AS1312
Datasheet - Application Information
9.1.1 Power-OK and Low-Battery-Detect Functionality
LBO goes low in startup mode as well as during normal operation if:
- The voltage at the LBI pin is below LBI threshold (0.6V). This can be used to monitor the battery voltage.
- LBI pin is connected to GND and VOUT is below 92.5% of its nominal value. LBO works as a power-OK signal in this case.
The LBI pin can be connected to a resistive-divider to monitor a particular definable voltage and compare it with a 0.6V internal reference. If LBI
is connected to GND an internal resistive-divider is activated and connected to the output. Therefore, the Power-OK functionality can be realized
with no additional external components.
The Power-OK feature is not active during shutdown and provides a power-on-reset function that can operate down to VIN = 0.7V. A capacitor to
GND may be added to generate a power-on-reset delay. To obtain a logic-level output, connect a pull-up resistor R
3
from pin LBO to pin VOUT
.
Larger values for this resistor will help to minimize current consumption; a 100kΩ resistor is perfect for most applications (see Figure 13 on page
12).
For the circuit shown in the left of Figure 12, the input bias current into LBI is very low, permitting large-value resistor-divider networks while
maintaining accuracy. Place the resistor-divider network as close to the device as possible. Use a defined resistor for R
2 and then calculate R1
as:
VIN
----------
R1 = R2
– 1
(EQ 18)
VLBI
Where:
is 0.6V
V
LBI
Figure 12. Typical Application with adjustable Battery Monitoring
L1
6.8µH
LX
3
VIN
0.7V to 5.0V
Low Battery Detect
8
6
VIN
LBO
R
3
C1
R1
22µF
V
OUT
4
1
2.5V to 5.0V
AS1312
VOUT
LBI
C
22µF
2
R
2
5
On
Off
7
REF
EN
C
REF
100nF
GND
2
Figure 13. Typical Application with LBO working as Power-OK
L1
6.8µH
LX
3
V
IN
0.7V to 5.0V
Low Battery Detect
8
6
VIN
LBO
R
3
C1
22µF
V
OUT
4
1
2.5V to 5.0V
AS1312
VOUT
LBI
C
2
22µF
5
On
Off
7
REF
EN
CREF
100nF
GND
2
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Revision 1.12
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