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PDF AX3503 Data sheet ( Hoja de datos )
| Número de pieza | AX3503 | |
| Descripción | 1A Synchronous Step-Down Converter | |
| Fabricantes | AXElite | |
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AX3503
1.5MHz, 1A Synchronous Step-Down
Converter
GENERAL DESCRIPTION
AX3503 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 35uA and drops to <1uA in shutdown. The 2.5V to 6V input
voltage range makes AX3503 ideally suited for single Li-Ion, two to four AA battery-powered
applications. 100% duty cycle provides low dropout operation, extending battery life in
portable systems. PWM pulse skipping mode operation provides very low output ripple
voltage for noise sensitive applications. Switching frequency is internally set at 1.5MHz,
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. AX3503 is available
in small SOT-23-5L and TDFN-6L (2*2) packages.
FEATURES
- 2.5V to 6V Input Voltage Range
- High Efficiency: Up to 94%
- 1.5MHz Constant Frequency Operation
- 1A Output Current at VIN=3.6V and VOUT=1.8V
- Quiescent Current: 35uA (input < 4.2V)
- No Schottky Diode Required
- 100% Duty Cycle in Dropout
- 0.6V Reference Allows Low Output Voltages
- Current Mode Operation for Excellent Line and Load Transient Response
- Current limit, Enable function
- Short Circuit Protect (SCP)
- ≤ 1µA Shutdown Current
- SOT-23-5L and TDFN-6L (2*2) Pb-Free packages
1/13
Axelite Confidential Materials, do not copy or distribute without written consent.
Rev.2.3 Dec.5, 2012
1 page  
AX3503
APPLICATION CIRCUIT
U1
VIN
SW
EN
C1 FB
4.7u
GND
AX3503
L1
2.2uH
R1
60K
R2
30K
Vout = 0.6 * (1+R1/R2)
R2=10K~30K
Vout=1.8V
C3
100p C2
10u
FUNCTION DESCRIPTIONS
Operation
AX3503 is a monolithic switching mode step-down DC-DC converter. It utilizes internal
MOSFETs to achieve high efficiency and can generate very low output voltage by using
internal reference at 0.6V. It operates at a fixed switching frequency, and uses the slope
compensated current mode architecture. This step-down DC-DC Converter supplies
1000mA output current at VOUT = 1.8V with input voltage range from 2.5V to 6V.
Current Mode PWM Control
Slope compensated current mode PWM control provides stable switching and
cycle-by-cycle current limit for excellent load and line 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. The OVDET
comparator controls output transient overshoots by turning the main switch off and keeping it
off until the fault is no longer present.
Idle Mode Operation
At very light loads, AX3503 automatically enters pulse skipping Mode. In the pulse
skipping Mode, the inductor current may reach zero or reverse on each pulse. The PWM
control loop will automatically skip pulses to maintain output regulation. The bottom
MOSFET is turned off by the current reversal comparator, IZERO, and the switch voltage will
ring. This is discontinuous mode operation, and is normal behavior for the switching
regulator.
5/13
Axelite Confidential Materials, do not copy or distribute without written consent.
Rev.2.3 Dec.5, 2012
5 Page 
AX3503
TYPICAL CHARACTERISTICS (CONTINUES)
Output Ripple(Very light Load)
VIN=3.3V, VOUT=1.2V, L=2.2uH, no Load
Output Ripple(light Load)
VIN=3.3V, VOUT=1.2V, L=2.2uH, IOUT=80mA
Output Ripple(Heavy Load)
Transient
VIN=3.3V, VOUT=1.2V, L=2.2uH, IOUT=200mA VIN=3.3V, VOUT=1.2V, L=2.2uH, IOUT=0A~1A
11/13
Axelite Confidential Materials, do not copy or distribute without written consent.
Rev.2.3 Dec.5, 2012
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet AX3503.PDF ] | |
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