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Re: Start up of Bandgap
You just need to bias for the core of bandgap then using either Vbg compare with a VT or the current which generate by delta Vbe/R compare with an other current to finish start up. Thus either Vbg>VT or delta Vbe>I then you can release start up circuit.
Best
When both PMOS and NMOS shutdown, ideally there is no more energy in inductor but actually there is still little energy in inductor and this energy will make that ringing. To reduce it we can damp energy when both MOS are off.
The current of main stage will effect to the speed of the comparator. You need to consider your delay requirement? Actually 0.8uA is pretty small current for a fast comparator.
Delta V2 is differential pair offset and feed back ratio. differential pair offset base on loop gain. Loop gain is depend on output current. The higher output current the less loop gain so offset will be bigger thus delta V2 become bigger.
it is not effective if use 12V LDMOS tfor input 5V. Beside the area get big you will have more parasitic capacitance but it is not big deal. You can good buffer for EAMP.
Re: DCDC design issue
If you didn't see the external RC then it should be internal. For DC-DC we need to have compensation to make output stable. About feedforward compensation, that is adding one zero and one pole by adding a feedforward cap from out put to FB.
BR,
Re: 12V HB led driver
If you want to drive more 30 LEDs I think you should make 3 string of 10 LEDs in parallel instead of 30 LEDs in series. You can refer ACT6358 of Active-semi.Inc. It has 1A peak current limit. To make the current in each string match to each other, you need to use some...
ldo 24v input
If you realy want to use LDO at last stage for better performance you can you a pre-regulator- a switching regulator to step down from 24V/30V to 3.6V or 4.2V then use a LDO to get 3.3V.
gm constant biasing
My way to make constant gm is making gm mostly relate to resistance then by making very good resistance I got gm quite good. The chip is OK.
You can use PWL command in Spice to get different Iout at different time. Also you can use VCR ( voltage controlled resistor) then define the voltage controlled to get different resistor.
Hope it help.
hspice output
I have ever seen this before and I found that when a very small current flow through a big mosfet then Hspice will show it cut off. I don't know is that right in Hspice.
It is not that difficult. Just do a regulator that has output less than 5V to satisfy process. Also the regulator need to have enough current to supply whole thing inside. If you decided output voltage and output current capacity for regulator then designing that regulator will be easy. You can...
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