Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2308
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 10L WDFN 3x3
Packages
n
Pb-Free Package and RoHS Compliant
General Description
The PAM2308 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
PA M 2 3 0 8 p r o v i d e s a p o w e r - s a v i n g P u l s e -
Skipping Modulation (PSM) mode to reduce
quiescent current under light load operation.
The PAM2308 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 0.1 μ A. Other key features
include under-voltage lockout to prevent deep
battery discharge.
Applications
n
n
n
n
n
Cellular Phone
Portable Electronics
Personal Information Appliances
Wireless and DSL Modems
MP3 Players
Typical Application
L1
V
OUT1
C
OUT1
10μF
C
Fw1
100nF
R11
1
EN1
FB1
PAM2308
LX1
VIN1
GND
10
8
9
C
IN1
4. μF
7
V
IN1
R12
2
R22
4
C
IN2
4.
7μF
V
IN2
GND
VIN2
LX2
L2
3
5
FB2 7
6
EN2
R21
C
FW2
100pF
V
OUT2
C
OUT2
10μF
V
OUTx
=
V
REF
1
+
Rx1
Rx2
Figure 1. Adjustable Voltage Regulator
(
)
Power Analog Microelectronics
,
Inc
www.poweranalog.com
1
07/2008 Rev 1.0
Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2308
Typical Application
V
OUT1
C
OUT1
10μF
1
L1
PAM2308
EN1
2
LX1
VIN1
GND
FB2
EN2
10
8
9
7
6
C
IN1
4.
7μF
V
IN1
C
IN2
4.
7μF
V
IN2
FB1
GND
VIN2
4
3
5
LX2
L2
V
OUT2
C
OUT2
10 μ F
V
OUTx
=
1.
2V,1.
5V,1.8V,2. 2.8V or 3.
5V,
3V
Figure 2. Fixed Voltage Regulator
Block Diagram
VINx
OSC
FBx
FREQ
SHIFT
-
+
- + +
1
.
5M
OSC
SLOPE
COMP
PWM
COMP
IAMP
+
-
S Q
EA
R1
R2
COMP
VIN
SWITCHING
LOGIC
AND
RS LATCH
BLANKING
CIRCUIT
MAIN
SWITCH
(
PCH
)
ANTI
-
SHOOT
-
THRU
R Q
LXx
SYNCHRONOUS
RECTIFIER
(
NCH
)
ENx
0
.
6VREF
SHUTDOWN
IRCMP
+
-
GND
Power Analog Microelectronics
,
Inc
www.poweranalog.com
2
07/2008 Rev 1.0
Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2308
Pin Configuration and Marking Information
TOP VIEW
WDFN-10L 3x3
EN1
FB1
VIN2
GND
LX2
1
2
3
4
5
10
9
L X1
GND
VIN1
FB2
EN2
2308v
1
v
2
XXXYW
8
7
6
v
1
: Output Voltage 1
v
2
: Output Voltage 2
(refer to “Ordering
Information”)
X: Internal Code
Y: Year
W: Week
GND
(Exposed Pad)
Pin No.
1
2
3
4
,
9
5
6
7
8
10
Pin Name
EN1
FB1
VIN2
GND
LX2
EN2
FB2
VIN1
LX1
Pin Function
Chip Enable of Channel 1
(
Active High
).V
EN1
≤V
IN1.
Feedback of Channel 1.
Power Input of Channel 2.
Ground.The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Pin for Switching of Channel 2.
Chip Enable of Channel 2
(Active
High). V
EN2
≤V
IN2.
Feedback of Channel 2.
Power I t of Channel 1.
npu
Pin for Switching of Channel 1.
Power Analog Microelectronics
,
Inc
www.poweranalog.com
3
07/2008 Rev 1.0
Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2308
Absolute Maximum Ratings
These are stress ratings only and functional operation is not implied
.
Exposure to absolute
maximum ratings for prolonged time periods may affect device reliability
.
All voltages are with
respect to ground
.
Input Voltage.................................
-
0.3V to 6.5V
E N 1,F B 1,L X 1,E N 2,F B 2 and LX2 Pin Voltage........
-
0
.
3V to
(
V
IN
+
0
.
3V
)
Junction Temperature................................150°C
Storage Temperature Range.......
-
65°C to 150°C
Soldering Temperature.....................260°C
,
10sec
Recommended Operating Conditions
Supply Voltage...............................2.5V to 5.5V
Ambient Temperature Range.........
-
40 °C to 85 °C
Junction Temperature Range.........-40°C to 125 °C
Thermal Information
Parameter
Thermal Resistance (Junction to ambient)
Thermal Resistance (Junction to case)
Power Dissipation
Symbol
θ
JA
θ
JC
P
D
Package
WDFN 3x3-10
WDFN 3x3-10
WDFN 3x3-10
Maximum
60
8.5
1.66
Unit
°C/W
°C/W
W
Power Analog Microelectronics
,
Inc
www.poweranalog.com
4
07/2008 Rev 1.0
Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2308
Electrical Characteristic
T
A
=25
O
C, V
IN
=3.6V, V
O
=1.8V, C
IN
=10μF, C
O
=10μF, L=2.2μH, unless otherwise noted.
PARAMETER
Input Voltage Range
Regulated Feedback Voltage
Reference Voltage Line Regulation
Regulated Output Voltage Accuary
Peak Inductor Current
Output Voltage Line Regulation
Output Voltage Load Regulation
Quiescent Current (per channel)
Shutdown Current (per channel)
Oscillator Frequency
Drain-Source On-State Resistance
SW Leakage Current (per channel)
High Efficiency
EN Threshold High
EN Threshold Low
EN Leakage Current
Over Temperature Protection
OTP
Hysteresis
SYMBOL
V
IN
V
FB
ΔV
FB
V
O
I
PK
LNR
LDR
I
Q
I
SD
f
OSC
R
DS(ON)
I
LSW
η
V
EH
V
EL
I
EN
OTP
OTH
±0.01
150
30
1.5
0.3
I
O
= 100mA
V
IN
=3V,V
FB
= 0.5V or
V
O
=90%
V
IN
= 2.5V to 5V, I
O
=10mA
I
O
=1mA to 1A
No load
V
EN
= 0V
V
O
= 100%
V
FB
= 0V or V
O
= 0V
I
DS
=100mA
P MOSFET
N MOSFET
1.2
-3
1.5
0.2
0.5
40
0.1
1.5
500
0.3
0.35
±0.01
96
0.45
0.5
1
0.5
1.5
70
1
1.8
Test Conditions
MIN
2.5
0.588
0.6
0.3
+3
TYP
MAX
5.5
0.612
UNITS
V
V
%/V
%
A
%/V
%
μA
μA
MHz
kHz
Ω
Ω
μA
%
V
V
μA
°C
°C
Power Analog Microelectronics
,
Inc
www.poweranalog.com
5
07/2008 Rev 1.0
ARM技术
