lm2648mtd National Semiconductor Corporation, lm2648mtd Datasheet - Page 22

• Manufacturer Part Number: lm2648mtd
• Description: Two-phase, Synchronous Step-down 3-channel Switching Regulator Controller
• Manufacturer: National Semiconductor Corporation

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Component Selection
Zero1:
Zero2: (if R
fb2
>>
R
c2
)
(Continued)
22
PROCEDURE
The following procedure will create a 20dB/decade loop gain
roll-off. First set fz2 approximately one half decade above
fdp. Since this zero is set using one of the feedback resis-
tors, the output voltage may have to be re-adjusted using
Rfb1 after the compensation has been set. Also, the DC loop
gain will increase as Rfb2 decreases.
Next, set fz1 approximately one half decade below fdp.
Set fp2 to be equal to fzESR.
Finally, set fp3 to 150kHz (half the switching frequency).
Once the compensation has been set, the bandwidth can be
most easily varied by using Rc2 to shift fp2, or by using Cc2
to shift fp3.