LTC3558
1
3558f
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
Linear USB Battery Charger
with Buck and
Buck-Boost Regulators
The LTC
®
3558 is a USB battery charger with dual high ef-
fi ciency 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 effi ciencies 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 profi le (0.75mm), thermally
enhanced, 20-lead (3mm
×
3mm) QFN package.
USB Charger Plus Buck Regulator and Buck-Boost Regulator
Battery Charger
n
Standalone USB Charger
n
Up to 950mA Charge Current Programmable via
Single Resistor
n
HPWR Input Selects 20% or 100% of Programmed
Charge Current
n
NTC Input for Temperature Qualifi ed 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 Profi le, 20-Lead, 3mm
×
3mm QFN Package
n
SD/Flash-Based MP3 Players
n
Low Power Handheld Applications
V
CC
NTC
PROG
SUSP
HPWR
EN1
4.7μH
10μF
649k
324k
10pF
22μF
10pF
LTC3558
GND
EXPOSED
PAD
1μF
2.2μH
1.74k
EN2
MODE
BAT
USB (4.3V TO 5.5V)
DIGITAL
CONTROL
PV
IN1
PV
IN2
SW1
FB1
SWAB2
SWCD2
V
OUT2
FB2
V
C2
1.2V AT 400mA
SINGLE
Li-lon CELL
(2.7V TO 4.2V)
105k
324k
15k
121k
3.3V AT 400mA
330pF
33pF
3558 TA01
+
CHRG
10μF
Demo Board
