SMB 1390 003-00 USB Charger IC

A charge pump does one job differently than a normal buck charger, and that's exactly why the SMB1390 003-00 shows up so often on fast-charging boards. Instead of stepping voltage down through an inductor, it divides the input voltage by two using switched capacitors. Less heat, higher efficiency, and no inductor eating up space on a phone board where every millimeter counts.Qualcomm designed this chip as a single-input, programmable single-cell Li-ion/Li-polymer charger. It's a divide-by-2 charge pump, which means it takes an input and delivers exactly half the voltage at double the current — that's the trick behind fast charging without frying the battery. You'll see it working alongside the main PMIC, not replacing it, splitting the charging load so the phone can pull more current without pushing more heat into one single point.On your bench, this part matters for a specific set of complaints. A phone charging slow, not entering fast charge mode, or showing "charging on hold" is often a charge pump fault, not a battery fault or a port fault. Before you jump to IC change, check the charging port and cable first — a worn port or bad cable throws the exact same symptoms. Once you've ruled those out and you're still seeing a charging issue with normal trickle charge but no fast charge kicking in, the SMB1390 line is where you look next.The 003-00 variant handles an input range of 3.6V to 12V and puts out 2.5V to 5V on the output side, with a 28V DC withstand rating that protects the chip during voltage spikes on the input rail. That withstand rating is what saves this IC — and your customer's board — when a bad charger or damaged cable sends an unexpected voltage spike through the line. Output current goes up to 6A per chip, and on boards designed for higher wattage charging, you'll find two of these ICs running in parallel with clock sync between them to cut down ripple current. If you're working on a board with dual charge pump ICs, always check both — a single failed unit on a dual setup still shows charging, just noticeably slower, and that's an easy miss if you only test one.Reflow work on this part needs a steady hand. It's a small BGA-style package sitting close to other components on a crowded board, so control your hot air temperature and airflow tightly — too much heat spreads to nearby parts, too little leaves a cold joint that shows up as an intermittent charging fault a week later. After reballing or IC change, always retest under load, not just on connection — some charge pump faults only show up once current actually starts flowing, not on a simple continuity check.This chip fits directly into your diagnostics workflow for board-level charging repair: isolate the fault to hardware, confirm it's not a software or battery calibration issue, check the port and cable, then move to charge pump IC testing and replacement. Keep it stocked next to your other charging-line parts — ISP tools, hot air station, and a decent multimeter are what you'll actually reach for during this job.