The MAX5087B from Maxim Integrated (now part of Analog Devices) is what a designer reaches for when a module must hang directly on a vehicle battery or a rough industrial supply and still feed clean 5 V logic. Its input stage tolerates 6.5 V to 45 V continuously, so the ordinary 12 V automotive rail - with its cold-crank sags and load-dump style surges toward 40 V - is simply inside the operating range rather than a fault condition. MAX5087BATE+T is the RoHS ("+"), tape-and-reel ("T") option in the thermally enhanced 16-TQFN with exposed pad.

Two numbers define its character. The first is 400 mA of guaranteed output - enough to run an MCU, CAN transceiver and sensor cluster from one device. The second is a no-load quiescent current of only 70 µA: an always-on telematics or body module powered through the MAX5087B barely touches the battery while the vehicle sleeps, and the EN pin can cut that to about 11 µA outright. Output voltage is preset to 5.0 V when SET is grounded (the MAX5087A sibling presets to 3.3 V); strap SET to an external divider from OUTSENSE instead and the same part regulates anywhere from 2.5 V to 11 V against an internal 1.235 V reference.

What separates this from a bare LDO is the built-in supervision. An open-drain RESET̅ output asserts whenever the output falls below roughly 92% of its nominal value and holds the processor in reset for a timeout you program with one capacitor on CT (t_RP ≈ C_T x 6.175 x 10⁴ seconds per farad) - power supply and voltage supervisor collapse into one package. Thermal shutdown and short-circuit protection guard the pass element; startup to a monitored, valid rail takes under 400 µs, and dropout is a modest 0.8 V (typ, light load). The exposed pad spreads heat from worst-case 45 V-in, 400 mA-out operation into the board.

Note: Values are taken from the Maxim MAX5087/MAX5087B datasheet. Confirm every parameter against the latest official documentation before committing a design.

MAX5087BATE+T is supplied in a 16-pin thin QFN with exposed pad, 5 mm x 5 mm x 0.75 mm on a 0.8 mm pitch (Maxim outline 21-0140, land pattern T1655+3). The exposed pad is the thermal path for linear dissipation - solder it to a generous copper pour stitched to the ground plane; electrically it sits at ground but must not serve as the only ground connection (pin 8 does that). With good copper the package handles roughly 2.6 W at +70 °C, which is what permits 400 mA from a high input without a heatsink. Six pins are no-connects, so routing stays loose despite the small body: 47 µF bulk on IN (pins 3/4), 15 µF+ low-ESR on OUT (pins 5/6), divider or strap at SET/OUTSENSE, pull-up on RESET̅, capacitor on CT. The full dimensional drawing is below.

Per the MAX5087/MAX5087B datasheet pin description, the 16-TQFN assigns (N.C. = no internal connection):

• Pins 1, 12-16 - N.C.: Not internally connected; may be left open.
• Pin 2 - EN: Enable input. High turns the regulator on; low enters ~11 µA shutdown. Tie to IN for always-on use.
• Pins 3, 4 - IN: Regulator input, 6.5-45 V; bypass with 47 µF to GND.
• Pins 5, 6 - OUT: Regulator output; stabilize with ≥15 µF low-ESR capacitance.
• Pin 7 - OUTSENSE: Output sense. Tie to OUT for the preset voltage; in adjustable mode it carries the feedback divider.
• Pin 8 - GND: Ground.
• Pin 9 - SET: Output programming. Ground for the preset 5.0 V; connect a divider (OUTSENSE→SET→GND) for 2.5-11 V.
• Pin 10 - RESET̅: Open-drain, active-low reset output; asserts below ~92% of nominal. Needs a ~10 kΩ pull-up.
• Pin 11 - CT: Reset-timeout programming capacitor; t_RP ≈ C_T x 6.175 x 10⁴ s/F.
• EP: Exposed pad - solder to the ground plane for heat spreading (thermal, not the substitute ground).

Closest options are the 3.3 V sibling and Maxim's other wide-input regulators. Confirm output voltage, current, supervision features and package before substituting.

Selection Tips: Keep the MAX5087B where a supervised 5 V rail up to 400 mA must come straight off a 12/24 V battery with minimum noise and parts count; pick the A-grade for 3.3 V systems. Below ~50 mA the MAX15006/15007 or 65 V MAX5023 cut standby current further, and when (V_IN-V_OUT) x I_OUT exceeds the TQFN's thermal budget, step to the switching MAX5035 and post-filter it.

Maxim Integrated, now part of Analog Devices, Inc. (ADI), has supplied automotive power management for decades, and the MAX5087 line is a typical example of its integration philosophy: regulator, precision reference and processor supervisor combined so a battery-connected module needs one IC and a handful of passives.

Under ADI the part carries full AEC-grade documentation - datasheet characterization to +125 °C, thermal data for the 21-0140 TQFN and application guidance on load-dump survival and reset timing - the references that matter when the same board must pass both EMC and cold-crank tests.