Datasheet

LTC4055/LTC4055-1
21
4055fb
TYPICAL APPLICATIONS
LTC4055/LTC4055-1 Confi gured for USB Application
with Wall Adapter
Figure 5 shows an LTC4055/LTC4055-1 confi gured for
USB applications with the optional wall adapter input. The
programming resistor (R
CLPROG
) is set to 105k which sets
up a nominal current limit of 467mA in high power mode
(92mA in low power). This is done to prevent the various
tolerances in the part and programming resistors from
allowing the input current supplied by V
BUS
to exceed the
500mA/100mA limits.
The programming resistor (R
PROG
) with a value of 60.4k
sets up a nominal charge current of approximately 800mA.
Note that this is the charge current when the wall adapter
is present. When the wall adapter is absent, the current
limit supersedes the charge current programming and
charge current is limited to 467mA.
+
IN1
IN2
CHRG
ACPR
WALL
V
NTC
NTC
OUT
Li-Ion
CELL
SUSPEND USB POWER
500mA/100mA SELECT
SHUTDOWN
10μF
R3
1Ω
10μF
TIMER PROG
LTC4055
CLPROG GND
4055 F05
TO LDOs,
REGs, ETC
BAT
SUSP
HPWR
SHDN
C
TIMER
0.1μF
R
PROG
60.4k
5V (NOM)
FROM USB
CABLE V
BUS
5V WALL
ADAPTER INPUT
R
CLPROG
105k
R1
34.8k
R2
10k
R
NTCBIAS
100k
NTC
100k
Figure 5. USB Power Control Application with Wall Adapter Input