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RE: DM 8148 EVM design

Viet Dinh
Genius 15310 points
FW to our forum.
 
Regards,
Viet
From: Saroor, Shaheen
Sent: Tuesday, July 31, 2012 10:07 AM
To: Wang, Wenbiao
Cc: Dinh, Viet; Taylor, Larry; Ramaswami, Nithya; Callsen, Gary
Subject: RE: DM 8148 EVM design
 
Hello Wenbiao,
 
Please see my response to your questions below.
 
Hi Shaheen,
 
Here are my answers for the below questions
 
1> In the EVM circuit schematic of DM8148, There are some coupling ceramic capacitors for the reference voltage of DDR3. See
the attachment(pullup capacitor.JPG). What is the purpose of those capacitors? Is this part of circuit(in blue ink) necessary? Can we remove them in our PCB?
 
These are decoupling capacitors for VREF_VTT. These are required to provide transient current demands (sink and source current). Yes they are part of the circuit, if not provided will cause noise in VTT line. At least 2 high frequency decoupling capacitors are required for each four pack resistor network.
 
2>There have so many integrated circuits (INA226AIDGSR) which are used for power monitor on the DM8148 EVM board.
What are their purposes? Can we remove them as well in our PCB? See the attachment(Power monitors.PDF).
 
These are used for measuring the current on the voltage rails. Can be removed if the current measurement is not required.
 
Thanks and Regards,
 
 
From: Wang, Wenbiao
Sent: Thursday, July 26, 2012 10:32 AM
To: Saroor, Shaheen
Cc: Dinh, Viet
Subject: DM 8148 EVM design
 
Shaheen,
 
One of our 8148 customers have a couple of questions related to their PCB design. Can you take look at them:
 
1> In the EVM circuit schematic of DM8148, There are some coupling ceramic capacitors for the reference voltage of DDR3. See
the attachment(pullup capacitor.JPG). What is the purpose of those capacitors? Is this part of circuit(in blue ink) necessary? Can we remove them in our PCB?
Shaheen> These are decoupling capacitors for VREF_VTT. These are required to provide transient current demands (sink and source current). Yes they are part of the circuit, if not provided will cause noise in VTT line. At least 2 high frequency decoupling capacitors are required for each four pack resistor network.
 
2>There have so many integrated circuits (INA226AIDGSR) which are used for power monitor on the DM8148 EVM board.
What are their purposes? Can we remove them as well in our PCB? See the attachment(Power monitors.PDF).
Shaheen> These devices are used for measuring the current on the voltage rails. They can be removed if the current measurement is not required.
 
 
Thanks,
Wenbiao