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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 TSOT23-5, TDFN22-8 and TDFN22-6
packages.
Features
Efficiency up to 95%
Only 40mA (typ) Quiescent Current
Output Current: Up to 1A
Internal Synchronous Rectifier
3MHz Switching Frequency
Soft Start
Under-Voltage Lockout
Short Circuit Protection
Thermal Shutdown
Small TSOT23-5, TDFN22-8 and TDFN22-6 Packages
RoHS Pass and Green Package
Applications
Smart Phone
MID
Portable Electronics
Wireless Devices
Cordless Phone
Computer Peripherals
Battery Powered Widgets
Electronic Scales
Digital Frame
3MHz, 1A STEP-DOWN DC-DC CONVERTER
Pin Assignments
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PAM2304
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Typical Applications Circuit
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PAM2304
1R
16.0
V
O
2R
Pin Descriptions
Pin
Name
EN 1 8 4
GND 2 — 6 Ground.
SW 3 5, 6 1 The drains of the internalmain and synchronous power MOSFET.
VIN
FB 5 1 3 Feedback voltage to internal error amplifier, the threshold voltage is 0.6V.
AGND — 2 — Analog Ground.
PGND — 4 — Main power ground return pin.
NC — 7 2 Not connected.
TSOT23 TDFN22-8 TDFN22-6
4 3 5 Chip main power supply pin.
Pin Name
Function
Enable Control Input. Force this pin voltage above 1.5V, enables the chip, and below 0.3V
shuts down the device.
Functional Block Diagram
PAM2304
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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 -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, 5 sec °C
Recommended Operating Conditions (@T
Parameter Rating Unit
Supply Voltage 2.7 to 5.5 V
Operation Temperature Range -40 to +85
Junction Temperature Range -40 to +125
= +25°C, unless otherwise specified.)
A
= +25°C, unless otherwise specified.)
A
°C
Thermal Information
Parameter Symbol Package Max Unit
TSOT23-5 (Note 1) 130
Thermal Resistance (Junction to Case)
Thermal Resistance (Junction to Ambient)
Internal Power Dissipation (TA = +25°C) PD
Note: 1. The maximun output current for TSOT23-5 package is limited by internal power dissipation capacity as
described in Application Information hereinafter.
θ
JC
θ
JA
PAM2304
Document number: DSxxxxx Rev. 1 - 1
TDFN22-8 23.4
TDFN22-6 25
TSOT23-5 250
TDFN22-8 70
TDFN22-6 68
TSOT23-5 400
TDFN22-8 1400
TDFN22-6 980
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°C/W
mW
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Electrical Characteristics (@T
Parameter Symbol Test Conditions Min Typ Max Units
Input Voltage Range
Regulated Feedback Voltage
Reference Voltage Line Regulation
Regulated Output Voltage Accuracy
Peak Inductor Current
Output Voltage Line Regulation LNR
Output Voltage Load Regulation LDR
Quiescent Current
Shutdown Current
Oscillator Frequency
Drain-Source On-State Resistance
SW Leakage Current
High Efficiency η 95 %
EN Threshold High
EN Threshold Low
EN Leakage Current
Over Temperature Protection OTP 150 °C
OTP Hysteresis OTH 30 °C
PAM2304
Document number: DSxxxxx Rev. 1 - 1
= +25°C, VIN = 3.6V, VO = 1.8V, CIN = 10µF, C
A
IN
FB
FB
IO = 100mA
O
VIN = 3V, VFB = 0.5V or VO = 90%
V
= 2.5V to 5V, IO = 10mA
IN
I
= 1mA to 800mA
O
No load 40 70 µA
Q
VEN = 0V
= 100%
V
O
VFB = 0V or VO = 0V
IDS = 100mA
±0.01 1 µA
1.5 V
EH
0.3 V
EL
±0.01 µA
P MOSFET 0.30 0.45 Ω
N MOSFET 0.35 0.50 Ω
V
∆V
f
R
DS(ON)
I
V
V
V
V
I
PK
I
I
SD
OSC
LSW
I
EN
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= 10µF, L = 1µH, unless otherwise specified.)
OUT
2.5 5.5 V
0.588 0.6 0.612 V
0.3 %/V
-3 +3 %
1.5 A
0.2 0.5 %/V
0.5 1.5 %
1 µA
3 MHz
1 MHz
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Typical Performance Characteristics (@T
= +25°C, CIN = 10µF, C
A
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= 10µF, L = 1µH, unless otherwise specified.)
