AD8150ASTZ Analog Devices Inc, AD8150ASTZ Datasheet - Page 27

• Manufacturer Part Number: AD8150ASTZ
• Description: IC,Telecom Switching Circuit,QFP,184PIN,PLASTIC
• Manufacturer: Analog Devices Inc

Specifications of AD8150ASTZ

• Function: Crosspoint Switch
• Circuit: 1 x 33:17
• Voltage Supply Source: Dual Supply
• Voltage - Supply, Single/dual (±): ±3 V ~ 5.5 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 184-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

POWER DISSIPATION
For analysis, the power dissipation of the AD8150 can be
divided into three separate parts. These are the control logic,
the data path circuits, and the (ECL or PECL) outputs, which
are part of the data path circuits, but can be dealt with
separately. The first of these, the control logic, is CMOS
technology and does not dissipate a significant amount of
power. This power will, of course, be greater when the logic
supply is 5 V than when it is 3 V, but overall it is not a significant
amount of power and can be ignored for thermal analysis.
The data path circuits operate between the supplies V
V
range from 3.3 V to 5 V. The current consumed by this section
will be constant, so operating at a lower voltage can save about
40 percent in power dissipation.
The power dissipated in the data path outputs is affected by
several factors. The first is whether the outputs are enabled or
disabled. The worst case occurs when all of the outputs are
enabled. The current consumed by the data path logic can be
approximated by
EE
. As described in the power supply section, this voltage can
I
CC
AD8150
=
CONTROL
30
LOGIC
Figure 41. Major Power Consumption Paths
GND
mA
V
V
I, DATA PATH
LOGIC
SS
DD
×
+
(
#
[
4
of
5 .
outputs
mA
V
EE
PATHS
GND
DATA
+
V
(
CC
I
enabled
OUT
20
I
OUT
)
mA
V
OUT
×
LOW – V
3
R
mA
OUT
)
CC
]
EE
and
Rev. A | Page 27 of 44
This says that there will always be a minimum of 30 mA
flowing. I
the number of enabled outputs and the programmed output
current.
The power dissipated in this circuit section will simply be the
voltage of this section (V
case, assume that V
the programmed output current is 25 mA. The power dissipated
by the data path logic will be
The power dissipated by the output current depends on several
factors. These are the programmed output current, the voltage
drop from a logic low output to V
outputs. A simplifying assumption is that one of each (enabled)
differential output pair will be low and draw the full output
current (and dissipate most of the power for that output), while
the complementary output of the pair will be high and draw
insignificant current. Thus, the power dissipation of the high
output can be ignored, and the output power dissipation for
each output can be assumed to occur in a single static low
output that sinks the full output-programmed current.
The voltage across which this current flows can also vary,
depending on the output circuit design and the supplies that are
used for the data path circuitry. In general, however, there will
be a voltage difference between a logic low signal and V
is the drop across which the output current flows. For a worst
case, this voltage can be as high as 3.5 V. Thus, for all outputs
enabled and the programmed output current set to 25 mA, the
power dissipated by the outputs is
P
P
=
=
3
CC
5
5 .
0 .
will increase by a factor that is proportional to both
V
V
(
25
{
25
mA
CC
mA
− V
)
×
+
CC
17
EE
[
4
− V
is 5.0 V, all outputs are enabled and
5 .
=
. 1
mA
=
EE
49
826
) times the current. For a worst
EE
W
+
, and the number of enabled
(
mW
25
mA
20
mA
×
AD8150
3
EE
mA
. This
)
]
×
17
}