DDR Termination Regulator
P
D
=
P
AVIN
+
P
VDDQ
+ P
VTT
I
AVIN
x
V
AVIN
x
I
VDDQ
=
V
VDDQ2
x
R
VDDQ
TJ2996
Where,
P
AVIN
=
P
VDDQ
=
V
VDDQ
To calculate the maximum power dissipation at
V
TT
both conditions at
V
TT
need to be examined,
sinking and sourcing current. Although only one equation will add into the total,
V
TT
cannot source and
sink current simultaneously.
P
VTT
= V
VTT
x I
LOAD
(Sinking)
or
P
VTT
= ( V
PVIN
- V
VTT
) x I
LOAD
(Sourcing)
The power dissipation of the TJ2996 can also be calculated during the shutdown state. During this
condition the output V
TT
will tri-state, therefore that term in the power equation will disappear as it
cannot sink or source any current (leakage is negligible). The only losses during shutdown will be
the reduced quiescent current at AV
IN
and the constant impedance that is seen at the V
DDQ
pin.
P
D
= P
AVIN
+ P
VDDQ
,
Where,
P
AVIN
= I
AVIN
x V
AVIN
P
VDDQ
= V
VDDQ
x I
VDDQ
= V
VDDQ2
x R
VDDQ
Jul. 2010 - Rev. 1.5.3
9/14
HTC
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
