LTC4066EUF#PBF Linear Technology, LTC4066EUF#PBF Datasheet - Page 24

• Manufacturer Part Number: LTC4066EUF#PBF
• Description: IC USB POWER MANAGER 24-QFN
• Manufacturer: Linear Technology

Specifications of LTC4066EUF#PBF

• Function: Power Management
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 4.35 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-WFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC4066/LTC4066-1
APPLICATIONS INFORMATION
Consider an example where the V
somewhere around 4.5V. Resistance on the WALL pin
should be kept relatively low (~10k) in order to prevent
false tripping of the wall comparator due to leakages as-
sociated with the switching element used to connect the
adapter to OUT. Pick R2 to be 10k and solve for R1:
The nearest 1% resistor is 26.7k. Therefore, R1 = 26.7k
and the rising trip point should be 4.50V.
The hysteresis is going to be approximately 110mV for
this example.
Power Dissipation
The conditions that cause the LTC4066/LTC4066-1 to
reduce charge current due to the thermal protection
feedback can be approximated by considering the power
dissipated in the part. For high charge currents and a wall
adapter applied to V
dissipation is approximately:
where P
voltage, V
charge current. It is not necessary to perform any worst-
case power dissipation scenarios because the LTC4066/
LTC4066-1 will automatically reduce the charge current
to maintain the die temperature at approximately 105°C.
24
P
R
R
V
D
HYST
1
1 10
=
=
= (V
R
D
(
2
BAT
Adapter
OUT
k
is the power dissipated, V
•
•
⎛
⎜
⎝
is the battery voltage and I
⎛
⎜
⎝
V
– V
1 225
TH
.
4 5
BAT
V
.
(
)
Adapter
WALL
≈
V
OUT
) • I
V
30
–
, the LTC4066/LTC4066-1 power
mV
BAT
1
⎞
⎟ =
⎠
)
•
–
⎛
⎜
⎝
10
1
1
⎞
⎟
⎠
+
k
TH
• .
26 7
(Adapter) is to be set
10
2 67 26 7
.
k
OUT
k
BAT
⎞
⎟ ≈
⎠
=
is the supply
is the battery
110 1
.
k
.
mV
However, the approximate ambient temperature at which
the thermal feedback begins to protect the IC is:
Example: Consider an LTC4066/LTC4066-1 operating from
a wall adapter with 5V at V
Li-Ion battery. The ambient temperature above which the
LTC4066/LTC4066-1 will begin to reduce the 0.8A charge
current, is approximately:
The LTC4066/LTC4066-1 can be used above 46°C, but the
charge current will be reduced below 0.8A. The charge
current at a given ambient temperature can be approxi-
mated by:
Consider the above example with an ambient tem-
perature of 55°C. The charge current will be reduced to
approximately:
Board Layout Considerations
In order to be able to deliver maximum charge current
under all conditions, it is critical that the Exposed Pad
on the backside of the LTC4066/LTC4066-1 package is
soldered to the board. Correctly soldered to a 2500mm
double-sided 1oz. copper board, the LTC4066/LTC4066-1
has a thermal resistance of approximately 37°C/W. Failure
T
T
T
T
I
I
BAT
BAT
A
A
A
A
= 105°C – P
= 105°C – (V
= 105°C – (5V – 3V) • 0.8A • 37°C/W
= 105°C – 1.6W • 37°C/W = 105°C – 59°C = 46°C
=
=
(
(
5
V
OUT
V
105
105
–
3
–
°
V
D
C
°
OUT
V
)
C T
• θ
BAT
–
•
–
55
37
JA
– V
)
A
°
°
• θ
C
C W
BAT
/
JA
OUT
) • I
=
providing 0.8A to a 3V
BAT
74
50
°
C A
• θ
°
C
/
JA
=
0 675
.
A
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