ncp3064b ON Semiconductor, ncp3064b Datasheet - Page 9

• Manufacturer Part Number: ncp3064b
• Description: 1.5 A, Step-up/down/ Inverting Switching Regulator With On/off Function
• Manufacturer: ON Semiconductor

of the NCP3064. Two main converter topologies are
demonstrated with actual test data shown below the circuit
diagrams.
parameters. Additionally, a complete application design aid
for the NCP3064 can be found at www.onsemi.com.
8. V
9. V
10. The calculated t
The Following Converter Characteristics Must Be Chosen:
less than 10% of the average inductor current I
set by R
converter output current capability.
value since it will directly affect line and load regulation. Capacitor C
electrolytic designed for switching regulator applications.
(See Notes 8, 9, 10)
Figures 16, 20 and 24 show the simplicity and flexibility
Figure 15 gives the relevant design equations for the key
V
V
I
DI
f − Maximum output switch frequency.
V
out
out
in
ripple(pp)
SWCE
F
L
I
V
− Output rectifier forward voltage drop. Typical value for 1N5819 Schottky barrier rectifier is 0.4 V.
− Nominal operating input voltage.
pk (Switch)
− Desired output current.
− Desired peak−to−peak inductor ripple current. For maximum output current it is suggested that DI
− Desired output voltage.
ripple(pp)
t on
t off
I
L(avg)
R
V
SC
t
C
on
− Darlington Switch Collector to Emitter Voltage Drop, refer to Figures 7, 5, 8 and 9.
L
out
SC
T
. If the design goal is to use a minimum inductance value, let DI
− Desired peak−to−peak output ripple voltage. For best performance the ripple voltage should be kept to a low
on
/t
off
must not exceed the minimum guaranteed oscillator charge to discharge ratio.
DI L
V in * V SWCE * V out
V in * V SWCE * V out
V TH
I L(avg) )
I pk (Switch)
V out ) V F
Step−Down
8 f C O
f
DI L
1
0.20
t on
t off
I out
R 2
R 1
t on
t off
) 1
) 1
2
DI L
2
) (ESR)
L(avg)
Figure 15. Design Equations
t on
. This will help prevent I
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2
APPLICATIONS
C T + 381.6 @ 10
9
[
transistors. This solution helps to increase output current and
helps with efficiency, still keeping the cost of materials low.
Another advantage of using the external transistor is higher
operating frequency, which can go up to 250 kHz. Smaller
size of the output components such as inductor and capacitor
can be used then.
V in * V SWCE
t on I out
V out ) V F * V in
f osc
V in * V SWCE
I out
It is possible to create applications with external
C O
V TH
I L(avg) )
I pk (Switch)
f
Step−Up
DI L
O
t on
t off
0.20
*6
t on
t off
R 2
R 1
should be a low equivalent series resistance (ESR)
) DI L @ ESR
t on
t off
) 1
pk (Switch)
* 343 @ 10
) 1
) 1
L
DI L
2
= 2(I
t on
from reaching the current limit threshold
L(avg)
*12
). This will proportionally reduce
[
V in * V SWCE
t on I out
Voltage−Inverting
V in * V SWCE
I out
C O
V TH
I L(avg) )
|V out | ) V F
I pk (Switch)
f
DI L
t on
t off
0.20
t on
t off
R 2
R 1
) DI L @ ESR
t on
t off
L
) 1
be chosen to be
) 1
) 1
DI L
2
t on