PIC16C621T-20E/SS - 8-Bit 20MHz OTP MCU, 1.75KB | Microchip
MPN: PIC16C621T-20E/SS ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.85 | $3.85 |
| 10 | $3.46 | $34.60 |
| 100 | $3.05 | $305.00 |
| 500 | $2.71 | $1,355.00 |
| 1,000 | $2.42 | $2,420.00 |
| 2,500 | $2.18 | $5,450.00 |
PIC16C621T-20E/SS Overview
A PIC (Peripheral Interface Controller) microcontroller is a compact 8-bit RISC processor designed by Microchip for embedded control applications. PIC16C-series parts belong to the mid-range family and follow the PIC -> 8-bit MCU -> microcontroller -> embedded processor taxonomy; the OTP variants (PIC16C, with a windowed UV-erasable cousin PIC16C) target cost-sensitive volume production where firmware is finalized before programming. These parts sit within the broader category of integrated circuits > microcontrollers > 8-bit microcontrollers.
Key features of the PIC16C621T-20E/SS include 13 digital I/O pins with individual direction control, an external oscillator interface supporting crystal, resonator, or RC modes, a programmable WDT with its own on-chip RC oscillator, a power-on reset circuit, and brown-out reset for safe recovery from low-voltage transients. The Harvard RISC architecture provides single-cycle instructions (excluding branches), enabling deterministic interrupt latency. The 20-pin SSOP (Shrink Small Outline Package) reduces board area compared with standard SOIC while retaining hand-solderability and standard 1.27 mm pin pitch.
Typical applications include industrial automation controllers, consumer appliance control boards, automotive body and chassis subsystems, sensor interface modules, and general-purpose embedded control where low cost, simple development, and small footprint are priorities. The 3.0V to 6.0V range covers both 3.3V and 5V supply rails common in legacy industrial designs.
When designing with this part, note that OTP memory can be programmed only once, so firmware must be fully validated before production programming. The -40C to +125C operating range supports automotive and industrial environments, but designers migrating from the -04 or -20 base parts should verify oscillator and timing parameters against the PIC16C621 datasheet electrical characteristics table.
This page synthesizes distributor pricing as of 2026-09-17, drop-in pin-compatible Microchip alternatives such as PIC16C621A and PIC16C620A, and practical design notes that complement the manufacturer datasheet.
Drop-in alternatives for PIC16C621T-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 PIC16C621T-20E/SS (same form factor and footprint) — differing in Core Architecture, Instruction Set, Package, Program Memory Type, RoHS Status.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C621-20E/SS
✅ Drop-In✓ In Stock
$2.45 / Unit
View Datasheet →PIC16C621A-20E/SS
✅ Drop-In✓ In Stock
$4.12 / Unit
View Datasheet →PIC16C620A-20E/SS
✅ Drop-In✓ In Stock
$1.62 / Unit
View Datasheet →PIC16C621AT-20E/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16F627A-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C621T-20E/SS Maximum Ratings & Electrical Characteristics
| Core Processor | PIC |
| Core Size | 8-Bit |
| Family | PIC 16C |
| Maximum Clock Speed | 20 MHz |
| Program Memory Type | OTP (One-Time Programmable) |
| Program Memory Size | 1.75 KB (1K x 14) |
| Data RAM Size | 80 x 8 bytes |
| Number of I/O Pins | 13 |
| Supply Voltage Range | 3.0 V to 6.0 V |
| Package / Case | 20-SSOP (0.295, 7.50 mm width) |
| Mounting Type | Surface Mount |
| Supplying Package | Tape & Reel (T/R) |
| Oscillator Type | External |
| Peripherals | Brown-out Detect/Reset, POR, WDT |
| Connectivity | Not specified |
| Operating Temperature Range | -40C to +125C |
| RoHS Status | Compliant |
| Lead-Free | Yes |
PIC16C621T-20E/SS Pin Configuration
| Pin 1 | RA2/AN2 — Bidirectional I/O / analog channel 2 (621A only) |
| Pin 2 | RA3/AN3 — Bidirectional I/O / analog channel 3 (621A only) |
| Pin 3 | RA4 — Bidirectional I/O / TOCKI |
| Pin 4 | RA5 — Bidirectional I/O / SS |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Bidirectional I/O / external interrupt |
| Pin 7 | RB1 — Bidirectional I/O |
| Pin 8 | RB2 — Bidirectional I/O |
| Pin 9 | RB3 — Bidirectional I/O |
| Pin 10 | RB4 — Bidirectional I/O / interrupt-on-change |
| Pin 11 | RB5 — Bidirectional I/O / interrupt-on-change |
| Pin 12 | RB6 — Bidirectional I/O / interrupt-on-change / ICSP clock |
| Pin 13 | RB7 — Bidirectional I/O / interrupt-on-change / ICSP data |
| Pin 14 | VDD — Positive supply (3.0V-6.0V) |
| Pin 15 | OSC2/CLKOUT — Oscillator output / clock out |
| Pin 16 | OSC1/CLKIN — Oscillator input / external clock in |
| Pin 17 | RA0 — Bidirectional I/O / analog channel 0 |
| Pin 18 | RA1 — Bidirectional I/O / analog channel 1 |
| Pin 19 | RA7 — Bidirectional I/O |
| Pin 20 | RA6 — Bidirectional I/O |
Typical Applications
PIC16C621T-20E/SS is suitable for 6 applications: Industrial Automation Controllers, Consumer Appliance Control Boards, Automotive Body and Chassis Subsystems, Sensor Interface and Signal Conditioning Modules, General-Purpose Embedded Control Boards, Legacy Embedded Replacement and Field Spares.
