PIC16LC621A-04/SO - 8-Bit 4MHz OTP MCU, 1.75KB | Microchip
MPN: PIC16LC621A-04/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.13 | $3.13 |
| 10 | $2.81 | $28.10 |
| 100 | $2.42 | $242.00 |
| 500 | $2.05 | $1,025.00 |
| 1,000 | $1.75 | $1,750.00 |
PIC16LC621A-04/SO Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, program memory, data RAM, and peripherals onto one die. The PIC16C family uses a Harvard RISC architecture that separates program and data buses for single-cycle instruction fetch and deterministic timing, enabling high code density at low clock rates. The PIC16LC621A-04/SO occupies the low-power CMOS "LC" tier within that family, optimized for applications that need OTP-based firmware with low static drain.
Key features include 13 bidirectional I/O pins, two 8-bit timers (Timer0 and Timer2-style modules), a Watchdog Timer with its own on-chip RC oscillator, and an analog comparator. A two-level deep hardware stack supports subroutine nesting, and the device supports direct, indirect, and relative addressing. Dual comparator inputs with programmable reference output make this part a frequent choice for simple sensor interfaces and battery-management front-ends.
Typical applications include low-cost consumer appliances, automotive body and interior modules (with -I/-E temperature grades available across the family), HVAC sensor interfaces, white-goods control boards, and the analog front-end of a switching power supply. The 18-SOIC footprint also supports through-hole legacy boards adapted to surface-mount assembly. For applications needing the same memory map but with field-reprogrammable Flash, designers typically migrate to the PIC16F627 family, which shares the same pinout.
When designing with this device, ensure Vdd decoupling uses a 100 nF ceramic capacitor placed within 5 mm of the package pins, and tie the MCLR pin high through the recommended 10 kohm pull-up to avoid spurious resets. The OTP memory means firmware revisions require a new part - plan for the Flash migration path (PIC16F627A-I/SO) on prototype spins.
This page consolidates distributor pricing, drop-in alternatives, and engineering design notes not found in a single manufacturer datasheet, and is intended to accelerate sourcing and BOM validation.
Drop-in alternatives for PIC16LC621A-04/SO — 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 PIC16LC621A-04/SO (same form factor and footprint) — differing in Package, Program Memory Size, I/O Pins, Program Memory Type, Core Architecture.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC621A-04I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC621A-04E/SO
✅ Drop-In✓ In Stock
$2.25 / Unit
View Datasheet →PIC16LC621A-04C/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC620A-04/SO
✅ Drop-In✓ In Stock
$2.15 / Unit
View Datasheet →PIC16LC620A-04E/SO
✅ Drop-In✓ In Stock
$2.07 / Unit
View Datasheet →PIC16F627T-04/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC621-04/SO
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
PIC16LC621A-04/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC16C, 8-bit RISC (Harvard) |
| Instruction Word Size | 14-bit (12-bit opcode class) |
| Data Path Width | 8-bit |
| Maximum Clock Frequency | 4 MHz |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 1.75 KB (1K x 14) |
| Data RAM | 96 bytes |
| Supply Voltage (VDD) | 2.5 V to 6.25 V |
| I/O Pins | 13 |
| Timers | Two 8-bit (Timer0 + Timer2-style) |
| Analog Comparator | Yes (dual input, programmable reference) |
| Watchdog Timer | Yes (with dedicated on-chip RC) |
| Stack Depth | 2 hardware levels |
| Addressing Modes | Direct, Indirect, Relative |
| Package | 18-pin SOIC (SO-18, 0.300 inch) |
| Mounting Type | Surface Mount |
| MSL Level | 1 |
| RoHS Status | Compliant |
PIC16LC621A-04/SO Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O / comparator reference output |
| Pin 2 | RA3 — Bidirectional I/O / analog comparator input |
| Pin 3 | RA4/T0CKI — Bidirectional I/O / Timer0 clock input |
| Pin 4 | MCLR — Master Clear reset input (active low) |
| 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 |
| Pin 11 | RB5 — Bidirectional I/O |
| Pin 12 | RB6 — Bidirectional I/O / serial programming clock |
| Pin 13 | RB7 — Bidirectional I/O / serial programming data |
| Pin 14 | VDD — Positive supply (2.5 V to 6.25 V) |
| Pin 15 | OSC2/CLKOUT — Oscillator output / clock out |
| Pin 16 | OSC1/CLKIN — Oscillator input / external clock in |
| Pin 17 | RA0 — Bidirectional I/O / analog comparator input |
| Pin 18 | RA1 — Bidirectional I/O / analog comparator input |
Typical Applications
PIC16LC621A-04/SO is suitable for 6 applications: Low-Cost Consumer Appliance Control, Automotive Interior and Body Electronics, HVAC Sensor Interface Front-End, Switching Power Supply Analog Front-End, White Goods Control Boards (Washer / Dishwasher / Refrigerator), Battery-Powered Sensor and Smart-Home Nodes.
