LP2997MX National Semiconductor, LP2997MX Datasheet - Page 9
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LP2997MX
Manufacturer Part Number
LP2997MX
Description
DDR-II Termination Regulator
Manufacturer
National Semiconductor
Datasheet
1.LP2997MX.pdf
(12 pages)
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
LP2997MX
Manufacturer:
NS/国半
Quantity:
20 000
Company:
Part Number:
LP2997MX/NOPB
Manufacturer:
TI
Quantity:
5 600
Part Number:
LP2997MX/NOPB
Manufacturer:
TI/德州仪器
Quantity:
20 000
Thermal Dissipation
top side of the board can also help. With careful layout it is
possible to reduce the θ
shown in Figure 1
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
sourcing, 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 follow-
ing equations:
Where,
P
VDDQ
= V
P
JA
D
VDDQ
and placing the LP2997 in a section of a
= P
P
AVIN
AVIN
JA
* I
= I
VDDQ
+ P
further than the nominal values
AVIN
VDDQ
= V
* V
(Continued)
AVIN
VDDQ 2
+ P
TT
, either sinking or
VTT
x R
VDDQ
9
To calculate the maximum power dissipation at V
conditions at V
current. Although only one equation will add into the total,
V
The power dissipation of the LP2997 can also be calculated
during the shutdown state. During this condition the output
V
will disappear as it cannot sink or source any current (leak-
age is negligible). The only losses during shutdown will be
the reduced 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
P
P
VDDQ
VTT
P
TT
= ( V
VTT
= V
need to be examined, sinking and sourcing
= V
VDDQ
P
PVIN
P
AVIN
D
VTT
= P
- V
* I
= I
x I
AVIN
VDDQ
VTT
AVIN
LOAD
) x I
+ P
x V
= V
(Sinking) or
LOAD
VDDQ
AVIN
VDDQ 2
(Sourcing)
x R
VDDQ
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TT
both