Power Electronics

1A Lithium-Ion Battery Charger

Semtech Corp. announced the SC824, a linear, triple mode, single-cell lithium-ion battery charger in a ten-lead 2x2mm MLPD package for handheld devices. It has 30V input voltage protection with 9.6V maximum input over-voltage protection (OVP) threshold. The 30V input rating protects portable systems against hot plug overshoots and faulty charging adapters. Under-voltage lock out (UVLO) is lowered to 2.85V in the SC824 so it will work well with voltage or current-limited adapters. When charging from USB, a proprietary under-voltage limiting feature reduces the charge current as needed to prevent VBUS collapsing below 4.5V in case of a weak host or hub.

The SC824 features include an NTC thermistor interface, multi-stage timer, and an extra indicator flag. The NTC is used to disable charging when the battery temperature falls above or below predetermined thresholds. The NTC interface may also enable or disable LDO mode when the battery is disconnected. The optional programmable multi-stage charge timer protects against a faulty battery, or terminates charging on timeout if the system load is too high to terminate charging on current. Two flags indicate valid input voltage, charger status and faults.

The SC824 incorporates the preferred and safest lithium-ion charging algorithm with multiple regulation loops of constant current (CC), constant voltage (CV), and constant die junction temperature (CTj). The CTj loop greatly simplifies the thermal design considerations. A tri-level logic input selects from three modes of charging: adapter mode, USB low power mode and USB high power mode. Additional charging functions include reverse current blocking, pre-qualification of a low-voltage battery, soft-start to reduce the burden on wall adapters with poor transient response, optional float charging or top-off charging with termination, auto- or forced-recharging and open/short-circuit protection.

The SC824 (Order code: SC824ULTRT) is available immediately in production quantities and is priced at $0.75 each in 3,000-piece lots. Evaluation boards (SC824EVB) are also available. .

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