How to design "current sense amp " in thr BUCK reg

[mitgrace]

Dear all:

Does any body know how to design ""current sense amp " in thr BUCK regulator , Now I use external Power MOS (PMOS and NMOS) . so that I don't how to detect the current ? and How to do the ramp compensation ?
Does anybody know that ? Any document ? Thanks

 

[andy2000a]

Re: How to design "current sense amp " in thr BUCK

please reading
bipolar an dmos integrated circuit design
10.9 switch regulator page 532 fig-10.33 show SG1524/3524
use current sense limit for output BJT device ...

another ua78s40 use series 0.3 ohms for current sense
if you use mos you can series resistor ..
as I know someone use Power MOSFET internal Rds ..
becuase power mos "ON" have 20~30m Ohm * 5A = 150mV ..
you can sense current ...

 

[mitgrace]

Re: How to design "current sense amp " in thr BUCK

Dear andy :
Thanks your comment , Actuall I use external PMOS and NMOS , so that I don't know where we can sense the current , Maybe lx , or Mos , But I don't have sense now , My specific is 3.3 to 1.8 Buck regulator , I am looging the PMOS/NMOS , Do you have any comment ? Thanks

 

[andy2000a]

Re: How to design "current sense amp " in thr BUCK

as I know , someone use split mos finger .. and use current-mirror for measure current ..

but I think use small resistor is easy way