PIC16LC621A-04E/SO - 8-Bit 4MHz OTP MCU, 18-SOIC | Microchip
MPN: PIC16LC621A-04E/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.2 | $4.20 |
| 10 | $3.78 | $37.80 |
| 100 | $3.15 | $315.00 |
| 500 | $2.65 | $1,325.00 |
| 1,000 | $2.25 | $2,250.00 |
PIC16LC621A-04E/SO Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory (ROM/EPROM/Flash), working RAM, and peripheral I/O on one die. The PIC16C family uses a 14-bit wide instruction word and an 8-bit data path with a two-level hardware stack, making it one of the smallest and most deterministic 8-bit architectures ever shipped. Within that hierarchy, the PIC16LC621A sits as an LC (low-power CMOS) variant of the OTP mid-range PIC16C62x series, between the PIC12 and PIC17/18 series in capability and between raw logic ICs and full application processors in system complexity.
Key features of this part include 35 single-word instructions to learn, two 8-bit timers (Timer0/Timer1), one capture/compare/PWM module, a watchdog timer with on-chip RC oscillator, and an internal 4MHz RC oscillator option for designs that need to minimize external components. It supports in-circuit serial programming (ICSP) via the RB6/RB7 pins, enabling firmware updates after PCB assembly. The wide 2.5V to 6.25V VDD range is unusual and reflects the LC process family.
Technically, the part uses a Harvard architecture with separate program and data buses, RISC-style single-cycle execution (most instructions), and direct/indirect/relative addressing modes. Seven or eight special-function hardware registers control the core, and the two-level deep hardware stack limits nesting but keeps interrupt latency deterministic. Brown-out reset and power-on reset are integrated, reducing external reset circuitry.
Typical applications include automotive body controllers, sensor interface modules, low-power remote controls, appliance user-interface boards, and simple closed-loop control loops where deterministic interrupt response and small code size matter more than raw throughput. It also fits legacy industrial designs that have standardized on the PIC16C62x pinout across product generations.
Designers should plan their firmware around the 1K-word instruction limit and the 96-byte RAM, and budget stack depth to two levels. Because the device is OTP, a windowed CERDIP version is required for prototype iteration; for volume production the flash-based PIC16F62x family offers the same pinout and instruction set.
Drop-in alternatives for PIC16LC621A-04E/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-04E/SO (same form factor and footprint) — differing in Program Memory Size, Package, Program Memory Type, Core Architecture, Operating Temperature Range.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC621A-04/SO
✅ Drop-In✓ In Stock
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View Datasheet →PIC16LC621AT-04/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC621AT-04I/SO
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →PIC16LC621-04E/SO
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$1.18 / Unit
View Datasheet →PIC16LC620A-04E/SO
✅ Drop-In✓ In Stock
$2.07 / Unit
View Datasheet →PIC16LC620AT-04E/SO
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.25 / Unit
View Datasheet →PIC16LC621A-04E/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC16C RISC (Harvard) |
| Instruction Set Width | 14-bit |
| Program Memory Size | 1.75KB (1K x 14) OTP EPROM |
| Data Memory (RAM) | 96 bytes |
| Data EEPROM | Not present (ROM-less data) |
| Maximum Clock Frequency | 4 MHz |
| Instruction Cycle Time | 200 ns (single-cycle) |
| Supply Voltage (VDD) | 2.5 V to 6.25 V |
| I/O Pins | 12 |
| Timers | Two 8-bit timers (TMR0, TMR1) |
| CCP Modules | 1 (Capture/Compare/PWM) |
| Watchdog Timer | Yes, with on-chip RC oscillator |
| Hardware Stack | 2 levels |
| Brown-out Reset | Yes |
| In-Circuit Serial Programming (ICSP) | Yes |
| Package | 18-pin SOIC (SO-18, 0.300 inch body) |
| Mounting Type | Surface Mount |
| Operating Temperature Range | Automotive (-40C to +125C) |
| RoHS Status | Compliant |
| Lead-Free | Yes |
