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Description
The PAM2320 is a 3A step-down DC-DC converter. At heavy load,
the constant-frequency PWM control performs excellent stability and
transient response. No external compensation components are
required.
The PAM2320 supports a range of input voltages from 2.7V to 5.5V,
allowing the use of a single Li+/Li-polymer cell, multiple Alkaline/NiMH
cell, and other standard power sources. The output voltage is
adjustable from 0.6V to the input voltage. The PAM2320 employs
internal power switch and synchronous rectifier 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
1µA. Other key features include over-temperature and short circuit
protection, and under-voltage lockout to prevent deep battery
discharge.
The PAM2320 delivers 3A maximum output current while consuming
only 42µA of no-load quiescent current. Ultra-low R
MOSFETs and 100% duty cycle operation make the PAM2320 an
ideal choice for high output voltage, high current applications which
require a low dropout threshold.
The PAM2320 is available in PSOP8 package.
DS(ON)
integrated
Features
• Output Current: Up to 3A
• Output Voltage: 0.6V to V
• Input Voltage: 2.7 to 5.5V
• Efficiency up to 95%
• 42µA (typ) No Load Quiescent Current
• Shutdown Current: <1µA
• 100% Duty Cycle Operation
• 1.5MHz Switching Frequency
• Internal Soft Start
• No external Compensation Required
• Current Limit Protection
• Thermal Shutdown
• PSOP-8 Package
IN
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3A LOW NOISE STEP-DOWN DC-DC CONVERTER
Pin Assignments
Applications
• 5V or 3.3V Point of Load Conversion
• Telecom/Networking Equipment
• Set Top Boxes
• Storage Equipment
• Video Cards
• DDR Power Supply
PAM2320
PAM2320
Document number: DSxxxxx Rev. 1 - 0
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Typical Applications Circuit
Pin Descriptions
Pin
Number
PSOP-8
Pin Name
1 NC
2 VIN
3 SW
4 GND
5 FB
6 NC
7 EN
8 NC
Functional Block Diagram
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PAM2320
⎞
⎛
1R
⎟
V
Not Connected.
Bias supply. Chip main power supply pin.
The drains of the internal main and synchronous power MOSFET.
Ground
Feedback voltage to internal error amplifier, the threshold voltage is 0.6V.
Not Connected.
Enable control input. Force this pin voltage above 1.5V, enables the chip, and below 0.3V shuts down
the device.
Not Connected.
⎜
16.0O
⎜
⎝
+×=
⎟
2R
⎠
Function
PAM2320
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PAM2320
Absolute Maximum Ratings (@T
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.
Parameter Rating Unit
Input Voltage VIN
SW Pin Voltage
FB Pin Voltage
EN Pin Voltage -0.3 to +6.0 V
Maximum Junction Temperature 150 °C
Storage Temperature Range -65 to +150 °C
Soldering Temperature 300, 5sec °C
Recommended Operating Conditions (@T
Parameter Rating Unit
Supply Voltage 2.7 to 5.5 V
Junction Temperature Range -40 to +125
Ambient Temperature Range -40 to +85
= +25°C, unless otherwise specified.)
A
6 V
-0.3 to (V
-0.3 to (V
+0.3)
IN
+0.3)
IN
= +25°C, unless otherwise specified.)
A
V
V
°C
Thermal Information
Parameter Symbol Package Max Unit
Thermal Resistance (Junction to Ambient)
Thermal Resistance (Junction to Case)
Internal Power Dissipation (@TA= 25°C)
θ
JA
θ
JC
P
D
PAM2320
Document number: DSxxxxx Rev. 1 - 0
PSOP-8 90
PSOP-8 14
PSOP-8 1100 mW
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°C/W
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PAM2320
Electrical Characteristics (@T
Parameter Symbol Test Conditions Min Typ Max Units
Input Voltage Range
Output Voltage Range
UVLO Threshold
Regulated Output Voltage Accuracy
Regulated Feedback Voltage
FB Leakage Current
Output Voltage Line Regulation LNR
Output Voltage Load Regulation LDR
Quiescent Current
Shutdown Current
Current Limit
Oscillator Frequency
Drain-Source On-State Resisitance
High Efficiency η 95 95 %
Analog Soft-Start Time
EN Threshold High
EN Threshold Low
EN Leakage Current
Over Temperature Protection OTP 150 °C
OTP Hysteresis OTH 30 °C
PAM2320
Document number: DSxxxxx Rev. 1 - 0
= +25°C, VIN = 3.6V, VO = 1.8V, CIN = 22µF, C
A
IN
O
Rising
V
IN
Hysteresis 240 mV
V
V
V
UVLO
VIN Falling
V
IO = 0 to 3A
O
V
I
f
R
DS(ON)
V
V
I
FB
I
I
SD
LIM
OSC
t
I
EN
0.591 0.600 0.609 V
FB
VO =1V
V
= 2.5V to 5V
IN
I
= 0A to 3A
O
No Load 42 90 µA
Q
VEN = 0V
From enable to output regulation 0.5 3 ms
S
1.5 V
EH
0.3 V
EL
High Side 0.85 mΩ
Low Side 60 mΩ
VIN = VEN = 0V
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= 22µF, L = 2.2µH, unless otherwise specified.)
O
2.7 5.5 V
0.6
VIN
V
2.4 2.5 V
1.8 V
-3 +2 %
0.2 µA
0.2 %/V
0.5 %/A
1 µA
4 A
1.2 1.5 1.8 MHz
-1.0 +1.0 µA
October 2012
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Typical Performance Characteristics (@T
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= +25°C, CIN = 33µF, CO = 22µF, unless otherwise specified.)
