Ap3409/a, Pin descriptions, Functional block diagram – Diodes AP3409/A User Manual
Page 3
AP3409/A
Document number: DS36789 Rev.
2 - 2
3 of 11
January 2014
© Diodes Incorporated
AP3409/A
A Product Line of
Diodes Incorporated
Pin Descriptions
Pin Number
Pin Name
Function
AP3409
AP3409A
1
1
SHDN/RT
Oscillator resistor input. Connect a resistor to GND from this pin to set the
switching frequency. Forcing this pin to V
DD
to shutdown the device
2
2
GND
Signal ground. All small-signal ground, such as the compensation
components and exposed pad should be connected to this, which in turn
connects to PGND at one point
3, 4
3, 4
SW
Internal power switch output. Connect this pin with one terminal of the
inductor
5
5
PGND
Power ground. Connect this pin as close as possible to C
IN
and C
OUT
6, 7
6
PVDD
Power Input Supply. Decouple this pin to PGND with a capacitor
8
7
VDD
Signal input supply. Decouple this pin to GND with a capacitor. Normally
V
DD
is equal to V
PVDD
–
8
PGOOD
Power good indicator. This pin is open-drain logic output that is pulled to
ground when the output voltage is not within ±12.5% of regulation point
9
9
FB
Feedback voltage. This pin is the inverting input of internal error amplifier.
It senses the converter output voltage through an external resistor
divider. The internal reference voltage is 0.8V, which determines the
output voltage through the resistor divider
10
10
COMP
Compensation input. This pin is the output of internal error amplifier.
Connect external compensation elements to this pin to stabilize the
control loop
Functional Block Diagram
SD
Oscillator
SUM
CS
0.8V
EA
OCP
D
ri
v
e
r
Control
Logic
OTP
UVLO
V
REF
0.4V
SHDN/RT
PVDD
SW
GND
PGND
VDD
FB
COMP
1
2
10
3, 4
5
6, 7
8
9
PWM
Clamp
SS
DC
Functional Block Diagram of AP3409