PIC16C621A-04I/P - 8-Bit 4MHz OTP MCU 1.75KB | Microchip
MPN: PIC16C621A-04I/P ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.85 | $2.85 |
| 10 | $2.52 | $25.20 |
| 100 | $2.1 | $210.00 |
| 500 | $1.75 | $875.00 |
| 1,000 | $1.5 | $1,500.00 |
PIC16C621A-04I/P Overview
An 8-bit microcontroller (MCU) is a programmable single-chip computer that integrates a CPU, RAM, non-volatile program storage, and I/O peripherals. The PIC16C family uses a RISC architecture, where each instruction executes in one instruction cycle (4 clock periods). One-time programmable (OTP) program memory is one-time-writable using a device programmer, making it suitable for low-to-medium volume production where firmware is finalized before assembly and where field re-programmability is not required.
Key features include a 4 MHz internal oscillator option with selectable clock modes, a 14-bit wide instruction word optimized for compact code, a hardware USART/SCI, an analog comparator, and a watchdog timer for reliable operation in noisy industrial environments. The 13 bidirectional I/O pins can source/sink 25 mA per pin, allowing direct LED driving without external buffers. Compared to flash-based PIC16F alternatives, the OTP memory provides slightly tighter code security because bit-stream extraction from the device is not straightforward.
Typical applications include appliance control boards, sensor signal conditioning, motor-driver front-ends, simple user-interface controllers, and white-goods replacement of discrete logic. The 18-pin PDIP package is breadboard-friendly and remains popular for engineering samples, university coursework, and legacy field service where through-hole rework is preferred over surface-mount.
When designing with the PIC16C621A, ensure that MCLR is properly biased with a 10 kΩ pull-up and decoupling capacitors are placed within 5 mm of VDD/VSS. Programming the OTP memory requires a Microchip device programmer (such as the MPLAB PM3) because in-system programming is not supported on this OTP member of the PIC16C family.
Drop-in alternatives for PIC16C621A-04I/P — 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 PIC16C621A-04I/P (same form factor and footprint) — differing in Mounting Type, Package, Program Memory Type, Core Architecture, Program Memory Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16F627A-I/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621A-04/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16F628A-04I/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C622A-04I/P
✅ Drop-In✓ In Stock
$1.95 / Unit
View Datasheet →PIC16C621-04I/P
✅ Drop-In✓ In Stock
$1.38 / Unit
View Datasheet →PIC16C620A-04I/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621A-04I/P Maximum Ratings & Electrical Characteristics
| Manufacturer | Microchip Technology |
| Series | PIC 16C |
| Core Processor | PIC |
| Core Size | 8-Bit |
| Maximum Clock Frequency | 4 MHz |
| Instruction Execution Time | 200 ns (1 cycle = 4 clocks) |
| Program Memory Type | OTP (One-Time Programmable EPROM) |
| Program Memory Size | 1.75 KB (1K x 14) |
| RAM Size | 96 bytes |
| Number of I/O Pins | 13 |
| Supply Voltage (VDD) | 3.3 V to 5.5 V (PIC16C621A industrial range) |
| Operating Temperature Range | -40C to +85C (industrial grade, suffix -I) |
| Package | 18-Pin PDIP (0.300 in / 7.62 mm pitch) |
| Mounting Type | Through-Hole (DIP) |
| Number of Instructions | 35 (single-word) |
| RoHS Status | Compliant |
| Lead-Free | Yes |
PIC16C621A-04I/P 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/VPP — Master Clear reset input (active low) / Programming voltage |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Bidirectional I/O port B bit 0 / External interrupt input |
| 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 — Bidirectional I/O port B bit 6 |
| Pin 13 | RB7 — Bidirectional I/O port B bit 7 |
| Pin 14 | VDD — Positive supply voltage |
| Pin 15 | OSC2/CLKOUT — Oscillator crystal output / Clock output |
| Pin 16 | OSC1/CLKIN — Oscillator crystal input / External clock input |
| Pin 17 | RA0 — Bidirectional I/O port A bit 0 |
| Pin 18 | RA1 — Bidirectional I/O port A bit 1 |
Typical Applications
PIC16C621A-04I/P is suitable for 7 applications: Industrial Sensor Signal Conditioning, Appliance Control Boards, LED Display and Indicator Drivers, Motor Driver Front-End Controllers, User Interface and Keypad Controllers, Legacy Replacement of Discrete Logic, Educational and Prototyping Platforms.
