Package footprint and board integration
The LTC3308AEV#TRPBF: The 12-LQFN (2x2) package with exposed pad means the thermal path runs through the center pad to the PCB copper plane — the 2x2 mm footprint is tight enough that the output inductor and input/output caps sit close to the IC, but the pad's solder paste coverage and via pattern under the die set the junction-to-board thermal resistance.
Switching frequency and inductor selection
The 1 MHz to 3 MHz switching frequency range is adjustable via the RT pin resistor — higher frequencies shrink the inductor (down to 0.47 µH at 3 MHz) but increase switching losses and push the EMI fundamental above the AM band. At 2.2 MHz, a 1 µH inductor with a saturation rating above 5 A (the peak current limit) keeps the ripple below 30% of the 4 A output. The frequency is set by a resistor to ground, so the RT pin's voltage is fixed at 0.6V; the formula is fSW (MHz) = 10000 / RRT (kΩ). Synchronous rectification with an internal low-side FET means no external Schottky diode is needed — the bottom FET's Rds(on) is around 30 mΩ typical, so the body diode conducts only during the dead time. This keeps the efficiency above 90% at 3.3V output and 2A load, but the dead time still generates enough reverse recovery charge to matter in a 2 MHz layout — keep the SW node copper area small to reduce radiated emissions.
Automotive temperature range and AEC-Q100 qualification
The AEC-Q100 qualification means the part passed the full suite of reliability tests (HTOL, HAST, TC, ESD) at the Grade 1 stress levels, so it is suitable for engine-bay ECUs, transmission controllers, and body-control modules that see 125°C junction in summer stop-and-go traffic. The series is Automotive, AEC-Q100, which means the part carries the automotive-grade documentation package — PPAP, IMDS, and the 8D corrective-action process are available from Analog Devices for production releases. The ROHS3 compliance is the standard lead-free solder joint requirement for automotive assemblies; no additional exemption documentation is needed for the typical reflow profile.
Input voltage range and output adjustability
The minimum input of 2.25V is below the 2.5V typical for a 3.3V rail at dropout, so the part starts up even when the upstream rail dips during cranking. The maximum input of 5.5V is the abs-max for the internal FETs — a 5V rail with 10% tolerance (5.5V) is at the edge, so a TVS clamp at 5.8V is cheap insurance. The adjustable output from 0.5V to 5.5V covers the common core voltages for modern MCUs (1.2V, 1.8V, 3.3V) and the full 5V rail — the 0.5V minimum is set by the internal reference of 0.5V, so the FB pin must see exactly 0.5V at the target output. The feedback resistor divider sets the output; the top resistor is typically 100 kΩ for a 3.3V output, giving a bottom resistor of 17.8 kΩ (1% standard value).
No stock-holding claim is made; the part is quoted per the buyer's volume and lead-time requirements. The 12-LQFN package is common enough that multiple date-code lots are typically available from the supply chain.