USB Power Supply ripple - How much?

  • Thread starter Thread starter Alexandre Heil Franca
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A

Alexandre Heil Franca

Hi there!

I am building a device that should include a USB-Host. As a USB-Host, it must
supply 5V x 500mA. I am not able to find any reference about the max.
ripple for this power supply.
Does anyone could point me any reference? Does anyone know how much it
should be?

Thanks in advance!

Best regards,

Alexandre
 
Alexandre Heil Franca said:
Hi there!

I am building a device that should include a USB-Host. As a USB-Host,
it must supply 5V x 500mA. I am not able to find any reference about
the max. ripple for this power supply.
Does anyone could point me any reference? Does anyone know how
much it should be?

Thanks in advance!

Best regards,
Click to expand...
You might try downloading the spec listed here:
http://www.usb.org/developers/docs/
 
Hi there!

I am building a device that should include a USB-Host. As a USB-Host, it must
supply 5V x 500mA. I am not able to find any reference about the max.
ripple for this power supply.
Does anyone could point me any reference? Does anyone know how much it
should be?
Click to expand...

References should be linked somewhere on http://www.usb.org

I vaguely recall some figure like 100mA, but that might be
wrong. Ideally you should be able to do better than that,
if the supply is borderline then power smoothing could be
built into the device.
 
In comp.sys.ibm.pc.hardware.misc Alexandre Heil Franca said:
Hi there!
Click to expand...
I am building a device that should include a USB-Host. As a USB-Host, it must
supply 5V x 500mA. I am not able to find any reference about the max.
ripple for this power supply.
Does anyone could point me any reference? Does anyone know how much it
should be?
Click to expand...

If you use a 3-point 5V 1.5A regulator or an LM317T under normal design
parameters, you should be fine.

Arno
 
Hi, thanks,

Hmmm... I did not find any reference to ripple requirements in the spec.

Best regards,

Alexandre
 
Hi, thanks,

Hmmm... I did not find any reference to ripple requirements in the spec.

Best regards,

Alexandre
 
Hi, thanks for your answer,

I forsee a switching regulator to do the job. The reason for this is the
big dropout (5V from 12V). I can build a relative cheap switching supply
if ripple does not care, but once there is any severe requirement on
ripple, things get expensiver...
I really wasn't able to find any reference to this point at "www.usb.org".
I must still check, if for client-devices a power supply or supply bus
filter is mandatory. If so, there is no big problem on ripple.

Best regards,

Alexandre
 
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