Datasheet

SLUU111 – June 2002
7
1-MHz, 3.3-V, High-Efficiency Synchronous Buck Converter With TPS43000 PWM Controller
The transfer function for the compensator is calculated as:
A(s) +
(
1 ) s C1 R2
) (
1 ) s C3
(
R1 ) R3
))
s R1 C1
ǒ
1 )
ǒ
C2
C1
Ǔ
) s C2 R2
Ǔ
(
1 ) s C3 R3
)
The compensator values are calculated as:
C1 = 270 pF, C2 = 3.0 pF, C3 = 560 pF, R1 = 100 kΩ, R2 = 115 kΩ, and R3 = 5.76 kΩ.
10 100 1 k 10 k 100 k
–200
–175
–150
–125
–100
–75
–50
–25
0
25
50
1 M
Gain – dB
f – Output Frequency – Hz
POWER STAGE GAIN AND PHASE
vs
FREQUENCY
GAIN
PHASE
Figure 2.
2.5 MOSFETs and Diode
For a 3.3-V output voltage, the lower the R
DS(on)
of the MOSFET, the higher the efficiency.
Also, considering the 1-MHz switching frequency, Si3442DV (R
DS(on)
= 65 mΩ) and
Si3443DV (R
DS(on)
= 70 mΩ) are chosen for fast switching speed.