MSP430F5529: Clock configuration for USB application

Chirag Patel46

Prodigy 50 points

Part Number: MSP430F5529
Other Parts Discussed in Thread: MSP430F5528

Hello,

I am using MSP430F5529 launchpad for USB application.

Is it possible that i can run the USB application on 1.8V?

if yes then what are the clock configuration required to run USB application?

over 9 years ago

0 Ryan Brown1 over 9 years ago

TI__Guru**** 223787 points

Hello Chirag,

So long as the VBUS pin is supplied with 3.76 to 5.5 V then you will be able to suspend the USB with a VCC of 1.8 V. However USB operation with USB PLL enabled (as is necessary for USB commands) requires a PMMCOREVx value of 2 or 3 for proper operation which requires VCC to be greater than 2.2 V. The minimum processor frequency required for USB operation is 1.5 MHz, an external high-frequency crystal (HFXT) of 4 MHz is typically recommended.

Regards,
Ryan

0 Chirag Patel46 over 9 years ago in reply to Ryan Brown1

Prodigy 50 points

Hello Ryan,

Thank you for the reply.

I want to use USB operation with USB PLL disabled.

As per msp430f5528.pdf datasheet page no. 19 5.3 Recommended Operating Conditions

I am configuring PMMCOREVx = 0 to use USB application at 1.8V.

But as you stated " However USB operation with USB PLL enabled requires a PMMCOREVx value of 2 or 3 for proper operation which requires VCC to be greater than 2.2 V"

What is the meaning of proper operation here?

If i configure USB for 1.8V with USB PLL disabled Am I be not getting a Proper operations or what impact happens on USB operations?

Regards,

Chirag Patel

0 Clemens Ladisch over 9 years ago in reply to Chirag Patel46

Guru 327240 points

The PLL is required for USB. Without the PLL, USB will not work at all.

The USB connection already supplies 5 V power. Why don't you want to use it?

0 Chirag Patel46 over 9 years ago in reply to Clemens Ladisch

Prodigy 50 points

Hello Clemens,

Thanks for your prompt reply.
We have two scenario for USB operation of MSP430F5528 MCU :
1) AVCC & DVCC supply is 1.8V instead of 3.3V & USB PLL Enable.
2) AVCC & DVCC supply is 1.8V instead of 3.3V & USB PLL disable.

We just want to know if we apply the 1.8V supply for MCU, is it affect the USB Operation of MCU ?
As per datasheet, USB operation with USB PLL Disable is possible. You can refer the datasheet of MCU for the same. (Page 19, Block 5.3 Recommended Operating Condition)

According to datasheet we have set USB_EN = 1, UPLLEN = 0 and PMMCOREVx = 0 to operate USB at 1.8V.

Waiting for your reply.

0 Clemens Ladisch over 9 years ago in reply to Chirag Patel46

Guru 327240 points

The datasheet is misleading. The USB PLL must be disabled only when the host tells the device to suspend. This is a valid state of the USB system, but nothing actually happens on the bus; "suspended" is not really what you expect to be described as "USB operation".

0 Ryan Brown1 over 9 years ago in reply to Clemens Ladisch

TI__Guru**** 223787 points

Clemens is correct and I apologize that my response was misleading, you must supply at least 2.2 V for proper USB operation.

Regards,
Ryan

0 zrno soli over 9 years ago in reply to Clemens Ladisch

Guru 34983 points

Chirag Patel46 said:

I am using MSP430F5529 launchpad for USB application.

Is it possible that i can run the USB application on 1.8V?

Don't know about 5529, but I didn't found till today even one 550x sample, that was not able to work with USB, on default VCORE and 1.8V VCC.

Clemens Ladisch said:
The PLL is required for USB. Without the PLL, USB will not work at all.

Than this should be impossible, but it is working just fine. USB with bypassed PLL (48 MHz XT2).

http://forum.43oh.com/topic/3909-msp430f550x-based-logic-analyzer/#comment-69255

0 Clemens Ladisch over 9 years ago in reply to zrno soli

Guru 327240 points

USB with bypassed PLL (48 MHz XT2).

forum.43oh.com/.../

That just overclocks the CPU; it does not bypass the PLL.

0 zrno soli over 9 years ago in reply to Clemens Ladisch

Guru 34983 points

Clemens Ladisch said:

That just overclocks the CPU; it does not bypass the PLL.

PLL is bypassed. USB (CDC) is working. XT2 is 48 MHz (used as USB clock directly).

PLL can't work with 48 MHz XT2, because of dividers. Highest possible XT2 with PLL enabled is 32 MHz.

0 Clemens Ladisch over 9 years ago in reply to zrno soli

Guru 327240 points

PLL is bypassed.

How would it be possible to configure the USB module like this?

PLL can't work with 48 MHz XT2, because of dividers.

DIVQ = 16, DIVM = 16 would work just fine.

0 zrno soli over 9 years ago in reply to Clemens Ladisch

Guru 34983 points

Clemens Ladisch said:

How would it be possible to configure the USB module like this?

DIVQ = 16, DIVM = 16 would work just fine.

I asked here... https://e2e.ti.com/support/microcontrollers/msp430/f/166/p/268483/938004#938004

and there was no answer from TI, so I checked by myself. "Reserved input lines" are direct XT1 / XT2 connection to USB module.

About dividers, you are right.

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MSP430F5529: Clock configuration for USB application