about using IRSM005-800MH - newbie.. need help

[JINHOON]

Hi all,

it is first time using  IRSM005-800MH .

I encountered some trouble.

I have circuit like below.

what I'm expecting is high side FET turn on. and to see V_LOAD : 35V. with V_HGATE=50(=35+15)V

but , high side is not turned on at all. V_LOAD : 0V, with V_HGATE=0V.

I'm afraid , I'm taking something wrong using this device.

My purpose  is just to use  this device as  high side load switch.

please help me.

what I found is V_HGATE just follows VS level. no boost-up to enable gate of the FET.  whether HIN is enabled or not.

[AZIZ_HASSAN]

Hi,

Thank you for posting at Infineon community.

I understood your problem and I am sorry that you are facing this issue. 

There are few points I would like to highlight and request you to check the same.

1) Try to reduce the 10 ohm resistor and see whether its turning or not because internal switch is MOSFET and generally resistor needs to be of lower value.

2) Can you tell the boost capacitor value used by you. Did you do proper calculations as per your application switching frequency.

3) I request you to check once again the recommendations given in data sheet.

I hope this will solve your problem. If not please let me know with gate voltage waveforms and what value of voltage you have connected as per pin configurations.

BR,

AZIZ HASSAN

[JINHOON]

AZIZ, should I apply switching something?

I'm not using low side FET at all.. means LIN is stuck at gnd. 

in this case can I expect right operation of High side FET ?

if all the circuit condition is static condition  as shown in my figure. High side FET should be turned on or not?

I want to know what is right application . when I just want to use high side FET as a switch.

HIN is high. FET is ON.  

HIN is low(or gnd). FET is OFF.

it's all I need. ^^

* bottstram cap is 1uF as depicted

thank you...

JINHOON

[JINHOON]

AZIZ, should I apply switching something?

I'm not using low side FET at all.. means LIN is stuck at gnd. 

in this case can I expect right operation of High side FET ?

if all the circuit condition is static condition  as shown in my figure. High side FET should be turned on or not?

I want to know what is right application . when I just want to use high side FET as a switch.

HIN is high. FET is ON.  

HIN is low(or gnd). FET is OFF.

it's all I need. ^^

* bottstram cap is 1uF as depicted

thank you...

JINHOON

[AZIZ_HASSAN · Accepted solution]

Hi,

Thank you for your details as they helped me to understand your operation.

The top will not switch ON because you are not switching the bottom one. Since, the top switch source is at floating during turn off and when you turn on the top  the source of top goes to +DC voltage and you need to give +15v (gate) with respect to either floating or high voltage (+DC)source point.  There are two ways to switch ON the top switch in such cases-

1) If you are using bottom switch then you can use bootstrap capacitor to charge during bottom turn on and once it is turn off you can use it as high side gate supply in addition to 15 volt.

2) If you are not switching bottom switch, even though you connect a bootstrap capacitor , it will not charge and your top MOSFET or device will not turn on(because the top switch source is floating  when not turn on and when you turn on, the source is at +DC high voltage and with respect to that the gate voltage will be negative and hence top will not turn on. To avoid this we use bootstrap capacitor charging if not then we use isolated gate voltage). If you don't want to switch the bottom device, then in that case you need to give a isolated gate voltage to top( use a 1:1 isolation transformer) to switch on the top device.

I hope you understood.

BR,

AZIZ HASSAN

[JINHOON]

thank you AZIZ !

I fully understood.

I think misused this device for my application

JH