LTC4075HVXEDD#TRPBF Linear Technology, LTC4075HVXEDD#TRPBF Datasheet - Page 12

• Manufacturer Part Number: LTC4075HVXEDD#TRPBF
• Description: IC CHARGER LI-ION 10-DFN
• Manufacturer: Linear Technology

Specifications of LTC4075HVXEDD#TRPBF

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 4.3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-WFDFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LTC4075HVX
Using a Single Charge Current Program Resistor
The LTC4075HVX can 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.
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 current program resistor.
In this circuit, the programmed charge current from both the
wall adapter supply is the same value as the programmed
charge current from the USB supply:
12
Figure 2. Dual Input Charger with Independant Charge Currents
ADAPTER
Figure 3. Dual Input Charger Circuit. The Wall Adapter Charge
Current and USB Charge Current are Both Programmed to be
500mA
I
WALL
PORT
CHRG DC
ADAPTER
USB
WALL
PORT
USB
−
1μF
=
I
1μF
CHRG USB
1μF
−
R
2k
1%
IDC
IUSB
1μF
and R
=
R
2k
1%
R
1.24k
1%
ISET
IDC
1000
R
ISET
DCIN
USBIN
IUSB
IDC
DCIN
USBIN
IUSB
IDC
LTC4075HVX
IUSB
LTC4075HVX
V
GND
GND
. Figure 2 shows a
ITERM
ITERM
BAT
BAT
4075hvx F03
4075hvx F02
800mA (WALL)
R
1k
1%
R
1k
1%
500mA (USB)
ITERM
ITERM
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 af-
fected 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 20k (I
= 50mA); however, additional capacitance on these nodes
reduces the maximum allowed program resistor.
Power Dissipation
When designing the battery charger circuit, it is not neces-
sary to design for worst-case power dissipation scenarios
because the LTC4075HVX automatically reduces the charge
current during high power conditions. The conditions that
cause the LTC4075HVX to reduce charge current through
thermal feedback can be approximated by considering the
power dissipated in the IC. Most of the power dissipation
is generated from the internal charger MOSFET. Thus, the
power dissipation is calculated to be:
P
age (either DCIN or USBIN), V
and I
temperature at which the thermal feedback begins to
protect the IC is:
Example: An LTC4075HVX operating from a 5V wall
adapter (on the DCIN input) is programmed to supply
800mA full-scale current to a discharged Li-Ion battery
with a voltage of 3.3V.
D
P
T
T
is the dissipated power, V
A
A
D
BAT
= 125°C – P
= 125°C – (V
= (V
is the charge current. The approximate ambient
IN
– V
BAT
D
IN
) • I
• θ
– V
JA
BAT
BAT
) • I
IN
BAT
BAT
is the input supply volt-
is the battery voltage
• θ
JA
4075hvxf
CHRG