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PDF AS1322 Data sheet ( Hoja de datos )
| Número de pieza | AS1322 | |
| Descripción | DC-DC Step-Up Converters | |
| Fabricantes | ams | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AS1322 (archivo pdf) en la parte inferior de esta página. Total 18 Páginas | ||
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AS1322
Low Voltage, Micropower, DC-DC Step-Up Converters
1 General Description
The AS1322A and the AS1322B are synchronous, fixed frequency,
very high-efficiency DC-DC boost converters capable of supplying
3.3V at 150mA from a single AA-supply. Compact size and minimum
external parts requirements make these devices perfect for modern
portable devices.
High-speed switching frequency (1.2MHz) and internally
compensated PWM current mode design provide highly-reliable DC-
DC conversion, especially when driving white LEDs.
The converters are available as the standard products listed in Table
1.
Table 1. Standard Products
Model
Light Load Switching
AS1322A
Automatic Powersave Operation
AS1322B
Continuous Switching
The devices contain two internal MOSFET switches: one NMOS
switch and one PMOS synchronous rectifier.
Anti-ringing control circuitry reduces EMI by damping the inductor in
discontinuous mode, and the devices exhibit extremely low
quiescent current (< 1µA) in shutdown.
In shutdown mode the battery is connected to the output and VOUT
is held at approximately VIN - 0.6V.
The AS1322 is available in a 6-pin TSOT-23 package.
Figure 1. Typical Application Diagram – Single Cell to 3.3V
Synchronous Boost Converter
2 Key Features
95% Efficiency
Single-Cell Operation
Delivers 160mA @ 3.3V (from Single AA Cell)
Delivers 220mA @ 5.0V (from Two AA Cells)
Delivers 570mA @ 3.3V (from Two AA Cells)
Low Start-Up Voltage: 0.85V
High-Speed Fixed-Frequency: 1.2MHz
Internal PMOS Synchronous Rectifier
Automatic Powersave Operation (AS1322A)
Continuous Switching at Light Loads (AS1322B)
Anti-Ringing Control Minimizes EMI
Logic Controlled Shutdown (< 1µA)
Output Range: 2.5 to 5.0V
6-pin TSOT-23 Package
3 Applications
The AS1322 is ideal for low-power applications where ultra-small
size is critical as in medical diagnostic equipment, hand-held
instruments, pagers, digital cameras, remote wireless transmitters,
MP3 players, LCD bias supplies, cordless phones, GPS receivers,
and PC cards.
L1
4.7µH
AA Battery
C1
10µF
On
Off
6
VIN
4
SHDNN
1 SW
AS1322
5
VOUT
2 GND
3
FB
R1
1.02MΩ
1%
R2
604kΩ
1%
C2
10µF
VOUT
3.3V
160mA
www.ams.com/DC-DC_Step-Up/AS1322
Revision 1.10
1 - 18
1 page  
AS1322
Datasheet - Typical Operating Characteristics
7 Typical Operating Characteristics
Figure 3. Powersave mode threshold vs. VIN,
VOUT = 3.0V
30
25
20
15
10
5
0
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5
Battery Voltage (V)
Figure 5. Output Voltage vs. Temperature;
VOUT = 3.3V, IOUT = 10mA
3.36
3.34
3.32
3.3
3.28
3.26
3.24
-50
-25 0 25 50 75
Temperature (°C)
Figure 7. Startup Voltage vs. Output Current;
100
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.1
5V
3.3V
1 10
Output Current (mA)
100
Figure 4. Efficiency vs. Output Current,
VOUT = 3.3V
100
90 VIN = 2.4V
80 VIN = 1.5V
70
VIN = 1.0V
60
50
40
30
1
10 100
Output Current (mA)
Figure 6. Output Voltage vs. Battery Voltage;
VOUT = 3.3V, IOUT = 10mA
3.5
1000
3
2.5
2
1.5
1
0.5
0
0 0.5 1 1.5 2 2.5 3
Battery Voltage (V)
Figure 8. Output Current vs. Battery Voltage;
VOUT = 3.3V, 3% Tolerance
1000
900
800
700
600
500
400
300
200
100
0
0.5 1 1.5 2 2.5
Battery Voltage (V)
3.5
3
www.ams.com/DC-DC_Step-Up/AS1322
Revision 1.10
5 - 18
5 Page 
AS1322
Datasheet - Application Information
9.1 Output Voltage Ripple
The AS1322 is designed to work at high efficiency. In order to reduce the output ripple the following improvements are recommended:
Use a higher output capacitor, up to 44µF and a higher input capacitor (22µF).
Use smaller values for the resistor divider. R1 should be about 300kΩ. To avoid a high leakage current from pin VOUT through the resistor
divider to GND, R1 should not be less than 100kΩ.
To reduce the output ripple it’s also possible to speed up the feedback loop. To achieve this, place a 22pF (C4 in Figure 20) capacitor in
parallel to R1. Via C4 the fast transients are shorted to the FB pin and the feedback loop is even faster. A 1MΩ resistor for R1 slows down
the FB loop.
Due to noise and to their non linear behavior, the use of potentiometers is not recommended.
Figure 20. AS1322 - Typical Application for lower Output Voltage Ripple
L1
4.7µH
2xAA Battery
C1
22µF
On
Off
6
VIN
4
SHDNN
1 SW
AS1322
2 GND
5
VOUT
C4
22pF
3
FB
R1
250kΩ
VOUT = 2.8V
C2
22µF
C3
22µF
R2
196kΩ
Note: For correct measurements of the output ripple connect the oscilloscope probe as close as possible to the positive plate of the COUT
and connect the GND of the oscilloscope probe to the negative plate of the COUT. This will reduce the inductive coupling and will
deliver a more accurate measurement result.
The output ripple is getting higher as VIN is getting closer to VOUT. Figure 21 shows that the above mentioned improvements reduce the output
voltage ripple. If VIN is higher than VOUT the AS1322 stops switching and VIN is connected to VOUT via the inductor and the internal P-FET.
Figure 21. Output Voltage Ripple vs. Input Voltage; VOUT = 2.8V, IOUT = 0.8mA
125
Cout = 44µF
100
Cout = 66µF
Cout = 44µF + C4 = 22pF
75
50
25
0
0.5 1 1.5 2 2.5 3 3.5
Input Voltage (V)
www.ams.com/DC-DC_Step-Up/AS1322
Revision 1.10
11 - 18
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet AS1322.PDF ] | |
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