LM5007MMX/NOPB

The Texas Instruments LM5007MMX/NOPB is a step-down switching regulator with an integrated 80V N-channel MOSFET, capable of delivering 500mA output current. The wide 9.5V to 80V input range makes it suitable for industrial, telecom (48V bus), and automotive applications. The constant on-time (COT) control architecture eliminates the need for loop compensation components, simplifying design. The internal high-voltage start-up bias regulator operates from the input supply and switches to an external bias when available for improved efficiency. The smart current limit feature reduces the on-time during overload, limiting both switch current and power dissipation. The 525kHz pseudo-fixed switching frequency provides a good balance between efficiency and component size.

The LM5007MMX/NOPB operates as a constant on-time (COT) buck converter: 1) On-Time Generation: The on-time is set by an internal one-shot timer, programmed by an external RON resistor connected to VIN. The on-time is inversely proportional to VIN, naturally maintaining approximately constant switching frequency (525kHz). 2) Regulation: The FB pin monitors the output voltage through a resistor divider. When FB drops below the 2.5V internal reference, a new on-time cycle is initiated. This hysteretic control inherently provides stability without external compensation. 3) Current Limit: The smart current limit monitors the switch current. When the peak current exceeds the threshold, the on-time is reduced to limit average current while maintaining switching frequency, preventing thermal runaway during sustained faults. 4) Bias Regulator: The internal VCC regulator starts from VIN using an internal 80V LDO, then optionally switches to an external VCC supply (from the output) for improved efficiency at higher input voltages.

• 48V telecom bus to 5V/3.3V point-of-load conversion
• Automotive 12V/24V battery to logic supply regulation
• Industrial 24V to 12V step-down with 80V transient protection