SC2603EVB SEMTECH [Semtech Corporation], SC2603EVB Datasheet - Page 5

• Manufacturer Part Number: SC2603EVB
• Description: Simple PWM Boost Controller
• Manufacturer: SEMTECH [Semtech Corporation]

POWER MANAGEMENT
Over Current Protection
The over-current protection is implemented by a sensing
resistor and an internal current-limit comparator with a
threshold of 70mV. If the switching current through the
sensing resistor causing voltage to drop at the CS pin
reachs 70mV, the SC2603 will immediately turn the gate
pulse off to limit the current through the power switch.
The figure below shows over-current waveforms. At t1,
the input current I
builds up until it hits the OCP threshold at t2. At t2, V
begins to drop as I
and I
happening. 1) V
this point, the internal oscillator runs into frequency shift
mode and shifts the frequency to one fourth of the oper-
ating frequency. 2) The diode starts conducting current
without limit causing V
Finally, V
input supply current limit.
A RC filter at the CS pin is necessary to filter out noise to
ensure accurate sensing.
The value of the sensing resistor can be caculated by
the following equation:
Where I
MOSFET.
Application Information
© 2005 Semtech Corp.
R
S
V
V
=
I
I
IN
OUT
OUT
IN
IN
70
remain the same. At t3, there two events are
PEAK
IN
t0
mV
and V
t1
is the input peak current through the power
/
OUT
OUT
I
PEAK
Over Current Waveforms
OUT
both drops to zero and I
IN
is at half of its regulating voltage. At
begins to increase as the load I
starts increasing toward t3 while V
IN
t2
to fall due to supply current limit.
t3
t4
IN
becomes the
OUT
OUT
IN
5
SC2603
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