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Effects of bond wire on LDO design

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Q

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I am designing on chip LDO.
Is it fair enough in circuit simulation to model the bond wire by a sires inductor then followed by the pad capacitance, knowing that I have only pads models in my PDK(0.13um) ?

Also which pad is used for my case(input voltage could reach 3V )? And what value is suitable for bond wire ?
 

Bond Wire

Bond wire normally affects high frequency circuits. For LDO, I don't think it is important.
 

Re: Bond Wire

I think the bond wire inductance and pad capacitance will determine the fastest variation in input voltage & so determines if the PSRR of the designed LDO is adequate at that frequency or not.

please ,if I am wrong correct for me.
 

Bond Wire

What do u mean by the input voltage? The Power Supply of LDO?
 

Re: Bond Wire

The bond wire inductance only have effects at high frequency.at GHz,it is about 1nH/mm.
 

Bond Wire

Bonding wire will have little influence for LDO high frequency characteristic but usually will degrade load regulation.
 

Re: Bond Wire

leo_o2 said:
Bonding wire will have little influence for LDO high frequency characteristic but usually will degrade load regulation.
Click to expand...
Do you mean this for off chip cap LDO ? Or in general ?
If in general ,please explain .
 

Bond Wire

Normally, bond wire length ~ 1-3 mm, and its inductance ~ 0.8 * (length) nH
 

Re: Bond Wire

I have a related question.

How to determine the length and width of the pads?

and in case of designing ldo (with thick oxide transistors) is an ESD used or just directly the bond wire connected to the pad and the pad to the ct ?? (what I know is that ESD is used for all cases?)
 

Bond Wire

I think the bandwidth of LDO is small. The L(banding wire) C(output capacitor) is far beyond it.
 

Bond Wire

the bondwire might start effecting ur circuits around 100Mhz if ur caps of the LDO are not so small. Be aware of ur PSRR > 100Mhz
if u want to use the LDO as a power supply of analog circuits.
 

Re: Bond Wire

u only need worry bondwire for high speed design for LDO not tht crucial
 

Re: Bond Wire

Would by any chance this bondwire be close to other bondwires connecting high freq I/Os. In that case magnetic coupling effects may have an impact especially in the high freq circuit. I think that you should basically worry about the magnetic coupling of this bondwire with other bondwires in the chip...

--pad
 

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