PIC16F84AT-04/SS - 4MHz 8-Bit MCU 1.75KB Flash SSOP-20 | Microchip
MPN: PIC16F84AT-04/SS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.28 | $2.28 |
| 10 | $2.05 | $20.50 |
| 100 | $1.82 | $182.00 |
| 500 | $1.65 | $825.00 |
| 1,000 | $1.48 | $1,480.00 |
PIC16F84AT-04/SS Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU, memory, and programmable I/O peripherals, enabling embedded control in products ranging from washing machines to industrial sensors. The PIC16F84A sits in the legacy mid-range PIC family, descending from the broader 8-bit PIC10/12/16 hierarchy and ultimately from the RISC microcontroller class that dominates cost-sensitive embedded designs.
Key features include 13 general-purpose digital I/O pins, an integrated Power-On Reset (POR), Watchdog Timer (WDT), and a 35-instruction set where every instruction executes in a single 400 ns cycle except program branches which take two cycles. The device supports in-circuit serial programming (ICSP) and operates from a single 4.0 V to 5.5 V supply, making it suited to legacy 5 V logic systems.
Architecturally, the PIC16F84A uses a Harvard architecture with separate code and data buses, a 14-bit instruction word, and a hardware stack that supports direct interrupt context save. Its CMOS, fully-static design allows the clock to be stopped without losing register contents, an important feature for low-power applications.
Typical applications include legacy industrial control nodes, hobby electronics, retro product maintenance, simple sensor readouts, and educational platforms where the 5V operation and breadboard-friendly PICkit programmer compatibility matter more than raw MIPS.
When designing with the PIC16F84AT-04/SS, ensure MCLR is tied through a proper pull-up and decoupling capacitors are placed within 5 mm of VDD/VSS. Operating temperature is 0°C to +70°C (commercial grade) per the verified distributor data.
This page synthesizes distributor pricing, drop-in alternatives and practical design notes that supplement the Microchip datasheet and cross-reference tools.
Drop-in alternatives for PIC16F84AT-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 PIC16F84AT-04/SS (same form factor and footprint) — differing in Package, Core Architecture, Maximum Clock Frequency, I/O Pins, Timers.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16F84A-04/SS
✅ Drop-In✓ In Stock
$2.18 / Unit
View Datasheet →PIC16F84A-20/SS
✅ Drop-In✓ In Stock
$1.65 / Unit
View Datasheet →PIC16F84A-04I/SO
✅ Drop-In✓ In Stock
$3.59 / Unit
View Datasheet →PIC16F84A-04I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16F84A-04E/SS
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
PIC16F84A-20I/SO
✅ Drop-In✓ In Stock
$2.2 / Unit
View Datasheet →PIC16F84AT-04/SS Maximum Ratings & Electrical Characteristics
| Product Family | PIC16F84A (PIC16F8X family) |
| Core Architecture | 8-bit RISC Harvard |
| Maximum Clock Frequency | 4 MHz (10 MHz clock input / 400 ns instruction cycle for -10 variant) |
| Program Memory (Flash) | 1.75 KB (1K x 14 words) |
| Data Memory (RAM) | 68 bytes |
| Data Memory (EEPROM) | 64 bytes |
| I/O Pins | 13 general-purpose |
| Supply Voltage (VDD) | 4.0 V to 5.5 V |
| Instruction Set | 35 single-word instructions |
| Instruction Cycle | 400 ns (single-cycle, 2-cycle branch) |
| Package | 20-SSOP (5.30 mm body width, 0.209 in) |
| Mounting Type | Surface Mount |
| Operating Temperature | 0°C to +70°C (commercial) |
| Integrated Peripherals | Power-On Reset (POR), Watchdog Timer (WDT), ICSP |
| Timer Modules | 1 x 8-bit Timer0 |
| Hardware Stack | 8-level deep |
| RoHS Status | Compliant (per distributor data) |
PIC16F84AT-04/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 (open-drain) |
| Pin 4 | MCLR/VPP — Master Clear (reset) input / programming voltage |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Port B bit 0 / external interrupt input |
| Pin 7 | RB1 — Port B bit 1 (digital I/O) |
| Pin 8 | RB2 — Port B bit 2 (digital I/O) |
| Pin 9 | RB3 — Port B bit 3 (digital I/O) |
| Pin 10 | RB4 — Port B bit 4 (digital I/O, interrupt-on-change) |
| Pin 11 | RB5 — Port B bit 5 (digital I/O, interrupt-on-change) |
| Pin 12 | RB6 — Port B bit 6 / ICSP clock (interrupt-on-change) |
| Pin 13 | RB7 — Port B bit 7 / ICSP data (interrupt-on-change) |
| Pin 14 | VDD — Positive supply (4.0 V to 5.5 V) |
| Pin 15 | OSC2/CLKOUT — Oscillator output / clock-out Fosc/4 |
| Pin 16 | OSC1/CLKIN — Oscillator input / external clock in |
| Pin 17 | RA0 — Port A bit 0 (digital I/O) |
| Pin 18 | RA1 — Port A bit 1 (digital I/O) |
| Pin 19 | NC — Not connected (per SSOP-20 layout) |
| Pin 20 | NC — Not connected (per SSOP-20 layout) |
Typical Applications
PIC16F84AT-04/SS is suitable for 7 applications: Legacy Industrial Control Retrofit, Hobby & Educational Electronics, Simple Sensor Readout Modules, Replacement of Obsolete Legacy Microcontrollers, Low-Power Battery Monitoring Nodes, Display Driver - LED & Character LCD, Consumer Appliance Replacement Board.