Industrial Sensor Signal Conditioning
The PIC16C621A-04I/P suits industrial sensor signal conditioning because of its integrated analog comparator, 13 high-current (25 mA) I/O pins, and -40C to +85C industrial temperature rating. The on-chip comparator thresholds a conditioned analog signal from a bridge sensor or thermistor and produces a clean digital output to drive an opto-coupler or relay coil. With 1.75 KB of OTP memory and 96 bytes of RAM, the MCU handles linearization look-up tables and basic hysteresis control, while the 4 MHz clock provides 200 ns instruction execution fast enough for 1 kHz closed-loop sampling.
Recommended
Appliance Control Boards
The PIC16C621A-04I/P is well matched to appliance control boards where its 13 high-current I/O pins drive relays, triac gates, LEDs, and seven-segment displays directly without external buffers. The 35-instruction RISC core simplifies firmware for state-machine control of washing machines, dishwashers, and microwave ovens, while 96 bytes of RAM is sufficient for keypad de-bounce and timing. The OTP program memory secures the firmware against bit-stream extraction in cost-sensitive consumer products. Microchip's legacy support and through-hole PDIP make it easy to rework field returns.
Recommended
LED Display and Indicator Drivers
The PIC16C621A-04I/P drives LED displays and indicator panels because each of its 13 I/O pins can source or sink 25 mA, allowing direct multiplexing of small seven-segment or matrix LED arrays without driver transistors. The 4 MHz clock supports smooth PWM dimming in the audible-frequency range, while the on-chip watchdog timer prevents display lock-up in unattended installations. OTP memory locks the lighting patterns at production, preventing unauthorized re-flashing in commercial signage. Designers can also use the analog comparator to implement ambient-light feedback for brightness control.
Recommended
Motor Driver Front-End Controllers
The PIC16C621A-04I/P acts as a motor-driver front-end, generating PWM signals, monitoring current sense inputs via the on-chip analog comparator, and sequencing enable logic for H-bridge power stages. Its 4 MHz CPU clock supports 8-bit PWM at 15.6 kHz - well above the audible band - while the 35-instruction core keeps control-loop latency under 10 microseconds. The -40C to +85C industrial rating tolerates under-the-hood automotive and white-goods thermal stress. OTP memory locks calibrated motor parameters for OEM production.
Recommended
User Interface and Keypad Controllers
The PIC16C621A-04I/P runs as a user-interface controller scanning keypads, debouncing mechanical switches, and updating LCD or LED indicators in industrial HMIs and consumer appliances. With 13 I/O pins the device handles up to a 4x4 matrix keypad (8 lines) plus four indicator outputs without external logic. The 96-byte RAM stores de-bounce timers, mode flags, and short user-ismsets, while 1.75 KB of OTP memory holds the keypad map and state-machine code. The industrial temperature grade supports harsh-environment HMIs in factories and outdoor kiosks.
Recommended
Legacy Replacement of Discrete Logic
The PIC16C621A-04I/P replaces discrete 74-series logic in legacy designs where a small amount of programmability simplifies state machines, sequencing, or encoding tasks. The 35-instruction RISC core replaces dozens of glue-logic gates, while the 13 I/O pins provide flexible I/O mapping. OTP memory locks the logic behavior at production time, preventing field modification - useful in security and metering equipment. The 18-pin PDIP through-hole package remains popular for one-off legacy service boards and university laboratory work where socketed parts simplify thermal management.
