Single-cell Li-Ion charger with USB input and over-voltage protection
The MAX8934AETI+ from Maxim Integrated is a single-cell Li-Ion/Polymer linear battery charger IC in the Smart Power Selector™ family. It accepts a USB or adapter input up to 6.6V and delivers a programmable constant-current charge up to 1.5A to a 4.2V battery pack. The device integrates over-voltage fault protection on the input, and the charge current and timer are programmable via external components. The operating temperature range of -40°C to 85°C suits it for industrial portable equipment, handheld instruments, and outdoor IoT nodes where the charger must survive cold starts and hot enclosures.
1.5A charge current — sizing the power path
The 1.5A maximum charge current is the rating that drives the thermal design. In a 28-WFQFN exposed-pad package, the linear regulator drops the input-to-battery voltage as heat, so at full current with a 5V input and a depleted 3.0V cell, the power dissipation is roughly 3W. That demands a solid thermal via array under the exposed pad to keep the junction temperature within the -40°C to 85°C operating range. For lower dissipation, the current is programmable — the constant-current loop lets you set a lower limit with a single resistor, which is the usual move when charging from a USB port that may share a 500 mA budget.
Active production — no LTB pressure
The MAX8934AETI+ carries an active lifecycle status, so there is no last-time-buy clock running on this part. It is ROHS3 compliant, meeting the current exemption-free RoHS directive. For a new design going into production, this means the charger IC is not a supply-chain risk item — you can qualify it into the BOM without planning for an end-of-life migration within the product's expected run.
Package and footprint notes
The device is supplied in a 28-WFQFN with exposed pad, surface-mount package, and the supplier device package is a 28-TQFN measuring 4x4 mm. The exposed pad is the primary thermal path — the PCB layout must include a thermal via pattern under the pad to the ground plane. The package is compatible with standard reflow profiles for MSL-rated QFN packages.