Diodes AP6503A - Manual (Page 2)

AP6503A
Document number: DS36000 Rev. 2 - 2
2 of 15
www.diodes.com
December 2012
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UC
T
AP6503A
Pin Descriptions
Pin
Number
Pin
Name
Function
1 BS
High-Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel MOSFET switch. Connect a
0.01µF or greater capacitor from SW to BS to power the high side switch.
2 IN
Power Input. IN supplies the power to the IC, as well as the step-down converter switches. Drive IN with a 4.75V
to 23V power source. Bypass IN to GND with a suitably large capacitor to eliminate noise on the input to the IC.
See Input Capacitor.
3 SW
Power Switching Output. SW is the switching node that supplies power to the output. Connect the output LC filter
from SW to the output load. Note that a capacitor is required from SW to BS to power the high-side switch.
4 GND Ground (Connect the exposed pad to Pin 4).
5 FB
Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive voltage divider
connected to it from the output voltage. The feedback threshold is 0.925V. See Setting the Output Voltage.
6 COMP
Compensation Node. COMP is used to compensate the regulation control loop. Connect a series RC network
from COMP to GND. In some cases, an additional capacitor from COMP to GND is required. See Compensation
Components.
7 EN
Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator; low to
turn it off. Attach to IN with a 100k
Ω pull up resistor for automatic startup.
8 SS
Soft-Start Control Input. 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 floating.
EP EP EP exposed thermal pad connect to Pin 4 GND
Functional Block Diagram
E
+
-
+
-
+
-
+
-
+
-
+
1.1V
0.3 V
INTERNAL
REGULATORS
Logic
5V
SHUTDOWN
COMPARATOR
0.9V
+
-
ERROR
AMPLIFIER
LOCKOUT
COMPARATOR
8
7
5
+
-
80/240 KHz
OSCILLATOR
CURRENT
SENSE
AMPLIFIER
OVP
RAMP
CLK
CURRENT
COMPARATOR
EN OK disable
IN < 4.10V
2
1
3
4
6
FB
6uA
EN
COMP
2.5V
SS
0.923 V
GND
SW
BS
IN
100m Ω
100m Ω
IN
Figure 3. Functional Block Diagram