Recommended
Educational and Prototyping Platforms
The PIC16C621A-04I/P is used in educational settings and prototype development platforms because of its breadboard-friendly 18-pin PDIP package, simple 35-instruction RISC core, and low-cost Microchip programmer support (MPLAB PM3, PICkit 2 with adapter). Students learn fundamentals of embedded programming - GPIO, timers, watchdog, comparator - without the complexity of modern peripherals. The 1.75 KB OTP forces disciplined code design, while identical die variants allow quick comparison between PIC16C621, PIC16C621A, and PIC16C622A silicon revisions. The Microchip PIC16C62X datasheet provides complete register maps for instructional use.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621A-04I/P — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16F627A-I/P | PIC16C621A-04/P | PIC16F628A-04I/P | PIC16C622A-04I/P |
|---|---|---|---|---|---|
| Package | 18-PDIP | 18-PDIP - same | 18-PDIP - same | 18-PDIP - same | 18-PDIP - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Core / Architecture | PIC 8-bit RISC, 35 instructions | PIC 8-bit RISC, 35 instructions | PIC 8-bit RISC, 35 instructions | PIC 8-bit RISC, 35 instructions | PIC 8-bit RISC, 35 instructions |
| Maximum Clock Frequency | 4 MHz | 20 MHz | 4 MHz | 20 MHz | 4 MHz |
| Program Memory Type | OTP EPROM (1K x 14) | Flash (1K x 14) | OTP EPROM (1K x 14) | Flash (2K x 14) | OTP EPROM (1K x 14) |
| Program Memory Size | 1.75 KB | 1.75 KB | 1.75 KB | 3.5 KB | 1.75 KB |
| RAM Size | 96 bytes | 128 bytes | 96 bytes | 224 bytes | 96 bytes |
| I/O Pins | 13 | 16 | 13 | 16 | 13 |
| Operating Temperature | -40C to +85C (industrial) | -40C to +85C (industrial) | 0C to +70C (commercial) | -40C to +85C (industrial) | -40C to +85C (industrial) |
| Lifecycle Status | NRND | Active | NRND | Active | NRND |
Key Differentiators
- Industrial temperature grade at low cost (vs PIC16C621A-04/P)
- Flash in-system programmability (vs PIC16F627A-I/P)
- Doubled program memory and RAM (vs PIC16F628A-04I/P)
- Second analog comparator and voltage reference (vs PIC16C622A-04I/P)
Design Notes
Place a 0.1 uF decoupling capacitor within 5 mm of the VDD pin (pin 14) and a bulk 10 uF electrolytic on the same rail. The PIC16C621A's internal brown-out and power-on reset circuits require clean VDD rise-time; slow rise below 0.05 V/ms can cause undefined startup. For battery-powered applications, verify quiescent current from the manufacturer datasheet because PIC16C OTP variants do not always support sleep modes with full RAM retention.
Do not confuse the PIC16C621A-04I/P (4 MHz industrial) with the PIC16C621A-20I/P (20 MHz industrial) or the PIC16C621A-04/P (4 MHz commercial). The 4 MHz silicon has a guaranteed maximum clock of 4 MHz; operation above that can cause program-counter corruption. Also remember that OTP memory can only be programmed once - test firmware on a PIC16F627A-I/P emulator part before committing to the OTP flow. Always verify with the Microchip PIC16C62X datasheet DS30235D before board bring-up.
The 18-pin PDIP through-hole package has 0.300 inch (7.62 mm) row spacing, so any PCB layout can use a standard DIP-18 socket for easy rework. Place MCLR (pin 4) pull-up resistor (typically 10 kOhm) and a 100 nF cap to ground for reliable reset behavior. Keep the OSC1/OSC2 traces short and surround them with a ground guard ring to reduce EMI coupling; for crystals, follow the Microchip PIC16C62X datasheet recommended capacitor values for the selected oscillator mode (RC, LP, XT, HS).
Each RB port pin can source or sink 25 mA, but the total current per port is limited; refer to the Microchip PIC16C62X datasheet absolute maximum ratings to avoid latch-up. Add series resistors on LED-driving outputs to limit inrush, and clamp inductive loads with flyback diodes. The analog comparator inputs share pins with digital I/O - if both functions are needed, isolate the comparator pin with a small RC network to prevent digital switching noise from corrupting threshold detection.
Compliance Information
RoHS compliant per Microchip product page. Lead-free. Halogen-free status not explicitly confirmed in available search data and is set to unknown. AEC-Q100 not applicable (industrial/consumer MCU, not automotive-qualified).
