TPS61378-Q1: TPS61378-Q1

Hi Srijesh,

Srijesh Kumar said:

Q1)What is the Minimum Current requirement for EN pin?

EN is connected to the MOS gate in the internal circuit, it's not driven by current.

Srijesh Kumar said:

Q2)is there any impact in using High value resistor at EN pin?

In your application the 2.2MΩ is no need, EN can be connected to Vin directly.

Please note that the internal pull-down resistor at EN is enabled only when EN is low.

Regards

Lei

Hi Lei,

Thanks for the response

From TI: "Please note that the internal pull-down resistor at EN is enabled only when EN is low"

Q) Can you please confirm on above point?

We have done Measurements at Booster EN pin and following are observations.

       1)Irrespective of Booster Enable/Disable condition, there is no much change in EN voltage is observed

Please find the measurement waveforms,

-

-Zoomed Picture

So if internal pull-down resistor at EN is enabled only when EN is low, then EN voltage was expected to be Input voltage (According to our schematic design) when booster was in enable condition in above diagram, but it is not.

Please find the attached schematic design,

Also from Datasheet functional block diagram, there is a pulldown resistor at EN pin by default.

Please clarify on above point.

Hi Srijesh,

How do you disable the booster when the EN is still high? Pull down the Vin?

Regards

Lei

Hi,

Booster EN voltage was below 0.7 V, which according to datasheet is below Booster threshold voltage.

At Booster disable condition, EN voltage was around 0.67 Approx

Hi Srijesh,

Do you force a voltage (~0.67V) at EN pin (or at point TP783) and keeping Vin unchanged when disable the device?

Regards

Lei 

Hi,

Not like that.

Due to External 2.21M Resistor and internal 800K resistor, it is forming a voltage divider at EN pin.

So, when Vin (VBAT_INT in our design) reaches around 2.6 V, Voltage at EN pin will be less than 0.7V and booster is getting disabled.

Hi Srijesh,

Thank you for your information.

I just verified and confirmed that for the TPS61378-Q1, the 800kΩ pull down resistor at EN is always there! No matter EN is low or high.

Sorry for the confusion!

Go back to your original question:

Srijesh Kumar said:

Q1)What is the Minimum Current requirement for EN pin?

Again the EN is not driven by current. The enable/disable status is decided by the voltage on the EN pin.

Srijesh Kumar said:

Q2)is there any impact in using High value resistor at EN pin?

In your application the 2.2MΩ is no need, EN can be connected to Vin directly.

If using a high value resistor at EN pin, you will have the issue that even the Vin is above the UVLO, the device may be disabled.

Well, if a higher UVLO is specially wanted in your application, I suggest to use a external resistor divider to get a more accurate EN voltage from Vin.

Regards

Lei