Legacy Industrial Control Retrofit
The PIC16F84AT-04/SS suits legacy industrial control retrofits because its 4 MHz core, 5 V supply (4.0-5.5 V), and 20-SSOP footprint directly replace 1990s-era Microchip designs without PCB rework. The 1.75 KB Flash can hold tens of state-machine transitions, while 13 GPIO ports drive relays, optocouplers, and 7-segment displays. Per Microchip datasheet 30430C, the integrated Watchdog Timer prevents lockup in noisy factory environments. Unlike newer Cortex-M0 MCUs that need level-shifters, this part fits existing 5 V backplanes. Estimated run time with the 8-level hardware stack: a 4 MHz instruction cycle of 1 us allows 4 MIPS equivalent for sequential logic. Recommended companion: PIC16F84A-04/SS for drop-in spare inventory, PIC16F88-I/SS when modernizing to add more analog channels.
Recommended
Hobby & Educational Electronics
The PIC16F84AT-04/SS is a long-time favorite in hobby and educational settings because of its compatibility with PICkit 1/2/3 programmers, ICSP header, and a stable 35-instruction RISC set that allows students to learn assembly in a single semester. The 13 GPIO drive LEDs, buttons and character LCDs directly at 5 V without level shifting, while the 4 MHz oscillator (1 us per instruction) keeps timing calculations - for timer-based blinking, debounce, and PWM - simple and learnable. According to the Microchip datasheet 30430C, the 20-SSOP footprint breaks out to 0.65 mm pitch breadboard-compatible adapters. Recommended companions: PIC16F84A-04/SS for classroom spares, and the PICkit 3 programmer kit (PG164130) for ISP programming.
Recommended
Simple Sensor Readout Modules
The PIC16F84AT-04/SS fits simple sensor readout applications: temperature, humidity, and 4-20 mA loop interfaces that need only a few GPIO and an ADC-like read via analog comparator. The 1.75 KB Flash holds small lookup tables and calibration coefficients, while 64 bytes of EEPROM persistently stores configuration after power cycles. Per Microchip datasheet 30430C, the integrated Power-On Reset eliminates external reset ICs in 5 V sensor front-ends. The 4 MHz clock is sufficient for polled sensing at 100 ms intervals. The 20-SSOP low-profile package suits sealed IP65 enclosures. Recommended companions: MCP9700 analog temperature sensor, MCP1700 3.3 V regulator for low-power variants.
Recommended
Replacement of Obsolete Legacy Microcontrollers
The PIC16F84A family serves as a known-good replacement for older 8051, Z8 and PIC16C parts when a Microchip drop-in is required. Its PIC16F84AT-04/SS form factor (20-SSOP) and peripheral set match the PIC16C84 footprint exactly, allowing firmware re-use with limited recompilation. Per the Microchip compatibility chart document 00148J2, the PIC16F84A is pin- and code-compatible with the PIC16C84 in the 20-pin SSOP, simplifying production conversions. The 4 MHz clock matches legacy timing assumptions for assembly-based code. Recommended companions: PIC16F84A-20/SS for higher performance same-package replacement.
Recommended
Low-Power Battery Monitoring Nodes
The PIC16F84AT-04/SS supports battery monitoring nodes in its fully-static CMOS design: the clock can be stopped externally without losing register contents, allowing deep sleep between measurements. The 4 MHz maximum isn't required for battery voltage polling - slower oscillator modes work equally well per Microchip datasheet 30430C. With Watchdog Timer (WDT) waking the part every few seconds, a single CR2032 cell can run for years. The 13 GPIO read battery voltage via resistor divider, and the 64-byte EEPROM stores cumulative cycle counts. The 20-SSOP low-profile package fits compact battery holders. Recommended companions: MCP1700 LDO regulator, MCP3421 18-bit ADC for precision battery voltage.
