Educational Electronics and Hobby Projects, Smart Card and Access Control Readers, Battery-Powered Sensor Endpoints, Small Appliance Control Boards, Automotive Interior Lighting Controllers, Legacy Board Repair and Obsolescence Management.
Industrial Control Logic Replacement
The PIC16F84AT-04I/SO fits industrial control replacement boards needing modern flash memory while preserving the classic 18-SOIC footprint. Its 1.75 KB Flash stores ladder-logic replacement sequences, 64-byte EEPROM retains calibration constants through power cycles, and 13 I/O pins drive relays, optocouplers, and discrete indicators. The industrial -40C to +85C rating covers factory-floor enclosures. Compared to legacy bipolar logic, the PIC16F84A delivers software-reconfigurable behavior with the same PCB area, enabling field upgrades via ICSP without removing the MCU. Designers migrating from PIC16C84 OTP parts gain 1M-cycle EEPROM endurance.
Recommended
Educational Electronics and Hobby Projects
The PIC16F84AT-04I/SO remains a staple in university embedded courses and hobbyist projects because of its simple 35-instruction RISC architecture and forgiving 4 MHz timing budget. With 1.75 KB Flash, students can fit complete UART-driven demos, LED patterns, and sensor-reading firmware. The 13 I/O pins map directly to common trainer-board peripherals (LCD, switches, EEPROM). ICSP allows in-class firmware uploads without removing the chip. Its 5V operation matches breadboard-friendly TTL logic. Compared to modern Cortex-M0 parts, the PIC16F84A offers a gentler learning curve for first-time MCU programmers.
Recommended
Smart Card and Access Control Readers
The PIC16F84AT-04I/SO suits low-cost RFID and keypad-based access controllers where the 13 I/O pins drive a 4x4 matrix keypad, status LEDs, a magnetic-door relay, and a Wiegand card-reader interface. Its 68-byte RAM handles small protocol buffers, while the 64-byte EEPROM stores up to 50 user codes with 1M-cycle endurance. The 200 ns instruction cycle at 4 MHz is fast enough for 26-bit Wiegand decoding in real time. Industrial temperature rating ensures operation in outdoor enclosures. Compared to an ASIC, the PIC16F84A adds programmability for protocol updates.
Recommended
Battery-Powered Sensor Endpoints
The PIC16F84AT-04I/SO fits low-duty-cycle remote sensor nodes using its Sleep mode plus watchdog wake-up. With Sleep current measured in microamps and an on-chip watchdog timer, the MCU can sleep for seconds between sensor reads, achieving years of life on 2x AA cells. The 4 MHz clock is sufficient for one-shot ADC sampling via external sigma-delta converter. The 64-byte EEPROM logs calibration offsets and timestamps across power cycles. Compared to always-on designs, this Sleep-mode approach reduces average current by 100x, making sealed-battery sensors practical.
Recommended
Small Appliance Control Boards
The PIC16F84AT-04I/SO integrates small appliance control (coffee makers, fan timers, washing-machine sub-boards) where its 13 I/O pins handle keypad inputs, seven-segment displays, triac firing outputs, and motor-direction relays. The 1.75 KB Flash holds appliance state-machine firmware, and the 64-byte EEPROM stores user preferences through power cycles. Industrial -40C to +85C rating supports behind-panel thermal loads. Compared to electromechanical cam timers, the PIC16F84A enables software-defined wash cycles without mechanical wear.
Recommended
Automotive Interior Lighting Controllers
Although not AEC-Q100 qualified, the PIC16F84AT-04I/SO drives interior-LED mood lighting and courtesy-lamp fade controllers in non-safety automotive subsystems (glove-box lights, footwell LEDs, puddle lamps). Its 13 I/O pins PWM-shift multiplex RGB channels via external FETs, and the 64-byte EEPROM stores the last user-selected color across key cycles. The industrial -40C to +85C rating covers cabin temperatures. Compared to discrete 555-timer designs, the PIC16F84A offers software-configurable fade curves and color presets at the same BOM cost.
Recommended
Legacy Board Repair and Obsolescence Management
The PIC16F84AT-04I/SO is the go-to repair-and-replacement part for legacy boards originally designed around the PIC16C84 OTP or PIC16F84 mask parts. Its drop-in 18-SOIC pinout and identical instruction set allow field-replacement without firmware updates or PCB rework. The 1M-erase-cycle EEPROM rating exceeds the original PIC16F84 spec by 10x, extending service intervals. Compared to redesigning the host board around a modern MCU, swapping in a PIC16F84A restores production-line uptime within hours, avoiding the qualification cost of a new silicon.
