AD8151AST Analog Devices Inc, AD8151AST Datasheet - Page 21

• Manufacturer Part Number: AD8151AST
• Description: IC CROSSPOINT SWIT 33X17 184LQFP
• Manufacturer: Analog Devices Inc

Specifications of AD8151AST

• Rohs Status: RoHS non-compliant
• Function: Crosspoint Switch
• Circuit: 1 x 33:17
• Voltage Supply Source: Dual Supply
• Voltage - Supply, Single/dual (±): ±3 V ~ 5.25 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 184-LQFP
• Number Of Arrays: 1
• Differential Data Transmission: Yes
• Operating Supply Voltage (typ): Not RequiredV
• Mounting: Surface Mount
• Operating Temperature (max): 85C
• Cascading Capability: No
• Line Code: NRZ
• On-chip Buffers: Yes
• On-chip Mux/demux: No
• Operating Supply Voltage (max): Not RequiredV
• Operating Supply Voltage (min): Not RequiredV
• Lead Free Status / RoHS Status: Not Compliant

Data Path Supplies
The data path supplies have more options for their voltage levels.
The choices here affect several other areas, such as power
dissipation, bypassing, and common-mode levels of the inputs
and outputs. The more positive voltage supply for the data paths
is V
supply is V
The maximum allowable voltage across these supplies is 5.5 V.
The first choice in the data path power supplies is to decide
whether to run the device as ECL or PECL. For ECL operation,
V
between –3.3 V to –5 V. This makes the common-mode voltage
of the inputs and outputs a negative voltage (see Figure 39).
The proper way to run the device is to dc-couple the data paths
to other ECL logic devices that use ground as the most positive
supply and use a negative voltage for V
to be ac-coupled, it is not necessary to have the input/output
common mode at the same level as the other system circuits,
but it is probably more convenient to use the same supply rails
for all devices. For PECL operation, V
and V
common mode of the inputs and outputs is at a positive voltage.
These can then be dc-coupled to other PECL operated devices.
If the data paths are ac-coupled, then the common-mode levels
do not matter (see Figure 40).
CC
0.1μF
CC
is at ground potential, while V
AD8151
CC
0.1μF
(Pin 41, Pin 98, Pin 149, and Pin 171). The more negative
Figure 40. Power Supplies and Bypassing for PECL Operation
Figure 39. Power Supplies and Bypassing for ECL Operation
is a positive voltage from 3.3 V to 5 V. Thus, the
AD8151
+3.3V TO +5V
CONTROL
EE
LOGIC
+3.3V TO +5V
, which appears on many pins that are not listed here.
GND
CONTROL
LOGIC
V
V
GND
DD
SS
V
V
DD
SS
–3.3V TO –5V
PATHS
DATA
+3.3V TO +5V
GND
PATHS
V
V
DATA
CC
EE
GND
V
V
CC
EE
EE
0.1μF
(ONE FOR EVERY TWO V
is at a negative supply
EE
0.1μF
(ONE FOR EACH V
4 REQUIRED)
EE
is at ground potential
. However, if the part is
CC
EE
PIN,
PINS)
Rev. B | Page 21 of 40
POWER DISSIPATION
For analysis, the power dissipation of the AD8151 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 control logic is CMOS technology and does not
dissipate a significant amount of power. This power is, of
course, greater when the logic supply is 5 V rather than 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
is constant, so operating at a lower voltage can decrease power
dissipation by about 35 percent. 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
I
This equation states that a minimum I
I
of enabled outputs and the programmed output current.
The power dissipated in this circuit section is simply the voltage
of this section (V
worst case, assume that V
enabled, and the programmed output current is 25 mA. The
power dissipated by the data path logic is
P = 5.0 V {35 mA + [4.5 mA + (25 mA/20 mA × 3 mA)] × 17} = 876 mW
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 is low and draws the full output current
(and dissipates most of the power for that output), while the
complementary output of the pair is high and draws insignifi-
cant current.
CC
CC
EE
= 35 mA + [I
. As described in the power supply section, this voltage can
increases by a factor that is proportional to both the number
AD8151
CONTROL
Figure 41. Major Power Consumption Paths
LOGIC
GND
OUT
V
V
CC
I, DATA PATH
LOGIC
SS
DD
/20 mA × 3 mA)] × (no. of outputs enabled)
– V
EE
) times the current. To calculate the
CC
V
– V
EE
PATHS
GND
DATA
V
EE
CC
EE
is 5.0 V, all outputs are
, and the number of enabled
CC
of 35 mA always flows.
I
OUT
V
OUT
LOW – V
R
OUT
AD8151
CC
EE
and