PAM PAM2309

PAM2309
1A Step-Down DC-DC Converter
Features
General Description
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The PAM2309 is a step-down current-mode, DCDC converter. At heavy load, the constantfrequency PWM control performs excellent
stability and transient response. To ensure the
longest battery life in portable applications, the
PA M 2 3 0 9 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 to
save power.
Efficiency up to 96%
Only 40 μ A(TYP.) Quiescent Current
Output Current: Up to 1A
Internal Synchronous Rectifier
1.5MHz Switching Frequency
Soft Start
Under-Voltage Lockout
Short Circuit Protection
Thermal Shutdown
5-pin Small SOT23-5, DFN2x2 6-Pin and
QFN3x3 16-Pin Packages
n Pb-Free Package
The PAM2309 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
output voltage is adjustable from 0.6V to the input
voltage. All versions employ internal power switch
and synchronous rectifierfor 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
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Cellular Phone
Portable Electronics
Wireless Devices
Cordless Phone
Computer Peripherals
Battery Powered Widgets
Electronic Scales
Digital Frame
The PAM2309 is available in SOT23-5, DFN2x2 6Pin and QFN3x3 16-Pin packages.
Typical Application
V IN
L
VIN
Vo
SW
C IN
10μF
R1
GND
VOUT/FB
C FW
Co
10μF
R2
EN
R1 ö
æ
VO = 0.5 ´ ç1 +
÷
è R2 ø
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PAM2309
1A Step-Down DC-DC Converter
Block Diagram
1.5M
OSC
+
IAMP
-
VIN
+ - +
SLOPE
COMP
PWM
COMP
VOUT/FB
FREQ
SHIFT
OSC
S Q
R1
R Q
-
R2
+
VIN
RS LATCH
EA
MAIN
SWITCH ( PCH )
SWITCHING
LOGIC
AND
BLANKING
CIRCUIT
ANTI SHOOT THRU
SW
SYNCHRONOUS
RECTIFIER ( NCH )
COMP
0.5VREF
EN
+
IRCMP
-
SHUTDOWN
GND
Pin Configuration & Marking Information
NC
SW
Top View
QFN 3x3 16L
5 SW
2
VIN
3
VOUT/FB
5
GND
4
SW
GND
GND
GND
VOUT/FB
1
P2309V
XXXYW
2
3
12
VIN
11
VIN
VIN
VIN
10
4
9
5
6
7
EN
NC
4 VOUT/FB
EN
6
NC
EN 3
1
BLV
YW
BLVYW
GND 2
16 15 14 13
NC
GND
VIN 1
SW
SW
Top View
DFN 2x2 6L
Top View
SOT23 - 5
8
BL: Product Code
of PAM2309
V: Output Voltage
Y: Year
W: Week
X: Internal Code
Pin Description
Name
Function
VIN
Chip main power supply pin
GND
Ground
EN
Enable control input. Force this pin voltage above 1.5V, enables the chip, and below
0.3V shuts down the device.
VOUT: Output voltage feedback pin, an internal resistive divider divides the output
VOUT/FB
voltage down for comparison to the internal reference voltage.
FB: Feedback voltage to internal error amplifier, the threshold voltage is 0.5V.
SW
The drains of the internal main and synchronous power MOSFET.
NC
No connection
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PAM2309
1A Step-Down DC-DC Converter
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 6.0V
EN, FB Pin Voltage.............................- 0.3V to V IN
SW Pi n Voltage......................- 0.3V to ( V IN+0.3V )
Junction Temperature.................................150°C
Storage Temperature Range...........-65°C to 150°C
Soldering Temperature......................300°C , 5sec
Recommended Operating Conditions
Supply Voltage................................2.5V to 5.5V
Operation Temperature Range.........-40 °C to 85 °C
Junction Temperature Range........-40 °C to 125 °C
Thermal Information
Parameter
Package
Symbol
Note
Thermal Resistance
(Junction to Case)
Thermal Resistance
(Junction to Ambient)
Internal Power Dissipation
SOT23-5
20
QFN 3x3
12
SOT23-5
102
θJA
DFN 2x2
34
SOT23-5
400
PD
QFN 3x3
°C/W
68
QFN 3x3
DFN 2x2
Unit
130
θJC
DFN 2x2
Maximum
980
mW
1470
Note:
The maximun output current for SOT23-5 package is limited by internal power dissipation capacity as
described in Application Information hereinafter.
