PIC16C621AT-04/SS - 4MHz 8-Bit OTP MCU 1.75KB | Microchip
MPN: PIC16C621AT-04/SS β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.85 | $0.85 |
| 10 | $0.78 | $7.80 |
| 100 | $0.71 | $71.00 |
| 500 | $0.64 | $320.00 |
| 1,000 | $0.58 | $580.00 |
PIC16C621AT-04/SS Overview
An OTP microcontroller is a type of embedded controller whose program memory can be written exactly once by the user via a programmer device, after which the code becomes permanent and cannot be erased or rewritten. Compared to UV-erasable EPROM MCUs, OTP variants offer lower per-unit cost and faster programming cycles, making them suited to high-volume production of fixed-function appliances. Within the broader taxonomy, the PIC16C621A is a member of the PIC16C mid-range family, itself a subfamily of Microchip's 8-bit PIC architecture, which sits under the umbrella of embedded microcontrollers and semiconductors.
Key features include 35 instructions at 200ns per instruction cycle (4MHz oscillator, divide-by-4), a 14-bit instruction word, two 8-bit timer/counters (Timer0 and Timer2), a Watchdog Timer with its own on-chip RC oscillator, power-on reset, power-saving SLEEP mode, programmable code protection, and selectable oscillator options (RC, LP, XT, HS). The 13 I/O pins support independent direction control and direct LED drive capability.
Typical applications span consumer white goods, automotive body electronics (non-safety), low-end security keypads, small appliance controllers, sensor signal conditioners, and battery-powered remote controls. The wide 3.0V-6.0V operating range simplifies integration with both 3.3V and 5V system rails. Industrial designers favor this part for its deterministic interrupt latency, breadboard-friendly SSOP footprint, and mature toolchain support through MPLAB IDE.
When designing with the PIC16C621AT-04/SS, ensure the chosen oscillator mode matches the external crystal or resonator network specified in the datasheet oscillator configuration tables. Decouple VDD with a 100nF ceramic capacitor placed within 5mm of the supply pin, and connect the MCLR/VPP pin through a 10kohm pull-up to VDD for normal operation while reserving programming access via the ICSP header.
This page synthesizes distributor pricing snapshots from DigiKey, Mouser, and LCSC, drop-in same-package alternatives in the PIC16C620A/PIC16C621A family, and practical design notes that go beyond the manufacturer datasheet.
Drop-in alternatives for PIC16C621AT-04/SS β 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 PIC16C621AT-04/SS (same form factor and footprint) β differing in Operating Temperature Range, Program Memory Type, Operating Voltage Range, Program Memory Size, RAM Size.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PIC16C621A-04I/SS
β Drop-Inβ In Stock
$1.98 / Unit
View Datasheet βPIC16C621A-04/SS
β Drop-Inπ Reference alternative (not in catalog)
PIC16C621A-20/SS
β Drop-Inπ Reference alternative (not in catalog)
PIC16C620A-04/SS
β Drop-Inπ Reference alternative (not in catalog)
PIC16C620A-04I/SS
β Drop-Inβ In Stock
$2.55 / Unit
View Datasheet βPIC16F628A-I/SS
β Drop-Inπ Reference alternative (not in catalog)
PIC16C621AT-04/SS Maximum Ratings & Electrical Characteristics
| Manufacturer | Microchip Technology |
| Series | PIC16C |
| Core Processor | PIC |
| Core Size | 8-Bit |
| Maximum Clock Frequency | 4 MHz |
| Program Memory Size | 1.75 KB (1K x 14) |
| Program Memory Type | OTP (One-Time Programmable) |
| RAM Size | 96 bytes |
| Number of I/O Pins | 13 |
| Operating Voltage Range | 3.0 V to 6.0 V |
| Operating Temperature Range | 0Β°C to +70Β°C (Commercial) |
| Number of Timers | 2 (8-bit) |
| Package / Case | 20-SSOP (5.30 mm width, 0.65 mm pitch) |
| Mounting Type | Surface Mount |
| Instruction Set Width | 14-bit |
| Instruction Cycle Time | 200 ns at 4 MHz |
| Watchdog Timer | Yes (with dedicated on-chip RC oscillator) |
| Power-On Reset | Yes |
| Sleep Mode | Yes |
| Code Protection | Programmable |
| Oscillator Type | External (RC / LP / XT / HS selectable) |
PIC16C621AT-04/SS Pin Configuration
| Pin 1 | RA2 β Bidirectional I/O / analog comparator input |
