MB39C313 Datasheet, PDF (22/52 Pages) Fujitsu Component Limited. – 4ch System Power Management IC for LCD Panel

MB39C313
■ APPLCATION MANUAL
1. Buck Converter Design
(1) Buck Converter Block Diagram
A
R1
R2
Cff1
15
FBB
L priority
enb1
Error
− Amp1
+
+
1.213 V
VTH
1.213 V ± 1.5%
+
VB
REG
PWM
COMP1
+
−
PWM
Logic
Control
−
0.9 V
+
OSC_CTL
fOSC or
fOSC/2 or
fOSC/4
Current
Limit
−
0.6 V
SCP COMP
OSC
Saw tooth
VINB ^Generator
<<CH1 (Buck)>>
BOOT
(SWB + 4 V)
17
VINB
20 21
DRV
RON = (230 mΩ
at VGS = 4 V)
18 ^SWB
ILIM
COMP
LEVEL
CONV
CBOOT
A
Vlogic
(3.3 V/1.5 Amax)
(2) Inductor Selection
The inductor can range from 10 μH to 15 μH. The current flow through the inductor must below the saturation
current rating of the inductor. The maximum current flowing through the inductor can be found from the
following formula:
ΔIL
ILMAX ≥ IOMAX
2
ΔIL =
Vin × Vout
VOUT
×
L
Vin × fOSC
Where
ILMAX = Maximum current through inductor [A]
IOMAX = Maximum load current [A]
ΔIL = Inductor ripple current peak-to-peak value [A]
Vin = Input voltage [V]
Vout = Output voltage [V]
fOSC = switching frequency [Hz] (500 kHz or 750 kHz)
Inductor current
ILMAX
IOMAX
0
ΔIL
t
22
DS04–27267–1E