NCP3064 查看數據表（PDF） - ON Semiconductor

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NCP3064

Inverting Converter, Switching Regulator - Buck Boost, ON/OFF Function 1.5 A

ON Semiconductor 

NCP3064, NCP3064B, NCV3064

APPLICATIONS

Figures 16, 20 and 24 show the simplicity and flexibility

of the NCP3064. Two main converter topologies are

demonstrated with actual test data shown below the circuit

diagrams.

Figure 15 gives the relevant design equations for the key

parameters. Additionally, a complete application design aid

for the NCP3064 can be found at www.onsemi.com.

It is possible to create applications with external

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.

(See Notes 8, 9, 10)

Step−Down

Step−Up

ton

toff

ton

CT

IL(avg)

Ipk (Switch)

RSC

L

Vripple(pp)

Vout ) VF

Vin * VSWCE * Vout

Vout ) VF * Vin

Vin * VSWCE

ton

toff

ǒ Ǔ f

ton

toff

)

1

ton

toff

ǒ Ǔ f

ton

toff

)

1

CT

+

381.6 @ 10*6

fosc

*

343

@

10*12

Iout

ǒ Ǔ Iout

ton

toff

)

1

IL(avg)

)

DIL

2

IL(avg)

)

DIL

2

0.20

Ipk (Switch)

0.20

Ipk (Switch)

ǒ Ǔ Vin * VSWCE * Vout

DIL

ton

Ǹǒ Ǔ2

DIL

1

8 f CO

) (ESR)2

ǒ Ǔ Vin * VSWCE

DIL

ton

[

ton Iout

CO

)

DIL

@

ESR

Vout

ǒ Ǔ VTH

R1

R2

)

1

ǒ Ǔ VTH

R1

R2

)

1

8. VSWCE − Darlington Switch Collector to Emitter Voltage Drop, refer to Figures 7, 5, 8 and 9.

9. VF − Output rectifier forward voltage drop. Typical value for 1N5819 Schottky barrier rectifier is 0.4 V.

10. The calculated ton/toff must not exceed the minimum guaranteed oscillator charge to discharge ratio.

Voltage−Inverting

|Vout| ) VF

Vin * VSWCE

ton

toff

ǒ Ǔ f

ton

toff

)

1

ǒ Ǔ Iout

ton

toff

)

1

IL(avg)

)

DIL

2

0.20

Ipk (Switch)

ǒ Ǔ Vin * VSWCE

DIL

ton

[

ton Iout

CO

)

DIL

@

ESR

ǒ Ǔ VTH

R1

R2

)

1

Figure 15. Design Equations

The Following Converter Characteristics Must Be Chosen:

Vin − Nominal operating input voltage.

Vout − Desired output voltage.

Iout − Desired output current.

DIL − Desired peak−to−peak inductor ripple current. For maximum output current it is suggested that DIL be chosen to be

less than 10% of the average inductor current IL(avg). This will help prevent Ipk (Switch) from reaching the current limit threshold

set by RSC. If the design goal is to use a minimum inductance value, let DIL = 2(IL(avg)). This will proportionally reduce

converter output current capability.

f − Maximum output switch frequency.

Vripple(pp) − 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 CO should be a low equivalent series resistance (ESR)

electrolytic designed for switching regulator applications.

http://onsemi.com

9

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