Proper input/output bypass capacitors?

LDO regulators can be kind of unforgiving sometimes.  I've had
issues with LM2931 based circuits due to incorrect bypassing.

400 mA does seem a bit high for Iq.  Have you looked at the
output on a scope to see if it's wildly fluctuating or something?

Mike H.

On Wed, 10 Nov 2004 10:08:09 -0800 (PST), alan smith <> wrote:
> Looking at a Fairchild FAN1589, its a 2.7A LDO, 1.2V
> out device.
> 
> Given the formula in the datasheet that Pd=
> (Vin-Vout)*Iout, I have a 3.3V source, 800mA load.
> 
> In calculations then, it comes out to be 1.68W
> dissipation.  Not too bad.  So given that the load is
> 0.96W, adding the Pd gives about 2.64W.
> 
> All this is being done to calculate the load for the
> source supply...so I would imagine 2.64W or 800mA.
> 
> Well, one never to trust calculations always I wired
> it up and what did I find...1200mA or nearly 4W being
> pulled on the device.  Pretty far off for just a error
> in mesurement.
> 
> Am i missing something in my analysis?
> 
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