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PDF AX3531 Data sheet ( Hoja de datos )
| Número de pieza | AX3531 | |
| Descripción | 2A Synchronous Step-Down Converter | |
| Fabricantes | AXElite | |
| Logotipo |  |
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AX3531
1.25MHz, 2A Synchronous Step-Down
Converter
GENERAL DESCRIPTION
AX3531 is a high efficiency monolithic synchronous buck regulator using a constant
frequency, current mode architecture. The device is available in an adjustable version.
Supply current with no load is 200uA and drops to <1uA in shutdown. The 2.8V to 5.5V input
voltage range makes AX3531 ideally suited for single Li-Ion, two to three AA
battery-powered applications. 100% duty cycle provides low dropout operation, extending
battery life in portable systems. Switching frequency is internally set at 1.25MHz, allowing
the use of small surface mount inductors and capacitors. The internal synchronous switch
increases efficiency and decreases need of an external schottky diode. Low output voltages
are easily supported with the 0.6V feedback reference voltage. AX3531 is available in small
TSOT-23-6L package.
FEATURES
- 2.8V to 5.5V Input Voltage Range
- Output Voltage from 0.6V to VIN
- High Efficiency: Up to 96%
- 1.25MHz Constant Frequency Operation
- Up to 2A Output Current
- Quiescent Current: 200uA (Typical)
- No Schottky Diode Required
- Current Mode Operation for Excellent Line and Load Transient Response
- Current limit, Enable function
- Short Circuit Protect (SCP)
- Build in soft start function
- ≤ 1µA Shutdown Current
- TSOT-23-6L Pb-Free package
1/10
Axelite Confidential Materials, do not copy or distribute without written consent.
Rev.1.0 Jul.22, 2011
1 page  
AX3531
Current Mode PWM Control
Slope compensated current mode PWM control provides stable switching and
cycle-by-cycle current limit for excellent load and line transient responses and protection of
the internal main switch (P-Ch MOSFET) and synchronous rectifier (N-CH MOSFET). During
normal operation, the internal P-Ch MOSFET is turned on for a certain time to ramp the
inductor current at each rising edge of the internal oscillator, and switched off when the peak
inductor current is above the error voltage. The current comparator, ICOMP, limits the peak
inductor current. When the main switch is off, the synchronous rectifier will be turned on
immediately and stay on until either the inductor current starts to reverse, as indicated by the
current reversal comparator, IZERO, or the beginning of the next clock cycle.
APPLICATION INFORMATION
Setting the Output Voltage
Application circuit item shows the basic application circuit with AX3531 adjustable
output version. The external resistor sets the output voltage according to the following
equation:
V OUT
0.6V
1
R1
R2
Table 1 Resistor select for output voltage setting
VOUT
R2
R1
1.2V 100K 100K
1.5V 100K 150K
1.8V 100K 200K
2.5V 150K 470K
3.3V 120K 540K
Inductor Selection
For most designs, the AX3531 operates with inductors of 2.2µH to 3.3µH. Low
inductance values are physically smaller but require faster switching, which results in some
efficiency loss. The inductor value can be derived from the following equation:
V V V
OUT
IN OUT
L V I f
IN L OSC
Where is inductor Ripple Current. Large value inductors lower ripple current and small
value inductors result in high ripple currents. Choose inductor ripple current approximately
20% of the maximum load current 2000mA, ΔIL=400mA.
5/10
Axelite Confidential Materials, do not copy or distribute without written consent.
Rev.1.0 Jul.22, 2011
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet AX3531.PDF ] | |
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