Schematic question and confirmation, value 0.1, value 0.1 about DK-TM4C123G

Hello Chris,

First of all TI EVM's and LaunchPads are only meant for evaluation and not meant for production systems. So there can be capacitors and resistances or some components that may not be fully populated/designed for. With respect to the specifics

1./ PAGE 1, on the extreme left there is a single capacitor alone named C2, is it a decoupling capacitor ? or what is it doing alone here ? where should it be placed on the PCB layout (close to a pîn in particular) ?

>> C2 seems to be a decoupling capacitor for the JTAG connector's 3.3V reference voltage.

2./Still on page 1, I see on the JTAG, the signal EXTDBG it goes to the bus for debugging but I don't see on which pin it is landing on the MCU

>> The DK-TM4C123G uses a TM4C123GH6PM for debugger. The EXTDBG pin is sensed by second micro to see if an external debugger is used. Again note we do not provide the binary for the on board debugger.

3./ On page 2 there is the CAN transceiver, on the schematic it got only one cpaacitor on VCC. however if you look at the datasheet of this component here on page 25, you find out a layout that indicate several other capacitor and resistor to add around the component. Can you confirm the schematic of the DK is proper ?

>> Please refer to the start of my post on EVM's and LP.

4./ Page 2, on the micro SD card area, there is capacitor C5 which is also isolated from any connection, can you please clarify the use of this capacitor and the position on the layout (is it supposed to be close to VDD ?)

>> This is a decoupling cap for the SD Card

5./ Page 3, two converter 5V to 3V and 3.3V are used , one is U8 and one is U5, they seems to do the sames things, why using two, and not only one ? Can you also confirmed they are used for power the circuit from a 5V usb power port ?

>> The U8 component is for 3.3V supply to the MCU;s. The U5 is used for Analog reference voltage

6./On all pages, there are some square pin named H? can you confirm those are test point ?

>> They may be test point or header pins as per the application

7../ On page 3, on the right there is U15. I don't understand the use of it., I have read this : but I don't see why we use this.

>> It is used as a current measurement circuit.

8./ PAGE 3, there is a whole line of decoupling capacitor, they have different value. How do we know which capacitor should go on which pin ?

>> Please refer to the System Design Guidelines for TM4C123x device class.

9./ PAGE 3 there is resistor R34 value 0.1, can you confirm the value and unit ?

>> It is used as a current sense resistor.

10./ I have difficulties to understand what is the differences using ICDI vs JTAG. Is it just the fact that we can use USB port to load firmware into the chip that make it different with ICDI ?

>> ICDI is the name of the on board emulator. It performs USB 2 JTAG. So any other JTAG emulator that supports Cortex M4 should be good.

Regards
Amit

Hi Amit, 

Thank you for your detailed answer.

A few more questions however:

1./  once our schematic is achieved and reworked, who can help us to review this schematic for potential mistake reviewing ?

2./ You mention the DK and EVM are meant for evaluation. However what else can we use to build our schematic as reference design appart the 1500 pages guide on the TM4C123G which doesn't give a global view (IMO) of the circuit.

i don't see any other document as well documented to design a schematic and PCB than the DK and EVM who are already design who are stabilized and proved to be functionnal.

So, I don't see what else we could get inspired from. The typical technic for PCB designer is to reuse what is existing and normally supplied by chip manufacturer as being stabilized (DK, EV etc...). We need to start from something 

3./ Can you recommend which programmer can be used for JTAG purpose programming with this chip ?

Rgds

Hello Chris,

1./ once our schematic is achieved and reworked, who can help us to review this schematic for potential mistake reviewing ?

>> I guess someone in your organization who can the schematic and layout v/s the System Design Guidelines

2./ You mention the DK and EVM are meant for evaluation. However what else can we use to build our schematic as reference design appart the 1500 pages guide on the TM4C123G which doesn't give a global view (IMO) of the circuit.

>> There are other evaluation designs from 3rd party like MikroE.

i don't see any other document as well documented to design a schematic and PCB than the DK and EVM who are already design who are stabilized and proved to be functionnal.

So, I don't see what else we could get inspired from. The typical technic for PCB designer is to reuse what is existing and normally supplied by chip manufacturer as being stabilized (DK, EV etc...). We need to start from something

>> True, but the first design always needs to be a full grounds up work.

3./ Can you recommend which programmer can be used for JTAG purpose programming with this chip ?

>> Quite a lot. You may use XDS100. XDS110, etc

Regards
Amit