PIC16C621-20E/SS - 8-Bit 20MHz OTP MCU 1.75KB | Microchip
MPN: PIC16C621-20E/SS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.95 | $3.95 |
| 10 | $3.55 | $35.50 |
| 100 | $3.12 | $312.00 |
| 500 | $2.78 | $1,390.00 |
| 1,000 | $2.45 | $2,450.00 |
PIC16C621-20E/SS Overview
What is an OTP microcontroller? An OTP (One-Time-Programmable) microcontroller is a type of embedded processor that contains EPROM-based program storage which can be written once and then behaves like ROM for the rest of the device's lifetime. Microcontrollers (MCUs) belong to a product hierarchy from PIC16C family -> PIC16 architecture -> 8-bit microcontroller -> embedded controller -> semiconductor IC. OTP MCUs offer the cost advantage of ROM parts while allowing late-stage firmware customization before the final mask ROM commit, making them ideal for low-to-medium volume production runs where mask-ROM NRE costs cannot be justified.
The PIC16C621-20E/SS leverages Microchip's enhanced PIC16C mid-range core with a Harvard architecture featuring separate program and data buses, enabling simultaneous instruction fetch and operand access. The 14-bit wide instruction word and 35-instruction set deliver compact code density (~2:1 over comparable 8-bit CISC cores), while the 20MHz oscillator input yields a 200ns instruction cycle, providing predictable real-time interrupt response for automotive body controllers, sensor interfaces, and battery-powered industrial nodes. Built-in peripherals include an 8-bit ADC-less analog comparator block, two Capture/Compare/PWM (CCP) modules (family-feature), and synchronous/asynchronous serial via the USART.
Typical applications include automotive body electronics (seat controllers, mirror adjusters, lighting modules), industrial sensor interface boards, low-power remote sensor nodes, home appliance control boards, and embedded control for legacy replacement of discrete logic. The PIC16C621-20E/SS variant specifically targets automotive-grade deployment (Automotive temperature grade per the Partstack terminal-form entry) at 20MHz maximum frequency.
When designing with this device, ensure that OTP programming accounts for firmware revision control, as OTP memory cannot be erased or rewritten once programmed. Provide adequate decoupling (100nF + 10uF bulk) near VDD, follow Microchip AN529 emitter-follower layout recommendations for the analog comparator inputs, and validate MCLR pull-up timing against in-system ICSP programmer requirements.
Drop-in alternatives for PIC16C621-20E/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 PIC16C621-20E/SS (same form factor and footprint) — differing in Program Memory Type, Package, Program Memory Size, Instruction Set, Watchdog Timer.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C620A-20E/SS
✅ Drop-In✓ In Stock
$1.62 / Unit
View Datasheet →PIC16C621-20/P
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →PIC16C621-04E/P
✅ Drop-In✓ In Stock
$2.85 / Unit
View Datasheet →PIC16C620T-20E/SS
✅ Drop-In✓ In Stock
$3.89 / Unit
View Datasheet →PIC16C58B-20E/SS
✅ Drop-In✓ In Stock
$2.78 / Unit
View Datasheet →PIC16C621-20E/SS Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC16C / 8-bit RISC |
| Program Memory Type | OTP (One-Time-Programmable EPROM) |
| Program Memory Size | 1.75 KB (1K x 14) |
| RAM | 80 bytes |
| EEPROM Data Memory | 128 bytes |
| Maximum CPU Frequency | 20 MHz |
| Instruction Cycle Time | 200 ns at 20 MHz |
| Instruction Set | 35 instructions, 14-bit word |
| Operating Voltage Range | 2.5 V to 6.0 V |
| Timers | 2 x 8-bit (Timer0, Timer1) |
| Watchdog Timer | Yes, with on-chip RC oscillator |
| Analog Comparator | Yes (2 channels) |
| I/O Pins | 13 |
| Package | 20-pin SSOP |
| Mounting Type | Surface Mount (Gull-wing) |
| Temperature Grade | Automotive / Industrial (E = Extended) |
