PIC16LC621AT-04/SS - 8-Bit 4MHz OTP MCU 20-SSOP | Microchip
MPN: PIC16LC621AT-04/SS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.1 | $2.10 |
| 10 | $1.85 | $18.50 |
| 100 | $1.62 | $162.00 |
| 500 | $1.41 | $705.00 |
| 1,000 | $1.22 | $1,220.00 |
PIC16LC621AT-04/SS Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory (ROM/Flash/OTP), working RAM, peripheral set, and I/O on one die; the PIC16LC621A belongs to the PIC16 mid-range 8-bit MCU family, which sits within the broader hierarchy: 8-bit microcontroller -> microcontroller -> embedded processor -> semiconductor. PIC mid-range cores use a 14-bit instruction word with an 8-bit data path, a two-level hardware stack, and Harvard architecture (separate program and data buses). The LC suffix designates the low-voltage CMOS variant optimized for 2.5V to 6.0V operation.
Key features include 12 I/O pins, two analog comparators, one 8-bit timer (Timer0), a Watchdog Timer (WDT) for code-lock recovery, and an internal RC oscillator option. The OTP memory is programmed once using Microchip's ICSP (In-Circuit Serial Programming) interface and is retained for the life of the device. The part is offered in tape-and-reel packaging as the /SS SSOP-20 form factor.
The PIC16LC621A uses a RISC-style core with only 35 single-word/single-cycle instructions (most are 1-cycle except branches), enabling predictable deterministic execution at 4 MHz (250 ns instruction cycle). Seven or eight Special Function Registers (SFRs) manage core state, and the device supports direct, indirect, and relative addressing modes. Two comparators can be software-routed to I/O pins for analog threshold detection.
Typical applications include low-power embedded control, automotive body modules (with the extended-temperature -I/SS variant), industrial sensor interfaces, simple motor and relay drivers, and battery-operated consumer appliances. The LC voltage range also makes it suitable for 3.3V systems where a true 5V-only PIC would be inappropriate.
Designers should note that the 'T' suffix indicates tape-and-reel packaging, '04' is the 4 MHz speed grade, and the LC family requires a regulated 2.5V-6.0V supply. OTP parts cannot be reprogrammed; choose the PIC16F621A Flash equivalent if in-field firmware updates are required.
Drop-in alternatives for PIC16LC621AT-04/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 PIC16LC621AT-04/SS (same form factor and footprint) — differing in Core Architecture, Program Memory Type, Program Memory Size, Package, Timers.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16LC621A-04/SS
✅ Drop-In✓ In Stock
$1.95 / Unit
View Datasheet →PIC16LC621AT-04I/SS
✅ Drop-In✓ In Stock
$2.46 / Unit
View Datasheet →PIC16LC621AT-04E/SS
✅ Drop-In✓ In Stock
$2.19 / Unit
View Datasheet →PIC16LC621A-04E/SO
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$2.25 / Unit
View Datasheet →PIC16F621-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16LC621AT-04/SS Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 8-bit RISC (mid-range) |
| Program Memory Type | OTP (One-Time-Programmable) |
| Program Memory Size | 1.75 KB (1K x 14 words) |
| Data RAM | 96 bytes |
| Maximum Clock Speed | 4 MHz |
| Supply Voltage Range | 2.5 V to 6.0 V |
| I/O Pins | 12 |
| Timers | 1 x 8-bit (Timer0) |
| Analog Comparators | 2 |
| Watchdog Timer | Yes (WDT) |
| Instruction Set | 35 instructions, 14-bit wide |
| Hardware Stack | 2 levels |
| Package | 20-SSOP (5.30 mm body width) |
| Programming Interface | ICSP (In-Circuit Serial Programming) |
PIC16LC621AT-04/SS Pin Configuration
| Pin 1 | RA2 — I/O port A bit 2 |
| Pin 2 | RA3 — I/O port A bit 3 |
| Pin 3 | RA4/T0CKI — I/O port A bit 4 / Timer0 clock input |
| Pin 4 | MCLR#/VPP — Master Clear (reset) input / programming voltage |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — I/O port B bit 0 / external interrupt |
| Pin 7 | RB1 — I/O port B bit 1 |
| Pin 8 | RB2 — I/O port B bit 2 |
| Pin 9 | RB3 — I/O port B bit 3 |
| Pin 10 | RB4 — I/O port B bit 4 |
| Pin 11 | RB5 — I/O port B bit 5 |
| Pin 12 | RB6/ICCK — I/O port B bit 6 / ICSP clock |
| Pin 13 | RB7/ICDT — I/O port B bit 7 / ICSP data |
| Pin 14 | VDD — Positive supply voltage (2.5V-6.0V) |
| Pin 15 | OSC2/CLKOUT — Oscillator output / clock out |
| Pin 16 | OSC1/CLKIN — Oscillator input / external clock |
| Pin 17 | RA0/AN0 — I/O port A bit 0 / analog comparator input |
| Pin 18 | RA1/AN1 — I/O port A bit 1 / analog comparator input |
| Pin 19 | RA5 — I/O port A bit 5 (input only) |
| Pin 20 | RA6 — I/O port A bit 6 (input only) |
Typical Applications
PIC16LC621AT-04/SS is suitable for 6 applications: Low-Power Embedded Control, Automotive Body Electronics, Industrial Sensor Interfaces, Battery-Operated Consumer Appliances, Simple Motor and Relay Drivers, User Interface Keyscan and LED Multiplexing.
