L5953_07 STMICROELECTRONICS [STMicroelectronics], L5953_07 Datasheet - Page 26

• Manufacturer Part Number: L5953_07
• Description: Multiple switching voltage regulator
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Application note
6.1
6.2
6.3
6.3.1
6.3.2
26/31
Part list on evaluation board
REG1 output voltage
V
V
Timing capacitor
The value for this capacitor has to be chosen according the wanted power-on delay T
where I
output voltage.
Feedback resistors for REG2
where VLR is the required output voltage for REG2.
External components for PWM regulator
Bootstrap capacitor
The suggested value for the bootstrap capacitor is C6 = 100nF
Here following you find the criteria for the selection of the inductor L1, the free-wheeling
diode D2, the output filter capacitor C7, the feedback resistor R1, R2 and the compensation
network R3, C8, R4, C9 to have a Buck regulator working in continuous mode. Continuous
mode operation is recommended in order to reduce the stress of the output capacitor and of
the free-wheeling diode.
Inductor selection
The minimum value of the inductor L7 has to be so that the maximum inductor current ripple
ΔI
present when the switching frequency is minimum (f
maximum (V
C1 = 470 μF
STBY
STBY
L,max
ESR=65 mΩ
C7 = 470 μF
L1 = 180 μH
R1 = 2.2 kΩ
= 5V if pin ADJ left floating
= 3.3V if pin ADJ is connected to the pin V
CT1
is 20% to 30% of the maximum load current load I
is the source current used to charge the timing capacitor and V
in,max
R2 = 2 x 1.5 kΩ in
) so the minimum value for the inductor L
C2 = 220 nF
C8 = 56nF
parallel
C11
D1 = 1N4007 or
R5
C3 = 470 μF
C9 = 2.7 nF
R3 = 10 kΩ
MBR160
=
=
--------------------------------------------------------------- -
(
0.5 V
R6
⋅
⋅
⎛
⎜
⎝
--------------------------- - 1
V
STBY
I
CT1
ref REG2
V
D2 = MBR360
R4 = 220 kΩ
C10 = 10 μF
,
C4 = 10 μF
STBY
LR
⋅
)
T
+
sw,min
d
V
CTLHy
–
) and the input voltage is
o,max
⎞
⎟
⎠
min
.The maximum ripple is
is:
C11 = 4.7 nF
R5 = 3.3 kΩ
C5 = 1 μF
STBY
is the REG1
C6 = 100 nF
R6 = 1 kΩ
L5953
d
: