Diodes AP3503 - Manual (Page 2)

Data Sheet
340kHz, 3A Synchronous DC-DC Buck Converter AP3503
May. 2012 Rev. 1. 7 BCD Semiconductor Manufacturing Limited
2
Pin Configuration
MP Package
(PSOP-8)
1
2
3
4
8
7
6
5
Figure 2. Pin Configuration of AP3503 (Top View)
Pin Description
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 power MOSFET
2 IN
Supply power input pin. A capacitor should be connected between the
IN pin and GND pin to keep the 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. It is used to
compensate the control loop. Connect a series RC network from this
pin to GND. In some cases, an additional capacitor from this pin to
GND pin is required
7 EN
Control input pin. EN is a digital input that turns the regulator on or
off. Drive EN high/low to turn on/off the regulator. Pull up with
100k
Ω 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 0.1
µF
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