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PAM2309
1A Step-Down DC-DC Converter
Electrical Characteristic
T A=25 °C , V IN=3.6V, V O=1.8V, C IN=10μF, C O=10μF, L=4.7μH, unless otherwise noted.
PARAMETER
SYMBOL
Test Conditions
MIN
Input Voltage Range
VIN
2.5
Regulated Feedback Voltage
V FB
0.490
Reference Voltage Line Regulation
ΔVFB
Regulated Output Voltage Accuary
VO
Peak Inductor Current
IPK
TYP
0.5
MAX
UNITS
5.5
V
0.510
V
0.3
IO = 100mA
-3
VIN=3V,VFB = 0.5V or
%/V
+3
1.5
VO=90%
%
A
Output Voltage Line Regulation
LNR
VIN = 2.5V to 5V, IO=10mA
0.2
0.5
%/V
Output Voltage Load Regulation
LDR
IO=1mA to 800mA
0.5
1.5
%
Quiescent Current
IQ
No load
40
70
μA
Shutdown Current
ISD
VEN = 0V
0.1
1
μA
Oscillator Frequency
fOSC
1.5
1.8
MHz
Drain-Source On-State Resistance
SW Leakage Current
High Efficiency
VO = 100%
1.2
VFB = 0V or VO = 0V
500
kHz
P MOSFET
0.3
0.45
Ω
N MOSFET
0.35
0.5
Ω
ILSW
±0.01
1
μA
η
96
RDS(O N)
IDS=100mA
%
EN Threshold High
VEH
1.5
V
EN Threshold Low
VEL
EN Leakage Current
IEN
±0.01
μA
Over Temperature Protection
OTP
150
°C
OTP Hysteresis
OTH
30
°C
0.3
V
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PAM2309
1A Step-Down DC-DC Converter
Typical Performance Characteristics
Efficiency vs Output Current (Vo=1.2V)
100
90
80
70
60
50
40
30
20
10
0
Efficiency vs Output Current (Vo=1.5V)
100
90
Efficiency(%)
Efficiency(%)
T A=25 °C , C IN=10 μ F, C O=10 μ F, L=4.7 μ H, unless otherwise noted.
70
60
50
40
Vin=3.6V
2.5V
3.6V
30
Vin=4.2V
4.2V
Vin=5V
1
80
20
10
100
1
1000
100
90
90
80
80
Efficiency(%)
Efficiency(%)
Efficiency vs Output Current ( Vo=1.8V )
100
70
60
50
3.6V
70
60
50
3V
3.6V
30
4.2V
4.2V
20
20
1
10
100
Output Current(mA)
1
1000
90
Efficiency(%)
80
70
60
50
40
3V
30
3.6V
4.2V
20
1
10
10
100
1000
Output Current(mA)
Efficiency vs Output Current (Vo=2.8V)
100
Efficiency(%)
1000
Efficiency vs Output Current ( Vo=2.5V )
40
2.5V
30
100
Output Current(mA)
Output Current(mA)
40
10
100
1000
100
90
80
70
60
50
40
30
20
10
0
Eifficiency VS Output Current (Vo=3.3V)
Vin=3.6V
Vin=4.2V
Vin=5V
1
Output Current(mA)
10
100
1000
Output Current(mA)
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PAM2309
1A Step-Down DC-DC Converter
Typical Performance Characteristics
T A=25 °C , C IN=10 μ F, C O=10 μ F, L=4.7 μ H, unless otherwise noted.
