AS1343 austriamicrosystems AG, AS1343 Datasheet - Page 10

• Manufacturer Part Number: AS1343
• Description: DC-DC Boost Converter
• Manufacturer: austriamicrosystems AG

AS1343
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9 Application Information
Shutdown and Output Discharge
A logic low on the EN pin shuts down the AS1343 and a logic high on the EN pin powers on the device. In shutdown
mode the supply current drops to below 3µA and the POK pin is set to high impedance to maximize battery life.
When the battery disconnect switch is used, the battery is disconnected from the output and the output is discharged
down to 0V. The time for fully discharging the output depends on the C
Note: Pin EN should not be left floating. If the shutdown feature is not used, connect EN to V
Battery Disconnect
The AS1343 has an integrated PMOS switch that can be used to disconnect the battery during shutdown. The opera-
tion voltage of this switch is limited to 3.6V. When EN is high, the switch is closed and supplies the inductor. Due to the
R
Setting Output Voltage
Output voltage can be adjusted by connecting a voltage divider between pins
Figure 28. Typical Application
The output voltage can adjusted by selecting different values for R
200k Ω .
Calculate R
Where:
V
The input bias current of FB has a maximum value of 100nA which allows for large-value resistors. For less than 1%
error, the current through R
can be neglected in the calculation of V
Note: For the optimal operation condition the following ratio between V
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OUT
ON
resistance the efficiency is slightly lower if the battery disconnect switch is used.
= 5.5V to 42V, V
V
discharged during shutdown but the output also must be fully discharged before the device is enabled again.
CC
to 3.6V
= 0.9V
1
by:
10µF
On
Off
C
1
100kΩ
FB
= 1.25V; V
R
3
2
should be 100 times the feedback input bias current (I
PGND
POK
V
EN
CC
2
4
1
5
OUT
OUT
> V
.
IN
P
LOSS
R
1
AS1343
V
=
7
SWOUT
OUT
Revision 1.04
= I
R
IN
2
÷
² x R
⋅
⎛
⎝
V
6.8µH
V
-------------- 1
IN
V
L
OUT
1
FB
ON
≤
12
–
1
and R
⎞
⎠
OUT
OUT
2
3, 8
GND
6
LX
9
VOUT
10
FB
and on the load.
. For R
and V
VOUT
2.2MΩ
165kΩ
D1
2
R
R
FB
IN
, select a value between 10k and
1
2
). That’s why the feeback current
should be used:
and FB
(see Figure
CC
4.7µF
C
OUT
. The output will be
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V
28).
OUT
= 18V
(EQ 2)
(EQ 3)
10 - 17
(EQ 1)