Datasheet - Diodes Incorporated

A Product Line of
Diodes Incorporated
PAM2304
3MHz, 1A STEP-DOWN DC-DC CONVERTER
Description
Pin Assignments
The PAM2304 is a 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 PAM2304 provides a power-saving PulseSkipping Modulation (PSM) mode to reduce quiescent current under
light load operation to save power.
The PAM2304 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 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 under-voltage lockout to prevent
deep battery discharge.
The PAM2304 is available in TSOT25 and U-DFN2020-6 packages.
Features
Applications
•
Efficiency up to 95%
•
Smart Phone
•
Only 40µA (typ) Quiescent Current
•
MID
•
Output Current: Up to 1A
•
Portable Electronics
•
Internal Synchronous Rectifier
•
Wireless Devices
•
3MHz Switching Frequency
•
Cordless Phone
•
Soft Start
•
Computer Peripherals
•
Under-Voltage Lockout
•
Battery Powered Widgets
•
Short Circuit Protection
•
Electronic Scales
•
Thermal Shutdown
•
Digital Frame
•
Small TSOT25 and U-DFN2020-6 Packages
•
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
•
Halogen and Antimony Free. “Green” Device (Note 3) Notes:
1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
Typical Applications Circuit
R1 ⎞
⎛
⎟
V O = 0 .6 × ⎜ 1 +
⎝ R2 ⎠
PAM2304
Document number: DS36386 Rev. 2 - 2
1 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
Pin Descriptions
Pin
Name
TSOT25
U-DFN2020-6
Function
EN
1
4
GND
2
6
Enable Control Input. Force this pin voltage above 1.5V, enables the chip, and below
0.3V shuts down the device.
Ground.
SW
3
1
The drains of the internalmain and synchronous power MOSFET.
VIN
4
5
Chip main power supply pin.
FB
AGND
PGND
5
—
—
3
—
—
Feedback voltage to internal error amplifier, the threshold voltage is 0.6V.
Analog Ground.
Main power ground return pin.
NC
—
2
Not connected.
Functional Block Diagram
Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.)
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
Input Voltage
EN, FB Pin Voltage
SW Pin Voltage
Junction Temperature
Storage Temperature Range
Soldering Temperature
PAM2304
Document number: DS36386 Rev. 2 - 2
Rating
-0.3 to +6.0
-0.3 to VIN
-0.3 to (VIN +0.3)
150
Unit
V
V
V
°C
-65 to +150
300, 5 sec
°C
°C
2 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.)
Parameter
Rating
Unit
Supply Voltage
2.7 to 5.5
V
Operation Temperature Range
-40 to +85
Junction Temperature Range
-40 to +125
°C
Thermal Information
Parameter
Symbol
Thermal Resistance (Junction to Case)
θJC
Thermal Resistance (Junction to Ambient)
Max
TSOT25 (Note 4)
130
θJA
Internal Power Dissipation (TA = +25°C)
Note:
Package
PD
U-DFN2020-6
25
TSOT25
250
U-DFN2020-6
68
TSOT25
400
U-DFN2020-6
980
Unit
°C/W
mW
4. The maximun output current for TSOT25 package is limited by internal power dissipation capacity as
described in Application Information hereinafter.
Electrical Characteristics (@TA = +25°C, VIN = 3.6V, VO = 1.8V, CIN = 10µF, COUT = 10µF, L = 1µH, unless otherwise specified.)
