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SLG46517M PFET Power Switch

1 month ago

SLG46517M PFET Power Switch

Posted by Yuseungho 20 points 3 replies
0 upvotes

Dear,

I'm using the device SLG46517M which has two P-FET power switches. Now, I'm testing the device in emulation mode.

Here I attach my simplified design of the circuit.

The problem is that when the switch is off, the Vout node has too large spike and the spike discharges very slowly.

As a result, when it's off, it reaches almost twice the input voltage (~920mV with 500mV input). The load side now only has a fixed resistor which is 2Mohm just for test.

(I also attach the waveform)

When the switch is on, it outputs properly with the input voltage of 500mV.

As you can see, FSM(ASM) turns on OSC0 in GPAK when the condition is met, and the OSC0 triggers the PFET with 25kHz switching frequency.

I could not figure out what the problem is. I'd really appreciate if you could share your opinions.

Thank you.

Regards,

Seungho Yu

Attachment Size
simple circuit architecture 111.7 KB
oscilloscope waveform 223.86 KB

1 month ago

ssaravan

Hi Seungho Yu,

Thank you for reaching out. Could you please share your GPAK design file (.gp) so I can look into the problem?

Best Regards

Shivani

1 month ago

Yuseungho 20 points

Thank you for your answer.

Would you please tell me your email? 

Because the design file might be personal, I'd like to send you by email.

Thanks.

 

1 month ago

Yuseungho 20 points

I think the reason why the voltage discharges slowly is load resistor has too large resistance, which caused too high RC time constant.

I changed the load resistor from 2Mega ohm to 100 ohm, and find it shows reasonable waveform.

But I have another problem now. 

According to the datasheet of SLG46517M, PFET has minimum input voltage of 300mV.

But I found that to toggle the PFET on/off, input should be larger than about 700mV(experiment result).

When the input is larger than 300mV and small than certain value, PFET cannot outputs properly (different from that input voltage, around 50mV, almost no signal).

The design has not changed, it's same as before. 

Please tell me your email, then I would send you my design file.

I look forward to hearing from you.

Thank you.