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PAM2306 Schematic ( PDF Datasheet ) - Power Analog Micoelectronics

Teilenummer PAM2306
Beschreibung Dual High-Efficiency PWM Step-Down DC-DC Coverter
Hersteller Power Analog Micoelectronics
Logo Power Analog Micoelectronics Logo 




Gesamt 15 Seiten
PAM2306 Datasheet, Funktion
PAM2306
Dual High-Efficiency PWM Step-Down DC-DC Coverter
Features
n Efficiency up to 96%
n Only 40μA (Typ. per Channel) Quiescent
Current
n Output Current: Up to 1A per Channel
n Internal Synchronous Rectifier
n 1.5MHz Switching Frequency
n Soft Start
n Under-Voltage Lockout
n Short Circuit Protection
n Thermal Shutdown
n Small 12L WDFN3x3 Package
n Pb-Free Package and RoHS Compliant
Applications
n Cellular Phone
n Portable Electronics
n Personal Information Appliances
n Wireless and DSL Modems
n MP3 Players
General Description
The PAM2306 is a dual step-down current-mode,
DC-DC converter. At heavy load, the constant-
frequency PWM control performs excellent
stability and transient response. To ensure the
longest battery life in portable applications, the
PAM2306 provides a power-saving Pulse-
Skipping Modulation (PSM) mode to reduce
quiescent current under light load operation.
The PAM2306 supports a range of input voltages
from 2.5V to 5.5V, allowing the use of a single
Li+/Li-polymer cell, multiple Alkaline/NiMH cell,
USB, and other standard power sources. The dual
output voltages are available for 3.3V, 2.8V, 2.5V,
1.8V, 1.5V, 1.2V or adjustable. All versions
employ internal power switch and synchronous
rectifier for to minimize external part count and
realize high efficiency. During shutdown, the input
is disconnected from the output and the shutdown
current is less than 0.1μA. Other key features
include under-voltage lockout to prevent deep
battery discharge.
Typical Application
www.DataSheet4U.com
VIN2
CIN2
4 7μF
R12
CFw1
100 pF
VOUT1
L2
PAM2306
1 VIN2
EN2 12
2 LX2
3 GND
NC2 11
FB2 10
4 FB1
GND 9
5 NC1
8
LX1
R11 6 EN1
VIN1 7
L1
COUT2
10μF
R21
VOUT2
CFW2
100 pF
CIN1
4.7 μF
VIN1
R22
COUT1
10μF
( )VOUTx
=
VREF
1+
Rx1
Rx2
Figure 1. Adjustable Voltage Regulator
Power Analog Microelectronics,Inc
www.poweranalog.com
1
07/2008 Rev 1.0






PAM2306 Datasheet, Funktion
PAM2306
Dual High-Efficiency PWM Step-Down DC-DC Coverter
Typical Performance Characteristics
TA=25°C, C =IN 10μF, CO=10μF, L=4.7μH, unless otherwise noted.
Efficiency vs Output Current (Vo=1.2V)
100
90
80
70
60
50
40
30
20 Vin=3.6V
10 Vin=4.2V
Vi n= 5V
0
1 10 100 1000
Output Current(mA)
Efficiency vs Output Current (Vo=1.5V)
100
90
80
70
60
50
40
30
20
1
2.5V
3.6V
4.2V
10 100 1000
Output Current(mA)
Efficiency vs Output Current (Vo=1.8V)
100
90
80
70
60
50
40
30
20
www.DataS1heet4U.com
10 100
Output Current(mA)
2.5V
3.6V
4.2V
1000
Efficiency vs Output Current (Vo=2.5V)
100
90
80
70
60
50
40
30
20
1
3V
3.6V
4.2V
10 100 1000
Output Current(mA)
100 Efficiency vs Output Current (Vo=2.8V)
90
80
70
60
50
40
30
20
1
3V
3.6V
4.2V
10 100 1000
Output Current(mA)
Eifficiency VS Output Current (Vo=3.3V)
100
90
80
70
60
50
40
30
20 Vin=3.6V
Vin=4.2V
10 Vin=5V
0
1 10 100 1000
Output Current(mA)
Power Analog Microelectronics,Inc
www.poweranalog.com
6
07/2008 Rev 1.0

6 Page









PAM2306 pdf, datenblatt
PAM2306
Dual High-Efficiency PWM Step-Down DC-DC Coverter
For the condition where the step-down converter
is in dropout at 100% duty cycle, the total device
dissipation reduces to:
PD =IO2RDSONH +IQ VIN
Since R ,DS(ON) quiescent current, and switching
losses all vary with input voltage, the total losses
should be investigated over the complete input
voltage range. The maximum power dissipation
depends on the thermal resistance of IC
package, PCB layout, the rate of surrounding
airflow and temperature difference between
junction and ambient. The maximum power
dissipation can be calculated by the following
formula:
PD
=
TJ(MAX) -TA
θJA
Where TJ(max) is the maximum allowable
junction temperature 125°C.TA is the ambient
temperature and θJA is the thermal resistance
from the junction to the ambient. Based on the
standard JEDEC for a two layers thermal test
board, the thermal resistance θJA of DFN3X3 is
60°C/W. The maximum power dissipation at TA =
25°C can be calculated by following formula:
PD=(125°C-25°C)/60°C/W=1.66W
Setting the Output Voltage
The internal reference is 0.6V (Typical). The
output voltage is calculated as below:
www.DataSheet4U.com
VO=0.6×1æçè +
R1 ö
R2 ÷ø
The output voltage is given by Table 1.
Table 1: Resistor selection for output voltage
setting
Vo
1.2V
1.5V
1.8V
2.5V
3.3V
R1
100k
150k
200k
380k
540k
R2
100k
100k
100k
120k
120k
100% Duty Cycle Operation
As the input voltage approaches the output
voltage, the converter turns the P-channel
transistor continuously on. In this mode the
output voltage is equal to the input voltage minus
the voltage drop across the P - channel
transistor:
VOUT = VIN – ILOAD (Rdson + RL)
where Rdson = P-channel switch ON resistance,
ILOAD = Output current, RL = Inductor DC
resistance
UVLO and Soft-Start
The reference and the circuit remain reset until
the VIN crosses its UVLO threshold.
The PAM2306 has an internal soft-start circuit
that limits the in-rush current during start-up.
This prevents possible voltage drops of the input
voltage and eliminates the output voltage
overshoot. The soft-start acts as a digital circuit
to increase the switch current in several steps to
the P-channel current limit (1500mA).
Short Circuit Protection
The switch peak current is limited cycle-by-cycle
to a typical value of 1500mA. In the event of an
output voltage short circuit, the device operates
with a frequency of 400kHz and minimum duty
cycle, therefore the average input current is
typically 200mA.
Thermal Shutdown
When the die temperature exceeds 150°C, a
reset occurs and the reset remains until the
temperature decrease to 120°C, at which time
the circuit can be restarted.
Power Analog Microelectronics,Inc
www.poweranalog.com
12
07/2008 Rev 1.0

12 Page





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