Table of Contents
Advertisement
Chapter 25
Recommended Layout
Practices
25.1 Protecting Against ElectroStatic Discharge
Before handling the LH75400/01/10/11, read these electrostatic discharge (ESD) instruc-
tions to prevent damage to the devices.
• Always wear an ESD-preventive grounding wrist strap or observe similar ESD precau-
tions when working with the LH75400/01/10/11 board. Be sure the wrist strap makes
good skin contact. Do not remove the wrist strap until you finish working with the
LH75400/01/10/11 board.
• Avoid contact between equipment and clothing. The wrist strap only protects the equip-
ment from ESD voltages on the body; ESD voltages on clothing can still cause damage.
• Place the LH75400/01/10/11 board component side up on an antistatic mat. When an
LH75400/01/10/11 board is not being used, place it in a static-shielding bag.
• Handle an LH75400/01/10/11 board by the edges only; avoid touching the components,
traces, or any connector pins.
25.1.1 Special ESD Considerations
A typical application for the Analog-to-Digital converter in the LH75400/01/10/11 devices
is interfacing to a Touch Screen panel. Normally, this application requires filtering on the
inputs, and can be subject to ESD from users. It is recommended that ESD design precau-
tions and good board-design practices in general be followed for pins 89 through 96. An
example of a filter circuit that provides good ESD protection is shown in Figure 1.
The capacitors in this circuit should be ceramic, with a grade of X7R or better and rated for
50 Volts or higher. Designers should select capacitor values appropriate for their design.
For more information about suggested capacitance values, circuit, and layout recommen-
dations, refer to the appropriate sections in this chapter.
TO SoC PIN
C1
0.047 µF
GROUND (VSSA)
Figure 25-1. ESD Filter Circuit Example
6/17/03
TO TOUCH
SCREEN
ANALOG
LH754xx-99
25-1
Advertisement
Table of Contents
