AAP2406 [EUTECH]
1.5MHz, 600mA Synchronous Step-Down Converter; 为1.5MHz ， 600mA同步降压转换器
| 型号： | AAP2406 |
| 厂家： | 
EUTECH MICROELECTRONICS INC |
| 描述： | 1.5MHz, 600mA Synchronous Step-Down Converter |
| 文件： | 总11页 (文件大小：733K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
芯美 子
AAP2406
1.5MHz, 600mA Synchronous
Step-Down Converter
DESCRIPTION
FEATURES
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High Efficiency
The AAP2406 is a constant frequency, current mode,
PWM step-down converter. The device integrates a
main switch and a synchronous rectifier for high
efficiency. The 2.5V to 5.5V input voltage range makes
the AAP2406 ideal for powering portable equipment
that runs from a single cell Lithium-Ion (Li+) battery or
3-cell NiMH/ NiCd batteries. The output voltage can be
regulated as low as 0.6V. The AAP2406 supports up to
600mA load current and can also run at 100% duty
cycle for low dropout applications, extending battery
life in portable systems.
Switching frequency is internally set at 1.5MHz,
allowing the use of small surface mount inductor and
capacitors. The internal synchronous switch increases
efficiency while eliminate the need for an external
Schottky diode. The AAP2406 is available in a low
profile 5 lead SOT package.
1.5MHz Constant Switching Frequency
600mA Available Load Current
270µA Typical Quiescent Current
2.5V to 5.5V Input Voltage Range
Adjustable Output Voltage as Low as 0.6V
100% Duty Cycle Low Dropout Operation
No Schottky Diode Required
Short Circuit and Thermal Protection
Over Voltage Protection
＜1µA Shutdown Current
Available in SOT23-5 Package
RoHS Compliant and 100% Lead(Pb)-Free
APPLICATIONS
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Cellular and Smart Phones
Portable Media Players/ MP3 Players
Digital Still and Video Cameras
Portable Instruments
WLAN PC Cards
Typical Application Circuit
Figure1.
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AAP2406
Block Diagram
Figure2.
Pin Configurations
Package Type
Pin Configurations
SOT23-5
Pin Description
PIN
EN
Pin
1
DESCRIPTION
Chip Enable pin. Forcing this pin above 1.5V enables the part. Forcing this pin below
0.3V shuts down the device. Do not leave EN floating.
GND
SW
2
Common ground
Switch Node Connection to Inductor. This pin connects to the drains of the internal
3
main and synchronous power MOSFET switches.
VIN
VFB
4
5
Supply voltage pin
Feedback pin
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Ordering Information
Order Number
Package Type
Marking
Operating Temperature range
e A □ □
AAP2406VIR1
SOT23-5
-40 °C to 85°C
AAP2406 □ □ □ □
Lead Free Code
1: Lead Free 0: Lead
Packing
R: Tape & Reel
Operating temperature range
I: Industry Standard
Package Type
V: SOT-23
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Absolute Maximum Ratings
Input Supply Voltage
EN, VFB Voltages
----------------------------------------------------------- -0.3V to 6V
-------------------------------------------------------------- -0.3V to VIN
P-Channel Switch Source Current (DC) ------------------------------------------ 800mA
N-Channel Switch Sink Current (DC) ---------------------------------------------- 800mA
Peak SW Sink and Source Current --------------------------------------------------
Operating Temperature Range ----------------------------------------------- -40°C to 85°C
Junction Temperature ------------------------------------------------------------------- 125°C
Storage Temperature
1.4A
------------------------------------------------------- -65°C to 150°C
Lead Temp (Soldering, 10sec) -------------------------------------------------------
ESD Rating (HBM) ------------------------------------------------------------------
260°C
2kV
Electrical Characteristics
Unless otherwise specified, TA=25°C, VIN=3.6V.
AAP2406
Typ
Symbol
Parameter
Conditions
Unit
Min
Max.
VIN
IVFB
Input Voltage Range
Feedback Current
2.5
5.5
V
nA
±30
270
IQ
ISHDN
IPK
Quiescent Current
Shutdown Current
Peak Inductor Current
VFB=0.5V
VEN=0V, VIN= 4.2V
VIN=3V, VFB=0.5V
370
1
1.4
µA
µA
A
1
1.2
0.6
VFB
Regulated Feedback Voltage (Note 1)
0.588
0.612
V
∆ Output Overvoltage
∆VOVL
∆VOUT
∆VOVL=VOVL- VFB
20
50
0.2
0.2
0.5
80
0.4
0.4
mV
%/V
%/V
%
Lockout
Output Voltage Line
Regulation
VIN=2.5V to 5.5V, ILOAD=0
VIN=2.5V to 5.5V
Reference Voltage Line
Regulation
∆VFB
Output Voltage Load
Regulation
VLOADREG
ILOAD=0mA to 600mA
VFB=0.6V
VFB=0V
ISW=100mA
ISW=-100mA
1.2
0.3
1.5
210
0.26
0.28
1.8
MHz
kHz
Ω
fOSC
Oscillator Frequency
RPFET
RDS(ON) of P-Channel FET
0.4
0.4
±1
1.5
1
RNFET RDS(ON) of N-Channel FET
Ω
ILSW
VEN
IEN
SW Leakage Current
EN Threshold
EN Leakage Current
VEN=0V, VSW=0V or 5V, VIN=5V
µA
V
µA
1.0
Note 1: The AAP2406 is tested in a proprietary test mode that connects VFB to the output of the error amplifier.