100
90
90
80
80
Efficiency(%)
Efficiency(%)
Efficiency VS Input Voltage ( Vo=1.2V )
100
70
60
50
Efficiency vs Input Voltage ( Vo=1.5V )
70
60
50
10mA
Io=10mA
40
40
Io=100mA
100mA
800mA
Io=800mA
30
30
3
3.5
4
4.5
5
2.5
5.5
3
3.5
Efficiency vs Input Voltage ( Vo=1.8V )
100
100
90
90
80
80
Efficiency(%)
Efficiency(%)
4.5
5
5.5
Input Voltage(V)
Input Voltage(V)
70
60
50
Efficiency vs Input Voltage ( Vo=2.5V )
70
60
50
10mA
10mA
40
40
100mA
100mA
800mA
800mA
30
30
2.5
3
3.5
4
4.5
5
5.5
3
3.5
4
Input Voltage(V)
4.5
5
5.5
Input Voltage(V)
Eifficiency VS Input Voltage (Vo=3.3V)
Efficiency vs Input Voltage ( Vo=2.8V )
100
100
90
90
80
Eifficiency(%)
Efficiency(%)
4
70
60
50
10mA
40
100mA
80
70
60
50
40
30
20
Io=10mA
Io=100mA
10
800mA
Io=800mA
30
0
3
3.5
4
4.5
5
3.5
5.5
3.75
4
4.25
4.5
4.75
5
5.25
5.5
Input Voltage(V)
Input Voltage(V)
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PAM2309
1A Step-Down DC-DC Converter
Typical Performance Characteristics
T A=25 °C , C IN=10 μ F, C O=10 μ F, L=4.7 μ H, unless otherwise noted.
Output Voltage VS Load Current
Reference Voltage VS Input Voltage
1.215
0.500
1.210
0.498
1.205
Output Voltage(V)
0.502
0.496
Vfb
0.494
0.492
0.490
0.488
I=100mA
0.486
I=600mA
1.200
1.195
1.190
1.185
Vo=1.2V
1.180
Vin=3.6V
I=800mA
1.175
0.484
2
3
4
5
0
6
200
Input Voltage
800
1.194
0.515
Output Voltage(V)
Reference Voltage(V)
600
Output Voltage VS Temperature
Reference Voltage VS Temperature
0.520
400
Load Current(mA)
0.510
0.505
1.193
1.192
1.191
1.19
Vo=1.2V
0.495
1.189
Vin=3.6V
0.490
1.188
0.500
Io=100mA
0
50
100
20
150
70
Temperature(℃）
Temperature(℃）
Output Voltage VS Output Current
Reference Voltage VS Load Current
0.504
1.205
Output Voltage(V)
Load Current(mA)
Vo=1.2V
1.203
0.500
0.496
0.492
0.488
Vin=2.7V
0.484
1.201
1.199
1.197
1.195
2.5V
1.193
3.6V
1.191
Vin=3.6V
4.2V
5V
Vin=4.2V
0.480
120
1.189
0
200
400
600
800
10
1000
110
210
310
410
510
610
710
810
Output Current(mA)
Reference Voltage(V)
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PAM2309
1A Step-Down DC-DC Converter
Typical Performance Characteristics
T A=25 OC, C IN=10 μ F, C O=10 μ F, L=4.7 μ H, unless otherwise noted.
Dynamic Supply Current VS Temperature
60
Vo=1.2V
Dynamic Supply Current(uA)
Dynamic Supply Current(uA)
Dynamic Supply Current VS Input Voltage
50
45
40
35
30
ILoad=0A
25
20
15
10
5
0
50
40
30
Vo=1.2V
20
Vin=3.6V
10
ILoad=0A
0
2.5
3.5
4.5
40
5.5
60
80
120
140
Temperature(℃）
Input Voltage(V)
R dson VS Input Voltage
0.4
100
Rdson VS Temperature
0.6
0.5
0.3
0.4
Rds(on)
RDS(ON)
Vin=3.6V
0.35
0.25
0.3
0.2
0.2
0.15
0.1
0.1
0
Vin=4.2V
Vin=3.6V
Vin=2.7V
2
3
4
Input Voltage
5
20
6
120
Oscillator Frequency VS Temperature
Oscillator Frequency VS Supply Voltage
1.58
Oscillator Frequency(MHz)
1.8
Oscillator Frequency(MHz)
70
Temperature(℃)
1.7
1.6
1.5
1.4
1.3
1.2
Vin=3.6V
1.56
1.54
1.52
1.50
2
3
4
5
Supply Voltage(V)
6
7
20
40
60
80
100
120
140
Temperature(℃）
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PAM2309
1A Step-Down DC-DC Converter
Typical Performance Characteristics
T A=25 °C ,C IN=10 μ F, C O=10 μ F, L=4.7 μ H, unless otherwise noted.
Load Transient
Io=0-500mA, Vo=3.3V, Vin=5V
Load Transient
Io=0-1A, Vo=1.2V, Vin=3.6V
Output
Current
Output
Current
Voltage
Output
Voltage
Output
Start-up from Shutdown
Vo=1.8V, Vin=3.6V
Enable
Voltage
Output
Inductor
Current
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PAM2309
1A Step-Down DC-DC Converter
Application Information
The basic PAM2309 application circuit is shown
in Page 1. External component selection is
determined by the load requirement, selecting L
first and then Cin and Cout.
