ADD8708

Rev. 0 | Page 11 of 16

VOLTAGE REGULATOR

The on-board voltage regulator provides a regulated voltage to

the resistor chain to provide stable gamma voltages.

and a reference voltage set the output of the regulator. The

typical values of these parts are shown in Figure 23. In addition,

see the Tap Point and Regulator Voltage Request Form in this

data sheet.

1.2V

+

–

55k

Ω

5k

Ω

Figure 23. Voltage Regulator

The internal resistors have a typical accuracy of 0.1%. External

resistors can be used to adjust the regulator voltage; however, it

is not recommended. Please contact your local sales office for

further details.

MAXIMUM POWER DISSIPATION

The maximum safe power dissipation in the ADD8708 package

the die. At approximately 150°C, the glass transition tempera-

ture, the properties of the plastic change. Even temporarily

exceeding this temperature limit may change the stresses that

the package exerts on the die, permanently shifting the para-

metric performance of the ADD8708. Exceeding a junction

temperature of 175°C for an extended period can result in

changes in the silicon devices, potentially causing failure.

LAND PATTERN

The LFCSP package comes with a thermal pad. Soldering down

this thermal pad dramatically improves the heat dissipation of

the package. It is necessary to attach vias that connect the

soldered thermal pad to another layer on the board. This

provides an avenue to dissipate the heat away from the part.

Without vias, the heat is isolated directly under the part.

Subdivide the solder paste, or stencil layer, for the thermal pad

to reduce solder balling and splatter. It is not critical how the

subdivisions are arranged, as long as the total coverage of the

solder paste for the thermal pad is greater than 50%. The land

pattern is critical to heat dissipation. A suggested land pattern is

shown in Figure 22.

The thermal pad is attached to the substrate. In the ADD8708,

thermal pad should be soldered to an area on the board that is

pad to ground adversely affects the performance of the part.