LT3504 데이터 시트보기 (PDF) - Linear Technology

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LT3504

Quad 40V/1A Step-Down Switching Regulator with 100% Duty Cycle Operation

Linear Technology 

LT3504

Applications Information

Overvoltage Transient Protection

Figure 9 shows the complete application circuit for a

4-output step-down regulator with 100% duty cycle

operation that withstands 180V surges. Under normal

operating conditions (VIN < 33V), the VSKY rail supplies

gate drive to MOSFET Q1, providing the LT3504 with a low

resistance path to VSUPPLY. In the event that a supply surge

occurs, Zener diode D1 clamps Q1’s gate voltage to 36V.

The source-follower configuration prevents VIN from rising

any further than about 33V (a VGS below the Zener clamp

voltage ). Figure 10 shows the LT3504 regulating all four

channels through a 180V surge event without interruption.

VSUPPLY

3.2V to 30V

SURGE PROTECTION TO 180V

Q1

R2

10Ω 100k

D2

6.8V

D1

36V

R3 D3

1k

SKY

SW4

2.2µF

C1

SW5

DA4

0.1µF

FB4

L5

10µH

LT3504

SW3

VIN

C1: Sanyo 50CE22BS

D1: BZT52C36-7-F

D2: BZT52C6V8-7-F

D3: BAT54-7-F

D4–D7: ON SEMI MBRM140T3

L3, L4: SUMIDA CDRH5D28-8R2 (8.2µH)

L1, L2: CDRH5D28-4R2 (4.2µH)

L5: TAIYO YUDEN CBC2016T100M (10µH)

Q1: FQB34N20L

C2 +

22µF

EN/UVLO

DA3

VIN

FB3

VIN

VIN

VIN

SW2

RUN/SS1

1µF

×4

RUN/SS2

RUN/SS3

RUN/SS4

DA2

FB2

0.1µF

SW1

RT/SYNC

DA1

18.2k

FB1

GND

L4

8.2µH

D4 22pF

L3

8.2µH

D5 43pF

L2

4.2µH

D6 82pF

L1

4.2µH

D7 100pF

fSW = 1MHz

Figure 9. Complete Quad Buck Regulator with 180V Surge Protection

53.6k

5V/1A

10µF

10.2k

31.6k

3.3V/1A

10µF

10.2k

21.5k

10.2k

2.5V/1A

22µF

12.7k

1.8V/1A

22µF

10.2k

3504 F09

VSUPPLY

50V/DIV

VIN

50V/DIV

VOUT1,2,3,4

2V/DIV

100ms/DIV

3504 F10

Figure 10. Overvoltage Protection Withstands 180V Surge

For more information www.linear.com/LT3504

3504fa

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