Parameter
Symbol
Test Conditions
Min
Input Voltage Range
VIN
2.5
Regulated Feedback Voltage
VFB
0.588
Reference Voltage Line Regulation
Regulated Output Voltage Accuracy
Peak Inductor Current
0.6
Max
-3
IO = 100mA
Units
5.5
V
0.612
V
0.3
∆VFB
VO
Typ
%/V
+3
%
VIN = 3V, VFB = 0.5V or VO = 90%
1.5
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
%
40
70
µA
IPK
Quiescent Current
IQ
No load
Shutdown Current
ISD
VEN = 0V
Oscillator Frequency
Drain-Source On-State Resistance
SW Leakage Current
High Efficiency
fOSC
MHz
VFB = 0V or VO = 0V
1
MHz
ILSW
±0.01
1
µA
η
95
VEL
Document number: DS36386 Rev. 2 - 2
3
Ω
Ω
EN Threshold Low
PAM2304
µA
VO = 100%
0.45
0.50
VEH
Over Temperature Protection
OTP Hysteresis
1
0.30
0.35
RDS(ON)
EN Threshold High
EN Leakage Current
A
IDS = 100mA
P MOSFET
N MOSFET
%
1.5
V
0.3
V
IEN
±0.01
µA
OTP
OTH
150
30
°C
°C
3 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
Typical Performance Characteristics (@TA = +25°C, CIN = 10µF, COUT = 10µF, L = 1µH, unless otherwise specified.)
PAM2304
Document number: DS36386 Rev. 2 - 2
4 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
Typical Performance Characteristics (cont.)
(@TA = +25°C, CIN = 10µF, COUT = 10µF, L = 1µH, unless otherwise specified.)
PAM2304
Document number: DS36386 Rev. 2 - 2
5 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
Typical Performance Characteristics (cont.)
(@TA = +25°C, CIN = 10µF, COUT = 10µF, L = 1µH, unless otherwise specified.)
PAM2304
Document number: DS36386 Rev. 2 - 2
6 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
Application Information
The basic PAM2304 application circuit is shown on Page 2. External component selection is determined by the load requirement, selecting L first
and then CIN and COUT.
Inductor Selection
For most applications, the value of the inductor will fall in the range of 1μH. 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 VIN or VOUT also increases the ripple current as
shown in Equation 1. A reasonable starting point for setting ripple current is ∆IL = 400mA (40% of 1A).
ΔIL =
⎛
⎞
⎜1 − V OUT ⎟
⎟
VIN ⎠
1
Equation (1)
(f )(L ) VOUT ⎜⎝
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-resistance inductor.
CIN and COUT Selection
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:
CIN required IRMS ≅ IOMAX
[VOUT (VIN − VOUT )]1/ 2
VIN
This formula has a maximum at V = 2VOUT, where IRMS =IOUT/2. This simple worst-case condition is commonly 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
manufacturer if there is any question. 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 IRIPPLE(P-P) requirement. The
output ripple ∆VOUT is determined by:
⎛
1 ⎞
⎟
ΔV OUT ≅ ΔIL ⎜⎜ ESR +
8fCOUT ⎟⎠
⎝
Where f = operating frequency, COUT = output capacitance and ∆IL = ripple current in the inductor. For a fixed output voltage, the output ripple is
highest at maximum input voltage since ∆IL increases with input voltage.
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 formulations. 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 PAM2304. 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:
PD = IO 2
VO
DS( ON)H +
(VIN − VO )RDS(ON)L
VIN
+ (tSW FS IO + IQ ) VIN
IQ is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses.
PAM2304
Document number: DS36386 Rev. 2 - 2
7 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
Application Information (cont.)
Thermal Consideration (cont.)
For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to:
PD = IO 2 RDS(ON)H + IQ VIN
Since RDS(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 =
T J(MAX ) − T A
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 of TSOT25 package is
250°C/W. The maximum power dissipation at TA = +25°C can be calculated by following formula:
PD = (125°C-25°C)/250°C/W = 0.4W
Setting the Output Voltage
The internal reference is 0.6V (Typical). The output voltage is calculated as below:
R1 ⎞
⎛
⎟
V O = 0 .6 × ⎜ 1 +
R2 ⎠
⎝
The output voltage is given by Table 1.
