AM1808 pin configuration and RESET signal

g.f.

Other Parts Discussed in Thread: AM1808

Hi,

I have questions about AM1808 pins and RESET.

Q1.
In AM1808 datasheet(sprs653e) page.58, there are following description for unused SATA_VDD.
//////////////////////////////////////////////////////////////////////
Prior to silicon revision 2.0, this supply must be connected to a static 1.2V nominal supply.
For silicon revision 2.0 and later, this supply may be left unconnected for additional power
conservation.
//////////////////////////////////////////////////////////////////////
My customer's AM1808 is rev2.1 and not using SATA.
All SATA signal except SATA_VDD are configured as listed in
"Table 3-31 Unused SATA Signal Configuration".
They are connecting SATA_VDD to CVDD(1.3V) via 0 ohm resistor.
Is there any problem connecting SATA_VDD to CVDD(1.3V) via "0 ohm" resistor?
If there are problem, can you tell the details of problem?

Q2.
In AM1808 TRM(spruh82a) page.1573, there are following description for USB0_ID.
//////////////////////////////////////////////////////////////////////
For OTG mode or device only mode of operation, do NOT connect the USB0_ID pin,
that is, leave the pin floating
//////////////////////////////////////////////////////////////////////
My customer are using USB0 as Device.
But they are connecting USB0_ID to 3.3V via 10k ohm.
By this connection, is there a possibility that a problem occurs?

And they are requiring CPU internal circuit around USB_ID pin.
Is it available? I guess internal circuit is not available to provide to the user.

Q3.
In AM1808 datasheet(sprs653e) page.58, there are following description for
unused USB1_DP and USB1_DM.
//////////////////////////////////////////////////////////////////////
VSS or No Connect
//////////////////////////////////////////////////////////////////////
My customer are connecting USB1_DP and USB1_DM to GND via 0 ohm resistor.
I understood that connecting to GND is okay, but is there a problem using 0 ohm resistor?

Q4.
OSCVSS pin are NC in my customer's board.
Is it okay? If there are possibility that a problem occurs, please let me know the details.

Q5.
During RESET(K14 pin) assertion, if this reset signal flaps in High/Low,
is there possibility that CPU malfunction?

best regards,
g.f.

over 10 years ago

0 Senthilkumar Srinivasan over 10 years ago

TI__Mastermind 43660 points

g.f,

1. Connecting SATA_VDD to power source should be fine for Rev 2.1, it would consume more power on that particular rail. However the nominal voltage for SATA_VDD is 1.2V only, when you connect this to 1.3V you may violate the maximum recommendation of 1.32V if the voltage fluctuates. Please ensure this.

2. You are suppose to connect the USB0_ID pin to voltage source. For device mode of operation, you have to leave pin floating. Else you may not expect the proper operation. Please follow the recommendations provided in data manual and TRM.

3. I presume you are using USB0 and not using USB1. In that case, yes, you can connect unused USB1_DP and USB1_DM to VSS/Ground. Using 0 ohm resistor should be fine.

4. What is the clock your customer are using ? Crystal oscillator or external clock input ? For crystal oscillator, you are required to connect OSCVSS to crystal as shown in figure 6-6 in data manual. For external clock input, you have to connect it to ground. If you are not following this recommendation, we are not guarantee for proper operation.

5. During RESET condition, the K14 pin should be in low state for the time mentioned in section 6.4.3 Reset Electrical Data Timings. If the condition is not met, the device may not initialized properly.

Regards,
Senthil

0 g.f. over 10 years ago in reply to Senthilkumar Srinivasan

Guru 15520 points

Hi Senthil,

Thank you for the reply.
I understood.

But sorry, let me ask again about the "Q5 Reset signal" to make me sure.
I want to ask about RESET timing requirement.
I wrote 3 cases about RESET timing in the attached file.
Can you please check the attached file?

best regards,
g.f.

