Texas Instruments DS125DF111EVM, User Manual

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HIGH
SIGNAL
RESISTOR
SIGNAL
LOW
4-LEVEL CONTROL
HIGH RESISTOR FLOAT LOW
PIN HEADER CONNECTION
Setup
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6 SNLU158A – January 2014 – Revised January 2016
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DS125DF111EVM Evaluation Board
5 Setup
This section describes the jumpers and connectors on the EVM as well as how to properly connect, set
up, and use the DS125DF111EVM.
The DS125DF111EVM can be used in three different modes:
1. Pin Control Mode – provides access to selected signal integrity settings.
2. SMBus Slave Mode – provides full access to signal integrity and control settings.
3. EEPROM Mode – provides full access to signal integrity and control settings. EEPROM mode is a
convenient method of programming one or more DS125DF111 devices on system power up when an
SMBus master (microcontroller or similar) is unavailable in the design.
This EVM and documentation focus on Pin Control and SMBus Slave Mode to highlight the ease-of-use
and excellent low-jitter performance of the DS125DF111.
5.1 Pin Control Mode
In Pin Control Mode, the external control pins on the DS125DF111 are used to configure the signal
integrity and control settings of the device. In this mode, only a subset of the VOD and de-emphasis
(DEMA/B) levels are available. Due to the limited number of control pins, a limited bandwidth 4-level input
scheme has been implemented across the control pin interface. This allows for improved DE and VOD
control with fewer physical pins.
The four levels are defined below:
Table 1. Four-Level Logic Settings
Level Input Pin Setting
Low - 0 1 k Ω to GND
Resistor - R 20 k Ω to GND
Float - F Open
High - 1 1 k Ω to V
DD
The EVM interfaces to this 4-level I/O using the setup in Figure 2 . Only one shunt connection is required
to access any of the four levels. This methodology minimizes the risk of improper connections that could
damage the board or board power supply.
Figure 2. 4-Level I/O Control on DS125DF111EVM