The selection of Cout is driven by the required
effective series resistance (ESR).
Typically, once the ESR requirement for Cout
has been met, the RMS current rating generally
far exceeds the I RIPPLE(P-P) requirement. The
output ripple △Vout is determined by:
Inductor Selection
For most applications, the value of the inductor
will fall in the range of 1μH to 4.7μH. Its value is
chosen based on the desired ripple current.
Large value inductors lower ripple current and
small value inductors result in higher ripple
currents. Higher V IN or Vout also increases the
ripple current as shown in equation 1. A
reasonable starting point for setting ripple
current is △I L = 400mA (40% of 1A).
DIL =
1
æ VOUT ö
VOUT ç 1÷
f
L
VIN ø
( )( )
è
1 ö
æ
VVOUT @VIL ç ESR+
÷
8fCOUT ø
è
Where f = operating frequency, C OUT =output
capacitance and Δ I L = ripple current in the
inductor. For a fixed output voltage, the output
ripple is highest at maximum input voltage since
Δ I L increases with input voltage.
(1)
Using Ceramic Input and Output Capacitors
Higher values, lower cost ceramic capacitors are
now becoming available in smaller case sizes.
Their high ripple current, high voltage rating and
low ESR make them ideal for switching regulator
applications. Using ceramic capacitors can
achieve very low output ripple and small circuit
size.
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 1.4A rated inductor should be enough for
most applications (1A + 400mA). For better
efficiency, choose a low DC-resis tance inductor.
Vo
1.2V
1.5V
1.8V
2.5V
3.3V
L
2.2μH
2.2μH
2.2μH
4.7μH
4.7μH
When choosing the input and output ceramic
capacitors, choose the X5R or X7R dielectric
formulations. These dielectrics have the best
temperature and voltage charac teristics of all
the ceramics for a given value and size.
C IN and C OUT Selection
Thermal consideration
In continuous mode, the source current of the top
MOSFET is a square wave of duty cycle
Vout/Vin. To prevent large voltage transients, a
low ESR input capacitor sized for the maximum
RMS current must be used. The maximum RMS
capacitor current is given by:
é VOUT (VIN - VOUT )ùû
CIN required IRMS @ IOMAX ë
VIN
Thermal protection limits power dissipation in
the PAM2309. When the junction temperature
exceeds 150°C, the OTP (Over Temperature
Protection) starts the thermal shutdown and
turns the pass transistor off. The pass transistor
resumes operation after the junction
temperature drops below 120°C.
1
2
For continuous operation, the junction
temperature should be maintained below 125°C.
The power dissipation is defined as:
This formula has a maximum at V IN =2Vout,
w h e r e I RMS= I OUT/ 2 . T h i s s i m p l e w o r s t - c a s e
condition is com monly used for design because
even significant deviations do not offer much
relief. Note that the capacitor manufacturer's
ripple current ratings are often based on 2000
hours of life. This makes it advisable to further
derate the capacitor, or choose a capacitor rated
at a higher temperature than required. Consult
the manufac turer if there is any question.
PD =IO 2
VORDSONH + (VIN -VO )RDSONL
VIN
+ (t SW FSIO +IQ )VIN
I Q is the step-down converter quiescent current.
The term tsw is used to estimate the full load
step-down converter switching losses.
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PAM2309
1A Step-Down DC-DC Converter
Table 1: Resistor selection for output voltage
setting
For the condition where the step-down converter
is in dropout at 100% duty cycle, the total device
dis sipation reduces to:
PD =IO 2RDSONH +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 =
Vo
R1
R2
1.2V
330k
240k
1.5V
360k
180k
1.8V
470k
180k
2.5V
510k
130k
3.3V
680k
120k
100% Duty Cycle Operation
As the input voltage approaches the output
voltage, the converter turns the P-chan nel
transistor continuously on. In this mode the
output voltage is equal to the input voltage minus
the voltage drop across the P - channel
transistor:
TJ(MAX) -TA
θJA
Where TJ(max) is the maximum allowable
junction temperature 125°C.T A is the ambient
temperature and θ JA 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 θ JA of SOT23-5
package is 250°C/W, DFN2X2 102°C/W, and
QFN3X3 68°C/W, respectively. The maximum
power dissipation at T A = 25°C can be calculated
by following formula:
V OUT = V IN – I LOAD (R dson + R L)
where R dson = P-channel switch ON resistance,
I L O A D = Output current, R L = Inductor DC
resistance
UVLO and Soft-Start
The reference and the circuit remain reset until
the VIN crosses its UVLO threshold.