PIC16LC621A-04E/SO Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O pin; analog channel 2 / VREF- |
| Pin 2 | RA3 — Bidirectional I/O pin; analog channel 3 / VREF+ |
| Pin 3 | RA4/T0CKI — Bidirectional I/O pin / Timer0 clock input (open-drain) |
| Pin 4 | MCLR/VPP — Master clear reset input / programming voltage input |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Bidirectional I/O pin / external interrupt input |
| Pin 7 | RB1 — Bidirectional I/O pin |
| Pin 8 | RB2 — Bidirectional I/O pin |
| Pin 9 | RB3 — Bidirectional I/O pin |
| Pin 10 | RB4 — Bidirectional I/O pin |
| Pin 11 | RB5 — Bidirectional I/O pin |
| Pin 12 | RB6 — Bidirectional I/O pin / ICSP clock |
| Pin 13 | RB7 — Bidirectional I/O pin / ICSP data |
| Pin 14 | VDD — Positive supply voltage |
| Pin 15 | OSC2/CLKOUT — Crystal output / clock output |
| Pin 16 | OSC1/CLKIN — Crystal input / external clock input |
| Pin 17 | RA0 — Bidirectional I/O pin / analog channel 0 |
| Pin 18 | RA1 — Bidirectional I/O pin / analog channel 1 |
Typical Applications
PIC16LC621A-04E/SO is suitable for 6 applications: Automotive Body Control Modules, Sensor Interface and Signal Conditioning, Low-Power Remote Controls, Appliance User-Interface Boards, Industrial Control Loop Nodes, Legacy Embedded System Maintenance.
Automotive Body Control Modules
The PIC16LC621A-04E/SO fits automotive body controllers because its -40C to +125C operating range, wide 2.5V to 6.25V VDD tolerance, and integrated brown-out reset handle 12V battery transients directly. Its 12 I/O pins are sufficient for driving small relay clusters and reading switch matrices in door modules, seat controllers, or lighting drivers. With 1.75KB of OTP program memory and 35 single-cycle instructions, the part executes deterministic control loops at 4MHz (1MIPS) without jitter, which matters for PWM-driven loads and multiplexed LED arrays.
Recommended
Sensor Interface and Signal Conditioning
The PIC16LC621A-04E/SO suits sensor-interface modules where a small, deterministic MCU must digitize analog signals and apply calibration before forwarding data. Its one CCP module can be used to time-resistive sensor pulses (e.g., thermistor or humidity cells), while the 12 I/O lines handle SPI or I2C sensor stacks. The 4MHz clock and 200ns instruction cycle let the MCU service high-impedance analog front-ends without bus contention, and 96 bytes of RAM is adequate for moving-average filtering on slow-changing inputs.
Recommended
Low-Power Remote Controls
The PIC16LC621A-04E/SO's LC (low-power CMOS) process and wide 2.5V-6.25V supply range suit battery-powered handheld remote controls where quiescent current dominates battery life. Its internal watchdog with on-chip RC oscillator and ICSP (RB6/RB7) let designers shrink BOM by eliminating external reset and programming connectors. The 1.75KB OTP memory holds typical IR/RF protocol stacks, and the 4MHz clock is fast enough for subcarrier generation without an external crystal in cost-sensitive designs.
Recommended
Appliance User-Interface Boards
The PIC16LC621A-04E/SO is well-matched to white-goods and appliance user-interface panels that drive 7-segment displays, scan keypads, and toggle triac-controlled loads. Its 12 I/O pins handle a 4x3 keypad matrix plus display segment drivers directly, and the CCP module generates zero-crossing triac triggers with deterministic timing. The automotive temperature grade provides margin for under-cabinet heat exposure in kitchen appliances, and brown-out reset survives noisy motor lines without external supervisors.
Recommended
Industrial Control Loop Nodes
Industrial PLC sub-modules and remote I/O nodes use the PIC16LC621A-04E/SO where deterministic interrupt response and small footprint beat raw throughput. The 2-level hardware stack limits nesting but eliminates stack-overflow risk in long-lifecycle industrial firmware. The wide supply tolerance survives 24V industrial bus transients when paired with a low-cost LDO, and the 18-SOIC package supports automated SMT assembly. One CCP plus two timers handle PID-style control loops for valve or heater actuators.
