SC4501 Datasheet, PDF (4/21 Pages) Semtech Corporation – 2Amp, 2MHz Step-Up Switching Regulator with Soft-Start

SC4501
POWER MANAGEMENT
PBilnocDkeDsciarigprtaiomns (MSOP-8)
Pin
Pin Name Pin Function
1
COMP The output of the internal transconductance error amplifier. This pin is used for loop compensation.
2
FB
The inverting input of the error amplifier. Tie to an external resistive divider to set the output voltage.
Shutdown Pin. The accurate 1.1V shutdown threshold and the 4.6uA shutdown pin current
hysteresis allow the user to set the undervoltage lockout threshold and hysteresis for the switching
3
SHDN
regulator. Pulling this pin below 0.1V causes the converter to shut down to low quiescent current.
Tie this pin to IN if the UVLO and the shutdown features are not used. This pin should not be left
floating.
4
GND
Ground. Tie to the ground plane.
5
SW
Collector of the internal power transistor. Connect to the boost inductor and the rectifying diode.
6
IN
Power Supply Pin. Bypassed with capacitors close to the pin.
7
ROSC
A resistor from this pin to the ground sets the switching frequency.
8
SS
Soft-Start Pin. A capacitor from this pin to the ground lengthens the start-up time and reduces start-
up current.
Exposed Pad The exposed pad must be soldered to the ground plane on the PCB for good thermal conduction.
Block Diagram
IN
6
SW
5
4.6µA
SHDN
3
1.1V
+
CMP
-
VOLTAGE
REFERENCE
THERMAL
SHUTDOW N
INTERNAL
SUPPL Y
ENABLE
CLK
REG
FB
2
COMP
1
SS
8
1.242V
REG_GOOD
ENABL E
+
EA
-
ROS C
7
REG
1.5µA
CLK
-
PWM
+
R
Q
S
+
ILIM
-
I-LIMIT
+
Σ
+
OSCILLATOR
SLOP E COMP
+
ISEN
-
R_SENSE
4
GND
© 2005 Semtech Corp.
Figure 2. SC4501 (MSOP-8) Block Diagram.
4
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