ltc4096 Linear Technology Corporation, ltc4096 Datasheet - Page 12

• Manufacturer Part Number: ltc4096
• Description: Dual Input Standalone Li-ion Battery Chargers
• Manufacturer: Linear Technology Corporation

LTC4096/LTC4096X
APPLICATIONS INFORMATION
Using a Single Charge Current Program Resistor
In applications where the programmed wall adapter charge
current and USB charge current are the same, a single
program resistor can be used to set both charge currents.
Figure 3 shows a charger circuit that uses one charge cur-
rent program resistor. In this circuit, one resistor programs
the same charge current for each input supply.
The LTC4096 can also program the wall adapter charge
current and USB charge current independently using two
program resistors, R
charger circuit that sets the wall adapter charge current
to 800mA and the USB charge current to 500mA.
12
I
CHRG DC
(
)
=
I
CHRG USB
DCIN
1
(
IDC
4.2V
+ –
∆V
BAT
10
)
and R
=
1000
+
–
+
–
–
+
CURR-LIM
R
ISET
DCIN UVLO
IUSB
V
. Figure 4 shows a
Figure 2. Input Power Present Output (PWR) Circuit
DCON
PWR
3
DCON
120mA MAX
Stability Considerations
The constant-voltage mode feedback loop is stable without
any compensation provided a battery is connected to the
charger output. However, a 4.7µF capacitor with a 1Ω
series resistor is recommended at the BAT pin to keep
the ripple voltage low when the battery is disconnected.
When the charger is in constant-current mode, the charge
current program pin (IDC or IUSB) is in the feedback loop,
not the battery. The constant-current mode stability is
affected by the impedance at the charge current program
pin. With no additional capacitance on this pin, the charger
is stable with program resistor values as high as 20KΩ
(I
nodes reduces the maximum allowed program resistor.
CHRG
USBON
= 50mA); however, additional capacitance on these
USBIN UVLO
CURR-LIM
+
–
+
–
–
+
BAT
–
∆V
4V
10
+
4096 BD
USBIN
2
4096xf