Product Overview
LM621N BLDC Commutator IC - 5V Logic, 40V Load, Hall Sensor Interface, Through-Hole DIP-18
Condition
Single unit available. Unused NOS sourced from an electronics parts distributor that was winding down operations. Evaluation: Visual inspection only. Function testing not performed. Covered by our satisfaction guarantee.
Ships same business day from Idaho. Packed carefully.
Product Overview
National Semiconductor LM621N is a brushless DC motor commutator IC in an 18-pin plastic DIP through-hole package. It reads Hall effect sensor inputs to determine rotor position and drives external power transistors to switch current to the correct motor windings in sequence. Operates from a 5V logic supply (VCC1) while supporting motor load voltages up to 40V (VCC2). Supports 3-phase and 4-phase brushless DC motors with Hall sensor placements at 30, 60, and 90 degrees. Output drive current is 35mA peak, intended to switch external MOSFETs or BJTs rather than drive a motor load directly. National Semiconductor was acquired by Texas Instruments; buyers seeking original National-branded parts for legacy repair or restoration specifically target this part number.
Key Features
- Logic supply voltage (VCC1): 5V DC
- Motor load voltage (VCC2): up to 40V
- Output drive current: 35mA peak (for driving external power stage transistors)
- Motor compatibility: 3-phase and 4-phase brushless DC motors
- Hall sensor placement: supports 30°, 60°, and 90° shaft position sensor configurations
- Package: 18-pin plastic DIP (PDIP-18), through-hole
- No internal thermal shutdown - external protection required per datasheet
- Shoot-through protection supported via dead-time adjustment
Applications
- 3-phase and 4-phase brushless DC motor drive circuits
- Robotics axis control using legacy BLDC motors
- Repair and restoration of older industrial BLDC motor controllers
- DIY BLDC motor drive projects requiring through-hole commutation logic
Frequently Asked Questions
Can this chip drive a brushless motor directly without external transistors?
No. The LM621N provides 35mA peak output current, which is sufficient to switch external MOSFETs or BJTs. External power transistors are required for any practical motor load. This chip handles commutation logic only.
Will this work with a brushed DC motor or stepper motor?
No. The LM621N is specifically a brushless DC motor commutator. It is not compatible with brushed motors or stepper motors.
What logic supply voltage does this require?
5V DC for the logic supply (VCC1). Motor load voltage (VCC2) can be up to 40V. Both supplies are required for operation.
Does this part have internal thermal shutdown protection?
No. The LM621N does not include internal thermal shutdown protection. External thermal management must be addressed in the system design. This is confirmed by the manufacturer datasheet.
Is this an original National Semiconductor part or a Texas Instruments rebranded version?
This is an original National Semiconductor-branded unit sourced from a distributor that was winding down operations. Buyers seeking period-correct National Semi parts for legacy repair should verify the chip markings upon receipt.
The LM621N has been out of active production for decades. Unused units in original condition are increasingly difficult to source. Verify pinout and supply requirements against the National Semiconductor datasheet before installation.
