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PDF AS1337 Data sheet ( Hoja de datos )
| Número de pieza | AS1337 | |
| Descripción | DC-DC Step-Up Converter | |
| Fabricantes | austriamicrosystems AG | |
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Hay una vista previa y un enlace de descarga de AS1337 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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Datasheet
www.DataSheet4U.com
AS1337
200mA, DC-DC Step-Up Converter with Buck Mode
1 General Description
The AS1337 is a synchronous, fixed frequency,
highefficiency DC-DC boost converter capable of
supplying 3.3V @ 200mA from two AA Cells. Com-
pact size and minimum external parts require-
ments make these devices perfect for modern
portable devices. The AS1337 offers automatic
powersave mode to increase efficiency at light
loads. For input voltages higher than VOUT the
AS1337 will switch in a step down mode, so that a
Buck Boost function is realized.
The AS1337A offers a shutdown mode where the
battery is connected directly to the output enabling
the supply of real-time-clocks or memories.
The AS1337 offers a POK (open-drain) feature
which detects output power fail of 10%.
The AS1337 is available in a TDFN (3x3mm) 8-pin
package.
2 Key Features
! Input Voltage Range: 0.65V to 4.5V
! Low Start-Up Voltage: 0.85V
! Output Voltage Range: 2.5V to 5.0V
! Delivers 200mA @ 3.3V (from two AA Cell)
! up to 97% Efficiency
! High-Speed Fixed-Frequency: 1.2MHz
! Single-Cell Operation
! Internal PMOS Synchronous Rectifier
! Automatic Powersave Operation
! Anti-Ringing Control Minimizes EMI
! Logic Controlled Shutdown (< 1µA)
! TDFN (3x3mm) 8-pin Package
3 Applications
The AS1337 is ideal for low-power applications
where ultra-small size is critical as in medical diag-
nostic equipment, hand-held instruments, pagers,
digital cameras, remote wireless transmitters, MP3
players, LCD bias supplies, cordless phones, GPS
receivers, and PC cards.
Figure 1. AS1337 - Typical Application Diagram – Dual Cell to 3.3V Synchronous Boost Converter
3.6V
Buck Mode
VOUT=3.3V
VIN Curve
Boost Mode
1.6V
L1
4.7µH
VIN = 2xAA
1.6V to 3.6V
LX
CIN
10µF
VIN
On
Off EN
GND
AS1337
VOUT
FB
POK
PGND
VOUT = 3.3V
COUT
22µF
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Revision 1.03
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1 page  
AS1337
Datasheet - Typical Operating Characteristics
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7 Typical Operating Characteristics
VOUT = 3.3V, CIN = 10µF, COUT = 22µF, L1 = 4.7µH, TAMB = +25°C (unless otherwise specified).
Figure 3. Efficiency vs. IOUT - Down Conversion Mode
100
Figure 4. Efficiency vs. IOUT - Step-up Mode
100
90 90
80 80
70 70
60 60
50
40
30
0.1
Vin = 3.5V
Vin = 4.0V
1 10 100
Output Current (mA)
1000
Figure 5. Efficiency vs. Input Voltage
100
50
40
30
0.1
Vin = 1.5V
Vin = 2.0V
Vin = 3.0V
1 10 100
Output Current (mA)
1000
Figure 6. Output Current vs. Input Voltage
500
90
400
80
70 300
60
Iout = 1mA
50
Iout = 10mA
Iout = 30mA
40 Iout = 100mA
Iout = 200mA
30
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
Input Voltage (V)
Figure 7. Min. Operating Voltage vs. Temperature
0.85
200
100
0
0.5 1 1.5 2 2.5 3 3.5 4
Input Voltage (V)
Figure 8. Switching Frequency vs. Temperature
1.5
4.5
0.75 1.4
1.3
0.65
1.2
0.55
1.1
0.45 1
0.35
-45 -30 -15 0 15 30 45 60 75 90
Temperature (°C)
0.9
-45 -30 -15 0 15 30 45 60 75 90
Temperature (°C)
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Revision 1.03
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5 Page 
AS1337
Datasheet - Application Information
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Component Selection
Only three power components are required to complete the design of the buck-boost converter, except the additional
two resistors for the voltage divider to set VOUT. The high operating frequency and low peak currents of the AS1337
allow the use of low value, low profile inductors and tiny external ceramic capacitors.
Inductor Selection
The inductor should have low ESR to reduce the I²R power losses, and must be able to handle the peak inductor
current without saturating. High-frequency ferrite core inductor materials reduce frequency dependent power losses
compared to less expensive powdered iron types, which result in improved converter efficiency.
A 4.7µH to 15µH inductor value with a >850mA current rating and low DCR is recommended. For applications where
radiated noise is a concern, a toroidal or shielded inductor can be used.
Capacitor Selection
A 10µF capacitor is recommend for CIN as well as a 22µF for COUT. Small-sized ceramic capacitors are recommended.
X5R and X7R ceramic capacitors are recommend as they retain capacitance over wide ranges of voltages and temper-
atures.
Output Capacitor Selection
Low ESR capacitors should be used to minimize VOUT ripple. Multi-layer ceramic capacitors are recommended since
they have extremely low ESR and are available in small footprints. A 1 to 10µF output capacitor is sufficient for most
applications. Larger values up to 22µF may be used to obtain extremely low output voltage ripple and improve tran-
sient response.
An additional phase lead capacitor may be required with output capacitors larger than 10µF to maintain acceptable
phase margin. X5R and X7R dielectric materials are recommended due to their ability to maintain capacitance over
wide voltage and temperature ranges.
Input Capacitor Selection
Low ESR input capacitors reduce input switching noise and reduce the peak current drawn from the battery. Ceramic
capacitors are recommended for input decoupling and should be located as close to the device as is practical. A 4.7µF
input capacitor is sufficient for most applications. Larger values may be used without limitations.
Table 4. Recommended External Components
Name
CIN
COUT
L1
Part Number
GRM219R60J106KE19
GRM21BR60J226ME39
MOS6020-472ML
Value
10µF
22µF
4.7µH
Rating
6.3V
6.3V
1.82A
Type
X5R
X5R
50mΩ
Size
Manufacturer
0805
0805
Murata
www.murata.com
6.8x6.0x2.4mm
Coilcraft
www.coilcraft.com
PCB Layout Guidelines
The high-speed operation of the AS1337 requires proper layout for optimum performance.
! A large ground pin copper area will help to lower the device temperature.
! A multi-layer board with a separate ground plane is recommended.
! Traces carrying large currents should be direct.
! Trace area at pin FB should be as small as is practical.
! The lead-length to the battery should be as short as is practical.
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