BD4154FV

Technical Note

11/15

www.rohm.com

2009.05 - Rev.A

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

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Application Circuit (Circuit for ExpressCard

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Heat loss

Thermal design should allow the device to operate within the following conditions. Note that the temperatures listed are the

allowed temperature limits. Thermal design should allow sufficient margin from these limits.

1. Ambient temperature Ta can be no higher than 100°C.

2. Chip junction temperature Tj can be no higher more than 150°C.

Chip junction temperature Tj can be determined as follows:

①

Chip junction temperature Tj is calculated from IC surface temperature TC under actual application conditions:

Tj=TC+θj-cxW

＜

Reference value＞

θj-c:SSOP-B20

35/W

②

Chip junction temperature Tj is calculated from ambient temperature Ta:

Tj=TC+θj-axW

＜

Reference value＞

θ

j-a:SSOP-B20

250℃/W

(IC only)

153.8℃/W Single-layer substrate

(substrate surface copper foil area: less than 3%)

Most of heat loss in the BD4154FV occurs at the output switch. The power lost is determined by multiplying the

on-resistance by the square of output current of each switch.

CPPE#(12pin)

CPUSB#(11pin)

V3(6,7pin)

V3AUX(17pin)

V15(13,14pin)

PERST#(8pin)

RCLKEN(19pin)

V3_IN(4,5pin)

V3AUX_IN(18pin)

V15_IN(15,16pin)

PERST_IN#(1pin)

EN(2pin)

SYSR(3pin)

CPPE#(1)

CPUSB#(2)

3.3V(3)

3.3Vaux(4)

1.5V(5)

PERST#(6)

3.3V(7)

3.3Vaux(8)

1.5V(9)

SysReset#(10)

BD4154FV

GND(10pin)