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[SOLVED] LDO tps7a4701 not working as intended.

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jesuschrist

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Hi. For my LNA design I was using tps7a4701 as a regulator to supply DC voltage to circuit. I designed the pcb according to datasheet and used any-out option and it should give 4V all times. Now i get a variable output at the output of LDO. when i give Vin=3V, ı get Vout=3V and this goes all the way to 5.42 volts Vout caps at 5.42 V even if i increase Vin.You can see the soldering below.What could be the cause of this ? ti.jpg
 

Hi,

The circuit does exactly what it is supposed to do.

V_out = V_ref + (∑ ANY-OUT Pins to Ground)

Where V_ref = 1.4V (I assume you missed this)

You selected: 3.2V + 0.8V = 4.0V.
Thus v_out = 1.4V + 4.0V = 5.4V

***
You need to set ANY_out to 4.0V -1.4V = 2.6V
--> use ANY_Out: 1.6V + 0.8V + 0.2V

Mind: this is an LDO. It can´t increase voltage, just decrease.
If your input voltage is 3.0V then the output will be something below 3.0V


Klaus
 
thank you looks like i misunderstood the datasheet. Well i adjusted the resistor after Vdc from 10 ohm to 56 ohm and now it works.
 

Hi,

Well i adjusted the resistor after Vdc from 10 ohm to 56 ohm and now it works.
Click to expand...
Makes no sense for your posted problem.

Klaus
 

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