AP6503A

Document number: DS36000 Rev. 4 - 2

2 of 15

www.diodes.com

March 2017

© Diodes Incorporated

AP6503A

Typical Applications Circuit

AP6503A

L1

10μH

R1

26.1k

Ω

R2

10k

Ω

C5

10nF

C2

47μF

C1

22μF

C4

0.1μF

ON

OFF

IN

SS

EN

COMP

SW

BST

FB

C3

6.8nF

R3

6.8k

Ω

GND

INPUT

OUTPUT

3.3V

3

5

6

4

8

7

2

1

Figure 2. Typical Application Circuit

Pin Descriptions

Pin

Number

Pin

Name

Function

1

BST

High-Side Gate Drive Boost Input. BST supplies the drive for the high-side N-Channel MOSFET switch. Connect

a 0.01µF or greater capacitor from SW to BST 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 BST 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 100kΩ 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

LOAD CURRENT (A)

Efficiency vs. Load Current

E

F

F

I

C

I

E

N

C

Y

(

%

)

0

1

2

3

V

= 12V

IN

V

= 5V

IN

V

= 3.3V

L = 10µH

OUT

40

50

60

70

80

90

100