Low-Cost Consumer Appliance Control
The PIC16LC621A-04/SO is a strong fit for low-cost consumer appliances such as coffee makers, small kitchen gadgets, and countertop devices where BOM cost is paramount. Its 1.75 KB OTP EPROM and 96 B RAM are sufficient for simple state-machine firmware (button debounce, relay sequencing, LED indicators), while the 2.5 V to 6.25 V VDD range lets the same PCB accept either a 3.3 V or 5 V supply rail. The dual analog comparator with programmable voltage reference is useful for over-temperature sensing with an NTC thermistor, eliminating the need for an external comparator IC. At typical 4 MHz operation, instruction throughput is 1 MIPS, which is more than adequate for time-deterministic appliance sequencing. Its commercial 0 C to +70 C operating range matches most indoor appliance environments. Design tip: budget for an external 4 MHz ceramic resonator or crystal because internal oscillator accuracy on the PIC16C family is loose.
Recommended
Automotive Interior and Body Electronics
The PIC16LC621A-04/SO is well suited to interior automotive body modules such as dome-light controllers, seat heaters, mirror adjusters, and keyless-entry receivers when the industrial -I temperature grade (PIC16LC621A-04I/SO) is selected. Its 13 I/O pins handle multiplexed keypad scanning, LED PWM dimming via Timer2, and relay or MOSFET driver outputs without external logic. The on-chip dual comparator simplifies battery-voltage monitoring and brownout detection, important for cranking transients in 12 V automotive rails. At 4 MHz, the 1 MIPS instruction throughput is deterministic, critical for LIN or simple UART-based body-network protocols. The SOIC-18 footprint is also friendly to automotive PCB assembly lines that prefer gull-wing leads over QFN. Design tip: pair with an external TVS diode on the VDD rail because automotive load-dump pulses can exceed 40 V.
Recommended
HVAC Sensor Interface Front-End
The PIC16LC621A-04/SO serves well as the analog front-end controller in HVAC sensor-interface boards where NTC temperature sensors, humidity cells, and CO2 detectors all feed analog signals into the system. Its dual analog comparator with programmable on-chip voltage reference lets the firmware implement window-discriminator threshold logic for each sensor, offloading comparator hardware from the main MCU. The 96 B RAM and 1.75 KB OTP are sufficient for sensor linearization tables and modest state machines. The 2.5 V to 5.5 V range is convenient for 3.3 V fan-controller boards. The 18-SOIC package is easy to hand-prototype on through-hole-to-SMD adapter boards during HVAC controller validation. Design tip: drive each sensor with a dedicated RC low-pass filter to attenuate HVAC compressor noise before the comparator input.
Recommended
Switching Power Supply Analog Front-End
The PIC16LC621A-04/SO is a useful auxiliary controller in the analog front-end of low-power AC-DC or DC-DC switchers, providing primary-side regulation feedback, housekeeping telemetry, or PWM housekeeping for digital-controlled converters. The on-chip dual analog comparator handles primary-side current sensing and over-voltage protection, while the programmable VREF can be repurposed as a soft-start reference. Its 2.5 V to 6.25 V VDD range is compatible with both 3.3 V and 5 V digital subsystems downstream. The 1 MIPS instruction throughput is enough for housekeeping loops that do not need the main switcher timing. For higher-frequency digital control, the PIC16F627A-I/SO Flash variant preserves the SOIC-18 footprint. Design tip: bypass VDD with a 100 nF X7R ceramic placed within 5 mm of the pins to suppress switching-noise injection into the comparator reference.
Recommended
White Goods Control Boards (Washer / Dishwasher / Refrigerator)
The PIC16LC621A-04/SO is a strong match for white-goods control boards where a robust 8-bit MCU drives motor relays, valve solenoids, and indicator LEDs in washers, dishwashers, and refrigerators. The dual analog comparator supports water-level sensing via pressure transducers and NTC thermistor temperature monitoring for wash-cycle thermal protection. With 13 I/O pins, the MCU can directly drive up to 13 relays or sink LEDs without external logic, while Timer0 and Timer2 modules generate the timing-critical PWM and one-shot delays used in cycle sequencing. OTP memory provides tamper-resistance against firmware cloning - valuable for appliance makers protecting proprietary wash algorithms. The 18-SOIC surface-mount package is compatible with high-volume pick-and-place assembly lines. Design tip: add a software-based brownout counter to ride through motor-start voltage sags.
