sc4808b-1 Semtech Corporation, sc4808b-1 Datasheet - Page 13

• Manufacturer Part Number: sc4808b-1
• Description: Sc4808b-1 High-performance Dual Ended Pwm Controller
• Manufacturer: Semtech Corporation

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.
OVER CURRENT
Two levels of over current protection are provided by the
SC4808B-1. 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 950mV. 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 (see page 18 for calculation of softstart time), normal
operation is achieved, unless the over current condition is
still present.
POWER MANAGEMENT
Application Information (Cont.)
2006 Semtech Corp.
F
5
4
3
2
1
SYNC
REF
FB
CS
RC
SYNC
Vin
SC4808
2.2u,16V
U4
C26
LUVLO
OUTB
OUTA
GND
VCC
56.2k
R23
6
7
8
9
10
10k
R33
VCC
C33
0.1u,25V
R28
10
C23
0.1u
C34
0.1u
1
1
VCC
VCC
3
2
3
2
5
5
EN
SC1301A
U3
EN
SC1301A
U6
4
4
D_B
D_A
Gate_B
Gate_A
13
SC4808B-1
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