Texas Instruments LV32EVK01 Evaluation Kit LV32EVK01/NOPB LV32EVK01/NOPB 数据表
产品代码
LV32EVK01/NOPB
DS92LV3241/3242 Evaluation Kit Users Manual Version 1.0
JP4,VR1: Pre-Emphasis Feature Selection
Reference Description
Reference Description
OPEN
(floating)
CLOSED
(Path to GND)
JP4
Pre-Emphasis – helps to
increase the eye pattern
opening in the LVDS
streams by providing current
boost
increase the eye pattern
opening in the LVDS
streams by providing current
boost
Disabled –
no jumper
no jumper
(Default)
Enabled –
With jumper
With jumper
JP4 &
VR1
VR1
Pre-Emphasis adjustment
(via screw)
JP1 MUST have a jumper to
use VR1 potentiometer.
VR1 = 0
(via screw)
JP1 MUST have a jumper to
use VR1 potentiometer.
VR1 = 0
Ω to 20 kΩ,
JP1 + VR1 + 12 k
Ω
(
R34) =
~12 k
Ω (maximum pre-
emphasis) to
~32 k
~32 k
Ω (minimum pre-
emphasis*).
I
I
PRE
= [1.2/(R
PRE
)] x 40,
R
PRE (minimum)
> 12 k
Ω
*Note: maximum is based on resistor
value. In this case ~32K
value. In this case ~32K
Ω
value is based
on the ~12k
Ω
fixed resistor plus ~20K
Ω
maximum potentiometer value. User can
use hundreds of k Ohms to reduce the pre-
emphasis value.
use hundreds of k Ohms to reduce the pre-
emphasis value.
Clockwise
increases
R
R
PRE
value
which
decreases
pre-
emphasis
decreases
pre-
emphasis
Counter-
Clockwise
Clockwise
decreases
R
R
PRE
value
which
increases
pre-
emphasis
increases
pre-
emphasis
Pre-emphasis user note:
Pre-emphasis must be adjusted correctly based on application frequency, cable quality,
cable length, and connector quality. Maximum pre-emphasis should only be used under
worse case conditions; for example at the upper frequency specification of the part
and/or low grade cables at maximum cable lengths. Typically all that is needed is
minimum pre-emphasis. Users should start with no pre-emphasis first and gradually
apply pre-emphasis until there is clock lock and no data errors. The best way to monitor
the pre-emphasis effect is to hook up a differential probe across the AC-coupling
capacitors for the (+) and (-) inputs of the LVDS channels on the DS92LV3242 Rx demo
board (NOT across the AC-coupling capacitors for the LVDS channels on the
DS92LV3241 Tx demo board).
Pre-emphasis must be adjusted correctly based on application frequency, cable quality,
cable length, and connector quality. Maximum pre-emphasis should only be used under
worse case conditions; for example at the upper frequency specification of the part
and/or low grade cables at maximum cable lengths. Typically all that is needed is
minimum pre-emphasis. Users should start with no pre-emphasis first and gradually
apply pre-emphasis until there is clock lock and no data errors. The best way to monitor
the pre-emphasis effect is to hook up a differential probe across the AC-coupling
capacitors for the (+) and (-) inputs of the LVDS channels on the DS92LV3242 Rx demo
board (NOT across the AC-coupling capacitors for the LVDS channels on the
DS92LV3241 Tx demo board).
National Semiconductor Corporation
Date: 9/28/2009
Page 8 of 34
Page 8 of 34