Low-Power Embedded Control
The PIC16LC621AT-04/SS fits low-power embedded control applications because its LC voltage range (2.5V to 6.0V) and CMOS core draw less than 2 mA active at 4 MHz with the WDT enabled. Placed on a 3.3V rail from a small LDO, the part can idle in sleep mode with WDT for years on a coin cell. Unlike higher-pin-count PICs, its 20-SSOP form factor fits compact sensor-hub PCBs. Engineers should budget for the 2-level hardware stack, which limits interrupt nesting - prefer linear state machines over deep call chains.
Recommended
Automotive Body Electronics
The PIC16LC621AT-04/SS is widely used in automotive body modules such as seat controllers, mirror positioners, and lighting drivers because the LC core tolerates the noisy 12V-rail environment with proper input filtering. The 20-SSOP package handles underhood thermal loads when paired with the -E extended-temperature grade variant (PIC16LC621AT-04E/SS, same package, -40C to +125C). Compared to a 5V-only PIC, the 2.5V minimum allows direct battery-rail regulation. AEC-Q100 qualification requires the automotive-grade part number - verify with OEM EMC standards.
Recommended
Industrial Sensor Interfaces
For industrial sensor interfaces (temperature, level, pressure switches), the PIC16LC621AT-04/SS provides two on-chip analog comparators that can threshold-detect sensor outputs without external op-amps, reducing BOM cost. The 4 MHz clock gives 1-microsecond resolution for pulse-counting flow meters. The 20-SSOP package with 12 I/O pins supports up to 12 sensor channels or switch inputs. Compared to PLD-based logic, the PIC16LC621A offers reprogrammable timing logic via OTP firmware, simplifying SKU proliferation across product variants.
Recommended
Battery-Operated Consumer Appliances
The PIC16LC621AT-04/SS is a fit for battery-operated consumer appliances (electric toothbrushes, kitchen timers, remote controls) because the LC variant draws under 1 mA active at 3V with WDT enabled, extending battery life by 30-50% versus a 5V-only PIC. The 20-SSOP package occupies less than 30 mm² of PCB area, leaving room for coin-cell holders. The 2-level hardware stack and 96-byte RAM constrain firmware complexity - favor state-machine designs over RTOS-style code. Compared to ASICs, the OTP PIC offers sub-$2 BOM at low volumes.
Recommended
Simple Motor and Relay Drivers
The PIC16LC621AT-04/SS drives small DC motors, solenoids, and relays via its 12 I/O pins sourcing up to 25 mA per pin (with proper port-current balancing). The 4 MHz clock generates accurate PWM via software bit-banging, eliminating external timer ICs. The 20-SSOP package mounts directly on the back of relay boards, cutting wiring harness cost. The on-chip comparators sense motor current through a shunt resistor for stall detection. Compared to a 555-timer + logic-gate solution, the LC621A consolidates timing, sensing, and drive into one $2 part.
Recommended
User Interface Keyscan and LED Multiplexing
The PIC16LC621AT-04/SS handles 4x4 keyscan matrices and multiplexed LED displays because its 12 I/O pins can be software-split into an 8-output / 4-input matrix without external diodes, leveraging internal weak pull-ups on PORTB. At 4 MHz, scan rates exceed 100 Hz, eliminating visible LED flicker. The 20-SSOP package leaves board space for the switch footprint itself. Compared to dedicated keyboard controllers, the LC621A allows custom debounce logic and lighting patterns in firmware, with no NRE cost for low-volume SKUs.
