MP3430 — 90V STEP-UP CONVERTER WITH APD CURRENT MONITOR

MP3430 Rev 1.11

www.MonolithicPower.com

13

4/25/2013

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(V)

(mA)

L

(µH)

(MΩ)

(kΩ)

(FB to GND)

Diode

(Schottky

Small Signal)

(µF

100V)

(µF)

30

2.5

3.3

27.4

40

2.5

2.7

20.5

50

2.5

2.0

16.2

60

2.0

1.5

13.3

70

0.9

1.5

11.5

80

0.5

1.2

10.0

90

0.5

1.0

1.0

8.87

BAT46W

0.1

10

Design Example:

Desired Parameters:

Calculations:



















k

.

.

.

M

V

V

V

R

R

FB

OUT

FB

TOP

BOTTOM

2

16

8

0

50

8

0

1

Inductor

Choose L = 2.0µH

First Consideration (most important)

MAX,REVERSE

OUT

I

V

40pF /L 50

40pF / 2 H 224mA







 

MAX,REVERSE

Re verseCurrent

IN,MIN

1.6 L I

1.6 2 H 224mA

t

194ns

V1

2.7 1



 







SOUT

OUT

2L f

I

22 1.3 2.5

K

0.00026

V

1000

50 1000

 











2

2

OUT

1

IN,MIN

2V

K

0.00026

2 50

D2.2

1

1

2.2

1

1

4V

4

2.7

0.639













































IN

21

OUT

IN,MIN

V

2.7

D

D

0.639

0.0365

V

V

50 2.7









31

2

D

1 D

D

1 0.639 0.0365 0.325





 





3

S

Re verseCurrent

D

t

250ns t

194ns







So 2.0µH is good.

Second Consideration

2

IN,MIN

IN,MIN

2

CRIT

OUT

OUT

2

CRIT,MIN

OUT

SOUT

VV

KD D'

1

VV

2.7

2.7

1

0.00276

50

50

K

V

1000

0.00276 50 1000

L21 H

2f

I

2 1.3 2.5

 











 



 



 









 



 









 





Third Consideration:

IN,MIN

1

L,PEAK

S

VD

2.7 0.639

I664mA 900mA

L f

2.0 1.3













Make sure the inductor has at least 20% more

capability than the saturation current

DIODE

2

DIODE,RMS

RMS

PK

D

0.0365

I

I

I

664

73mA

33









Make sure diode average current rating is above

this value

Output Capacitor

APD

2

OUT,RIPPLE

SOUT

I(1 D )

V0.001

fC

2.5 (1 0.0365)

0.001 19mV

1.3 0.1