| ICSP | Yes (In-Circuit Serial Programming) |
| Code Protection | Programmable |
PIC16C621-20E/SS Pin Configuration
| Pin 1 | MCLR/VPP — Master Clear (reset, active low) / Programming voltage input |
| Pin 2 | RA0/AN0 — Digital I/O / Analog comparator channel 0 |
| Pin 3 | RA1/AN1 — Digital I/O / Analog comparator channel 1 |
| Pin 4 | RA2/AN2 — Digital I/O / Analog comparator channel 2 |
| Pin 5 | RA3/AN3 — Digital I/O / Analog comparator channel 3 |
| Pin 6 | RA4/T0CKI — Digital I/O / Timer0 clock input |
| Pin 7 | RA5/SS — Digital I/O / Synchronous serial port slave select |
| Pin 8 | OSC1/CLKIN — Oscillator input / External clock input |
| Pin 9 | OSC2/CLKOUT — Oscillator output / Clock output |
| Pin 10 | RC0 — Digital I/O port C bit 0 |
| Pin 11 | RC1 — Digital I/O port C bit 1 |
| Pin 12 | RC2/CCP1 — Digital I/O / Capture Compare PWM channel 1 |
| Pin 13 | RC3 — Digital I/O port C bit 3 |
| Pin 14 | RC4 — Digital I/O port C bit 4 |
| Pin 15 | RC5 — Digital I/O port C bit 5 |
| Pin 16 | RC6 — Digital I/O port C bit 6 |
| Pin 17 | RC7 — Digital I/O port C bit 7 |
| Pin 18 | RB0/INT — Digital I/O port B bit 0 / External interrupt |
| Pin 19 | RB1 — Digital I/O port B bit 1 |
| Pin 20 | VDD — Positive supply voltage (2.5V to 6.0V) |
Typical Applications
PIC16C621-20E/SS is suitable for 6 applications: Automotive Body Electronics, Industrial Sensor Interface Boards, Low-Power Remote Sensor Nodes, Home Appliance Control Boards, Embedded Replacement of Discrete Logic, HVAC Fan and Blower Controllers.
Automotive Body Electronics
The PIC16C621-20E/SS's automotive (E) temperature grade (-40C to +125C) and 20MHz core make it well suited for body controllers such as seat position modules, mirror adjusters, and lighting drivers. Its 1.75KB OTP stores state-machine logic for motor control and switch debouncing without requiring firmware updates, while the analog comparator block enables current sensing for window lift and door lock actuators. The 80 bytes RAM is sufficient for typical 8-bit automotive I/O expansion tasks, and ICSP allows end-of-line programming during ECU assembly.
Recommended
Industrial Sensor Interface Boards
Industrial sensor interface boards benefit from the PIC16C621-20E/SS's on-chip analog comparator for threshold detection without external ADC, plus two 8-bit timers for pulse counting and PWM actuator control. The 2.5V to 6.0V operating range supports 3.3V and 5V industrial buses, while the SSOP-20 footprint enables compact DIN-rail PCB designs. With 1.75KB OTP and 35-instruction RISC core, the part executes deterministic control loops at 200ns per instruction for real-time encoder quadrature decoding.
Recommended
Low-Power Remote Sensor Nodes
The PIC16C621-20E/SS achieves the low-power credentials required for battery-powered remote sensor nodes: 15 μA typical at 5V/4MHz and 1 μA typical at 3V/32 kHz per the PIC16C62x datasheet. The on-chip watchdog timer with internal RC oscillator eliminates external components, while the analog comparator serves as a brown-out detector or external event trigger to wake the CPU. OTP memory locks the firmware against accidental field rewrite, preserving battery cell life across years of unattended operation in remote installations.
Recommended
Home Appliance Control Boards
Home appliance controllers (washing machines, dishwashers, microwave ovens) benefit from the PIC16C621-20E/SS's 20 MIPS performance for keypad scanning, LED multiplexing, and relay sequencing. Its 128-byte EEPROM retains user settings through power cycles without external memory, and the 13 GPIO pins drive direct LED indicators and triac interfaces. Microchip's mature PIC16C application notes cover washing-machine motor control algorithms, making this MCU a low-risk choice for legacy appliance redesign.