SOT-25 package:
The PAM2309 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).
P D=(125°C-25°C)/250°C/W=0.4W
DFN2*2 package:
P D=(125°C-25°C)/102°C/W=0.984W
QFN3*3 package:
Short Circuit Protection
P D=(125°C-25°C)/68°C/W=1.47W
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.
Setting the Output Voltage
The internal reference is 0.5V (Typical). The
output voltage is calculated as below:
æ R1 ö
VO=0.5×1+
ç R2 ÷
è
ø
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.
The output voltage is given by Table 1.
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PAM2309
1A Step-Down DC-DC Converter
PCB Layout Check List
When laying out the printed circuit board, the following checklist should be used to ensure proper operation of
the PAM2309. These items are also illustrated graphically in Figure 1. Check the following in your layout:
1. The power traces, consisting of the GND trace, the SW trace and the VIN trace should be kept short, direct
and wide.
2. Does the V FB pin connect directly to the feedback resistors? The resistive divider R1/R2 must be con nected
between the (+) plate of C OUT and ground.
3. Does the (+) plate of CIN connect to VIN as closely as possible? This capacitor provides the AC current to
the internal power MOSFETs.
4. Keep the switching node, SW, away from the sensitive VFB node.
5. Keep the (–) plates of C IN and C OUT as close as possible.
Figure 1 :PAM2309 Suggested Layout
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PAM2309
1A Step-Down DC-DC Converter
Ordering Information
PAM 2309 X X X xxx X
Shipping Packing
Output Voltage
Number of Pins
Package Type
Pin Configuration
Pin Configuration
A Type
Package Type
Number of Pins
Output Voltage
ADJ: Adjustable
A: SOT-23
B: 5
1. VIN
J: QFN 3x3
E: 16
2. GND
G: DFN 2x2
F: 6
3. EN
4. VOUT/FB
5. SW
B Type :
16 pins
C Type:
1. NC
2. EN
3. VIN
4. SW
5. GND
6 : VOUT/FB
Part Number
Output Voltage
Marking
Package Type
Shipping Packing
PAM2309AABADJR
ADJ
BLAYW
SOT23-5
3,000Units/Tape&Reel
PAM2309BJEADJR
ADJ
P2309A
QFN3x3
3,000Units/Tape&Reel
PAM2309CGFADJR
ADJ
BLAYW
DFN2x2-6
3,000Units/Tape&Reel
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PAM2309
1A Step-Down DC-DC Converter
Outline Dimensions
SOT23-5
e
b
REF.
A
A1
A2
c
D
E
E1
L
L1
θ
b
e
e1
A2
A1
A
E1
E
D
e1
Millimeter
Min
Max
1.10MAX
0
0.10
0.70
1
0.12REF.
2.70
3.10
2.60
3.00
1.40
1.80
0.45REF.
0.60REF.
0º
10º
0.30
0.50
0.95REF.
1.90REF.
Power Analog Microelectronics , Inc
www.poweranalog.com
08/2009 Rev 1.1
14
PAM2309
1A Step-Down DC-DC Converter
Outline Dimensions
DFN 2x2
Power Analog Microelectronics , Inc
www.poweranalog.com
08/2009 Rev 1.1
15
PAM2309
1A Step-Down DC-DC Converter
Outline Dimensions
3x3 mm QFN 16
DIMENSIONS (Millieters)
MIN
TYP
MAX
A
0.70
0.75
0.80
A1
0.00
0.02
0.05
A2
0.20
b
0.18
0.25
0.30
D
2.90
3.00
3.10
D1
1.55
1.70
1.80
E
2.90
3.00
3.10
E1
1.55
1.70
1.80
e
L
0.50BSC
0.30
0.40
0.50
N
16
aaa
0.08
bbb
0.10
Power Analog Microelectronics , Inc
www.poweranalog.com
08/2009 Rev 1.1
16