PIC16C621AT-04I/SS - 4MHz 8-bit OTP MCU 1.75KB Flash | Microchip
MPN: PIC16C621AT-04I/SS ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.1 | $4.10 |
| 10 | $3.65 | $36.50 |
| 100 | $3.1 | $310.00 |
| 500 | $2.65 | $1,325.00 |
| 1,000 | $2.2 | $2,200.00 |
PIC16C621AT-04I/SS Overview
An 8-bit microcontroller (MCU) is a single-chip computer integrating an 8-bit CPU core, program memory (ROM/EPROM/Flash/OTP), data RAM, working registers, and configurable I/O peripherals. The PIC16C621A belongs to the Microchip mid-range family — sitting in the hierarchy: PIC microcontroller -> 8-bit MCU -> mid-range PIC16C series -> OTP CMOS PIC -> embedded controller -> semiconductor. This category is widely used for cost-sensitive, deterministic real-time control in appliances, automotive subsystems, and industrial equipment.
The device delivers 13 digital I/O pins, two analog comparators, a 4 MHz internal clock option, and 25 mA source/sink per I/O for direct LED drive. It operates from 2.5 V to 5.5 V across the industrial -40 °C to +85 °C range. The architecture uses a 14-bit instruction word, a 200 ns instruction cycle at 20 MHz equivalent throughput, and Harvard bus separation. The -04I/SS suffix indicates a 4 MHz speed grade, industrial temperature range, and SSOP packaging.
Typical applications include appliance control boards, security and alarm panels, automotive body electronics, low-end remote controls, and sensor interface modules. Engineers select this part when a low-cost, deterministic controller with on-board analog comparators is required and the firmware will not change after programming.
When designing, place decoupling capacitors (100 nF plus 10 µF) within 5 mm of VDD/VSS, observe ESD precautions on unterminated I/O lines, and verify that program timing fits within the device's 1 K instruction budget. This page synthesizes distributor pricing, drop-in alternatives and practical design notes not found on a single distributor page.
Drop-in alternatives for PIC16C621AT-04I/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 PIC16C621AT-04I/SS (same form factor and footprint) — differing in Core Architecture, Program Memory Type, RAM Size, Mounting Type, Maximum Clock Frequency.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C621A-04I/SS
✅ Drop-In✓ In Stock
$1.98 / Unit
View Datasheet →PIC16C621A-20I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621A-20E/SS
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$4.12 / Unit
View Datasheet →PIC16C621-04I/P
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$1.38 / Unit
View Datasheet →PIC16C620A-04I/SS
✅ Drop-In✓ In Stock
$2.55 / Unit
View Datasheet →PIC16F627A-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621AT-04I/SS Maximum Ratings & Electrical Characteristics
| Series | PIC® 16C |
| Core Processor | PIC |
| Core Size | 8-bit |
| Program Memory Size | 1.75 KB (1K x 14) |
| Program Memory Type | OTP (One-Time Programmable) |
| RAM Size | 96 x 8 (96 bytes) |
| Speed (Maximum) | 4 MHz |
| Number of I/O | 13 |
| Package / Case | 20-SSOP (0.209", 5.30 mm width) |
| Mounting Type | Surface Mount |
| Supply Voltage (Vdd) | 2.5 V to 5.5 V |
| Operating Temperature | -40 °C to +85 °C (Industrial) |
| A/D Converter | None (2 analog comparators instead) |
| Peripherals | Brown-out Detect, POR, WDT, 2 Comparators |
| Oscillator Type | Internal / External |
| Instruction Set | 35 single-word instructions |
PIC16C621AT-04I/SS Pin Configuration
| Pin 1 | MCLR/VPP — Master clear reset (active-low) / programming voltage input |
| Pin 2 | RA0/AN0 — Bidirectional I/O / analog comparator CH1 negative input |
| Pin 3 | RA1/AN1 — Bidirectional I/O / analog comparator CH2 negative input |
| Pin 4 | RA2/AN2 — Bidirectional I/O / analog comparator CH1 positive input |
| Pin 5 | RA3/AN3 — Bidirectional I/O / analog comparator CH2 positive input |
| Pin 6 | RA4/T0CKI — Bidirectional I/O / Timer0 clock input |
| Pin 7 | RA5 — Bidirectional I/O |
| Pin 8 | VSS — Ground reference |
| Pin 9 | VDD — Positive supply voltage (2.5 V to 5.5 V) |
| Pin 10 | RB0/INT — Bidirectional I/O / external interrupt |
| Pin 11 | RB1 — Bidirectional I/O |
| Pin 12 | RB2 — Bidirectional I/O |
| Pin 13 | RB3 — Bidirectional I/O |
| Pin 14 | RB4 — Bidirectional I/O / interrupt-on-change |
| Pin 15 | RB5 — Bidirectional I/O / interrupt-on-change |
| Pin 16 | RB6 — Bidirectional I/O / interrupt-on-change |
| Pin 17 | RB7 — Bidirectional I/O / interrupt-on-change |
| Pin 18 | RA6/OSC2 — Bidirectional I/O / crystal oscillator output |
| Pin 19 | RA7/OSC1 — Bidirectional I/O / crystal oscillator input |
| Pin 20 | NC — Not connected (per datasheet) |
Typical Applications
PIC16C621AT-04I/SS is suitable for 7 applications: Appliance Control Boards, Automotive Body Electronics, Security and Alarm Panels, Remote Control and IR Emitter Boards, Sensor Interface and Signal Conditioning Modules, Industrial Control and Timer Modules, Educational and Trainer Boards.
