MC34063E ST Microelectronics, MC34063E Datasheet - Page 9

• Manufacturer Part Number: MC34063E
• Description: DC/DC Converter Contolr Circuits
• Manufacturer: ST Microelectronics

Calculation
NOTES:
V
V
THE FOLLOWING POWER SUPPLY CHARACTERISTICS MUST BE CHOSEN:
V
V
I
f
V
series resistance and board layout. The ripple voltage should be kept to a low value since it will directly affect the line and load regulation.
Step-Up With External NPN Switch
OUT
MIN
t
(t
C
I
R
C
L
on
PK(switch)
SAT
F
IN
OUT
RIPPLE
(min)
on
T
SC
O
= Forward voltage drop of the output rectifier
/t
= Nominal input voltage
= Minimum desired output switching frequency at the selected values of V
= Desired output current
off
Parameter
+ t
= Saturation voltage of the output switch
= Desired output voltage, |V
off
= Desired peak to peak output ripple voltage. In practice, the calculated capacitor value will and to be increased due to its equivalent
) max
(Discontinuous mode)
V
-------------------------------------- -
V
------------------------------------------------------- -
IN min
2I
I
PK switch
OUT
out(max)
OUT
V
0.3/I
IN min
4.5x10
-------------------------------
V
| = 1.25(1+R
Step-Up
+
ripple p p
–
1/f
I
V
PK(switch)
out
V
[(t
F
min
sa t
–
on
t
-5
–
o n
V
t
/t
V
on
–
IN min
off
s at
t
on min
)+1]
2
/R
1
)
V
------------------------------------------------------- -
IN min
----------------------------------------------------------- -
V
(Continuous mode)
IN min
I
----------------------------------------------------- -
I
PK s witc h
P K swit ch
0.3/I
–
8V
Step-Down
V
4.5x10
V
2I
OUT
ripple p
sat
–
IN
1/f
out(max)
PK(switch)
V
and I
min
–
+
sat
-5
t
V
V
on
t
on
out
–
O
F
–
+
V
p
O UT
t
off
t
on min
(Discontinuous mode)
V
-------------------------------------- -
IN min
2I
I
Voltage Inverting
PK switch
out(max)
0.3/I
4.5x10
-------------------------------
V
------------------------------ -
V
ripple p p
V
–
1/f
I
O UT
PK(switch)
IN
out
V
MC34063A/E
[(t
min
sa t
–
on
t
-5
o n
V
+
t
/t
on
–
sa t
off
V
t
on min
)+1]
F
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