AD8152 datasheet(19/32 Pages) AD

19 / 32 page

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, IOUT. 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

INP

INN

IOUT

OUTP

OUTN

OUTPUT TERMINATIONS

VOL = VTTO – (IOUT

25 )

DRIVEN DEVICE

TERMINATIONS

OPTIONAL COUPLING CAPACITORS

SWITCH

MATRIX

OUTPUT

PRE-

DRIVER

I = 32mA

I = .25 IOUT

IOUT

P =

(Vindiffrms)

100

(VOL) (IOUT)

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

VIN/(RTERMINATION) 2 mA

0.25

¥ IOUT 0.5 ¥ IOUT

IOUT

Current per Active Channel

for Differential

VIN = 800 mV p-p Sine

566 mV rms/100

VOUT = 800 mV p-p

= 5.66 mA

2 mA

4 mA

8 mA

16 mA

2.5 V Operation (VCC – VEE = 2.5 V, VTTO = 2.5 V, IOUT = 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

17%

13.6%

51%

3.3 V Operation (VCC – VEE = 3.3 V, VTTO = 3.3 V, IOUT = 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

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

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