ADD8707 Analog Devices, Inc., ADD8707 Datasheet - Page 13

• Manufacturer Part Number: ADD8707
• Description: 12-channel Gamma Buffers With Vcom And Regulator
• Manufacturer: Analog Devices, Inc.

VOLTAGE REGULATOR
The on-board voltage regulator provides a regulated voltage to
the resistor chain to provide stable gamma voltages.
The output of the regulator is set by the two mask program-
mable internal resistors R1 and R2, and a reference voltage. In
the ADD8707, the typical values of these parts are shown in
Figure 26. To request a different regulator voltage, please refer
to the Tap Point and Regulator Voltage Request Form in this
data sheet.
The internal resistors have a typical accuracy of 0.1%. External
resistors can be used to adjust the regulator voltage, though it is
not recommended. Contact a sales office for further details.
MAXIMUM POWER DISSIPATION
The maximum safe power dissipation in the ADD8707 package
is limited by the associated rise in junction temperature (TJ) on
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 ADD8707. Exceeding a junction
temperature of 175°C for an extended period can result in
changes in the silicon devices, potentially causing failure.
V
1.2V
5kΩ
REF
R
Figure 26. Voltage Regulator
1
+
–
55kΩ
R
2
V
REG OUT
Rev. A | Page 13 of 20
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.
This reduces 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 27.
The thermal pad is attached to the substrate. In the ADD8707,
the substrate is connected to V
thermal pad should be soldered to an area on the board that is
electrically isolated or connected to V
pad to ground adversely affects the performance of the part.
DD
. To be electrically safe, the
DD
. Attaching the thermal
ADD8707