Rainbow-electronics MAX8709 Manual do Utilizador descarregar pdf (Página 22)

MAX8709

High-Efficiency CCFL Backlight

Controller with SMBus Interface

22 ______________________________________________________________________________________

3) Route high-speed switching nodes away from sen-

sitive analog areas (CCI, CCV, REF, V

, I

SEC

ILIM). Make all pin-strap control input connections

(ILIM, etc.) to analog ground or V

rather than

power ground or V

4) Mount the decoupling capacitor from V

to GND

as close as possible to the IC with dedicated

traces that are not shared with other signal paths.

5) The current-sense paths for LX1 and LX2 to GND

must be made using Kelvin-sense connections to

guarantee the current-limit accuracy. With 8-pin

SO MOSFETs, this is best done by routing power

to the MOSFETs from outside using the top copper

layer, while connecting GND and LX inside (under-

neath) the 8-pin SO package.

6) Ensure the feedback connections are short and

direct. To the extent possible, IFB, VFB, and ISEC

connections should be far away from the high-volt-

age traces and the transformer.

7) To the extent possible, high-voltage trace clear-

ance on the transformer’s secondary should be

widely separated. The high-voltage traces should

also be separated from adjacent ground planes to

prevent lossy capacitive coupling.

8) The traces to the capacitive voltage-divider on the

transformer’s secondary need to be widely sepa-

rated to prevent arcing. Moving these traces to

opposite sides of the board can be beneficial in

some cases (see Figure 10).

NOTE: DUAL MOSFET N2 IS MOUNTED ON THE BOTTOM SIDE OF THE PC BOARD DIRECTLY UNDER N1.

HIGH-CURRENT PRIMARY CONNECTION HIGH-VOLTAGE SECONDARY CONNECTION

LAMP

N1 N2

Figure 10. High-Voltage Components Layout Example

Chip Information

TRANSISTOR COUNT: 7116

PROCESS: BiCMOS

28 27 26 25 24 23 22

891011 12 13 14

MAX8709ETI

THIN QFN

TOP VIEW

REF

ILIM

LOT

GND

ISEC

SDA

SCL

BATT

CCV

CCI

IFB

N.C.

VFB

GH2

LX2

BST2

BST1

LX1

GH1

GL1

GL2

PGND

N.C.

SUS

Pin Configuration

1 2 ... 17 18 19 20 21 22 23

Comentários a estes Manuais

Sem comentários

Rainbow-electronics MAX8709 Manual do Utilizador Página 22

Comentários a estes Manuais

Manuais e produtos relacionados com Sensores Rainbow-electronics MAX8709