n Standalone USB Charger
n Up to 950mA Charge Current Programmable via
n HPWR Input Selects 20% or 100% of Programmed
n NTC Input for Temperature Qualiﬁed Charging
n Internal Timer Termination
n Bad Battery Detection
Switching Regulators (Buck and Buck-Boost)
n Up to 400mA Output Current per Regulator
n 2.25MHz Constant-Frequency Operation
n Power Saving Burst Mode® Operation
n Low Proﬁle, 20-Lead, 3mm × 3mm QFN Package
n SD/Flash-Based MP3 Players
n Low Power Handheld Applications
Linear USB Battery Charger
with Buck and
The LTC®3558 is a USB battery charger with dual high ef-
ﬁciency switching regulators. The device is ideally suited
to power single-cell Li-Ion/Polymer based handheld ap-
plications needing multiple supply rails.
Battery charge current is programmed via the PROG pin
and the HPWR pin with capability up to 950mA of current
at the BAT pin. The CHRG pin allows battery status to be
monitored continuously during the charging process. An
internal timer controls charger termination.
The part includes monolithic synchronous buck and buck-
boost regulators that can provide up to 400mA of output
current each and operate at efﬁciencies greater than 90%
over the entire Li-Ion/Polymer battery range. The buck-
boost regulator can regulate its programmed output voltage
at its rated deliverable current over the entire Li-Ion range
without drop out, increasing battery runtime.
The LTC3558 is offered in a low proﬁle (0.75mm), thermally
enhanced, 20-lead (3mm × 3mm) QFN package.
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners.
USB Charger Plus Buck Regulator and Buck-Boost Regulator
USB (4.3V TO 5.5V)
(2.7V TO 4.2V)
1.2V AT 400mA
324k 10pF 10μF
3.3V AT 400mA