WEBENCH® Tools/TPS82140: What will be the max output current at -1.7v Output?

Hi KPK,

Thanks for sharing your schematic.

I see EN is connected to 3.3V, whereas Vin is 5V. Please prevent the condition that 5Vin goes away and 3.3V is still present. This will violate the abs max rating of EN and damage the device. If you just want to turn it on, connect EN directly to 5Vin.

As well, we recommend 88uF of output cap nominal. Therefore, you need about 20uF more at your load's input.

Where does the -0.9V come from? The FB pin is regulated to -0.8V.

How much output current do you need? The design guide at the TIDA-01405 link you shared discusses this topic in section 1.4.3. The output current is limited mostly by stability and thermals than the current limit circuitry. If you need 2A output current, please use the higher current TPS82130.

Webench does not support simulations of this device as an inverter.

If you need 1A or less, the TPS63710 is a more efficient and lower noise device.

hi Chris,

See my answer below: 

I see EN is connected to 3.3V, whereas Vin is 5V. Please prevent the condition that 5Vin goes away and 3.3V is still present. This will violate the abs max rating of EN and damage the device. If you just want to turn it on, connect EN directly to 5Vin.
-> In our design 5v is always ON. Only after the CPU system power up the 3.3v we want to enable the Regulator. So our system will never violate the abs max rating.

As well, we recommend 88uF of output cap nominal. Therefore, you need about 20uF more at your load's input.
-> We have about 200uF connected to -1.7v. They are placed on other schematic sections.

Where does the -0.9V come from? The FB pin is regulated to -0.8V.
-> The schematic text is wrong. It should be -0.8v

How much output current do you need? The design guide at the TIDA-01405 link you shared discusses this topic in section 1.4.3. The output current is limited mostly by stability and thermals than the current limit circuitry. If you need 2A output current, please use the higher current TPS82130.
-> TPS82130 order lead time is 1 year. So we want to see if TPS82140 can work in our application.
-> Nominal usage is -1.7v @ 0.1A. Peak Requirement is -1.7v@1.5Amps. Only for 6secs the current increases to 1.5Amps and then for next 60 secs it is 0.1A. 
-> Temperature of module should generally be very well within operating rage with our current consumption pattern.

Can I get a conclusive answer as to what is the max output current based on our configuration. From the design guide I am not able to conclude how much current TPS82140 can deliver. We need to know what will be the max current that TPS82140 can deliver based on our usage described below. This will also help us to know how much margin we are operating with.

Best regards,

kpk

hi Chris,

The TIDUCV2 figure 7 is target for TPS82130 but I am using TPS82140 which is 2A rating. 

Can I check if you can share the similar chart target for TPS82140?

Best regards,

kpk

Hi KPK,

The thermal and stability performance of all these TPS82130/40/50 are the same, so those lines are the same as well.

For the lower current versions, you will have an additional line defined by the current limit of the device. The maximum output current is the lowest of all these lines. Section 1.4.1 of www.ti.com/.../tiducv2a.pdf explains how to calculate the peak current.