Electronic Component Distributor. Source::Texas Instruments
P.N:LM98640CVAL Desc:EVAL BOARD FOR LM98640
Web:http://www.hotenda.cn E-mail:[email protected] Phone:(+86) 075583794354
3.0 Functional Description
The LM98640CVAL Customer Evaluation Board
schematic is shown in Section 4.
3.1 Power Supply Connections
The power supplies on the LM98640CVAL
Customer Evaluation Board are configurable to
provide several options in powering the AFE
and other devices on board. There are two main
supplies for the device, +3.3V and +1.8V. The
sources for these supplies are selectable by
setting jumpers JP6 and JP7.
The default power configuration for the
LM98640CVAL Customer Evaluation Board is a
5V supply connected through the JR1
connector. The +3.3V and +1.8V supplies are
generated from this +5V supply using on board
regulators.
The user also has the option to use external
+3.3V and +1.8V supplies through the JR2 and
JR3 connectors.
The third option will allow the ex3.3V
supply to be sourced from the data output
HMZD connector. This configuration allows the
WV5 board to supply power to the
LM98640QML without the need for any other
external supplies.
Power for the optional analog input emitter
followers is derived from the Vext supply only.
This allows the emitter follower to be powered
up to 18V to allow signals from a CCD Sensor
with a high voltage range.
Power for an onboard pseudo CCD signal
generator is supplied by the ex5V and -
5V connections.
The polarity of the external power supply
connections are shown below.
3.2 AFE Analog Input Section
The Analog signals for the LM98640CVAL
Board enter through SMA connectors and there
are a variety of options onboard to modify or
condition the input signal to meet the
specifications of the LM98640QML analog
inputs.
Signals can be AC coupled using capacitors C2
and C5, the bias point for the AFE side of the
AC coupling capacitor can be set by using the
internal CLPIN features of the AFE or by using
the onboard resistor divider of R18, R19 and
R20, R21.
Signals can also be driven DC coupled and can
be 50
Ω
terminated near the SMA or near the
AFE input. Signals can also be filtered using
capacitors C43 and C44.
For signal sources that cannot drive a 50
Ω
load
an onboard emitter follower can be used. The
emitter follower has a dedicated supply through
Vext (JR5) and can be powered up to 18V.
A pseudo CCD signal generator can be used to
create a custom CCD signal for test and
evaluation purposes. The pseudo CCD signal
generator takes two signals and switches
between them based on the input clock. These
two signals can be set to create a CCD
waveform with a fixed reference level and
varying video level. The pseudo CCD signal
generator is powered from the +5V and -5V
supply connectors (JR1 and JR2).
The VCLP voltage signal can be supplied from
SMA J103 or generated by the internal VCLP
DAC of the AFE. If using the external VCLP the
user must ensure the internal VCLP DAC is
disabled. The VCLP signal can be externally
tied to the OS
X
+ pins using jumpers J40 and
J41.
To enable or disable any of these circuits the
appropriate solder bump jumpers must be
opened or closed. Refer to the Analog Input
schematic on sheet 2.
Figure 2. External Power Supply Connections
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