R2J20701NP_08 RENESAS [Renesas Technology Corp], R2J20701NP_08 Datasheet - Page 16

• Manufacturer Part Number: R2J20701NP_08
• Description: Peak Current Mode Synchronous Buck Controller with Power MOS FETs
• Manufacturer: RENESAS [Renesas Technology Corp]

R2J20701NP
REJ03G1459-0400 Rev.4.00 Jun 30, 2008
Page 16 of 27
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 π × Co × RCS × A0) ……(5)
F0 = 18500 / (2 π × 600 µF × 750 Ω × 12.674) = 516 Hz
Fzero = 10 × F0 = 5.16 kHz
Cf = (2 π × Fzero × Rf)
=
=
= 12.674
SQRT {70.687}
SQRT {Vin
SQRT {12 V
A0
Power stage and modulator
106.56
20 dB/dec
2
2
2
8
2
8
Nt / RCS
L
18500 / 750
F0
–1
360 nH
= (2 π × 5.16 kHz × 62 kΩ)
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
(0.172 V
W/ error amp. compensation
Af
–1
Asw
500 kHz
20 dB/dec
= 497 pF
18500 / 750 ) }
Fsw
(3)
BW/Af
Error amp. unity gain
frequency
BW
Freq. (Hz)