Product Overview
LM628N-6 Motion Control IC - 6MHz Clock, PID Filter, Quadrature Encoder Interface, 28-Pin DIP
Condition
Unused NOS sourced from an electronics distributor consolidating inventory. Condition is excellent with nothing out of the ordinary observed. Evaluation: Visual inspection only. Function testing not performed.
Ships same business day from Idaho. Packed carefully.
Product Overview
National Semiconductor LM628N-6 is a Precision Motion Controller IC designed to offload real-time servo loop computation from the host processor. It accepts high-level motion commands over an 8-bit parallel bus and manages trajectory generation, PID filtering, and DAC output independently. Maximum clock frequency is 6MHz. The N suffix denotes the 28-pin PDIP through-hole package. Long discontinued by National Semiconductor (now Texas Instruments), the LM628N-6 remains a sought replacement in legacy CNC, robotics, and servo drive systems.
Key Features
- Maximum clock frequency: 6MHz
- Package: 28-pin PDIP (through-hole)
- Host interface: 8-bit parallel bus
- Output: 8-bit or 12-bit parallel DAC data (requires external DAC — not interchangeable with LM629 PWM output)
- Feedback interface: Quadrature incremental encoder with index pulse
- Filter: Programmable digital PID with 32-bit position, velocity, and acceleration registers
- Trapezoidal velocity profile generation on-chip
- Supply voltage: 5V regulated (4.5V to 5.5V)
- Technology: NMOS — sensitive to ESD; handle with standard static precautions
Applications
- CNC milling machine and lathe servo axis control
- Automated pick-and-place and robotic joint positioning
- Satellite antenna pointing and tracking systems
- Legacy servo drive repair and board-level replacement
- DC and brushless DC motor closed-loop position control
Frequently Asked Questions
Is the LM628N-6 a drop-in replacement for the LM629?
No. The LM628 outputs parallel DAC data and requires an external DAC to drive the motor amplifier. The LM629 outputs a PWM signal directly. They are not pin-compatible or functionally interchangeable.
What is the difference between the LM628N-6 and LM628N-8?
Clock speed only. The LM628N-6 supports a maximum external clock of 6MHz. The LM628N-8 supports 8MHz. Package and pinout are identical.
What external components are required to operate this IC?
A host microcontroller connected via 8-bit parallel bus, a quadrature incremental encoder for position feedback, an external DAC to interface with the motor amplifier, and a regulated 5V supply with an external clock source.
How can I verify authenticity given counterfeit risk on legacy parts?
Inspect the chip markings for the original National Semiconductor logo and date code. This unit is sourced from a distributor consolidating inventory — not pulled from field equipment. Function testing was not performed; verify against the LM628/LM629 datasheet before installation.
The LM628N-6 has been out of production for many years. Available NOS stock is finite. Confirm your system's clock and DAC requirements against the National Semiconductor LM628/LM629 datasheet before ordering.
