LTC4069EDC-4.4#TRM Linear Technology, LTC4069EDC-4.4#TRM Datasheet - Page 13

• Manufacturer Part Number: LTC4069EDC-4.4#TRM
• Description: BATT CHARGER, LI ON, 750MA, 6DFN
• Manufacturer: Linear Technology

Specifications of LTC4069EDC-4.4#TRM

• Battery Type: Li-Ion
• Input Voltage: 5.5V
• Battery Charge Voltage: 4.4V
• Charge Current Max: 750mA
• Battery Ic Case Style: DFN
• No. Of Pins: 6
• No. Of Series Cells: 1
• Operating Temperature Range: -40°C To
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
battery current as shown in Figure 5. A 10k resistor has
been added between the PROG pin and the fi lter capacitor
to ensure stability.
Power Dissipation
The conditions that cause the LTC4069 to reduce charge
current through thermal feedback can be approximated
by considering the power dissipated in the IC. For high
charge currents, the LTC4069 power dissipation is
approximately:
where P
voltage, V
current. It is not necessary to perform any worst-case
power dissipation scenarios because the LTC4069 will
automatically reduce the charge current to maintain the
die temperature at approximately 115°C. However, the
approximate ambient temperature at which the thermal
feedback begins to protect the IC is:
Example: Consider an LTC4069 operating from a 5V wall
adapter providing 750mA to a 3.6V Li-Ion battery. The
ambient temperature above which the LTC4069 will begin
to reduce the 750mA charge current is approximately:
The LTC4069 can be used above 70°C, but the charge current
will be reduced from 750mA. The approximate current at
a given ambient temperature can be calculated:
P
T
T
T
T
T
I
BAT
A
A
A
A
A
D
= 115°C – P
= 115°C – (V
= 115°C – (5V – 3.6V) • (750mA) • 60°C/W
= 115°C – (1.05W • 60°C/W) = 115°C – 63°C
= 52°C
= (V
=
D
is the power dissipated, V
BAT
(
CC
V
CC
– V
is the battery voltage and I
115
–
BAT
V
D
°
CC
C T
BAT
• θ
) • I
–
– V
JA
)
BAT
A
• θ
BAT
JA
) • I
BAT
CC
• θ
is the input supply
JA
BAT
is the charge
Using the previous example with an ambient temperature
of 73°C, the charge current will be reduced to
approximately:
Furthermore, the voltage at the PROG pin will change
proportionally with the charge current as discussed in
the Programming Charge Current section.
It is important to remember that LTC4069 applications do
not need to be designed for worst-case thermal conditions
since the IC will automatically limit power dissipation when
the junction temperature reaches approximately 115°C.
Board Layout Considerations
In order to deliver maximum charge current under all
conditions, it is critical that the exposed metal pad on the
backside of the LTC4069 package is soldered to the PC board
copper and extending out to relatively large copper areas
or internal copper layers connected using vias. Correctly
soldered to a 2500mm
the LTC4069 has a thermal resistance of approximately
60°C/W. Failure to make thermal contact between the
Exposed Pad on the backside of the package and the copper
board will result in thermal resistances far greater than
60°C/W. As an example, a correctly soldered LTC4069 can
deliver over 750mA to a battery from a 5V supply at room
temperature. Without a backside thermal connection, this
number could drop to less than 500mA.
V
Many types of capacitors can be used for input bypassing;
however, caution must be exercised when using multi-layer
ceramic capacitors. Because of the self-resonant and high
Q characteristics of some types of ceramic capacitors, high
voltage transients can be generated under some start-up
conditions, such as connecting the charger input to a live
power source. For more information, refer to Application
Note 88.
CC
I
BAT
Bypass Capacitor
=
(
5
V
115
– .
3 6
°
C
V
–
)
2
•
73
60
double-sided 1 oz. copper board
°
C
°
C W
/
=
84
42
°
C A
°
C
/
LTC4069
=
500
13
mA
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