Diodes AP3513E - Manual (Page 2)

AP3513E
Document number: DS36692 Rev. 2 - 2
2 of 11
www.diodes.com
January 2014
© Diodes Incorporated
AP3513E
A Product Line of
Diodes Incorporated
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Pin Descriptions
Pin Number Pin Name Function
1 BS
Bootstrap pin. A bootstrap capacitor is connected between the BS pin and SW pin. The voltage
across the bootstrap capacitor drives the internal high-side NMOS switch.
2 IN
Supply input pin. A capacitor should be connected between the IN pin and GND pin to keep the DC
input voltage constant.
3 SW Power switch output pin. This pin is connected to the inductor and bootstrap capacitor.
4 GND Ground pin
5 FB
Feedback pin. This pin is connected to an external resistor divider to program the system output
voltage. When the FB pin voltage exceeds 1.1V, the over voltage protection is triggered. When the
FB pin voltage is below 0.3V, the oscillator frequency is lowered to realize short circuit protection.
6 COMP
Compensation pin. This pin is the output of the transconductance error amplifier and the input to the
current comparator. This pin is used to compensate the control loop. Connect a series RC network
from this pin to GND pin. In some cases, an additional capacitor from this pin to GND pin is
required.
7 EN
Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the
regulator, drive it low to turn off. Pull up with 100kΩ resistor for automatic startup.
8 SS
Soft-start control input pin. SS controls the soft start period. Connect a capacitor from SS to GND to
set the soft-start period. A 0.1µF capacitor sets the soft-start period to 15ms. To disable the soft-
start feature, leave SS unconnected.
– EP Exposed pad. It should be connected to GND in PCB layout.
Functional Block Diagram
S
R
Q
Q
INTERNAL
REGULATOR
OSCILLATOR
2
7
5
4
3
1
VA
BS
SW
GND
EA
6
COMP FB
EN
IN
COMPARATOR
8
SS
CURRENT
SENSE
AMPLIFIER
CLK
SLOP
COMP
PWM
COMPARATOR
1.1V
+
SCP
VA
VB
VB
5µA
180K/500K
0.925V
2. 5V
M1
M2
0.3V
COMPARATOR 1.5V
SHUTDOWN
LOCK