A
PAM2320
PAM2320
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Typical Performance Characteristics (cont.) (@T
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PAM2320
= +25°C, CIN = 33µF, CO = 22µF, unless otherwise specified.)
A
PAM2320
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Typical Performance Characteristics (cont.) (@T
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PAM2320
= +25°C, CIN = 33µF, CO = 22µF, unless otherwise specified.)
A
PAM2320
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PAM2320
Application Information
The basic PAM2320 application circuit is shown in Page 2. External component selection is determined by the load requirement, selecting L first
and then C
Inductor Selection
For most applications, the value of the inductor will fall in the range of 1μH to 3.3μH. Its value is chosen based on the desired ripple current and
efficiency. Large value inductors lower ripple current and small value inductors result in higher ripple currents. Higher V
the ripple current as shown in equation 3A reasonable starting point for setting ripple current is ΔI
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 4.2A rated inductor should be enough for most applications (3A + 1.2A). For better efficiency, choose a low DC-resistance inductor.
V
CIN and C
In continuous mode, the source current of the top MOSFET is a square wave of duty cycle V
ESR input capacitor sized for the maximum RMS current must be used. The maximum RMS capacitor current is given by:
This formula has a maximum at V
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
manufacturer if there is any question.
The selection of C
Typically, once the ESR requirement for C
output ripple ΔV
Where f = operating frequency, C
highest at maximum input voltage since ΔI
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.
When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formul ations. These dielectrics have the best
temperature and voltage characteristics of all the ceramics for a given value and size.
Thermal Consideration
Thermal protection limits power dissipation in the PAM2320. 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.
For continuous operation, the junction temperature should be maintained below +125°C. The power dissipation is defined as:
I
is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses.
Q
PAM2320
Document number: DSxxxxx Rev. 1 - 0
and C
IN
Δ
I
1.2V 1.5V 1.8V 2.5V 3.3V
O
L 1µH 1.5µH 2.2µH 2.2µH 3.3µH
OUT
C
IN
Δ
.
OUT
1
()()
Lf
⎛
⎜
−=
1
V
OUTL
⎜
⎝
⎞
V
OUT
⎟
Equation (1)
⎟
V
IN
⎠
Selection
[]
()
−
required
OUT
is determined by:
OUT
≈
2
=
IP
OD
≅
II
OMAXRMS
= 2V
IN
OUT
is driven by the required effective series resistance (ESR).
OUT
()
+
f8/1ESR
Δ
IV
LOUT
C
OUT
= output capacitance and ΔIL = ripple current in the inductor. For a fixed output voltage, the output ripple is
OUT
increases with input voltage.
L
()
−+
V
IN
VVV
V
IN
, where I
RMS
has been met, the RMS current rating generally far exceeds the I
RVVRV
2/1
OUTINOUT
=I
/2. This simple worst-case condition is commonly used for design because even
OUT
L)ON(DSOINH)ON(DSO
()
t
SW
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++
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or V
IN
= 1.2A (40% of 3A).
L
. To prevent large voltage transients, a low
OUT/VIN
(P-P) requirement. The
RIPPLE
VIIF
INQOS
also increases
OUT
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Application Information (cont.)
For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to:
2
OD
+=
VIRIP
INQH)ON(DS
PAM2320
Since R
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:
Where T
junction to the ambient. Based on the standard JEDEC for a two layers thermal test board, the thermal resistance θ
respectively. The maximum power dissipation at T
P
, quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input
DS(ON)
−
TT
A)MAX(J
=
P
D
J(max)
= (125°C - 25°C) /90°C/W = 1.11W (SOP-8)
D
θ
is the maximum allowable junction temperature +125°C. TA is the ambient temperature and θJA is the thermal resistance from the
JA
of SOP-8(EP) 90°C/W
JA
= +25°C can be calculated by following formula:
A
Setting the Output Voltage
The internal reference is 0.6V (Typical). The output voltage is calculated as below:
The output voltage is given by Table 1.
1R
Table 1: Resistor selection for output voltage setting.
V
O
V
O
1.2V 150k 150k
1.5V 225k 150k
1.8V 300k 150k
2.5V 475k 150k
3.3V 680k 150k
⎛
⎜
⎝
⎞
+=
1x6.0
⎟
2R
⎠
R1 R2
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:
where R
= P-Channel switch ON resistance, I
DS(ON)
()
+−=
RRIVV
LDSONLOADINOUT
= Output Current, RL = Inductor DC Resistance
LOAD
UVLO and Soft-Start
The reference and the circuit remain reset until the VIN crosses its UVLO threshold.
The PAM2320 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 make the output voltage rise up smoothly.
Short Circuit Protection
The switch peak current is limited cycle-by-cycle to a typical value of 4A. In the event of an output voltage short circuit, the device operates with
a frequency of 500kHz and minimum duty cycle, therefore the average input current is more smaller than current limit.
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.
PAM2320
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Ordering Information
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PAM2320
Part Number Output Voltage Package Type Standard Package
PAM2320BECADJR ADJ PSOP-8 25000 Units/Tape & Reel
Marking Information
PAM2320
Document number: DSxxxxx Rev. 1 - 0
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Package Outline Dimensions (All dimensions in mm.)
PSOP-8
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PAM2320
PAM2320
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PAM2320
DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
(AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).
Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes
without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the
application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or
trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume
all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated
website, harmless against all damages.
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Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings
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Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express
written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
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1. are intended to implant into the body, or
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the
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B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the
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IMPORTANT NOTICE
LIFE SUPPORT
PAM2320
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