PAM2304
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PAM2304
3MHz, 1A STEP-DOWN DC-DC CONVERTER
Description
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 Pulse-
Skipping 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 (Type C)
packages.
Features
Efficiency up to 95%
Only 40µA (typical) Quiescent Current
Output Current: up to 1A
Internal Synchronous Rectifier
3MHz Switching Frequency
Soft Start
Under Voltage Lockout
Short Circuit Protection
Thermal Shutdown
Small TSOT25 and U-DFN2020-6 (Type C) Packages
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Pin Assignments
Applications
Smart Phone
MID
Portable Electronics
Wireless Devices
Cordless Phone
Computer Peripherals
Battery Powered Widgets
Electronic Scales
Digital Frame
Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS), 2011/65/EU (RoHS 2) & 2015/863/EU (RoHS 3) compliant.
2. See https://www.diodes.com/quality/lead-free/ 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
2R1R
16.0
VO
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Pin Descriptions
Function
TSOT25
U-DFN2020-6
(Type C)
—
1
4
Enable Control Input. Force this pin voltage above 1.5V, enables the chip, and below 0.3V
shuts down the device.
2
6
Ground.
3
1
The drains of the internal main and synchronous power MOSFET.
4
5
Chip main power supply pin.
5
3
Feedback voltage to internal error amplifier, the threshold voltage is 0.6V.
—
—
Analog Ground.
—
—
Main power ground return pin.
—
2
Not Connected.
Functional Block Diagram
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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
Rating
Unit
Input Voltage
-0.3 to +6.0
V
EN, FB Pin Voltage
-0.3 to VIN
V
SW Pin Voltage
-0.3 to (VIN +0.3)
V
Junction Temperature
+150
°C
Storage Temperature Range
-65 to +150
°C
Soldering Temperature
+300, 5s
°C
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
°C
Junction Temperature Range
-40 to +125
Thermal Information
Parameter
Symbol
Package
Max
Unit
Thermal Resistance (Junction to Case)
θJC
TSOT25 (Note 4)
130
°C/W
U-DFN2020-6
(Type C)
25
Thermal Resistance (Junction to Ambient)
θJA
TSOT25
250
U-DFN2020-6
(Type C)
68
Internal Power Dissipation (TA = +25°C)
PD
TSOT25
400
mW
U-DFN2020-6
(Type C)
980
Note: 4. The maximun output current for TSOT25 package is limited by internal power dissipation capacity as described in Application Information hereinafter.
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PAM2304
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PAM2304
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
Typ
Max
Units
Input Voltage Range
VIN
—
2.5
—
5.5
V
Regulated Feedback Voltage
VFB
—
0.588
0.6
0.612
V
Reference Voltage Line Regulation
ΔVFB
—
—
0.3
—
%/V
Regulated Output Voltage Accuracy
VO
IO = 100mA
-3
—
+3
%
Peak Inductor Current
IPK
VIN = 3V, VFB = 0.5V or VO = 90%
—
1.5
—
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
—
—
1
µA
Oscillator Frequency
fOSC
VO = 100%
—
3
—
MHz
VFB = 0V or VO = 0V
—
1
—
MHz
Drain-Source On-State Resistance
RDS(ON)
IDS = 100mA
P MOSFET
—
0.30
0.45
Ω
N MOSFET
—
0.35
0.50
Ω
SW Leakage Current
ILSW
—
—
±0.01
1
µA
High Efficiency
η
—
—
95
—
%
EN Threshold High
VEH
—
1.5
—
—
V
EN Threshold Low
VEL
—
—
—
0.3
V
EN Leakage Current
IEN
—
—
±0.01
—
µA
Over Temperature Protection
OTP
—
—
+150
—
°C
OTP Hysteresis
OTH
—
—
+30
—
°C
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Typical Performance Characteristics (@TA = +25°C, CIN = 10µF, COUT = 10µF, L = 1µH, unless otherwise specified.)
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Typical Performance Characteristics (continued)
(@TA = +25°C, CIN = 10µF, COUT = 10µF, L = 1µH, unless otherwise specified.)
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PAM2304
Typical Performance Characteristics (continued)
(@TA = +25°C, CIN = 10µF, COUT = 10µF, L = 1µH, unless otherwise specified.)
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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 ΔIL = 400mA (40% of 1A).
V
V
1
V
Lf1
IIN
OUT
OUTL
Equation (1)
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:
VVVV
II
required
CIN
2/1
OUTINOUT
OMAXRMS
IN
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 ΔVOUT is determined by:
fC81
ESR
IV OUT
LOUT
Where f = operating frequency, COUT = output capacitance and ΔIL = ripple current in the inductor. For a fixed output voltage, the output ripple is
highest at maximum input voltage since ΔIL 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:
VIIF
t
V
RVVV
IP INQOS
SW
IN
L)ON(DSOIN
H)ON(DS
O
2
OD
IQ 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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PAM2304
Application Information (continued)
Thermal Consideration (continued)
For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to:
VIRIP INQH)ON(DS
2
OD
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:
JA
A)MAX(J
DTT
P
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:
2R1R
16.0
VO
The output voltage is given by Table 1.
Table 1: Resistor selection for output voltage setting
VO
R1
R2
1.2V
100k
100k
1.5V
150k
100k
1.8V
200k
100k
2.5V
380k
120k
3.3V
540k
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.
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Application Information (continued)
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
Output Voltage
Package
Packaging
PAM2304AABADJ
ADJ
TSOT25
3000 Units/Tape & Reel
PAM2304BKFADJ
ADJ
U-DFN2020-6 (Type C)
3000 Units/Tape & Reel
Marking Information
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Package Outline Dimensions (All dimensions in mm.)
Please see http://www.diodes.com/package-outlines.html for the latest version.
TSOT25
U-DFN2020-6 (Type C)
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
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
c
A1
L
E1 E
A2
D
e1
e5x b
4x 1
L2
A
D
D2
E
eb
L
E2
A A1 A3
Seating Plane
Pin #1 ID
Z (4x)
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Suggested Pad Layout
Please see http://www.diodes.com/package-outlines.html for the latest version.
TSOT25
U-DFN2020-6 (Type C)
Dimensions
Value (in mm)
C
0.950
X
0.700
Y
1.000
Y1
3.199
Dimensions
Value
(in mm)
C
0.650
X
0.350
X1
1.650
X2
1.700
Y
0.525
Y1
1.010
Y2
2.400
Y1
C C
X (5x)
Y (5x)
Y2
X1
X2
Y1
Y (6x)
X (6x) C
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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final and determinative format released by Diodes Incorporated.
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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.
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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
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