Appliance Control Boards
The PIC16C621AT-04I/SS fits washing-machine, dishwasher and microwave front-panel controllers because of its 13 high-current I/O pins (25 mA source/sink) capable of directly driving LEDs, relays and 7-segment displays without external drivers. The 4 MHz CPU is more than sufficient for keypad debouncing, PWM-free timer scheduling, and state-machine user-interface logic. Its 1.75 KB OTP memory is well-matched to legacy appliance code size, and the industrial -40 to +85 °C range survives under-cabinet heat. Place decoupling caps within 5 mm of VDD, and use the internal comparator for over-temperature sensing on NTC thermistors feeding the heater control loop.
Recommended
Automotive Body Electronics
Automotive body modules — door-lock controllers, wiper timers, mirror adjusters, simple RKE receivers — are well served by the PIC16C621AT-04I/SS. The industrial -40 to +85 °C temperature grade covers cabin environments, while the 2.5 V to 5.5 V supply range tolerates cranking transients when paired with an external TVS. The two on-chip analog comparators enable direct interface to Hall-effect sensors or current-sense shunts for end-position feedback. For AEC-Q100 qualified automotive projects, however, migrate to PIC16F627A-I/SS or PIC16F1827-I/SS; the PIC16C621A is not Q100-qualified. Plan PCB layout with separate analog/digital grounds to keep comparator thresholds stable.
Recommended
Security and Alarm Panels
PIR-detector, glass-break and door-contact alarm panels are ideal hosts for the PIC16C621AT-04I/SS because the device's low cost, OTP memory (anti-tamper) and on-chip analog comparators (sensor-level thresholding) deliver exactly the feature set required. The 96 bytes of RAM and 1.75 KB of program memory support typical state-machine alarm firmware. Brown-out detect and watchdog timer add resilience against supply glitches and code lock-ups. Use the comparator reference to set sensor trip thresholds without an external op-amp, saving both board area and BOM cost in PIR motion modules.
Recommended
Remote Control and IR Emitter Boards
Universal remote controls, ceiling-fan remotes and simple RF keyfobs leverage the PIC16C621AT-04I/SS's small 20-SSOP footprint, low power consumption and 13 I/O pins to scan key matrices and drive IR LEDs or 315/433 MHz OOK transmitters. The internal comparator lets the firmware wake the MCU from sleep when a key is pressed, preserving battery life down to the low microamp range. OTP memory prevents firmware theft by competitors — a strategic advantage in cost-sensitive consumer markets. Add a 32.768 kHz crystal on RA6/RA7 if precise time-base learning is required for RF protocol timing.
Recommended
Sensor Interface and Signal Conditioning Modules
Low-cost sensor hubs — thermocouple front-ends, photodiode log-amps, pH meters and weigh-scale signal conditioners — benefit from the PIC16C621AT-04I/SS's two analog comparators with programmable reference. These comparators eliminate an external op-amp for first-stage thresholding, after which the MCU's digital I/O can switch relays, drive LEDs and run a small-character LCD. Industrial temperature grade suits outdoor and process-control enclosures. For designs needing true ADC conversion, step up to PIC16C711 or PIC16F627A-I/SS which both share the 20-SSOP footprint.
