mic4724 Micrel Semiconductor, mic4724 Datasheet - Page 15

• Manufacturer Part Number: mic4724
• Description: 3a 2mhz Integrated Switch Buck Regulator With 6vmax Input
• Manufacturer: Micrel Semiconductor

By looking at the graph, phase margin can be affected to
a greater degree with higher output voltages.
The next bode plot shows the phase margin of a 1.8V
output at 3A without a feedforward capacitor.
Micrel, Inc.
June 2008
50
45
40
35
30
25
20
15
10
5
0
1
Obtainable using C
Max. Amount of Phase Boost
OUTPUT VOLTAGE (V)
2
Voltage
3
FF
V
vs. Output
REF
4
= 1V
5
15
As one can see, the typical phase margin, using the
same resistor values as before without a feedforward
capacitor results in 33.6 degrees of phase margin. Our
prior measurement with a feedforward capacitor yielded
a phase margin of 47 degrees. The feedforward
capacitor has given us a phase boost of 13.4 degrees
(47 degrees- 33.6 Degrees = 13.4 Degrees).
-10
-20
-30
60
50
40
30
20
10
0
100
V
IN
L=1µH
C
R1 = 10k
R2 = 12.4k
C
=3.3V, V
OUT
FF
= 0pF
= 4.7µF
1k
FREQUENCY (Hz)
Bode Plot
OUT
10k
=1.8V, I
PHASE
GAIN
100k
OUT
=3A
1M
M9999-062408-A
210
175
140
105
70
35
0
-35
-70
-105
MIC4724