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Non-Isolated DC/DC Forum
LM3481 Vcc range
I wish to use the shutdown facility on this device and wish to use the potential from the Vcc pin as the bias voltage but the data sheet does not specify a value for this potential, from the description I believe this to be around 6V, can you specify range and permited loading?
I would also like to know this, can some one at TI support please answer.
According the datasheet:
VSD - Shutdown signal threshold on FA/SYNC/SD pin:
Output = High (Shutdown) 1.31 typ
Output = Low (Enable) 0.68 typ
thanks for your response Albert, but Vcc is on pin 9 and is the LDO output, and not FA.
Well, the original question was to use Vcc as bias for shutdown. Thinking of it, I think it could not work because Vcc would also eventually dissapear (would it?) because of shutdown, and the output would oscillate.
I understand that what you want to know is the value of Vcc itself?
thanks Albert, you are correct, I am after the Vcc data only
Albert do you believe that Vcc is removed when the device is in shutdown? From the Functional block diagram Vin > 6V then Bias voltages are generated one of which is Vcc.
I wish to use Vcc to bias an optoisolator so that i can have an isolated stop / start control of the regulator.
As you can see in the data sheet (http://www.ti.com/product/lm3481 ) starting at page 2 pin descriptions in shut down mode the LM3481 only draw 5µA.On page 3 “absolute maximum Ratings” the FA/SYNC/SD pin is rated between -0.4V and 6V, which is the same as the VCC.Page 4 from the “electrical characteristics” the threshold is given for high and low under VSD which is typical for high (shutdown) 1.31V to a max off 1.4V and for low (enable) 0.4V to 0.68V, including NOTE 5 at page 5.Same information is also at page 11 of the data sheet including figure 9 and figure 10.
Vcc is off in the shutdown mode as all other outputs.
Hi Hans would you know what the maximum load current one can draw from the Vcc (pin 9)?
there is no information available about the maximum output current for VCC, but you can go to the online product folder from the LM3481 and then use WEBENCH for a design.
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