Table 1: Resistor selection for output voltage setting
VO
R1
R2
1.2V
1.5V
1.8V
2.5V
3.3V
100k
150k
200k
380k
540k
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 (RDS(ON) + RL )
where RDS(ON) = P-Channel Switch ON Resistance, ILOAD = Output Current, R = Inductor DC Resistance
UVLO and Soft-Start
The reference and the circuit remain reset until the VIN crosses its UVLO threshold.
The PAM2304 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 1MHz and minimum duty cycle, therefore the average input current is typically 200mA.
Thermal Shoutdown
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.
PAM2304
Document number: DS36386 Rev. 2 - 2
8 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
Application Information (cont.)
PCB Layout Check List
When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the PAM2304. 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 VFB pin connect directly to the feedback resistors? The resistive divider R1/R2 must be connected between the (+) plate of COUT 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 CIN and COUT as close as possible.
Ordering Information
Part Number
PAM2304AABADJ
PAM2304BKFADJ
Output Voltage
ADJ
ADJ
Package
TSOT25
U-DFN2020-6 (Type C)
Packaging
3000 Units/Tape & Reel
3000 Units/Tape & Reel
Marking Information
PAM2304
Document number: DS36386 Rev. 2 - 2
9 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
Package Outline Dimensions (All dimensions in mm.)
Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for the latest version.
TSOT25
D
e1
E
E1
L2
c
4x θ1
e
θ
L
5x b
A
A2
A1
TSOT25
Dim Min Max Typ
A
1.00
−
−
A1
0.01 0.10
−
A2
0.84 0.90
−
D
2.90
−
−
E
2.80
−
−
E1
1.60
−
−
b
0.30 0.45
−
c
0.12 0.20
−
e
0.95
−
−
e1
1.90
−
−
L
0.30 0.50
L2
0.25
−
−
θ
0°
8°
4°
θ1
4°
12°
−
All Dimensions in mm
U-DFN2020-6
A
A3
A1
Seating Plane
D
D2
Pin #1 ID
E
E2
Z (4x)
L
e
PAM2304
Document number: DS36386 Rev. 2 - 2
U-DFN2020-6
Type C
Dim Min
Max
Typ
A
0.57 0.63 0.60
A1 0.00 0.05 0.02
A3
––
––
0.15
b
0.25 0.35 0.30
D
1.95 2.075 2.00
D2 1.55 1.75 1.65
E
1.95 2.075 2.00
E2 0.86 1.06 0.96
e
––
––
0.65
L
0.25 0.35 0.30
Z
––
––
0.20
All Dimensions in mm
b
10 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
Suggested Pad Layout
Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version.
TSOT25
C
C
Dimensions Value (in mm)
C
0.950
X
0.700
Y
1.000
Y1
3.199
Y1
Y (5x)
X (5x)
U-DFN2020-6
X2
X1
Dimensions
Y (6x)
Y2
Y1
X (6x)
PAM2304
Document number: DS36386 Rev. 2 - 2
C
X
X1
X2
Y
Y1
Y2
Value
(in mm)
0.650
0.350
1.650
1.700
0.525
1.010
2.400
C
11 of 12
www.diodes.com
June 2014
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2304
IMPORTANT NOTICE
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.
Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel.
Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and
hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or
indirectly, any claim of personal injury or death associated with such unintended or unauthorized application.
Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings
noted herein may also be covered by one or more United States, international or foreign trademarks.
This document is written in English but may be translated into multiple languages for reference. Only the English version of this document is the
final and determinative format released by Diodes Incorporated.
LIFE SUPPORT
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:
A. Life support devices or systems are devices or systems which:
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
labeling can be reasonably expected to result in significant injury to the user.
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
failure of the life support device or to affect its safety or effectiveness.
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any
use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related
information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its
representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.
Copyright © 2014, Diodes Incorporated
www.diodes.com
PAM2304
Document number: DS36386 Rev. 2 - 2
12 of 12
www.diodes.com
June 2014
© Diodes Incorporated