r2j20702np Renesas Electronics Corporation., r2j20702np Datasheet - Page 16

• Manufacturer Part Number: r2j20702np
• Description: Peak Current Mode Synchronous Buck Controller With Power Mos Fets
• Manufacturer: Renesas Electronics Corporation.

R2J20702NP
REJ03G1782-0401 Rev.4.01
Jun 17, 2010
Gain (dB)
Equation (3)
The frequency of the pole established by the power stage and modulator is
Thus,
Therefore, the frequency of the zero established by Cf and Rf is
Therefore, we select the value 510 pF for Cf.
Basically, the transient response is faster when Cf is smaller, but too small a value will make the system-loop
unstable.
A0 =
F0 = Nt / (2   Co  RCS  A0) (5)
F0 = 22000 / (2   600 F  750   15.092) = 516 kHz
Fzero = 10  F0 = 5.16 kHz
Cf = (2   Fzero  Rf)
=
=
= 15.092
SQRT {12 V
SQRT {70.502}
SQRT {Vin
A0
Power stage and modulator
126.72
20 dB/dec
2
2
2
8
2
8
Nt / RCS
L
22000 / 750
F0
–1
360 nH
= (2   5.16 kHz  62 k)
Vin
Open loop converter
Fsw
L
40 dB/dec
12 V
Vin
Fzero
(VCS0
360 nH
500 kHz
Fsw
Figure 4
Nt / RCS) }
12 V
(0.145 V
W/ error amp. compensation
Af
–1
Asw
500 kHz
20 dB/dec
= 497 pF
22000 / 750 ) }
Fsw
(3)
BW/Af
Error amp. unity gain
frequency
BW
Target Specification
Page 16 of 27
Freq. (Hz)