r2j20751np Renesas Electronics Corporation., r2j20751np Datasheet - Page 13

• Manufacturer Part Number: r2j20751np
• Description: Peak Current Mode Synchronous Buck Controller With Power Mos Fets
• Manufacturer: Renesas Electronics Corporation.

R2J20751NP
R07DS0240EJ0100 Rev.1.00
Jan 26, 2011
Gain (dB)
equation (3),
The frequency of the pole established by the power stage and modulator is
Thus,
Thus,
Therefore, we select 1500 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 = 13700 / (2   600 F  820   9.871) = 448.967 Hz
Fzero = 10  F0 = 4.489 kHz
Cf = (2   Fzero  Rf)
=
=
= 9.871
SQRT {5 V
SQRT {Vin
SQRT {3.955}
A0
Power and modulator
20 dB/dec
19.63
2
2
8
8
Nt/RCS
13700 / 820
F0
–1
L
470 nH
= (2   4.489 kHz  24 k)
Vin
Converter open loop
L
40 dB/dec
Fsw
5 V
Fzero
Vin
470 nH
500 kHz
(VCS0
Fsw
Figure 4
5 V
Nt / RCS) }
Compensated error amp.
Af
(0.134 V
Asw
–1
20 dB/dec
500 kHz
= 1477 pF
Fsw
13700 / 820 ) }
BW/Af
(3)
Error amp. unity gain
frequency
BW
Page 13 of 25
Preliminary
Freq. (Hz)