AM1808 RESET.pdf

0 g.f. over 10 years ago in reply to Senthilkumar Srinivasan

Guru 15520 points

Hi Senthil,

Sorry, I have additional questions about AM1808.

Q6.
My customer are connecting USB_VDDA12 to GND via 0.22uF and FerriteBeads(200ohm, DC resistance=0.8ohm/Max)
for preventing the noise. The connection is : USB_VDDA12 pin - 0.22uF - FerriteBeads - VSS(GND).
But in the datasheed of AM1808, it said this pin must always be connected via a 0.22-μF capacitor to VSS(GND).
Is it okay to connect FerriteBeads?

Q7.
USB_REFCLKIN (A3pin) isn't used, so this pin is unconnected(NC).
In default setting, this A3 pin functions as "PRU0_R31[17]" which is input type IO.
Should they change PINMUX setting to GPIO(output) and left unconnected?
Or doesn't need to change PINMUX setting and just left unconnected ?

Q8.
In AM1808 datasheet page.58, there are following description:
//////////////////////////////////////////////////////////////////////////////////
If NMI is unused, it should be pulled-high externally through a 10k-ohm resistor to supply DVDD3318_B.
//////////////////////////////////////////////////////////////////////////////////
But I can't find NMI pin. Does AM1808 have NMI pin?

Sorry, for many questions. Please give me an anwser for Reset signal which I posted above too.

best regards,
g.f.

0 Senthilkumar Srinivasan over 10 years ago in reply to g.f.

TI__Mastermind 43660 points

g.f,

5. I do not have concrete answer for your RESET scenarios. As far as i know, the RESET signal should be held low right from power up and after clock stable for the specified time.

I am working on your other questions, will update you.

Regards,
Senthil

0 Senthilkumar Srinivasan over 10 years ago in reply to g.f.

TI__Mastermind 43660 points

g.f,

6. I don't see any necessity for ferrite bead. Only capacitor would be enough for decoupling.

7. If you are using PRU or other multiplexed functions, then you can configure this pin for that specific function. Else you can leave this pin unconnected without any configurations.

8. NMI pin is not available for AM1808.

Regards,
Senthil

0 g.f. over 10 years ago in reply to Senthilkumar Srinivasan

Guru 15520 points

Hi Senthil,

Thank you for the reply.
I understood.

I'm so sorry, I have additional question again.

In AM1808 PINMUX configurations, some pins can be selected as 3-stated pin.
If configured as 3-stated pins and it is unused pin(routed out),
can these pins just be unconnected?

If those pins are routed out, must they be pullup/down externally?

best regards,
g.f.

0 Senthilkumar Srinivasan over 10 years ago in reply to g.f.

TI__Mastermind 43660 points

g.f,

You cannot leave the tri-state pin unconnected for extended duration. The adverse effects of leaving tri-state pin unconnected are below.

At the intermediate voltage, the input buffer portion of the IO could draw excessive supply current from the IO supply (DVDD)
At the intermediate voltage, the input buffer could detect a transition multiple times due to noise and therefore will draw extra power on both core and IO supplies due to the multiple transitions.
At certain levels for a given unit (these will vary), very large current transients could be seen that could result in failures at the buffer.

If the pin has default tri-state and you are not configuring for any other function, it would be good to have a external pullup/down to have definite state.

Regards,

Senthil

0 g.f. over 10 years ago in reply to Senthilkumar Srinivasan

Guru 15520 points

Hi Senthil,

Thank you for the reply.
I understood.

By the way, even if the pin is not routed out and the pin is default tri-state,
should I also pull the pin externally?

In above case, I think I should configure the pin as GPIO output and unconnect the pin.

best regards,
g.f.

0 Senthilkumar Srinivasan over 10 years ago in reply to g.f.

TI__Mastermind 43660 points

g.f,

In this case, it would be good to have the pinmux to GPIO output and leave the pin unconnected.

Regards,
Senthil

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AM1808 pin configuration and RESET signal