PDMAX = VS x ISMAX +

6 (VS ± VOUTi) x

VOUTi

RLi

n

i = 1

LMH6586

www.ti.com

SNCS105D – JULY 2008 – REVISED MARCH 2013

The maximum power dissipation actually produced by an IC is the total quiescent supply current times the total

power supply voltage, plus the power in the IC due to the load, or:

where

•

VS = Supply voltage = 5V

•

ISMAX = Maximum quiescent supply current = 300 mA

•

VOUT = Maximum output voltage of the application = 2.6V

•

RL = Load resistance tied to ground = 150Ω

•

n = 1 to 16 channels

(2)

Calculating:

PDMAX = 2.2656

The required

θJA to dissipate PDMAX is = (TJMAX – TAMAX)/PDMAX

The table below shows the

θJA values with airflow and different heatsinks.

LMH6586VS 80-Pin TQFT

0 LFPM

0 LFPM

0 LFPM

0 LFPM @2.8 225 LFPM @

500 LFPM @

LMHXPT

@ 0.50 watt

@ 1.0 watt

@ 2.0 watt

watt

2.8 watt

2.8 watt

Analog Video Crosspoint Board

NO Heat Sink

32.2

30.9

29.4

28.6

26.8

25.3

Small Tower

25.5

24.6

23.6

22.9

19.2

15.9

x y = 9.57x9.69 mm/ht. 6.28 mm

Aluminum 12 rail

25.2

24.1

23.0

22.2

16.4

14.2

x y = 9.82x10.73 mm/ht.10.07 mm

Anodized 9 rail

24.4

23.3

22.1

21.3

15.6

13.6

x y = 6.10x7.30 mm/ht. 13.67 mm

Round Tower

24.2

23.9

22.9

22.4

18.2

15.4

diameter = 14.35 mm/ht. 4.47 mm

REXT RESISTOR

The REXT external resistor (pin 67) establishes the internal bias current and precise reference voltage for the

LMH6586. For optimal performance, REXT should be a 10 k

Ω 1% precision resistor with a low temperature

coefficient to ensure proper operation over a wide temperature range. Using a REXT resistor with less precision

may result in reduced performance against temperature, supply voltage, input signal, or part-to-part variations.

SYNC SEPARATOR OUTPUT

In addition to the 16 video outputs, the LMH6586 has an extra output (V_OUT16) which can select any input

channel. This channel's output buffer only has a gain of 1 since it is not meant to drive a 150

Ω video load.

Instead, this video output can be AC coupled to a non-terminated input of an external video sync separator, such

as TI's LMH1980 or LMH1981. The sync separator can extract the synchronization (sync) timing signals, which

can be useful for video triggering or phase-locked loop (PLL) clock generation circuits. Refer to the LMH1980 or

LMH1981 datasheet for more information about these sync separator devices.

I

2C INTERFACE

A microcontroller can be used to configure the LMH6586 via the I2C interface. The protocol of the interface

begins with a start pulse followed by a byte comprised of a seven-bit slave device address and a read/write bit as

the LSB. The two lowest bits of the seven-bit slave address are defined by the external connections of inputs

ADDR[1] (pin 72) and ADDR[0] (pin 71), where ADDR[0] is the least significant bit. Because there are four

different combinations of the two ADDR pins, it's possible to have up to four different LMH6586 devices with

unique slave addresses on a common I2C bus. See I2C Device Slave Address Lookup Table.

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