SS6580/L
n
BLOCK DIAGRAM
Over Current
-
+
PHASE
OCSET
200µA
SD
Built-In Soft Start
Power-On
Reset
VCC
+
-
REF
FB
COMP
PWM Comparator
+
-
Gate Control
UGATE
GND
Error AMP
Oscillator
n
PIN DESCRIPTIONS
connected to the FB pin to
compensate the voltage-control
feedback loop of the converter.
PIN 4: FB
- The error amplifier inverting input
pin. The FB pin and COMP pin are
used
to
compensate
the
voltage-control feedback loop.
- Ground pin.
PIN 1: OCSET - Current limit sense pin. Connect a
resistor R
OCSET
from this pin to the
drain of the external MOSFET.
R
OCSET
, an internal 200µA current
source (I
OCSET
), and the external
MOSFET on-resistance (R
DS(ON)
)
jointly set the over-current trip point
according
to
the
following
equation:
I
OCSET
×
R
OCSET
I
PEAK
=
R
DS(ON)
PIN 5: GND
If the FB pin voltage is sensed to
be below 50% of the internal
voltage reference VDAC, the
over-current comparator cycles the
soft-start function.
PIN 2:
SD
PIN 3:COMP
- Shutdown pin. Connect this pin to
ground for shutdown.
- External compensation pin. This
pin is connected to the error
amplifier
output
and
PWM
comparator. An RC network is
PIN 6: PHASE - Over-current
detection
pin.
Connect the PHASE pin to the
source of the external N-MOSFET.
This pin detects the voltage drop
across the MOSFET R
DS(ON)
for
over-current protection.
PIN 7: UGATE - External MOSFET gate drive pin.
Connect this pin to the gate of the
external MOSFET.
PIN 8: VCC
- The chip power supply pin.
Recommended supply voltage is
12V.
Rev.2.01 6/26/2003
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