Recommended
Recommended Products Summary
Engineering reference data for PIC16F84AT-04I/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16F84A-04I/SO | PIC16F84A-20I/SO | PIC16F84A-20/SO | PIC16F84A-04/SO | PIC16F84A-04E/SO | PIC16F84A-20E/SO |
|---|---|---|---|---|---|---|---|
| Package | 18-SOIC | 18-SOIC (tube) | 18-SOIC | 18-SOIC | 18-SOIC | 18-SOIC | 18-SOIC |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Maximum Clock Frequency | 4 MHz | 4 MHz | 20 MHz | 20 MHz | 4 MHz | 4 MHz | 20 MHz |
| Program Memory | 1.75 KB Flash | 1.75 KB Flash | 1.75 KB Flash | 1.75 KB Flash | 1.75 KB Flash | 1.75 KB Flash | 1.75 KB Flash |
| RAM | 68 bytes | 68 bytes | 68 bytes | 68 bytes | 68 bytes | 68 bytes | 68 bytes |
| EEPROM | 64 bytes | 64 bytes | 64 bytes | 64 bytes | 64 bytes | 64 bytes | 64 bytes |
| I/O Pins | 13 | 13 | 13 | 13 | 13 | 13 | 13 |
| Operating Temperature | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | 0 C to +70 C | 0 C to +70 C | -40 C to +125 C | -40 C to +125 C |
| Supply Voltage | 4.0 V to 5.5 V | 4.0 V to 5.5 V | 4.0 V to 5.5 V | 4.0 V to 5.5 V | 4.0 V to 5.5 V | 4.0 V to 5.5 V | 4.0 V to 5.5 V |
| Carrier Type | Tape & Reel | Tube | Tube | Tube | Tube | Tube | Tube |
Key Differentiators
- Industrial temperature range with same die as commercial variant (vs PIC16F84A-04/SO)
- Tape-and-reel packaging for SMT production (vs PIC16F84A-04I/SO)
- 4 MHz speed grade suitable for low-EMI designs (vs PIC16F84A-20I/SO)
Design Notes
The PIC16F84AT-04I/SO operates from a single 4.0 V to 5.5 V supply on VDD (pin 14) with VSS (pin 5) as ground. Place a 100 nF decoupling capacitor as close as possible to the VDD pin, with a 10 uF bulk capacitor on the same rail. The MCU's MCLR pin (pin 4) should be pulled up to VDD through a 10 kohm resistor for normal operation; tie directly to VDD if external reset is unused. Per Microchip datasheet 30430C, VDD rise time must be faster than the power-on reset timeout to guarantee clean startup.
Route the crystal or resonator between OSC1/RA7 (pin 15) and OSC2/RA6 (pin 16) with traces no longer than 5 mm each, surrounded by a ground pour to minimize EMI coupling. Keep the ICSP clock (RB6/PGC, pin 12) and data (RB7/PGD, pin 13) traces short and accessible for production programming headers. The 18-SOIC land pattern requires 1.27 mm pin pitch and standard SOIC-18 footprint; refer to Microchip package outline drawing 30009013 for exact land dimensions.
Do not exceed 4 MHz clock input at 5V on the '-04' speed grade; operation above this requires the PIC16F84A-20 variant. When migrating from the older PIC16F84 (non-A revision), note that EEPROM write-endurance improved from 100k to 1M cycles, so existing firmware does not require modification but can leverage longer data retention. Always disable the watchdog timer (WDTE configuration bit) during ICSP programming, or the programmer will time out before flash erase completes.
Estimated: With 13 GPIO pins split between 5 RA and 8 RB bits, separate the high-current switching outputs (relays, LEDs) from the low-level analog sense pins using a ground-plane split or star-ground topology to avoid digital switching noise coupling into the analog inputs. Place decoupling capacitors at the MCU VDD pin first, then at the periphery of any high-current output driver. Although the PIC16F84A has no internal ADC, the layout discipline helps when an external ADC is added.
Compliance Information
RoHS compliant per Microchip product page. Not AEC-Q100 qualified - this part is not intended for automotive safety-critical applications. For automotive interior lighting or non-safety subsystems, verify customer-specific qualification requirements.
