Ugly 75L05C

All LDO regulators seem to like being heavily bypassed. Actually you should add a little more to supress oscillation at lower temps, Depending upon the type of bypass cap of course. Lytics are the worst.

Cheers

"Martin Riddle"

And the data sheet is very clear about the need for a 0.1uF bypass on the output.

.... Phil

Got a link to the datasheet? Or did you mean 78L05 ?

Ed

Larger Cout? Minimum recommended value please?

Sorry about that; it is the TL750L05C, and the TI databook does not make it clear that bypassing is required. All it states is "All characteristics are measured with a 0.1uF capacitor across the input and a 10uF capacitor, with equivalent series resistance of less than 1 ohm, across the output." . That large cap at the output undoubtely is a large reason for the low output noise spec...

Still, that large current draw before 5V is a bit nasty...and that

Yes, i goofed; it is the TL750L05C i measured.

There is a graph on page 6 showing stable unstable regions for ESR values.They recomend a 10uf tant cap esr greater then 0.024 ohms less then 0.4 ohms.

By the way that is a pretty sparse data sheet. They don't state whether it is a PMOS or BJT LDO. I'm guessing it is a PMOS because they link to this data sheet "Fundamental Theory Of PMOS Low-Dropout Voltage Regulators" in the product folder.

If you don't need the full 150mA capability you could look at the MCP1791T-5002E.

PMOS LDO well characterised in the datasheet fixed 5V out wide input range 6 to 30V,70 mA output,thermal and foldback protection.

Data sheet.

I just got some of these I'm going to be testing them today.

Me again forgot to add it's stable with ceramic caps :)

On a sunny day (Wed, 22 Jul 2009 19:03:23 -0700) it happened Robert Baer wrote in :

Never seen one used without bypasing. I use 10uF :-)

It's more than a bypass.

Did you read this paragraph?

"The TL750L, TL751L series are low-dropout regulators. This means that capacitance loading is important to the performance of the regulator because it is a vital part of the control loop. The capacitor value and its equivalent series resistance (ESR) both affect the control loop and must be defined for the load range and temperature range. Figure 1 shows the recommended range of ESR for a given load with a 10-uF capacitor on the output"

See the following graph illustrating the 'tunnel of death' characteristic typical of LDOs. Note that it is potentially unstable with a ceramic output capacitor (very low ESR).

Best regards, Spehro Pefhany

Is not that tpical of a bad design? 'This capacitor is too good for this chip' LOL

Of course you could always put an 0.025 ohm resistor in series with the output, and use any cap you like.

Cheers

Phil Hobbs

Really thin PCB trace of sufficient length?

That like driving on ice with the hand-brake slightly pulled because the traction control electronics don't work too good :-)

And I bet that range is not guaranteed data. On many of my projects I wouldnt' even be allowed to use something like that unless guaranteed. On all the others it would make me lose sleep at night so I just never use LDO chips.

I'm told the ABS brakes on some vehicles get fooled when one wheel is on a (slippery) wet manhole cover or streetcar track. In a bad way.

CHEAP systems!

...Jim Thompson

Page six in a one page spec? Where are you looking?