OUT
PAM2304
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Typical Performance Characteristics (cont.)
(@TA = +25°C, CIN = 10µF, C
= 10µF, L = 1µH, unless otherwise specified.)
OUT
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PAM2304
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Typical Performance Characteristics (cont.)
(@TA = +25°C, CIN = 10µF, C
= 10µF, L = 1µH, unless otherwise specified.)
OUT
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PAM2304
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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 C
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 V
shown in Equation 1. A reasonable starting point for setting ripple current is ∆I
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 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 = 2V
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 ∆V
and C
IN
I
Selection
OUT
required
C
IN
OUT
.
OUT
1
Lf
1
V
OUTL
is determined by:
ESR
IV
LOUT
= 400mA (40% of 1A).
L
V
OUT
II
OMAXRMS
Equation (1)
V
IN
VVV
V
IN
, where I
OUT
OUT
1
fC8
OUT
RMS
has been met, the RMS current rating generally far exceeds the I
2/1
OUTINOUT
OUT
=I
/2. This simple worst-case condition is commonly used for design because even
OUT
is driven by the required effective series resistance (ESR).
IN
OUT/VIN
or V
also increases the ripple current as
OUT
. To prevent large voltage transients, a low
(P-P) requirement. The
RIPPLE
Where f = operating frequency, C
highest at maximum input voltage since ∆I
= output capacitance and ∆IL = ripple current in the inductor. For a fixed output voltage, the output ripple is
OUT
increases with input voltage.
L
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:
O
2
is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses.
I
Q
IP
OD
H)ON(DS
V
IN
RVVV
PAM2304
Document number: DSxxxxx Rev. 1 - 1
L)ON(DSOIN
t
SW
VIIF
INQOS
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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:
2
OD
VIRIP
INQH)ON(DS
PAM2304
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 TJ(max) is the maximum allowable junction temperature +125°C. T
the junction to the ambient. Based on the standard JEDEC for a two layers thermal test board, the thermal resistance of TSOT23-5 package is
250°C/W. 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
P
D
= (125°C-25°C)/250°C/W = 0.4W
D
A)MAX(J
JA
is the ambient temperature and θ
A
= +25°C can be calculated by following formula:
A
is the thermal resistance from
JA
Setting the Output Voltage
The internal reference is 0.6V (Typical). The output voltage is calculated as below:
1R
The output voltage is given by Table 1.
Table 1: Resistor selection for output voltage setting
V
O
V
O
1.2V 100k 100k
1.5V 150k 100k
1.8V 200k 100k
2.5V 380k 120k
3.3V 540k 120k
16.0
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:
= VIN – I
V
OUT
where R
DS(ON)
(R
LOAD
= P-Channel Switch ON Resistance, I
DS(ON)
+ RL )
= Output Current, R = Inductor DC Resistance
LOAD
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
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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 V
ground.
3. Does the (+) plate of C
4. Keep the switching node, SW, away from the sensitive V
5. Keep the (–) plates of C
pin connect directly to the feedback resistors? The resistive divider R1/R2 must be connected between the (+) plate of C
FB
connect to VIN as closely as possible? This capacitor provides the AC current to the internal power MOSFETs.
IN
node.
FB
and C
IN
as close as possible.
OUT
OUT
Ordering Information
and
Part Number Output Voltage Package Packaging
PAM2304AABADJ ADJ TSOT23-5 3000 Units/Tape & Reel
PAM2304BKFADJ
PAM2304CGCADJ
Marking Information
ADJ
ADJ
TDFN22-6 3000 Units/Tape & Reel
TDFN22-8 3000 Units/Tape & Reel
PAM2304
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Package Outline Dimensions (All dimensions in mm.)
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PAM2304
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Package Outline Dimensions (All dimensions in mm.)
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PAM2304
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Package Outline Dimensions (All dimensions in mm.)
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PAM2304
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PAM2304
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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).
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without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the
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website, harmless against all damages.
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final and determinative format released by Diodes Incorporated.
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
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Copyright © 2012, Diodes Incorporated
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IMPORTANT NOTICE
LIFE SUPPORT
PAM2304
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