Why there is some bulk current flowing?

[mvj]

Hi All,

The DAC in the image is drawing current from the bulk during switching from one level to the other. Can somebody pls tell me why this is happening and help me solve this problem.





Here are more details about the problem.
Process Used: AMS .35 High voltage CMOS process
Vmax = 27Volt - this is the voltage referece given to the DAC
Switch : PMOS switches, OFF = 27V, ON = 9.5V
Bulk voltage of all the switches = 27V

Bulks of all the PMOS switches are at 27V and none of the drain/source terminals are above 27V at any point in time, making sure that the drain/source to bulk diodes are always reverse biased. In such a case, why is there some bulk current flowing. Please help me out.

Thanks a lot in advance!!

Best Regards,
M

 

[leo_o2]

In many high voltage processes, there is current leakage in bulk.
Also bulk capacitance will lead to switching current leakage.

 

[mvj]

Thank you very much leo_o2.

Can you please explain what you mean by bulk capacitance causing switching current leakage? Also, is there a way to reduce this leakage current?

Thanks a lot in advance!!
M

 

[leo_o2]

Bulk capacitance needs to be charged and discharged. So there will be switching current.
It might be hard to reduce it.