Recommended
Battery-Powered Sensor and Smart-Home Nodes
The PIC16LC621A-04/SO is well-suited as a co-processor or housekeeping controller in battery-powered smart-home sensor nodes such as PIR motion detectors, door/window contact sensors, and HVAC-zone thermostatic radiator valves. Its CMOS LC process variant delivers low quiescent current, and the Watchdog Timer with its own on-chip RC oscillator allows the part to wake from sleep and service sensor interrupts without external components. The on-chip analog comparator handles battery-voltage telemetry and threshold-based wake events. The 2.5 V to 6.25 V VDD range is compatible with both 3.3 V coin-cell designs and 5 V USB-powered hubs. The 18-SOIC is also a serviceable retrofit for older through-hole PIR boards transitioning to SMD assembly. Design tip: use the Watchdog Timer to recover from RF-induced firmware stalls, which are common in dense wireless environments.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621A-04/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621A-04I/SO | PIC16LC621A-04E/SO | PIC16LC621A-04C/SO | PIC16LC620A-04/SO | PIC16F627T-04/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | SOIC-18 (0.300 inch) | SOIC-18 - same | SOIC-18 - same | SOIC-18 - same | SOIC-18 - same | SOIC-18 - same |
| Program Memory | 1.75 KB OTP EPROM | 1.75 KB OTP EPROM | 1.75 KB OTP EPROM | 1.75 KB OTP EPROM | 1.75 KB OTP EPROM | 1.75 KB Flash |
| Data RAM | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 128 bytes |
| Max Clock Frequency | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| Supply Voltage | 2.5 V to 6.25 V | 2.5 V to 6.0 V | 2.5 V to 6.25 V | 2.5 V to 6.25 V | 2.5 V to 6.25 V | 2.0 V to 5.5 V |
| Operating Temperature | 0 C to +70 C (commercial) | -40 C to +85 C (industrial) | -40 C to +125 C (extended) | 0 C to +70 C (commercial) | 0 C to +70 C (commercial) | -40 C to +85 C (industrial) |
| Analog Comparator | Yes (dual + VREF) | Yes (dual + VREF) | Yes (dual + VREF) | Yes (dual + VREF) | No | Yes (dual + VREF) |
| I/O Pins | 13 | 13 | 13 | 13 | 13 | 13 |
Key Differentiators
- Only 8-bit PIC16C family member with full analog comparator + VREF at this cost point (vs PIC16LC620A-04/SO)
- Wide 2.5 V to 6.25 V VDD supports both 3.3 V and 5 V rails (vs PIC16F627T-04/SO)
- Industrial and extended temperature grades share the same SOIC-18 footprint (vs PIC16LC621A-04/SO (this part, commercial))
Design Notes
Decouple VDD with a 100 nF X7R ceramic placed within 5 mm of the SOIC-18 pins, and add a 10 uF bulk tantalum or aluminum-polymer cap on the same rail. The PIC16LC621A-04/SO is rated for 2.5 V to 6.25 V VDD; operation near the 6.25 V limit reduces comparator accuracy and increases current drain, so target 5.0 V for typical designs and add a 6.2 V Zener clamp for transient protection on noisy industrial rails.
The MCLR pin must be pulled high through the datasheet-recommended 10 kohm resistor; a direct short to VDD disables in-circuit serial programming (ICSP) and complicates factory firmware updates. Also remember that OTP EPROM cannot be erased - every firmware bug on the production part requires a new reel of PIC16LC621A-04/SO, so budget the Flash-based PIC16F627A-I/SO for prototype spins and qualify both parts.
Route the OSC1/OSC2 traces as a short, symmetric pair away from switching nodes and crossing the IC at a 90-degree angle to high-current traces. Place the 4 MHz ceramic resonator or crystal as close as possible to the OSC pins with its load capacitors tied to a quiet analog ground. For boards mixing analog comparators with digital outputs, route the comparator input traces on the opposite side of the PCB from any PWM or relay-coil drive traces.
The PIC16LC621A-04/SO analog comparator inputs share package pins with digital I/O; configure the CMCON register to disable digital output drivers on those pins to avoid digital feed-through into the comparator reference. Use the on-chip programmable voltage reference (VREF) rather than a noisy external divider to maintain a stable threshold across load and temperature variations.
Compliance Information
Per the Microchip product page, the PIC16LC621A-04/SO is RoHS compliant and lead-free. It is not AEC-Q100 qualified; for AEC-Q100 automotive designs, migrate to a Flash equivalent from the PIC16F or PIC18 families.
