Specifications

68 Intel

Atom™ processor CE4100 Ref# 420826

Platform Design Guide

Intel Confidential

General layout design guide

• Dedicatedly isolated analog Ground reference plane is required for the whole VDAC

interface.

• Achievable shortest on-board VDAC trace length is preferred.

• All trace impedance is 55 Ω +/- 10% after the buffer/amplifier.

• Keep transmission lines as short as possible.

• Connect all the DAC grounds (analog) together by wide traces close to Video Buffer /

Connector.

• Do not place any extra stubs or probe points on the Video DAC section. Instead, use

component pads for any debug / probe purpose to minimize stubs.

• Place 37.5Ω Termination Resistor before and close to Integrated Filter/ Amplifier

• Shielding GND trace might be required for long trace length.

• Match / Balance All routing from the processor package bumps to Mini DIN 7 Connector

within 0.5”.

Split 75 Ω video termination into two series 55 Ω and 20 Ω resistors to match the board

transmission line (55 Ω) after the filter side and the rest (20 Ω) at the connector side. A

single 75 Ω resistor can be used if the board trace is less than 1”.

6.1.1 Video DAC Application Model Examples

There are two possible configurations for the DAC output: Active filter, and Passive filter.

Each of these is discussed below.

6.1.1.1 Active Filter Configuration

In the active filter configuration, a buffer/amplifier (Gain=2 with on-chip LPF) protects the

chip from any transients on the connecter/cable. This configuration requires 75Ω

termination at the TV.

This configuration is shown on in Figure 6-1. Leave the VDAC terminations set to their

defaul

t values of 37.5Ω and retain VBG_EXTR_VDAC at 1.1KΩ + 60.4Ω (1%) , as follows:

• VBG_EXTR_VDAC @ 1.1KΩ + 60.4Ω (default value)

• VDACOUTA_P @ 37.5Ω (default value)

• VDACOUTB_P @ 37.5Ω (default value)

• VDACOUTC_P @ 37.5Ω (default value)

• VDACOUTD_P @ 37.5Ω (default value)

Notes:

• This configuration has validated and the signal quality requirements are met with this

setup.

• The video buffer protects the Intel

Atom™ processor CE4100 from any current

transients on the connectors/cables.

• This can be recommended as a best possible configuration for customers.