LTC3558_15 Datasheet, PDF (30/32 Pages) Linear Technology – Linear USB Battery Charger with Buck and Buck-Boost Regulators

LTC3558
TYPICAL APPLICATIONS
USB
(4.3V TO 5.5V)
OR AC ADAPTER
110k
28.7K
V_CC
10μF
NTC
BAT
PV_IN1
PV_IN2
UP TO 500mA
10μF
+ ^SINGLE
Li-lon CELL
1
(2.7V TO 4.2V)
4.7μF
510Ω
100k (NTC)
NTH50603NO1
1.74k
LTC3558
CHRG
PROG
SUSP
SW1
FB1
SWAB2
4.7μH
1.8V AT 400mA
806k
10pF
10μF
649k
DIGITAL
CONTROL
HPWR
EN1
SWCD2
V_OUT2
EN2
MODE
FB2
GND
GND2
(EXPOSED
PAD)
V_C2
3558 TA02
2.2μH
3.3V AT 400mA
619k
10μF
200k
15k
150pF
Figure 12. Li-Ion to 3.3V at 400mA, 1.8V at 400mA and USB-Compatible Battery Charger
As shown in Figure 12, the LTC3558 can be operated
with no battery connected to the BAT pin. A 1Ω resistor
in series with a 4.7μF capacitor at the BAT pin ensures
battery charger stability. 10μF V_CC decoupling capacitors
are required for proper operation of the DC/DC converters.
A three-resistor bias network for NTC sets hot and cold
trip points at approximately 55°C and 0°C.
The battery can be charged with up to 950mA of charge
current when powered from a 5V wall adaptor, as shown
in Figure 13. CHRG has a LED to provide a user with a
visual indication of battery charge status. The buck-boost
regulator starts up only after V_OUT1 is up to approximately
0.7V. This provides a sequencing function which may be
desirable in applications where a microprocessor needs to
be powered up before peripherals. A Type III compensation
network improves the transient response of the buck-boost
switching regulator.
3558f
30