Product Overview
The Chip That Decides When a Lithium Cell Has Had Enough
Condition
New, unused old stock, sold each out of a small group of identical parts, so the photographed piece is representative rather than the exact chip that ships. In the photo the black small-outline body carries two legible lines: a script maker's logo followed by P77AB on top, and LM3621M below it. Eight leads run along each side, straight and evenly spaced, and no bent pins, solder or flux residue are visible in this photo. Against the millimeter scale the body reads right around 10 mm long with the lead tips spanning approximately 6 mm across, consistent with a narrow-body 16-pin SOIC.
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Product Overview
The LM3621M is a full-function constant voltage, constant current (CVCC) lithium-ion (Li+) battery charger controller in a 16-pin SOIC package. It holds 1% regulation accuracy over the specified temperature range without external precision resistors, and it sequences five charge modes: conditioning, fast, top-off, monitor, and maintenance. The controller also detects and flags defective batteries along with over-current and over-voltage fault events. Its architecture is built on high gain constant voltage and constant current control loops feeding a logic controller, a precision bandgap reference, wide bandwidth transconductance error amplifiers, comparators, and an output buffer, which is why the same part can front a switching charger, a linear charger, or an offline ac adapter charger. Cell count, charge voltage set point, supply range, and pin assignments are not confirmed here - verify against the datasheet before use.
Key Features
- Constant voltage, constant current (CVCC) charger controller for lithium-ion (Li+) batteries
- 1% regulation accuracy over the specified temperature range with no external precision resistors
- Five charge modes: conditioning, fast, top-off, monitor, and maintenance
- Detects and flags defective batteries, over-current events, and over-voltage events
- Designed to control a switching charger, a linear charger, or an offline ac adapter charger
- High gain control loops with logic controller, precision bandgap reference, transconductance error amplifiers, comparators, and output buffer
- 16-pin SOIC surface mount package, body approximately 10 mm long against the ruler in the photo
- Marked with a script maker's logo, P77AB, and LM3621M
Applications
- Repairing a charger board that was designed around the LM3621M and needs the original 16-pin SOIC footprint populated again
- Keeping a legacy Li-Ion charging product in service when the production line still expects this controller by part number
- Bench work where an engineer wants a known CVCC controller to drive an experimental linear or switching charge stage
- Restoring 1990s and 2000s portable equipment charging cradles that used a National Semiconductor charge controller
Frequently Asked Questions
What comes in one order of this part?
One LM3621M integrated circuit, sold each. The photo shows a single representative chip from our stock of this part number, and nothing else is included.
What is actually printed on the chip?
The top line reads P77AB with a script maker's logo ahead of it, and the second line reads LM3621M. We are not decoding the P77AB line as a date or lot code, only reporting what the camera shows.
Can this drive a switching charger, or only a linear one?
The LM3621 family was built to control a switching charger, a linear charger, or an offline ac adapter charger, so the topology is your choice. The external power stage, sense resistor, and cell configuration are your design work - verify the values against the datasheet before use.
Why buy two or three here instead of a full tube from a distributor?
This is a counted part, not a lot. You can take exactly the number your board needs, one for the repair and maybe a spare for the drawer, without committing to a minimum-order tube or reel of a part your design only uses once. Shipping is a flat $8, free once your order passes $28, and orders leave our Idaho warehouse the same or next business day.
Charging a lithium cell is mostly a question of knowing when to stop, and that whole judgment call fits inside sixteen leads and a body you could lose in a shirt pocket. If a charging board has gone quiet and its bill of materials points here, this is the part number it is asking for, new old stock and untested by us.
