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61 Threads found on Startup Bandgap
Hi Guys, I have a concern on the bandgap start up circuit design. I understand the need of a start up circuit in the bandgap design. But I'm not very sure, or need your feedback on the simulation outcome that Im observing. With the startup circuit added, the bandgap core output voltage is able to settle around 150us when (...)
This is your fundamental "box" for designing startup circuits. The startup current needs to be large enough to boot the loop in the worst case, and it needs to be low enough to not bother the loop setpoint in the "best" case. PVT can make this a thread-the-needle exercise especially if you want to stay simple (like diode-steered resistor pullup)
I would suspect that the Schmitt threshold is too close, but on the wrong side of, the bandgap output voltage and yet the startup circuit cannot be removed without the bandgap core collapsing. The startup looks too simple to me. Start with breaking that feedback loop and see where the startup can be removed (...)
You could start with just what "didn't work" means. A result you didn't like, or failure to produce a result at all? bandgap / PTAT loops without explicit startup mechanisms, can easily converge in one testbench and fail in another, because when they start up they're doing so on "numerical noise" which depends on the circuit matrix and algorithm
Add some deliberate leakage (a very low current source or large resistor) to prevent it starting. Then add the startup circuit and check it does start. You may be able to do it with "initial conditions" although I usually add deliberate leakage. Keith
The problem with all capacitive-based startup circuits is that it's not robust. You may have to simulate not only slow startups, but also brownout conditions. It may give a lot of headache if you have very strict criteria on your bandgap startup.
Hi Guys: I am working on a bandgap circuit for a internal regulator in a DC-DC converter. The core circuit is a simple BROKAW bandgap circuit and i need a startup circuit for it.The problem is the input voltage is from 5~23 and the high voltage MOSFET my process provide have a max Gate-Source voltage(Vgs) of 5,while the max (...)
this architecture is bad for low voltages. I like it since it is reliable. In your case you probably will have a bit high current through startup circuit - but you can fix it. Temeperature coefficiant - you can try to play with 1:n ratio. I noticed in my case that if I use usual 1:8 or 16, it does not work well so I went to 132 and made my own bipo
Node setting is cheating, and if your circuit requires cheating to work in simulation you will be busted in the real world. If your results are way off then suspect a startup problem. If slightly off, suspect a floating or unrealistically high impedance node somewhere that plays with the accuracy difference between tran and dc.
Will the bandgap ref work well if I add 2 cap and 2 res in the circuit? startup without any problem? stability for work?
Hi all, Could someone help me with the startup problem in my bandgap circuit? I have startup problem for lower temperatures .i.e if i simulate ckt for weak -40. I get output waveform as attached .. Thanks in advance rampat
hi all, i wanna do some research about the startup circuit of bandgap, please help me 1:how to analysis the numbers of the stable operating points of the circuit. as far as i know, some bandgap circuits have 2 stable operating points, some circuits have 3 stable operating points. I wanna know are there some methods to count the number
Hi All, I have a bandgap reference circuit, which works fine in simulation. (Both DC temperature sweep and transient sweep give satisfactory results.) As this is my first fabrication, I am a bit concerned about the start-up and also the stability of the circuits. startup the startup circuit I used is the one based on capacitor. (...)
hi. id like to know the causes of output fluctuations of a bandgap with startup circuit..and how to solve this problem. what are the things to consider when designing startup circuit for a bandgap?like do i need long channel device or minimum length. how to design W/L for a startup circuit? is there a (...)
Hi For 1.5V supply I would not use the classical bandgap approach The classical approach will show some serious problems in the low-temp/slow corners, especially during startup ... Look out for some papers about low voltage bandgaps. The basic idea there is, that you add a ptat and an iptat current. THis current is injected into a (...)
It is ~ 1.2 V typical reference voltage for conventional bandgap. Try to adjust your circuit to reach this value. In other words, you should get good Vref vs. Temp characteristic. Typically it obtained at ~1.2 V value of Vref for conventional bandgap. Well the truth is that my result is far from 1.2 value. At this sch
In your LDO, the reference voltage could also took from the BG output to further improve the PSRR. But some effort must be made to avoid startup problem in this configuration.
Hi this bandgap the startup circuit works fine untill I apply an offset (vos) to the opamp. With a positive offset, all it's ok but witha negative one the loop becomes open! Why does it happen? Any suggestion to avoid this bad behavior, please? TIA, CBs
Touching V+, V- nodes for startup is not recommended. A small offset current at V- could provide drastic change in curvature. This method also involves startup loop and you need to be careful that the startup current does not go on-off at steady state. The other minor problem is the lowering of supply rejection. The standard method is to (...)
hi, would you pls suggest a startup circuit for Conventional BGR,which consumes less current(in nA) and improves the response of the bandgap? Thanks