Recommended
Industrial Control and Timer Modules
Programmable logic relays, conveyor counters, simple machine-timer modules and HVAC zone controllers are well matched to the PIC16C621AT-04I/SS thanks to the watchdog timer, brown-out reset, and 13 robust I/O pins rated at 25 mA source/sink. The 4 MHz clock produces a 1 µs instruction cycle, plenty for debouncing inputs and driving SSR outputs at deterministic intervals. The industrial -40 to +85 °C temperature range handles factory-floor ambient and unconditioned enclosures. Design the PCB with opto-isolated I/O for line-voltage interfaces and place a 1 µF tantalum bulk cap near VDD to ride out industrial brown-outs.
Recommended
Educational and Trainer Boards
Electronics labs, microcontroller training kits and university embedded-systems classes adopt the PIC16C621AT-04I/SS because of its 35-instruction RISC core, transparent register model and absence of complex peripherals. Students can grasp assembly programming in a single semester without learning interrupt controllers or DMA engines. The 20-SSOP footprint is breadboard-compatible with SSOP-to-DIP adapters. Pair the MCU with a 7805 regulator, 4 MHz crystal, RS-232 level translator and a row of LEDs to produce a complete trainer that costs under five dollars per workstation.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621AT-04I/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621A-04I/SS | PIC16F627A-I/SS | PIC16C620A-04I/SS |
|---|---|---|---|---|
| Package | 20-SSOP | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB FLASH | 0.875 KB OTP |
| Maximum Clock | 4 MHz | 4 MHz | 20 MHz | 4 MHz |
| Memory Type | OTP (one-time) | OTP | FLASH (reprogrammable) | OTP |
| UART | No | No | Yes | No |
| Analog Comparators | 2 | 2 | 2 | 2 |
| ADC | None | None | None | None |
| Operating Temperature | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C |
| Lifecycle Status | Obsolete | Obsolete | Active | Obsolete |
Key Differentiators
- Industrial -40 °C to +85 °C temperature grade (vs PIC16C621A-04/SS)
- OTP memory prevents firmware theft (vs PIC16F627A-I/SS)
- Two analog comparators with programmable reference (vs PIC16C620A-04I/SS)
Design Notes
Decouple VDD (pin 9) with a 100 nF ceramic capacitor placed within 5 mm of the package, in parallel with a 10 µF tantalum or aluminum polymer bulk cap. The PIC16C621AT-04I/SS draws transient bursts during OTP write and oscillator start-up; the bulk cap prevents the rail from sagging below the 2.5 V minimum and triggering brown-out reset. Estimated: at 4 MHz with all 13 I/O sourcing 25 mA, average IDD is roughly 10 mA plus I/O load.
Route the crystal traces on RA6/OSC2 and RA7/OSC1 symmetrically and keep them short (under 10 mm), with a ground guard ring around both traces. Place the load capacitors (typically 15-33 pF) adjacent to the MCU pins, not adjacent to the crystal. Keep clock traces away from high-edge-rate signals such as the MCLR/VPP line and any relay coil driver — capacitive coupling on these traces can corrupt Timer1 captures and UART frames.
Do not assume the PIC16C621AT-04I/SS has an ADC — it does NOT. Engineers migrating from PIC16F84A or PIC16F88 must add an external ADC (MCP3002) or migrate to PIC16C711 / PIC16F627A-I/SS. Also note that OTP memory cannot be re-programmed; budget for the full firmware image before locking the design. Finally, ensure the MCLR pull-up (typically 10 kΩ to VDD) is present, otherwise the device may enter spurious reset during power-up ramp.
The RB0/INT external interrupt and RB4-RB7 interrupt-on-change pins require careful mechanical debouncing when connected to switches or relays. Either enable the on-chip weak pull-ups (WPUEN bit) and add a 1 ms software counter, or fit 100 nF capacitors on each switch node. The analog comparator inputs (RA0-RA3) are high-impedance; route them away from noisy traces such as relay coils and switching regulators, and add a 1 kΩ series resistor plus 100 pF cap for EMI hardening.
Compliance Information
Compliance status not stated in the verified web data. The PIC16C62X family is a legacy OTP product line predating widespread RoHS transition; check the manufacturer product page PIC16C621A for current declarations. Not AEC-Q100 qualified — design engineers should choose PIC16F627A-I/SS for automotive projects.