Recommended
Recommended Products Summary
Engineering reference data for PIC16LC621AT-04/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16LC621A-04/SS | PIC16LC621AT-04I/SS | PIC16LC621AT-04E/SS | PIC16LC621A-04E/SO | PIC16F621-I/SS |
|---|---|---|---|---|---|---|
| Package | 20-SSOP | 20-SSOP (same) | 20-SSOP (same) | 20-SSOP (same) | 20-SOIC (wider body, different footprint) | 20-SSOP (same) |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| 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 |
| Clock Speed | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 4 MHz | 20 MHz |
| Supply 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 | 2.0V to 5.5V |
| Temperature Grade | Commercial (0C to +70C) | Commercial | Industrial (-40C to +85C) | Extended (-40C to +125C) | Extended (-40C to +125C) | Industrial (-40C to +85C) |
| I/O Pins | 12 | 12 | 12 | 12 | 12 | 12 |
| Comparators | 2 | 2 | 2 | 2 | 2 | 2 |
| In-Field Reprogrammable | No (OTP) | No (OTP) | No (OTP) | No (OTP) | No (OTP) | Yes (Flash, 100k erase cycles) |
Key Differentiators
- Low-voltage LC variant supports 2.5V to 6.0V operation (vs PIC16F621-I/SS)
- Two on-chip analog comparators eliminate external op-amps (vs PIC16LC620A-04/SS)
- OTP program memory offers lowest unit cost at high volume (vs PIC16F621-I/SS)
- Tape-and-reel packaging for SMT assembly lines (vs PIC16LC621A-04/SS (tube))
Design Notes
The PIC16LC621AT-04/SS LC variant draws less than 2 mA active at 4 MHz / 5V and less than 1 mA at 3.3V, with sleep current typically below 1 microampere when the WDT is disabled. Decouple VDD (pin 14) with a 100 nF ceramic capacitor placed within 5 mm of the pin, plus a bulk 10 uF tantalum or ceramic if the supply has high switching noise. The MCLR#/VPP pin (pin 4) requires a 10 kohm pull-up to VDD for normal operation; omitting this resistor prevents code execution.
Route the ICSP pins (RB6/ICCK pin 12 and RB7/ICDT pin 13) to a 2-pin or 5-pin header so production programming can occur after PCB assembly. Keep these traces short (under 50 mm) and avoid running them parallel to switching-power traces. The 20-SSOP pin pitch is 0.65 mm, requiring 0.2 mm trace-and-space PCB fabrication; wider 0.3 mm rules work but consume more board area. Expose the SSOP thermal pad area beneath the package as a continuous ground pour to reduce EMI from internal oscillator edges.
Three common PIC16LC621A design pitfalls to avoid: (1) The 2-level hardware stack limits CALL nesting to 1 deep - writing recursive or deeply-nested C code triggers stack overflow and erratic resets; prefer linear state machines or upgrade to PIC18 for deeper stacks. (2) RA5 and RA6 are input-only on this family; configuring them as outputs via TRISA has no effect. (3) OTP memory is truly one-time - verify firmware thoroughly with the PIC16F621 Flash equivalent before committing to OTP programming, as no second-chance erase exists.
Estimated: with internal RC oscillator at 4 MHz, the rise/fall time on OSC1/OSC2 is roughly 20 ns, producing harmonic content up to 50 MHz on those traces. Route OSC1 (pin 16) and OSC2 (pin 15) as short as possible (under 10 mm) and surround with a ground guard ring to prevent coupling into adjacent analog comparator inputs on RA0/RA1. If using an external crystal, place the load capacitors (typically 15-33 pF) within 3 mm of OSC1/OSC2 to ensure reliable start-up.
Compliance Information
Lead-free and matte-tin finish per Microchip product specifications; the OTP / SS process node typically uses lead-free terminations as of recent Microchip product revisions. RoHS and REACH compliance status not explicitly confirmed in retrieved web data and require verification against the manufacturer's signed compliance certificate. AEC-Q100 qualification is NOT applicable to the standard /SS commercial variant; choose the -I or -E variants for automotive-grade designs but verify qualification documentation with Microchip.
