BD9202EFS Просмотр технического описания (PDF) - ROHM Semiconductor

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BD9202EFS

White backlight LED drivers

ROHM Semiconductor 

BD9202EFS

Technical Note

●Electricity Consumption Calculations

Pc(N)=ICC*VCC+2*Ciss*VREG*Fsw*Vcc*[VLED*N+ΔVf*(N-1)]*ILED

ICC

VCC

Ciss

Vsw

Fsw

Rload

Iload

VLED

N

ΔVf

ILED

：Maximum circuit current

：Power voltage

：External FET capacity

：SW gate voltage

：SW frequency

：LOAD SW ON resistance

：LOAD SW maximum inflowing current

：LED control voltage

：LED parallel numeric

：LED Vf variance

：LED output current

＜Sample calculation＞

When Pc(8)=21mA×30V+500pF×5V×600kHz×30V+[0.95V×8+ΔVf×7] ×75mA

ΔVf=1.2V (about 0.1V each),

Pc(8)=0.63W+0.045W+1.2W

=1.875W

Because this IC has a built-in driver circuit, there is a considerable amount of heat generated. Careful consideration is

necessary for substrate and heat dissipation design.

●PCB Board Circuit Diagram

CPUVDD

CP1=27pF

CP2=27pF

RFL1=5.1kΩ

RFL2=5.1kΩ

CREG=2.2uF

RSET=68kΩ

J5

1 LED1

2 PGND2

3 LED2

4 CP1

5 CP2

6 FAIL1

7 FAIL2

8 AGND

9 CPUDI

10 CPUDO

11 CPUVDD

12 CPUCLK

13 CPUCS

14 VCC

15 VREG

16 VREF

17 ISET

18 VSET

19 TEST

20 LED3

21 PGND3

22 LED4

VCC 14

RVCC＝300Ω

CVCC=10uF

LED8 44

PGND5 43

RVULO1

＝91kΩ

RUVLO2

=10kΩ

LED7 42

EN 41

TOUT2 40

RPC=300Ω

COMP 39

CPC＝1uF

BCT_SYNC_IN 38

CT_SYNC_IN 37

BCT_SYNC_OUT 36

CT_SYNC_OUT 35

UVLO 34

LOSDSW 33

RLD1

=5.1kΩ

RLD2

=5.1kΩ

CLD

Q1

L1

47uH

D1

PGND1 32

SWOUT 31

OVP 30

CS 29

RT 28

BRT 27

RCT=51kΩ

RBCT=51kΩ

RESR

CVOUT

=220uF

Q2

RLPF=100Ω

CLPF

=1000pF

RCS=51mΩ

CSGND

TOUT1 26

LED6 25

PGND4 24

LED5 23

1

2

3

4

RE-H42TD-1130

GND

J4

CT_SYNC_IN 37

J3

BCT_SYNC_IN 38

LED2 3

LED1 1

LED8 44

LED7 42

ROVP1=

560kΩ

LED6 25

LED5 23

ROVP2

=20kΩ LED3 20

LED4 22

1

2

3

4

5

6

7

8

9

10

11

12

12FDZ-BT

CPUVDD 11

CPUDCLK 12

CPUDO 10

CPUCS 13

PGND1 32

CPUDI 9

EN

41

VREF

VSET

J2

16

J1

18

BCT_SYNC_IN 38

BCT_SYNC_OUT 36

CT_SYNC_IN 37

CT_SYNC_OUT 35

1

2

3

4

5

6

7

8

08FDZ-ST (1)

1

2

3

4

5

6

7

8

08FDZ-ST (2)

○ The CVCC and CREG decoupling condensers should be placed as close as possible to the IC pin.

○ Because high current can flow through CSGND and PGND1~4, they should all be wired independently with low impedance.

○ Do not apply noise to 17-pin ISET, 18-pinVSET, 27-pin BRT, 28-pin RT and 39-pin COMP.

○ 1-pin LED, 3-pin LED2, 20-pin LED3, 22-pin LED4, 23-pin LED5, 25-pin LED6, 31-pin SWOUT, 35-pin CT_CYNC_OUT,

36-pin BCT_SYNC_OUT, 42-pin LED7 and 44-pin LED8 switch, so make sure they do not affect the surrounding pattern.

○ The thick-lined areas should be laid out as short as possible with broad pattern.

○ During normal use, the jumper configurations are J1～J4=Short and J5=open.

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© 2009 ROHM Co., Ltd. All rights reserved.

14/19

2009.04 - Rev.A

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