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PDF APS2415 Data sheet ( Hoja de datos )
| Número de pieza | APS2415 | |
| Descripción | Synchronous Step-Down Converter | |
| Fabricantes | Chipown | |
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APS2415
Chipown
1.2MHz, 1.5A
Synchronous Step-Down Converter
General Description
The APS2415 is a high efficiency monolithic
synchronous buck regulator using a constant frequency,
current mode architecture. The device is available in an
adjustable version and fixed output voltages, such as
1.2V, 1.5V, 1.8V, etc. Supply current with no load is
300uA and drops to <1uA in shutdown. The 2.5V to
6.5V input voltage range makes the APS2415 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 1.2MHz,
allowing the use of small surface mount inductors and
capacitors. The internal synchronous switch increases
efficiency and eliminates the need for an external
Schottky diode. Low output voltages are easily
supported with the 0.6V feedback reference voltage. The
APS2415 is available in a small SOT package.
Applications
z Cellular and Smart Phones
z Microprocessors and DSP Core Supplies
z Wireless and DSL Modems
z PDAs
z MP3 / MP4 /PMP Player
z Digital Still and Video Cameras
z Portable Instruments
Typical Application Circuit
Figure 1. Basic Application Circuit with
APS2415 adjustable version
Features
z High Efficiency: Up to 96%
z 1.2MHz Constant Switching Frequency
z 1.5A Output Current at VIN=3V
z Integrated Main switch and synchronous rectifier.
No Schottky Diode Required
z 2.5V to 6.5V Input Voltage Range
z Output Voltage as Low as 0.6V
z 100% Duty Cycle in Dropout
z Quiescent Current: 300µA(input < 4.2V)
z Slope Compensated Current Mode Control for
Excellent Line and Load Transient Response
z Short Circuit Protection
z <1uA Shutdown Current
z Soft start
z Space Saving 5-Pin SOT23 package
Package
SOT23-5L
100
95
90
85
80
75
70
65
60
55
50
0
η vs Io(Vo=1.8V)
Vin=2.5V
Vin=3.6V
Vin=4.2V
Vin=5V
Vin=6V
300 600 900 1200 1500
Io(mA)
Figure 2. Typical Efficiency Curve
8/F, ChuangYuan Building No.21-1 Changjiang Road, Wuxi New Destrict Tel: +86(510)8521-7718 http://www.chipown.com.cn V0.0
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1 page  
APS2415
Chipown
Operation
APS2415 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 1500mA output
current at Vout = 1.8V with input voltage range from
2.5V to 6.5V.
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.
converter decreases. Caution must be exercised to
ensure the heat dissipated not to exceed the maximum
junction temperature of the IC.
Note 5: The duty cycle D of a step-down converter is
defined as:
D
= TON
×
f OSC
×100%
≈ V OUT
VIN
×100%
Where TON is the main switch on time and fOSC is the
oscillator frequency (1.2MHz).
Maximum Load Current
The APS2415 will operate with input supply voltage as
low as 2.5V, however, the maximum load current
decreases at lower input due to large IR drop on the
main switch and synchronous rectifier. The slope
compensation signal reduces the peak inductor current
as a function of the duty cycle to prevent sub-harmonic
oscillations at duty cycles greater than 50%.
Conversely the current limit increases as the duty cycle
decreases.
Layout Guidance
When laying out the PCB board, the following
suggestions should be taken to ensure proper operation
of the APS2415. These items are also illustrated
graphically in Figure 4 & Figure 5.
Idle Mode Operation
At very light loads, the APS2415 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.
Dropout Operation
When the input voltage decreases toward the value of
the output voltage, the APS2415 allows the main switch
to remain on for more than one switching cycle and
increases the duty cycle (Note 5) until it reaches 100%.
The output voltage then is the input voltage minus the
voltage drop across the main switch and the inductor.
At low input supply voltage, the RDS(ON) of the
P-Channel MOSFET increases, and the efficiency of the
1. The power traces, including the GND trace, the SW
trace and the VIN trace should be kept short, direct
and wide.
2. The VFB pin should be connected directly to the
feedback resistor. The resistive divider R1/R2 must
be connected between the (+) plate of Cout and
ground.
3. Connect the (+) plate of C1 to the VIN pin as
closely as possible. This capacitor provides the AC
current to internal power MOSFET.
4. Keep the switching node, SW, away from the
sensitive VFB node.
5. Keep the (-) plates of C1 and C3 as close as
possible.
8/F, ChuangYuan Building No.21-1 Changjiang Road, Wuxi New Destrict Tel: +86(510)8521-7718 http://www.chipown.com.cn V0.0
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5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet APS2415.PDF ] | |
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