Datasheet

REV. A
AD8152
–19–
is powered down. Thus, the total number of active inputs will
affect the total power consumption.
The core of the device performs the crosspoint switching function.
It draws a fixed quiescent current whenever the AD8152 is
powered from VCC to VEE.
An output predriver section draws a current that is proportional
to the programmed output current, I
OUT
. This current always
flows from VCC to VEE. It is treated separately from the output
current, which flows from VTTO, and might not be the same
voltage as VCC.
The final section is the outputs. For an individual output, the
programmed output current will flow through two separate paths.
One is the on-chip termination resistor, and the other is the
transmission line and the destination termination resistor. The
nominal parallel impedance of these two paths is 25 W. The sum
INPUT
TERMINATIONS
INPUTS
OUT-
PUTS
VTTI
VEE
VCC
VTTO
VTT
50⍀
50⍀
INP
INN
50⍀
50⍀
I
OUT
OUTP
OUTN
50⍀
50⍀
OUTPUT TERMINATIONS
V
OL
= V
TTO
– (I
OUT
ⴛ 25⍀)
DRIVEN DEVICE
TERMINATIONS
OPTIONAL COUPLING CAPACITORS
SWITCH
MATRIX
OUTPUT
PRE-
DRIVER
I = 32mA
I = .25 I
OUT
50⍀
I
OUT
2
P =
P =
(V
indiffrms
)
2
100⍀
(V
OL
) (I
OUT
)
P =
I = 2mA
PER
ACTIVE
INPUT
Figure 9. Power Consumption Block Diagram
Table X. Power Consumption
Output
Input Output Switch +
Termination Input Output Termination Current Total
Resistors Stage Core Predriver Resistors Source Power
Quiescent Current 32 mA
Current per Active Channel V
IN
/ (R
TERMINATION
) 2 mA 0.25 ¥ I
OUT
0.5 ¥ I
OUT
I
OUT
Current per Active Channel
for Differential
V
IN
= 800 mV p-p Sine 566 mV rms/100
V
OUT
= 800 mV p-p = 5.66 mA 2 mA 4 mA 4 mA 8 mA 16 mA
2.5 V Operation (VCC – VEE = 2.5 V, VTTO = 2.5 V, I
OUT
= 16 mA)
Per Channel Power 3.2 mW 5 mW 10 mW 8 mW 33.6 mW
Power for All Channels Active 108.8 mW 170 mW 80 mW 340 mW 272 mW 1.03 W 2.0 W
Percentage of Total Power 5% 8% 4% 17% 13.6% 51%
3.3 V Operation (VCC – VEE = 3.3 V, VTTO = 3.3 V, I
OUT
= 16 mA)
Per Channel Power 3.2 mW 6.6 mW 13.2 mW 8 mW 46.4 mW
Power for All Channels Active 108.8 mW 224 mW 106 mW 449 mW 272 mW 1.47 W 2.63 W
Percentage of Total Power 4% 9% 4% 17% 10% 56%
AD8152 POWER CONSUMPTION
There are several sections of the AD8152 that draw varying
power depending on the supply voltages, the type of I/O coupling
used, and the status of the AD8152 operation. Figure 9 shows a
block diagram of these sections. These are described briefly below
and then in detail later in the data sheet. Table X summarizes the
power consumption of each section and is a useful guide as the
following sections are reviewed.
The first section is the input termination resistors. The power
dissipated in the termination resistors is the result of their being
driven by the respective driving stage. Also, there might be dc power
dissipated in the input termination resistors if the inputs are
dc-coupled and the driving source reference is a dc voltage that is
not equal to VTTI.
In the next section, the active part of the input stages, each input
is powered only when it is selected. If an input is not selected, it