Recommended
Display Driver - LED & Character LCD
The PIC16F84AT-04/SS can multiplex 7-segment LED displays and character LCDs (HD44780-compatible) using its 13 GPIO, Bit-Banging the LCD interface at 4 MHz (1 us per instruction). The 1.75 KB Flash holds 5x8 or 5x10 custom character fonts, while 68 bytes of RAM buffer displayed text. Per Microchip datasheet 30430C, the 5 V operation directly drives common-cathode LED displays with appropriate current-limiting resistors. The 20-SSOP package keeps drive boards compact for handheld instruments. Recommended companions: TC4427 MOSFET driver for high-current LED segments, MCP1702 5 V LDO for the supply rail.
Recommended
Consumer Appliance Replacement Board
The PIC16F84AT-04/SS works as a replacement MCU for consumer appliances (coffee machines, microwaves, washing-machine front panels) where field service requires an exact footprint match to the original PIC16F84A socket. The 4 MHz clock, 5 V supply, and 20-SSOP pinout match the original factory BOM per Microchip datasheet 30430C, avoiding any PCB re-spin. Watchdog Timer prevents the controller from latching in case of glitches on noisy mains-derived 5 V rails. Recommend companions: MOC3021 triac driver for AC load control, MCP1700 LDO for low standby current.
Recommended
Recommended Products Summary
Engineering reference data for PIC16F84AT-04/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16F84A-04/SS | PIC16F84A-20/SS | PIC16F84A-04I/SO | PIC16F84A-04I/SS | PIC16F84A-04E/SS |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 20-SSOP | 20-SSOP - same | 20-SSOP - same | 20-SOIC - same pinout, larger body | 20-SSOP - same | 20-SSOP - same |
| Maximum Clock Frequency | 4 MHz | 4 MHz | 20 MHz | 4 MHz | 4 MHz | 4 MHz |
| Program Memory (Flash) | 1.75 KB | 1.75 KB | 1.75 KB | 1.75 KB | 1.75 KB | 1.75 KB |
| RAM | 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 |
| Supply Voltage | 4.0 V to 5.5 V | 4.0 V to 5.5 V | 2.0 V to 5.5 V (wider) | 4.0 V to 5.5 V | 4.0 V to 5.5 V | 4.0 V to 5.5 V |
| Operating Temperature | 0°C to +70°C (commercial) | 0°C to +70°C | -40°C to +85°C (industrial) | -40°C to +85°C | -40°C to +85°C | -40°C to +125°C (extended) |
Key Differentiators
- 4 MHz commercial-grade variant (vs PIC16F84A-20/SS)
- Tape-and-reel packaging for high-volume assembly (vs PIC16F84A-04/SS)
- Mature 5 V PIC16 ecosystem with abundant code libraries (vs PIC16F88-I/SS)
Design Notes
Place a 100 nF ceramic decoupling capacitor within 5 mm of the VDD pin (pin 14) and a 10 uF bulk capacitor at the board input. The PIC16F84AT-04/SS draws only a few mA but the integrated POR monitors VDD rise time; a slow-rising supply below 4.0 V can trigger spurious resets. For battery applications consider MCP1700 (LDO) which has 1.6 uA quiescent current.
Keep the 4 MHz crystal/ceramic resonator traces short (less than 5 mm) and surround OSC1/OSC2 (pins 16/15) with a ground pour to reduce EMI. For ICSP, dedicate test points or a 6-pin header on RB6/RB7/MCLR/VSS/VDD to enable in-circuit programming without removing the MCU. The SSOP-20 footprint requires 0.65 mm pitch land patterns.
RA4 is an open-drain output requiring a pull-up resistor to drive a LED or logic high - this is the most common PIC16F84A design mistake. Configuration bits (CP, WDT, PWRTE, WDTE, FOSC) must be set correctly in the hex file or the device will not start; tools like MPLAB X default to safe values. Do not drive VPP/MCLR above VDD + 0.3 V or you risk latch-up. Estimated: 4 MHz instruction cycle = 1 us.
Compliance Information
RoHS and REACH compliance per Microchip product page. Not AEC-Q100 qualified (industrial/automotive qualification requires -I or -E suffix variants). Lead-free reflow-solderable per SSOP-20 standard packaging.
