AS1331
Datasheet - Detailed Description
Output Voltage Selection
The AS1331 is available in two versions (see Ordering Information on page 15). One version can only operate at one
fixed output voltage (see Figure 25) and the other version can operate with user-adjustable output voltages from 2.5V
to 3.3V by connecting a voltage divider between the pins VOUT and FB (see Figure 24).
Figure 24. LiIon to Adjustable Output Voltage
L1
6.8µH
SW1
SW2
4
2
5
8
LiIon
VIN
LBO
R3
R1
C1
10µF
VOUT
1
7
2.5V to 3.3V
AS1331-AD
VOUT
LBI
C2
22µF
10
6
On
Off
FB
EN
R2
PGND
9
GND
3
The output voltage can be adjusted by selecting different values for R1 and R2.
Calculate VOUT by:
R1
⎛
⎞
⎠
-----
VOUT = VFB × 1 +
(EQ 2)
⎝
R2
Where:
VFB = 1.25V, VOUT = 2.5V to 3.3V;
Figure 25. LiIon to 3.3V with POK - Fixed Output Voltage
L1
6.8µH
SW1
SW2
2
4
5
8
LiIon
VIN
LBO
R3
C1
VOUT
3.3V
300mA
1
7
10µF
AS1331-
3.3V
VOUT
LBI
C2
22µF
10
6
On
Off
FB
EN
PGND
3
9
GND
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