MC34163 ON Semiconductor, MC34163 Datasheet - Page 14

• Manufacturer Part Number: MC34163
• Description: (MC33163 / MC33163) Step-Up/Down/Inverting Switching Regulators
• Manufacturer: ON Semiconductor

The following Converter Characteristics must be chosen:
NOTES: 1. V
NOTES:
NOTES:
NOTES: 3.
(Notes 1, 2, 3)
Calculation
V
V
I pk (Switch)
ripple(pp)
ripple(pp)
I L(avg)
R SC
V out
t on
t off
t on
L
C T
V
2. V
3. The calculated t
I
V
D
out
out
I
in
L
p −
operating input voltage.
−
−
−
−
−
sat
F
Nominal operating input voltage.
Desired output voltage.
Desired output current.
Desired peak−to−peak inductor ripple current. For maximum output current it is suggested that
than 10% of the average inductor current I
threshold set by R
proportionally reduce converter output current capability.
Maximum output switch frequency.
Desired peak−to−peak output ripple voltage. For best performance the ripple voltage should be kept to a low value
since it will directly affect line and load regulation. Capacitor C
electrolytic designed for switching regulator applications.
− Output rectifier forward voltage drop. Typical value for 1N5822 Schottky barrier rectifier is 0.5 V.
− Saturation voltage of the output switch, refer to Figures 8 and 9.
DI L
V
V
in
on
in
ƒ
V
/t
8 C O
I L(avg) )
* V sat * V out
32.143 · 10 –6
off
ref
Step−Down
* V sat * V out
V out ) V F
I pk (Switch)
1
ƒ
SC
t on
t
must not exceed the minimum guaranteed oscillator charge to discharge ratio of 8, at the minimum
off
DI L
. If the design goal is to use a minimum inductance value, let
t on
t off
0.25
R 2
R 1
I out
ƒ
2
) 1
) (ESR) 2
) 1
DI L
2
Figure 28. Design Equations
t on
MC34163, MC33163
http://onsemi.com
L(avg)
. This will help prevent I
14
V out ) V F – V in
V
I out
V
32.143 · 10 –6
I L(avg) )
ƒ
ref
in
V
[
I pk (Switch)
Step−Up
in
t on
t
* V sat
DI L
off
t on I out
t on
t
R 2
R 1
– V sat
0.25
off
t on
t off
ƒ
O
C
) 1
O
should be a low equivalent series resistance (ESR)
) 1
) 1
DI L
2
t on
pk (Switch)
from reaching the current limit
D
I
L
= 2(I
L(avg)
Voltage−Inverting
I out
V
V
D
I L(avg) )
ƒ
32.143 · 10 –6
ref
I
). This will
in
|V out | ) V F
L
V
[
I pk (Switch)
be chosen to be less
in
* V sat
DI L
t on
t
off
t on
t
t on I out
R 2
R 1
off
0.25
* V sat
t on
t off
ƒ
C
) 1
O
) 1
) 1
DI L
2
t on