Industrial Automation Controllers
The PIC16C621T-20E/SS fits industrial automation controllers because its 20 MHz clock delivers 5 MIPS instruction throughput, sufficient to scan multiple digital inputs, debounce mechanical switches, and drive relay or triac outputs within a 1 ms control loop. The 13 I/O pins comfortably handle 8-10 optically-isolated inputs plus 2-3 actuator drivers, and the on-chip brown-out reset prevents corrupted EEPROM writes during industrial supply transients common on 24V-rail-derived 5V systems. Pin-compatible Microchip drop-ins (PIC16C621A-20E/SS, PIC16C620A-20E/SS) preserve layout when migrating between comparator and ADC variants across product families. The -40C to +125C operating range supports unenclosed cabinet mounting. Designers should add a TVS diode on VDD and a 100 nF decoupling capacitor within 1 cm of the IC.
Recommended
Consumer Appliance Control Boards
Consumer appliance control boards such as washing-machine front panels, microwave user interfaces, and dishwasher motor controllers benefit from the PIC16C621T-20E/SS's low unit cost and OTP memory that protects production firmware from unauthorized reprogramming. The 1.75 KB program memory holds typical user-interface state machines plus keypad scanning routines, while 80 bytes of RAM is adequate for 4-6 timer variables and a small state lookup table. The 3.0V to 6.0V range matches both 3.3V and 5V supply rails derived from rectified mains. The SSOP-20 package reduces PCB area in space-constrained front-panel modules. Replacement parts PIC16C621A-20E/SS and PIC16C620A-20E/SS share the SSOP-20 footprint, allowing quick re-spin if appliance variants need different peripheral mixes.
Recommended
Automotive Body and Chassis Subsystems
The PIC16C621T-20E/SS fits automotive body and chassis subsystems such as seat controllers, mirror adjusters, and lighting modules where its -40C to +125C operating temperature range covers under-dash and under-hood environments, and its small SSOP-20 footprint fits the cramped PCBs behind door panels. Brown-out reset handles automotive load-dump events by triggering a clean restart when battery voltage dips below the 3.0V minimum. The 20 MHz clock executes debounce, PWM generation, and LIN-like bit-banged communication tasks simultaneously within the body-controller latency budget. Drop-in alternatives PIC16C621A-20E/SS and PIC16C620A-20E/SS allow tier migration between comparator-based and ADC-based analog signal conditioning in the same SSOP-20 footprint, simplifying BOM management across vehicle trim levels.
Recommended
Sensor Interface and Signal Conditioning Modules
Sensor interface modules that combine two analog inputs with several digital control outputs pair well with the PIC16C621T-20E/SS thanks to its two on-chip analog comparators, which can implement window detectors, threshold switches, or simple delta-sigma A/D conversion without external op-amps. The 20 MHz instruction rate performs 8-bit successive-approximation algorithms in under 100 microseconds, while 80 bytes of RAM holds calibration coefficients and recent sample buffers. For designs requiring higher resolution, the PIC16C621A-20E/SS drop-in adds a true 8-bit ADC and remains SSOP-20 compatible. Brown-out detection prevents false alarms during low-voltage battery events common in wireless sensor nodes.
Recommended
General-Purpose Embedded Control Boards
Hobbyist, education, and small-volume OEM boards rely on the PIC16C621T-20E/SS for general-purpose I/O expansion, button-and-LED interfaces, and simple timing functions, where its 13 I/O pins deliver enough headroom for 8-bit parallel buses plus handshake signals, and its 1.75 KB OTP stores roughly 700-1000 mid-range instructions. The SSOP-20 footprint is breadboard-friendly with carrier boards, and the 3.0V to 6.0V supply range accepts USB-TTL serial-programmer power rails directly. Production programming is via the ICSP interface on pins RB6 and RB7, supported by Microchip's MPLAB X IDE and legacy PICSTART Plus tools. For new designs where code reuse is less critical, the PIC16F627A-I/SS flash-based drop-in removes OTP field-reprogramming risk.
Recommended
Legacy Embedded Replacement and Field Spares
Maintenance and repair of legacy equipment originally designed around the PIC16C621 family often requires the PIC16C621T-20E/SS as a like-for-like replacement, because field-deployed firmware is typically compiled against the original part's silicon and cannot tolerate peripheral-mapping changes. The T/R packaging format suits pick-and-place repairs on modern production lines, while the SSOP-20 package matches the original PCB land pattern exactly. Where field firmware migration is acceptable, the PIC16C621A-20E/SS and PIC16C620A-20E/SS drop-ins preserve pinout while adjusting peripheral subsets. Note that the part is marked obsolete by Microchip as of 2026-09-17, so repair stock should be procured now or migrated to the PIC16F627A-I/SS flash successor before remaining inventory is depleted.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C621T-20E/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C621-20E/SS | PIC16C621A-20E/SS | PIC16C620A-20E/SS | PIC16C621AT-20E/SS | PIC16F627A-I/SS |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 20-SSOP | 20-SSOP (tube) | 20-SSOP | 20-SSOP | 20-SSOP (T/R) | 20-SSOP |
| Core / Family | PIC 16C / 8-bit | PIC 16C / 8-bit | PIC 16C / 8-bit | PIC 16C / 8-bit | PIC 16C / 8-bit | PIC 16F / 8-bit Flash |
| Program Memory | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB OTP | 1.75 KB Flash |
| Maximum Clock | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| Data RAM | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 80 bytes | 128 bytes |
| I/O Pins | 13 | 13 | 13 | 13 | 13 | 16 |
| Supply Voltage | 3.0V to 6.0V | 3.0V to 6.0V | 3.0V to 6.0V | 3.0V to 6.0V | 3.0V to 6.0V | 2.0V to 5.5V |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Active |
Key Differentiators
- Tape-and-reel supply format (vs PIC16C621-20E/SS)
- Higher RAM and Flash for production designs (vs PIC16F627A-I/SS)
- Comparator-equipped versus comparator-free (vs PIC16C620A-20E/SS)
Design Notes
Place a 100 nF ceramic decoupling capacitor within 1 cm of the VDD pin (pin 14) and a 10 uF bulk capacitor near the SSOP-20 supply entry point to suppress digital switching noise. For industrial 24V-derived 5V rails, add a TVS diode (e.g., 5V SMAJ series) on VDD to clamp load-dump transients, and use a series ferrite bead if the design shares supply with relay coils. Brown-out reset is internally generated; no external supervisor IC is required.
Route the ICSP clock (RB6, pin 12) and ICSP data (RB7, pin 13) traces away from high-frequency switching nodes and oscillator traces to prevent programming noise coupling. Keep the OSC1/OSC2 traces short and symmetric, and place the crystal/resonator within 5 mm of the IC with a ground guard ring. The MCLR/Vpp pin (not exposed in this SSOP-20 variant; reset via internal POR-only configuration) requires no external pull-up on modern Microchip recommendations.
OTP memory can be programmed only once - validate firmware on a PIC16F62x or PIC16C62x-windowed (JW) sample before committing to production programming of PIC16C621T-20E/SS. The 'T' suffix indicates T/R packaging only, not a different silicon die; spec compliance is identical to the tube-supplied PIC16C621-20E/SS. Do not exceed 6.0V on VDD or use this part in designs expecting >85C operation without verifying the E (extended) vs I (industrial) temperature grade suffix in the order code.
Compliance Information
RoHS and lead-free compliant per Microchip product specifications. Not AEC-Q100 qualified - consult Microchip PIC16 family automotive datasheets (e.g., PIC16F6xxx-I/SS) for automotive-grade replacements. Halogen-free status not explicitly stated in the available data.