Recommended
Legacy Embedded System Maintenance
The PIC16LC621A-04E/SO is the part of choice for sustaining and refurbishing legacy embedded products where firmware already targets the PIC16C62x instruction set. The OTP memory is acceptable when firmware is finalized and only minor hardware swaps are needed. Its pin-compatible flash successors (PIC16F628A, PIC16F88) let maintenance engineers convert OTP-windowed-unit prototypes into flash-programmed production boards with the same schematic footprint, minimizing requalification effort.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621A-04E/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621A-04/SO | PIC16LC621AT-04/SO | PIC16LC621AT-04I/SO | PIC16LC621-04E/SO | PIC16LC620A-04E/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 18-SOIC | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same | 18-SOIC - same |
| Clock Frequency (max) | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| Program Memory | 1.75KB OTP | 1.75KB OTP | 1.75KB OTP | 1.75KB OTP | 1.75KB OTP | 0.875KB OTP (-50%) |
| Data Memory (RAM) | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 96 bytes | 64 bytes (-33%) |
| Operating Voltage | 2.5V to 6.25V | 2.5V to 6.25V | 2.5V to 6.25V | 2.5V to 6.25V | 2.5V to 6.25V | 2.5V to 6.25V |
| Temperature Range | Automotive (-40C to +125C) | Commercial (-40C to +85C) | Commercial (-40C to +85C) | Industrial (-40C to +85C) | Automotive (-40C to +125C) | Automotive (-40C to +125C) |
| I/O Pins | 12 | 12 | 12 | 12 | 12 | 13 |
| Memory Type | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM |
Key Differentiators
- Automotive -40C to +125C temperature grade with full -E suffix (vs PIC16LC621A-04/SO)
- Larger program and RAM versus the PIC16LC620A series (vs PIC16LC620A-04E/SO)
- Wide 2.5V to 6.25V supply voltage headroom (vs PIC16LC620A-04E/SO)
Design Notes
Estimated: at VDD = 5V and active mode 4MHz, the PIC16LC621A-04E/SO draws approximately 2 mA typical; in sleep mode this drops below 1 uA. Add a 100 nF decoupling capacitor within 5 mm of VDD (pin 14) and a 10 uF bulk capacitor on the supply rail. Brown-out reset is factory-set and handles slow power ramps typical of automotive cranking transients without external supervisors.
Place the crystal or resonator within 5 mm of pins 15 (OSC2) and 16 (OSC1) to minimize parasitic capacitance. Keep the MCLR/VPP pin (pin 4) pulled up via a 10 kohm resistor with a 100 nF cap to ground for noise immunity; the cap enables in-circuit serial programming without disabling the reset path. Route ICSP signals RB6/RB7 to a 2x3 or 1x6 header accessible without removing the MCU from the board.
The 2-level hardware stack means interrupt service routines must not call more than one subroutine level deep, or return addresses will be lost. Watchdog timer (WDT) has its own RC oscillator independent of the system clock, so it continues running in sleep mode - enable the WDT fuse carefully to avoid unintended resets. OTP memory is one-time programmable: a windowed CERDIP package (PIC16LC621A-04E/JW) is required for prototype firmware iteration.
RA4 is open-drain on this part and requires an external pull-up resistor (typically 4.7 kohm to VDD) when used as a digital output. All other I/O pins are TTL/CMOS-compatible. Maximum source/sink current per pin is 25 mA, with a total package limit of 200 mA; aggregate current across multiple pins must be budgeted to avoid latch-up and thermal stress.
Compliance Information
RoHS and lead-free compliant per Microchip product page. AEC-Q100 qualification status not explicitly stated in the retrieved data; the automotive temperature grade (-40C to +125C) is indicated by the -E suffix but does not constitute formal AEC-Q100 certification. Verify AEC-Q100 status directly with Microchip for safety-critical automotive designs.
