LTC4076EDD View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
LTC4076EDD Datasheet PDF : 16 Pages
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LTC4076
APPLICATIO S I FOR ATIO
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 2 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.
ICHRG(DC)
=
ICHRG(USB)
=
1000V
RISET
WALL
ADAPTER
LTC4076
DCIN
BAT
100mA
(USB, HPWR = LOW)
500mA
USB
PORT
1F
1F
USBIN
IUSB
HPWR
+
IDC
RISET
2k
1%
ITERM
GND
RITERM
1k
1%
4076 F02
Figure 2. Dual Input Charger Circuit. The Wall
Adapter Charge Current and USB Charge Current
are Both Programmed to be 500mA
The LTC4076 can also program the wall adapter charge
current and USB charge current independently using two
program resistors, RIDC and RIUSB. Figure 3 shows a
charger circuit that sets the wall adapter charge current
to 800mA and the USB charge current to 500mA.
Stability Considerations
The constant-voltage mode feedback loop is stable without
any compensation provided a battery is connected to the
charger output. However, a 1µF 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 char-
ger is stable with program resistor values as high as 20k
(ICHRG = 50mA); however, additional capacitance on these
nodes reduces the maximum allowed program resistor.
WALL
ADAPTER
USB
PORT
LTC4076
DCIN
BAT
USBIN
1F
1F
RIUSB
2k
1%
RIDC
1.24k
1%
HPWR PWR
IUSB CHRG
IDC
ITERM
GND
800mA (WALL)
100mA/500mA (USB)
1k 1k
RITERM
1k
1%
+
4.2V
1-CELL
Li-Ion
BATTERY
4076 F03
Figure 3. Full Featured Dual Input Charger Circuit
4076fa
12
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