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PDF AS1344 Data sheet ( Hoja de datos )
| Número de pieza | AS1344 | |
| Descripción | DC-DC Boost Converter | |
| Fabricantes | austriamicrosystems AG | |
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Datasheet
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AS1344
42V, DC-DC Boost Converter with adjustable Softstart
1 General Description
The AS1344 boost converter contains a 1.4A internal
switch in a tiny TDFN-10 3x3mm package. The device
operates from a 0.9V to 3.6V supply, and can boost volt-
ages up to 42V output.
The output voltage can easily be adjusted by an external
resistor divider.
The AS1344 uses a unique control scheme providing
the highest efficiency over a wide range of load condi-
tions. An internal 1.4A MOSFET reduces external com-
ponent count, and a fixed high switching frequency
(1MHz) allows for tiny surface-mount components.
The AS1344 also features power-OK circuitry which
monitors the output voltage.
The device also offers a Softstart function which limits
the current during startup. The current during startup
can be easily adjusted with the value of RV. For RV =
0Ω, there is no softstart.
Additionally the AS1344 features a low quiescent supply
current and a shutdown mode to save power. During
shutdown an output disconnect switch separates the
input from the output.
The AS1344 is ideal for LCD or OLED panels with low
current requirements and can also be used in a wide
range of other applications.
The device is available in a low-profile TDFN-10 3x3mm
package.
2 Key Features
! 5.5V to 42V Adjustable Output Voltage
! 0.9V to 3.6V Supply Voltage Range
! High Output Current:
- 30mA @ 12V VOUT, from 1.5V VCC
! Efficiency: Up to 85%
! Switching Frequency: 1MHz
! Output Disconnect Function
! Softstart Function with adjustable Current Limit
! Output Discharge Function
! Power-OK Output
! Quiescent Current: 22µA
! Shutdown Current: 0.1µA
! TDFN-10 3x3mm Package
3 Applications
The device is ideal for OLED display power supply, LCD
bias generators, mobile/cordless phones, palmtop com-
puters, PDAs and organizers, handy terminals, driving
LEDs or any other portable, battery-powered device.
Figure 1. AS1344 - Typical Application Diagram
VCC = 0.9V
to 3.6V
CIN R3
On VCC
Off GND
RV
VCC
POK
EN
L1
VIN SWOUT
AS1344
VOUT
D1
LX R1
FB
R2
VOUT = 5.5V to 42V
COUT
PGND
GND
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Revision 1.05
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1 page  
AS1344
Datasheet - Typical Operating Characteristics
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7 Typical Operating Characteristics
Parts used for measurments: 6.8µH (MOS6020-682) Inductor, 10µF (GRM21BR60J106KE19) CIN and 4.7µF
(GRM32ER71H475KA88) COUT, (PMEG4010BEA) D1;
Figure 3. Efficiency vs. Output Current; VOUT = 6V
100
Figure 4. Efficiency vs. Output Current; VOUT = 12V
100
90 90
80 80
70 70
60 60
50
40
30
0.1
Vin = 2.0V
Vin = 2.5V
Vin = 3.0V
Vin = 3.3V
1 10
Output Current (mA)
100
Figure 5. Efficiency vs. Output Current; VOUT = 18V
100
90
80
70
60
50
40
30
0.1
Vin = 2.5V
Vin = 3.0V
Vin = 3.3V
1 10
Output Current (mA)
100
Figure 7. Efficiency vs. Input Voltage; VOUT = 12V
100
50
40
30
0.1
Vin = 2.0V
Vin = 2.5V
Vin = 3.0V
Vin = 3.3V
1 10
Output Current (mA)
100
Figure 6. Efficiency vs. Output Current; VOUT = 24V
80
70
60
50
40
30
20
10
0
0.1
Vin = 2.5V
Vin = 3.0V
Vin = 3.3V
1 10
Output Current (mA)
100
Figure 8. Efficiency vs. Input Voltage; IOUT = 10mA
100
90 90
80 80
70 70
60 60
50
Iout = 10mA
40 Iout = 50mA
Iout = 100mA
30
0.9 1.2 1.5 1.8 2.1 2.4 2.7 3 3.3 3.6
Input Voltage (V)
50
40
30
0.9 1.2 1.5 1.8 2.1 2.4 2.7
Input Voltage (V)
Vout = 5.5V
Vout = 10V
Vout = 12V
Vout = 15V
3 3.3 3.6
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AS1344
Datasheet - Application Information
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9 Application Information
Shutdown and Output Discharge
A logic low on the EN pin shuts down the AS1344 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 COUT and on the load.
Note: Pin EN should not be left floating. If the shutdown feature is not used, connect EN to VCC. The output will be
discharged during shutdown but the output also must be fully discharged before the device is enabled again.
Battery Disconnect
The AS1344 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
RON resistance the efficiency is slightly lower if the battery disconnect switch is used.
PLOSS = IIN² x RON
(EQ 1)
Softstart Function
To limit the input current during startup a resistor RV can be connected between the pins VIN and VCC. For the corre-
lation between the resistor value, the supply voltage and the startup time see Figure 33. For the correlation between
resistor value, the supply voltage and the peak current see Figure 34. Connect VIN directly to VCC (no resistor) to dis-
able the softstart Function.
As an example some peak current and time values are listed at a given Rv in Table 4.
Table 4. Timing for Softstart @ VCC= 2.4V, COUT = 155µF,
RV [Ω]
0
1.0 1.5 2.0 2.4 3.0
IPEAK [A] 1.76 0.81 0.66 0.56 0.50 0.42
t [ms]
25
76 100 130 156 204
Figure 33. Startup Time; CIN = 150µF, COUT = 155µF
800
700
600
500
0 Ohm
1.0 Ohm
1.5 Ohm
2.0 Ohm
2.4 Ohm
3.0 Ohm
400
300
200
100
0
1 1.4 1.8 2.2 2.6 3 3.4
Input Voltage (V)
Figure 34. Peak Current; CIN = 10µF, COUT = 155µF
3.5
3
2.5
2
0 Ohm
1.0 Ohm
1.5 Ohm
2.0 Ohm
2.4 Ohm
3.0 Ohm
5.1 Ohm
1.5
1
0.5
0
1 1.4 1.8 2.2 2.6 3 3.4
Input Voltage (V)
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