LP2996LQX National Semiconductor, LP2996LQX Datasheet - Page 10

• Manufacturer Part Number: LP2996LQX
• Manufacturer: National Semiconductor

Specifications of LP2996LQX

• Voltage Regulator Type: Linear
• Topology: LDO
• Regulator Output Type: Fixed
• Polarity Type: Positive
• Number Of Outputs: Single
• Input Voltage (min): 2.2V
• Input Voltage (max): 5.5V
• Output Voltage: 1.159/1.259/1.359V
• Package Type: LLP EP
• Output Current: 1.5A
• Operating Temp Range: 0C to 125C
• Operating Temperature Classification: Commercial
• Pin Count: 16
• Mounting: Surface Mount
• Quiescent Current (max): 500uA
• Dc: 0352
• Lead Free Status / Rohs Status: Not Compliant

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where a θ
for this calculation is 0.036 mm for 1oz. Copper.
FIGURE 3. LLP-16 θ
Additional improvements in lowering the θ
achieved with a constant airflow across the package. Main-
taining the same conditions as above and utilizing the 2x2 via
array,
FIGURE 4. θ
Figure 4
JA
of 50.41°C/W can be obtained. Via wall thickness
JA
shows how the θ
vs Airflow Speed (JEDEC Board with 4
JA
vs # of Vias (4 Layer JEDEC Board))
Vias)
JA
varies with airflow.
JA
can also be
20057508
20057509
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Optimizing the θ
board exposed to lower ambient temperature allows the part
to operate with higher power dissipation. The internal power
dissipation can be calculated by summing the three main
sources of loss: output current at V
ing, and quiescent current at AVIN and VDDQ. During the
active state (when shutdown is not held low) the total internal
power dissipation can be calculated from the following equa-
tions:
Where,
To calculate the maximum power dissipation at V
ditions at V
current. Although only one equation will add into the total,
V
The power dissipation of the LP2996 can also be calculated
during the shutdown state. During this condition the output
V
disappear as it cannot sink or source any current (leakage is
negligible). The only losses during shutdown will be the re-
duced quiescent current at AVIN and the constant impedance
that is seen at the VDDQ pin.
TT
TT
cannot source and sink current simultaneously.
will tri-state, therefore that term in the power equation will
P
P
P
VDDQ
VDDQ
TT
VTT
P
need to be examined, sinking and sourcing
VTT
= ( V
JA
= V
= V
P
D
and placing the LP2996 in a section of a
= V
VDDQ
VDDQ
= P
P
P
P
PVIN
AVIN
AVIN
D
VTT
AVIN
= P
- V
* I
* I
= I
= I
x I
AVIN
VDDQ
VDDQ
VTT
+ P
AVIN
AVIN
LOAD
) x I
VDDQ
+ P
= V
= V
x V
* V
(Sinking) or
TT
LOAD
VDDQ
AVIN
VDDQ2
VDDQ2
, either sinking or sourc-
AVIN
+ P
(Sourcing
VTT
x R
x R
VDDQ
VDDQ
TT
both con-