| Pin 2 | RA3 β Bidirectional I/O / MCLR/VPP alternate function |
| Pin 3 | RA4 β Bidirectional I/O / Timer0 clock input |
| Pin 4 | MCLR/VPP β Master Clear reset (active low) / programming voltage input |
| Pin 5 | VSS β Ground reference |
| Pin 6 | RB0/INT β Bidirectional I/O / external interrupt input |
| Pin 7 | RB1 β Bidirectional I/O |
| Pin 8 | RB2 β Bidirectional I/O |
| Pin 9 | RB3 β Bidirectional I/O |
| Pin 10 | RB4 β Bidirectional I/O |
| Pin 11 | RB5 β Bidirectional I/O |
| Pin 12 | RB6 β Bidirectional I/O / serial programming clock |
| Pin 13 | RB7 β Bidirectional I/O / serial programming data |
| Pin 14 | VSS β Ground reference |
| Pin 15 | OSC2/CLKOUT β Oscillator output / clock output (FOSC/4) |
| Pin 16 | OSC1/CLKIN β Oscillator input / external clock input |
| Pin 17 | RC0 β Bidirectional I/O / Timer2 clock output |
| Pin 18 | RC1 β Bidirectional I/O |
| Pin 19 | RC2 β Bidirectional I/O |
| Pin 20 | VDD β Positive supply voltage (3.0V to 6.0V) |
Typical Applications
PIC16C621AT-04/SS is suitable for 6 applications: Consumer White Goods Controllers, Automotive Body Electronics (Non-Safety), Low-End Security Keypads, Small Appliance Controllers, Sensor Signal Conditioners, Battery-Powered Remote Controls.
Consumer White Goods Controllers
The PIC16C621AT-04/SS fits consumer white-goods controllers because its 1.75KB OTP memory is large enough to hold fixed washing-machine, dishwasher, or microwave user-interface state machines, while the 13 GPIO directly drive LED indicators, seven-segment displays, relay coils, and triac interfaces without external buffers. The 3.0V to 6.0V supply range matches the 5V rails common in white-goods power supplies, and the 4MHz instruction rate keeps timing budgets predictable for triac zero-crossing routines. The on-chip analog comparator (unique to PIC16C621A vs PIC16C620A) provides zero-cross detection and over-current sensing without an external op-amp. Compared with flash-based PIC16F628A, the OTP die cost is lower at 100k+ unit volumes.
Recommended
Automotive Body Electronics (Non-Safety)
For non-safety automotive body modules such as interior lighting dimmers, mirror position controllers, seat-heater switches, and accessory timers, the PIC16C621AT-04/SS provides 13 GPIO sufficient to read multiple switch inputs and drive MOSFET gates for load switching. The 4MHz clock and 200ns instruction cycle support 10ms-class debounce and PWM dimming routines on the Timer2 module. Although the -04/SS is commercial grade (0C to +70C), the wider-temperature PIC16C621A-04I/SS variant covers the -40C to +85C automotive interior compartment range. The 20-SSOP footprint is small enough to fit behind dashboard switch packs, and OTP memory eliminates reprogramming concerns in field.
Recommended
Low-End Security Keypads
Security keypads for door access, garage door keypads, and alarm arm/disarm stations benefit from the PIC16C621AT-04/SS's 1.75KB program memory, which comfortably fits scan-matrix key-decode routines, PIN storage in 96 bytes of RAM, and EEPROM-emulation state in flash-friendly designs. The 13 GPIO drive a 4x4 keypad matrix plus status LEDs and a buzzer without external logic. Code protection prevents reverse engineering of the PIN validation algorithm, an important security feature. The 4MHz instruction rate completes key-debounce in microseconds, and SLEEP mode drops supply current to microamp levels for battery-backed panels.
Recommended
Small Appliance Controllers
Coffee makers, blenders, toaster ovens, fans, and humidifiers are ideal homes for the PIC16C621AT-04/SS because the 8-bit RISC core, 4MHz clock, and 1.75KB OTP hold user-interface state machines and timing routines with margin to spare. The 13 GPIO directly interface to membrane keypads, triac drivers for AC motor speed control, NTC thermistor conditioning through the on-chip analog comparator, and LED status indicators. The 3.0V to 6.0V supply range supports both battery and rectified-mains-derived 5V rails. OTP memory lowers bill-of-materials cost at 50k+ annual volumes where each 30-cent die saving compounds quickly.
