MAX11505 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX11505

Four-Channel, Standard-Definition Video Filters

Maxim Integrated 

Four-Channel, Standard-Definition

Video Filters

Applications Information

Output Configuration

The MAX11504/MAX11505 outputs may be either DC-

or AC-coupled. If AC-coupled, choose a capacitor that

passes the lowest frequency content of the video signal,

and keep the line-time distortion within desired limits. The

capacitor value is a function of the input leakage and

impedance of the circuit being driven. Common industry

practice is to use a 220µF or larger coupling capacitor. If

any or all outputs are driving two parallel loads, see the

Junction Temperature Calculations section.

The MAX11504/MAX11505 outputs are fully protected

against short circuits either to the ground or the positive

supply of the device. The short-circuit protection cir-

cuitry limits the output current to 80mA (typical) per out-

put. Shorting more than one output simultaneously can

exceed the maximum package power dissipation.

Junction Temperature Calculations

Die temperature is a function of quiescent power dissi-

pation and the power dissipation in the output drivers.

Calculate the power dissipated PD using:

PD = PDS + PDO1 + PDO2 + PDO3 + PDO4

where PDS is the quiescent power dissipated in the die,

and given by:

PDS = VCC × ICC

and where PDOn is the power dissipated in the nth dri-

ver stage and given by:

PDOn

=

(VCC

−

VORMSn ) ×

RL

VORMSn

where VORMSn is the RMS output voltage and RL is the

load resistance.

Example - Assuming these conditions:

1) Video standard = 525/60/2:1.

2) Video format = RGB with syncs on all channels.

3) Picture content = 100% white.

4) The input signal is AC-coupled.

5) The output signal is DC-coupled.

6) VCC = 5.0V.

7) ICC = 24mA.

A sync tip exists at 280mV and peak white exists at

2.28V. The RMS voltage will be approximately 1.88V on

each output (80% of the peak-peak voltage, plus the

offset) giving:

PDS = 5 × 0.024 = 0.12W

PDOn

=

(5 − 1.88) × 1.88

75

= 0.078W

and

PD = 0.12 + 0.078 + 0.078 + 0.078 + 0.078 = 0.432W

The junction temperature is given by:

TJ = TA + (RθJA × PD)

where TJ = junction temperature, TA = ambient temper-

ature (assume +70°C) and RθJA = thermal resistance

junction to ambient.

From the Absolute Maximum Ratings section of the

data sheet, the derating factor is 8.8mW/°C above

+70°C. RθJA = 1/(derating factor) = 1/(8.8mW/°C) =

113°C/W.

Therefore:

TJ = 70 + 113 × 0.432 = +119°C

If there is only one video load on each output, the junc-

tion temperature lowers to:

TJ = +101°C

The above calculations assume the use of a multilay-

ered board with extensive ground planes for high ther-

mal efficiency. Using such a board is especially

important in applications where there are two video

loads on each channel.

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