FS8500 VPRE Gate Voltage Needed

[sathishraja17]

Hi Team,

We are trying to simulate the VPRE Voltage of PMIC FS8500.

We are in-need of the Gate voltage, Rise/Fall time and duty cycle of High side and Low side of PRE-GHS and PRE-GLS.

The supply is driven through external MOSFET's.

Thanks and Regards,

Sathish

[JozefKozon]

Hi Sathish,

please see below an answer from the application team and please find the file mentioned attached.

DESCRIPTION
 

The Rise/Fall time of HS or LS MOSFET is not fixed.

Customer can use attached tool to evaluate the switch time of HS and LS MOSFET. 

They can use the ratio of output and input voltage as the basic value for the duty cycle. And they can consider a dead time about 15-20ns.

With Best Regards,

Jozef

[sathishraja1]

Hi Jozef,

Is there any bootstrap circuitry that is used for driving the gate pin,because there is a pin "PRE_BOOT".

If so kindly do provide details regarding the gate drive circuitry.

Thanks,

Sathish

[JozefKozon]

Hi Sathish,

for the connection of the PRE_BOOT pin and for external components used, please refer to the Figure 42. in the FS84/FS85 datasheet and to the KITFS85FRDMEVM schematic. 

With Best Regards,

Jozef

[sathishraja1]

Hi Jozef,

I meant the Internal Boot strap circuit.PRE-BOOT pin internal circuit.

Does it have any diode to charge the capacitor? and to which supply is it connected..

PFB snapshot from datasheet.

Thanks and Regards,

Sathish

[JozefKozon]

Hi Sathish,

another customer had similar question regarding the PRE_BOOT and PRE_SW internal connection. Please see below an answer to him from an application engineer.

DESCRIPTION

PRE_SW is input and monitor source voltage of external High Side FET for internal bootstrap circuit.

PRE_SW is a reference internally, to work together with PRE_BOOT.

Then they can generate a high voltage to turn on HS MOS.

So PPRE_SW is just a node for internal circuit.

With Best Regards,

Jozef

[sathishraja1]

Hi Jozef,
It would be better if it's possible to provide us the high voltage value (internal) to turn on the HS MOS.
Because we are doing a Conducted emission Simulation of the circuit for which we need the approximate gate drive of the internal circuit.

Regards,
Sathish

[JozefKozon]

Hi Sathish,

for the BUK9K52-60E dual MOSFET used on our KITFS85SKTEVM the required Vgs voltage is 5V.

Maximum allowed VGS value is +/-10V.

With Best Regards,

Jozef