SC4808CMSTRT datasheet(9/24 Pages) SEMTECH

9 / 24 page

 2006 Semtech Corp.

www.semtech.com

SC4808C

POWER MANAGEMENT

It should be noted that if high speed/high current drivers

such as the SC1301 are used, careful layout guide lines

must be followed in order to minimize stray inductance,

which might cause negative voltages at the output of the

drivers. This negative voltage can be clamped to a reason-

able level by placing a small Schottky diode directly at the

output of the driver as shown below.

C34

0.1u

VCC

SC1301A

C23

0.1u

SC1301A

VCC

R28

2.2u,16V

C26

D_A

0.1u,25V

C33

R33

10k

SYNC

SC4808

REF

LUVLO

SYNC

GND

OUTB

OUTA

VCC

D_B

Gate_A

Gate_B

R23

56.2k

Vin

OVER CURRENT

Two levels of over current protection are provided by the

SC4808C. The current information is sensed at the CS pin

and compared to a peak current limit level of 525mV. If

the 525mV limit is exceeded, the OUTA and OUTB pulse

widths and duty cycle is reduced until the CS pin reaches a

second threshold of 700mV. At that point, the OUTA and

OUTB are disabled, and after a delay of 140µs, the inter-

nal softstart sequence is started. After the softstart dura-

tion, normal operation is achieved, unless the over cur-

rent condition is still present.

Application Information (Cont.)

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