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Tejas_P_R
Associate II
September 20, 2023
Solved

LD1086DT33TR Dropout voltage query

Hi Team,

We are using LD1086DT33TR regulator to generate 3.3V output from 5V input, But the the maximum dropout voltage given in the datasheet is 1.5V.Our dropout voltage is 1.7V (5V - 3.3V =1.7V) which is exceeding the max dropout voltage of the IC mentioned in datasheet ,My question is whether this IC is suitable for our requirement or we need to look for alternative.

Regards

Tejas

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Peter BENSCH
Peter BENSCHBest answer
ST Technical Moderator
September 20, 2023

Hi @Tejas_P_R,

Unfortunately, you are confusing a few parameters about LDOs (Low-Dropout Regulators): the dropout voltage is the difference between the input voltage and the output voltage. The LDO needs at least this dropout voltage to be able to regulate the output voltage. And for the LD1086 this minimum dropout voltage is typically 1.3V, but can go up to max 1.5V.

In the case of the LD1086DT33, the target output voltage is 3.3V, the input voltage according to your specification is 5V, which results in a voltage difference of 1.7V, which is easily above the required dropout voltage (1.7V > max 1.5V). In your case, the LD1086DT33 can regulate perfectly, even if the input voltage drops to 4.8V.

Clearer now?

Regards
/Peter

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6 replies

AScha.3
AScha.3
Super User
September 20, 2023

take another.

need 1,5A really ? maybe this:

https://www.mouser.de/ProductDetail/Diodes-Incorporated/AP7362A-33SP-13?qs=M%2FOdCRO8QQ3CiX1oDLy5Bg%3D%3D

if 1A is ok, take any ...like this:

https://www.mouser.de/ProductDetail/Texas-Instruments/TLV1117LV33DCYR?qs=tEz3BkPb1rwzXMb8FiWhow%3D%3D

 

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Tejas_P_RAuthor
Associate II
September 20, 2023

Hi AScha.3,

 The suggested part is also having a low dropout voltage so it is not meeting my requirement,(VIN=5V,VOUT=3.3, I=1.5A) Dropout voltage should be 1.7V or greater. 

Vincenzo
Vincenzo
ST Employee
September 20, 2023

Hi Tejas_P_R,

you are in good position, the dropout value is the minimum input voltage difference from output voltage and input voltage to guarantee the electrical specification of the DS. Just in case you need to pay attention to the power dissipation of the device in case you use the device with higher input voltage (in AMR table=30V). 3.3V on DS is obtained with 6.3Vin.

 

Best Regards

Vincenzo

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