AS1337
Datasheet - P i n A s s i g n m e n t s
4 Pin Assignments
Figure 2. Pin Assignments (Top View)
VOUT 1
LX 2
8 FB
7 VIN
AS1337
PGND 3
GND 4
6 POK
5 EN
9 GND
Pin Descriptions
Table 1. Pin Descriptions
Pin Name
VOUT
Pin Number
1
Description
Output Voltage.
Bias is derived from V
OUT
when V
OUT
exceeds V
IN
. PCB trace
length from V
OUT
to the output filter capacitor(s) should be as short and wide as
is practical.
Switch Pin.
Connect an inductor between this pin and V
IN
. Keep the PCB trace
lengths as short and wide as is practical to reduce EMI and voltage overshoot. If
the inductor current falls to zero, or pin EN is low, an internal 100Ω anti-ringing
switch is connected from this pin to V
IN
to minimize EMI.
Note:
An optional Schottky diode can be connected between this pin and V
OUT
.
Power Ground.
Provide a short, direct PCB path between this pin and the out-
put capacitor(s).
Ground
Enable Pin.
Logic controlled enable input.
1 = Normal operation
0 = Shutdown
Note:
In a typical application, EN should be connected to V
IN
through a 1MΩ
pull-up resistor.
POK.
High when V
OUT
is within regulation.
Input Voltage.
The AS1337 gets its start-up bias from V
IN
unless V
OUT
exceeds
V
IN
, in which case the bias is derived from V
OUT
. Thus, once started, operation
is completely independent from V
IN
. Operation is only limited by the output
power level and the internal series resistance of the supply.
Feedback Pin.
Feedback input to the g
m
error amplifier. Connect a resistor
divider tap to this pin. The output voltage can be adjusted from 2.5V to 5V by:
V
OUT
= 1.23V[1 + (R
1
/R
2
)]
Exposed Pad Ground
LX
2
PGND
GND
3
4
EN
5
POK
VIN
6
7
FB
GND
8
9
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