Recommended
Embedded Replacement of Discrete Logic
The PIC16C621-20E/SS replaces banks of 74HC logic with a single programmed MCU, saving PCB area in legacy industrial designs. With 35 instructions and 200ns instruction cycle, the part runs glue-logic replacement faster than discrete CMOS gates while adding software-configurable behavior. The 1.75KB OTP accommodates typical state-machine glue-logic patterns, and the SSOP-20 footprint keeps the solution compact. Designers can re-purpose unused GPIO for LED indicators, removing additional discrete drivers.
Recommended
HVAC Fan and Blower Controllers
HVAC blower controllers use the PIC16C621-20E/SS's analog comparator to detect tachometer feedback from brushless fans and adjust PWM duty cycle accordingly. The 20MHz core delivers precise PWM resolution for smooth fan-speed curves, while the watchdog prevents runaway blower operation in fault conditions. Its 2.5V to 6.0V operating range supports 24V industrial HVAC buses with simple LDO pre-regulation, and the 20-SSOP package survives high-vibration rooftop unit mounting.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621-20E/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C620A-20E/SS | PIC16C621-20/P | PIC16C621-04E/P | PIC16C620T-20E/SS | PIC16C58B-20E/SS |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 20-pin SSOP | 20-pin SSOP | 20-pin PDIP | 20-pin PDIP | 20-pin SSOP | 20-pin SSOP |
| Program Memory | 1.75 KB OTP | 512 B OTP | 1.75 KB OTP | 1.75 KB OTP | 512 B OTP | 3.25 KB OTP |
| RAM | 80 bytes | 36 bytes | 80 bytes | 80 bytes | 36 bytes | 73 bytes |
| Maximum Frequency | 20 MHz | 20 MHz | 20 MHz | 4 MHz | 20 MHz | 20 MHz |
| Temperature Grade | Automotive (E = Extended) | Extended | Commercial | Extended | Extended | Extended |
| Operating Voltage | 2.5V to 6.0V | 2.5V to 6.0V | 2.5V to 6.0V | 2.5V to 6.0V | 2.5V to 6.0V | 2.5V to 6.0V |
| EEPROM | 128 bytes | 128 bytes | 128 bytes | 128 bytes | 128 bytes | None |
Key Differentiators
- Larger program memory than PIC16C620A-20E/SS sibling (vs PIC16C620A-20E/SS)
- Higher speed grade than PIC16C621-04E/P variant (vs PIC16C621-04E/P)
- In-system ICSP programming eliminates socketed programming (vs PIC16C58B-20E/SS)
Design Notes
OTP memory is one-time-programmable and cannot be erased or rewritten once programmed. According to Microchip PIC16C62x family notes, this requires strict firmware revision control before production programming because every test firmware image consumes a part. For development, prototype with the flash-based PIC16F628-20I/SS in the same 20-SSOP footprint before committing OTP codes to production.
Estimated: place a 100nF ceramic decoupling capacitor within 5mm of the VDD pin (pin 20) and a 10uF bulk capacitor at the board's power entry. MCLR/VPP (pin 1) requires a 10kOhm pull-up to VDD for normal operation; during ICSP programming, voltage levels of 12V-13.5V are applied to this pin. Add a Schottky diode (e.g., 1N4148) from MCLR to VDD if in-circuit programming is required while the rest of the board is powered.
When using the analog comparator inputs (RA0-RA3), keep analog traces short and away from digital switching signals to prevent false comparator triggers. According to Microchip application note AN529, a 100ns settling time is required after switching the analog channel multiplexer; therefore sample comparator inputs at least one instruction cycle after channel changes. Add a small RC low-pass filter (10kOhm + 100pF) on comparator inputs in noisy environments.
Compliance Information
Automotive temperature grade (E = Extended) per Partstack terminal-form entry; RoHS compliant per Microchip product page. AEC-Q100 qualification status not explicitly stated in the verified data.