Choose Switching Regulator for Telit GM862-GPS module...
Choose Switching Regulator for Telit GM862-GPS module...
(OP)
Hi I want to use a step down regulator from 9 Volt battery to 3.8 Volts of GM862-GPS module of Telit. I have looked at maxim's regulators but I can't figure out which one is more suitable for the GSM. I want a regulator as simple as possible (with one DC output).....
Thanks in avanced :)
Thanks in avanced :)





RE: Choose Switching Regulator for Telit GM862-GPS module...
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Choose Switching Regulator for Telit GM862-GPS module...
Required output power.
Max input line change.
do you need isolation.
are you over 50watts in output power because if so then you need some PFC too.
but to me (if its low power) it sounds like a really easy job for an 8-pin voltage mode controller with perhaps some way for over current limit too.
or if you wanted better efficiency you could go for a synchronous buck controller IC.
its nice to have soft start
also UVLO.
If you want really really cheap and low component count then go for the TL497. This is also really easy to use...though the on-chip transistor is not fit for mega high frequency and only does i think 500mA.....but you can use it with external circuitry for higher powers as on the datasheet
I'm not sure whether or not it uses voltage mode or current mode control....but actually i think (suspect) its a hysteretic controller because it works in burst mode.
RE: Choose Switching Regulator for Telit GM862-GPS module...
Vout(3.4-4.2Volts), Iout max = 2A, and switching frequency at least 500kHz, but those I find have so many other characteristics that I get confused! I am new with all this ;)
RE: Choose Switching Regulator for Telit GM862-GPS module...
What I used successfully was a Linear Tech LT3481, and programmed it for about 1.1 MHz. Had to be careful selecting the inductor as many high-current SMT inductors are not designed for the frequency (mainly a skin-effect and wire-size issue).
Between National, Maxim, TI, Linear Tech, Micrel, and others, there are lots of choices in switching regulators which can get you confused as to which one is the "BEST" choice. What I used may not be the best for your application, but may provide another one for you to look at.
RE: Choose Switching Regulator for Telit GM862-GPS module...
htt
However in the datasheet only the inductance and the Rated DC current are specified. The SRF (self resonance freq)is not mentioned. Should I suppose that it is ok for the 800Khz I'll use?
RE: Choose Switching Regulator for Telit GM862-GPS module...
Power inductors generally don't list a SRF. This is usually done only for inductors used at RF. I quickly searched for an example, and came up with this:
http://specfinder.delevan.com/pdf/sds130.pdf
The part is only an example. Note that the test frequencies for the data are in the range you will be switching at. I don't know if the value or current capability are suitable for the LT part - I took a guess to get a part in the ballpark.
RE: Choose Switching Regulator for Telit GM862-GPS module...