What this buck controller does and where it fits
The Texas Instruments LM25085AMY/NOPB is a constant on-time (COT) step-down buck controller designed for input rails from 4.5V to 42V. It drives an external N-channel MOSFET and delivers a regulated output with up to 1MHz switching frequency, letting you shrink the inductor and output capacitor. The single-output, positive-configuration controller includes current limit and frequency control features, and it operates over the full -40°C to 125°C junction temperature range, making it a fit for industrial power supplies, automotive infotainment and body electronics, and 12V/24V distributed bus converters.
Package and footprint — 8-HVSSOP with exposed pad
The LM25085AMY/NOPB is offered in an 8-lead HVSSOP package (3.00mm width, PowerTSSOP variant) with an exposed thermal pad. The pad must be soldered to a copper plane on the PCB for adequate heat dissipation, especially at high input voltage or switching frequency. The part is also available in the 8-MSOP footprint (same body size, no pad) — verify which ordering code matches your assembly. The /NOPB suffix confirms lead-free (ROHS3 compliant) finish, no additional exemption paperwork needed.
Switching frequency and control loop
Switching frequency is adjustable up to 1MHz via a resistor on the RT pin. The constant on-time architecture gives fast transient response without a dedicated compensation network, but the frequency varies with input and output voltage — plan for that in the EMI filter design. The 100% duty cycle capability means the controller can pass the input straight through when the input drops near the output target, useful for automotive cold-crank scenarios.
Lifecycle and compliance
ROHS3 compliance is confirmed, covering EU and most global markets. No AEC-Q100 qualification is listed for this suffix — if automotive-grade is required, check the LM25085-Q1 variant.