a us t ria
m i c r o
s y s t e m s
AS1321
1 3 0 m A St e p - U p D C - D C C o n v e r t e r
D a ta S he e t
1 General Description
The AS1321 is a high-efficiency step-up DC-DC con-
verter designed to generate a fixed output voltage of
+5.0V.
The AS1321 achieves an efficiency of up to 96%. The
minimum input voltage is +1.5V, the output voltage is
fixed at +5.0V, and output current is up to 130mA
(@ 2V V
BATT
).
In order to save power the AS1321 features a shutdown
mode, where it draws less than 1µA. In shutdown mode
the battery is connected directly to the output enabling
the supply of real-time-clocks.
The AS1321 provides a power-on reset output that goes
high-impedance when the output reaches 90% of its reg-
ulation point.
The SHDNN trip threshold of the AS1321 can be used
as an input voltage detector that disables the device
when the battery voltage falls to a predetermined level.
An internal synchronous rectifier is included, which is
parallel with the external Schottky diode.
The AS1321 is available in a 6-pin SOT23 package.
2 Key Features
!
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Fixed Output Voltage: +5.0V
Output Current: Up to 130mA (@ 2V V
BATT
)
Internal Synchronous Rectifier
Shutdown Mode Supply Current: Less Than 1µA
Efficiency: Up to 96%
Minimum Input Voltage: +1.5V
Accurate Shutdown Low-Battery Cutoff Threshold
Battery Input Connected to Pin OUT in Shutdown
Mode for Backup Power
6-pin SOT23 Package
!
3 Applications
The AS1321 is ideal for low-power applications where
ultra-small size is critical as in medical diagnostic equip-
ment, hand-held instruments, pagers, digital cameras,
remote wireless transmitters, cordless phones, and PC
cards.
The device is also perfect as a local +5.0V supply or as
a battery backup.
Figure 1. Application Diagram
2
BATT
5
OUT
C
OUT
22µF
+5.0V
Output
R
1
100kΩ
RESETN
Output
+1.5 to +5.0V
Battery
C
IN
22µF
4
L1
10µH
LX
AS1321
6
RESETN
On
Off
1
SHDNN
3
GND
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