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AAP2406
Typical Operating Characteristics
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AAP2406
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AAP2406
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Application Information
Main Control Loop
The input capacitor RMS current varies with the input
voltage and the output voltage. The equation for the
maximum RMS current in the input capacitor is:
The AAP2406 uses a slop-compensated constant
frequency, current mode PWM architecture. Both the
main (P-Channel MOSFET) and synchronous
(N-channel MOSFET) switches are internal. During
normal operation, the AAP2406 regulates output voltage
by switching at a constant frequency and then
modulating the power transferred to the load each cycle
using PWM comparator. It sums three weighted
differential signals: the output feedback voltage from an
external resistor divider, the main switch current sense,
and the slope-compensation ramp. It modulates output
power by adjusting the inductor-peak current during the
first half of each cycle. An N-channel, synchronous
switch turns on during the second half of each cycle (off
time). When the inductor current starts to reverse or
when the PWM reaches the end of the oscillator period,
the synchronous switch turns off. This keep excess
current from flowing backward through the inductor,
from the output capacitor to GND, or through the main
and synchronous switch to GND.
V
V
O
O
I
= I
×
× 1 −
RMS
O
V
V
IN
IN
The output capacitor COUT has a strong effect on loop
stability.
The selection of COUT is driven by the required effective
series resistance (ESR).
ESR is a direct function of the volume of the capacitor;
that is, physically larger capacitors have lower ESR.
Once the ESR requirement for COUT has been met, the
RMS current rating generally far exceeds the IRIPPLE(P-P)
requirement. The output ripple ∆VOUT is determined by:
Inductor Selection
1
∆V
OUT
≅ ∆I ESR +
The output inductor is selected to limit the ripple current
to some predetermined value, typically 20%~40% of the
full load current at the maximum input voltage. Large
value inductors lower ripple currents. Higher VIN or
VOUT also increases the ripple current as shown in
equation. A reasonable starting point for setting ripple
current is ∆IL=240mA (40% of 600mA).
L
8fC
OUT
When choosing the input and output ceramic capacitors,
choose the X5R or X7R dielectric formulations. These
dielectrics have the best temperature and voltage
characteristics of all the ceramics for a given value and
size.
V
1
OUT
∆I
=
V
1 −
Output Voltage Programming
L
OUT
(f)(L)
V
IN
The output voltage is set by a resistive divider according
to the following formula:
The DC current rating of the inductor should be at least
equal to the maximum load current plus half the ripple
current to prevent core saturation. Thus, a 720mA rated
inductor should be enough for most applications
(600mA+120mA). For better efficiency, choose a low
DC-resistance inductor.
R2
R1
V
= 0.6V 1 +
OUT
The external resistive divider is connected to the output,
allowing remote voltage sensing as shown in Figure3.
CIN and COUT Selection
In continuous mode, the source current of the top
MOSFET is a square wave of duty cycle VOUT/VIN. The
primary function of the input capacitor is to provide a
low impedance loop for the edges of pulsed current
drawn by the AAP2406. A low ESR input capacitor sized
for the maximum RMS current must be used. The size
required will vary depending on the load, output voltage
and input voltage source impedance characteristics. A
typical value is around 4.7µF.
Figure3.
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AAP2406
Thermal Considerations
PC Board Layout Checklist
To avoid the AAP2406 from exceeding the maximum
junction temperature, the user will need to do a thermal
analysis. The goal of the thermal analysis is to determine
whether the operating conditions exceed the maximum
junction temperature of the part. The temperature rise is
given by:
When laying out the printed circuit board, the following
guidelines should be used to ensure proper operation of
the AAP2406.
1. The input capacitor CIN should connect to VIN as
closely as possible. This capacitor provides the AC
current to the internal power MOSFETs.
2. The power traces, consisting of the GND trace, the
SW trace and the VIN trace should be kept short,
direct and wide.
TR=(PD)(θJA)
Where PD=ILOAD2 × RDS(ON) is the power dissipated by
the regulator ; θJA is the thermal resistance from the
junction of the die to the ambient temperature.
The junction temperature, TJ, is given by:
3. The VFB pin should connect directly to the feedback
resistors. The resistive divider R1/R2 must be
connected between the COUT and ground.
4. Keep the switching node, SW, away from the
sensitive VFB node.
TJ=TA+TR
Where TA is the ambient temperature.
TJ should be below the maximum junction temperature
of 125°C.
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AAP2406
Packaging Information
SOT23-5
MILLIMETERS
INCHES
SYMBOLS
MIN.
-
MAX.
1.30
MIN.
-
0.000
MAX.
0.052
0.006
A
A1
D
E1
E
0.00
0.15
2.90
1.60
0.114
0.063
2.60
0.30
0.30
3.00
0.60
0.50
0.102
0.012
0.012
0.118
0.024
0.020
L
b
e
0.95
0.037
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