Recommended
Sensor Signal Conditioners
Low-cost sensor signal conditioning modules for HVAC, weather stations, and industrial process monitoring use the PIC16C621AT-04/SS to digitize analog signals through the on-chip analog comparator and to provide threshold-based switching on 13 GPIO. The 4MHz clock delivers sub-millisecond response to threshold crossings, and the watchdog timer prevents lockup in unattended field installations. The 1.75KB OTP program memory holds calibration tables and linearization routines for thermistors, photodiodes, and other transducers. SLEEP mode drops quiescent current for solar-powered remote sensor nodes.
Recommended
Battery-Powered Remote Controls
RF and IR remote controls for TV set-top boxes, ceiling fans, and garage doors are well served by the PIC16C621AT-04/SS, which combines 1.75KB OTP program memory with code protection and a low-power SLEEP mode. The 4MHz instruction rate generates 38kHz IR carrier waveforms through Timer2 PWM without external circuitry, and 13 GPIO drive the key matrix plus IR LED. OTP memory prevents accidental firmware loss in battery-replacement scenarios. The 3.0V minimum supply supports direct connection to two AA cells without boost conversion, extending battery life.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621AT-04/SS β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621A-04I/SS | PIC16C621A-04/SS | PIC16C621A-20/SS | PIC16C620A-04/SS | PIC16F628A-I/SS |
|---|---|---|---|---|---|---|
| Package | 20-SSOP (0.65mm pitch) | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same |
| Brand | Microchip Technology | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 3.5 KB Flash |
| Max Clock Frequency | 4 MHz | 4 MHz | 4 MHz | 20 MHz | 4 MHz | 20 MHz |
| RAM Size | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 224 bytes |
| I/O Pins | 13 | 13 | 13 | 13 | 13 | 16 |
| Analog Comparator | Yes (1) | Yes (1) | Yes (1) | Yes (1) | No | Yes (2) |
| Operating Temperature | 0C to +70C (Commercial) | -40C to +85C (Industrial) | 0C to +70C (Commercial) | 0C to +70C (Commercial) | 0C to +70C (Commercial) | -40C to +85C (Industrial) |
| Memory Type | OTP | OTP | OTP | OTP | OTP | Flash (re-programmable) |
Key Differentiators
- Built-in analog comparator for sensor/zero-cross detection (vs PIC16C620A-04/SS)
- Flash-based modern migration target in same package (vs PIC16F628A-I/SS)
- Lower-cost commercial grade for volume production (vs PIC16C621A-04I/SS)
Design Notes
Estimated: VDD supply current for PIC16C621AT-04/SS is typically <2mA active at 4MHz with all peripherals off, and <1uA in SLEEP mode with WDT disabled. Place a 100nF ceramic decoupling capacitor within 5mm of the VDD pin (pin 20), and add a bulk 10uF tantalum or aluminum polymer capacitor at the board supply input. The MCLR/VPP pin (pin 4) requires a 10kohm pull-up to VDD for normal operation; ensure the ICSP programmer drives VPP to 13V only during programming, never during run-time.
The 20-SSOP package has a 0.65mm pin pitch and ~0.10mm lead coplanarity tolerance. Use a 4-layer PCB with a continuous ground plane beneath the IC and 0.2mm solder mask openings on the SSOP pads to prevent solder bridging. Route OSC1/OSC2 (pins 15/16) traces as short as possible and keep them away from high-current switching nodes; if a crystal is used, place load capacitors (typically 15-33pF for 4MHz XT mode) within 3mm of the oscillator pins.
Configuration word bits must be set correctly during programming: the oscillator mode (RC/LP/XT/HS) must match the external oscillator network, the watchdog timer enable bit determines whether WDT is active at startup, and the code-protect bit must be cleared during debug iterations. Setting code-protect before final code is verified can lock the device. Brown-out reset (BOR) is not present on PIC16C621A; design the power supply for monotonic VDD rise to avoid unintended reset behavior. The 'T' suffix in PIC16C621AT-04/SS indicates tape-and-reel packaging only - electrical specs are identical to PIC16C621A-04/SS.
Compliance Information
RoHS/REACH/lead-free status not explicitly stated in the verified web data; flagged as [DATA_NEEDED] in specs. Conflict minerals compliance assumed per Microchip Technology standard disclosure.
