Diodes PAM2305 User Manual

A

f

Description

Product Line o

Diodes Incorporated

PAM2305

1A STEP-DOWN DC-DC CONVERTER

Pin Assignments

The PAM2305 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 PAM2305 provides a power-saving Pulse-

Skipping Modulation (PSM) mode to reduce quiescent current under

light load operation to save power.

The PAM2305 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, while the part number suffix

PAM2305-XX indicates pre-set output voltage of 3.3V, 2.8V, 2.5V,

1.8V, 1.5V, 1.2V or adjustable. 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 0.1µA. Other

key features include under-voltage lockout to prevent deep battery

discharge.

The PAM2305 is available in TSOT25, DFN2x2-6 Pin and QFN3x3-16
Pin packages.

Top View

TSOT25

Features

• Efficiency up to 96%

• Only 40µA(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 TSOT25, DFN2x2-6 Pin and QFN3x3-16 Pin

Packages

• Pb-Free Package

Applications

• Cellular Phone

• Portable Electronics

• Wireless Devices

• Cordless Phone

• Computer Peripherals

• Battery Powered Widgets

• Electronic Scales

• Digital Frame

PAM2305

Document number: DSxxxxx Rev. 2 - 6

1 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Typical Applications Circuit

Fixed Output Voltage Adjustable Output Voltage

Product Line o

Diodes Incorporated

1R

⎛

V

O

⎜
⎝

⎞

+×=

16.0

⎟

2R

⎠

PAM2305

Pin Descriptions

Pin

Name

TSOT25 DFN2x2-6L QFN3x3-16L

Package Name

VIN 1 3 9, 10, 11, 12

GND 2 5 1, 2, 3, 5

EN 3 2 7

VOUT/FB 4 6 4

SW 5 4 13, 14, 15
NC — 1 6, 8, 16

Functional Block Diagram

Function

Chip main power supply pin.

Ground.

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
voltage down for comparison to the internal reference voltage.

FB: Feedback voltage to internal error amplifier, the threshold voltage is 0.6V.

The drains of the internal main and synchronous power MOSFET.

No connection.

PAM2305

Document number: DSxxxxx Rev. 2 - 6

2 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Product Line o

Diodes Incorporated

PAM2305

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

SW Pin Voltage

Junction Temperature

Storage Temperature Range

Soldering Temperature

Recommended Operating Conditions (@T

Parameter Rating Unit

Supply Voltage 2.5 to 5.5 V

Operation Temperature Range -40 to +85

Junction Temperature Range -40 to +125

= +25°C, unless otherwise specified.)

A

-0.3 to V

-0.3 to (V

-65 to +150 °C

300, 5sec °C

IN

+0.3)

IN

150 °C

= +25°C, unless otherwise specified.)

A

V

V

°C

Thermal Information

Parameter Package Symbol Max Unit

TSOT25 (Note 1)

Thermal Resistance (Junction to Case)

Thermal Resistance (Junction to Ambient)

Internal Power Dissipation

Note: 1. The maximun output current for TSOT25 package is limited by internal power dissipation capacity as described in
Application Information here inafter.

DFN2x2-6 25

QFN3x3-16 14

TSOT25

DFN2x2-6 68

QFN3x3-16 35

TSOT25

DFN2x2-6 980

QFN3x3-16 1470

θ

JC

θ

JA

P

D

130

250

400

°C/W

mW

PAM2305

Document number: DSxxxxx Rev. 2 - 6

3 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Product Line o

Diodes Incorporated

PAM2305

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 96 %

EN Threshold High

EN Threshold Low

EN Leakage Current

Over Temperature Protection OTP 150 °C

OTP Hysteresis OTH 30 °C

PAM2305

Document number: DSxxxxx Rev. 2 - 6

= +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 0.3 0.45 Ω
N MOSFET 0.35 0.5 Ω

V

ΔV

f

R

DS(ON)

I

V

V

V

V

I

PK

I

I

SD

OSC

LSW

I

EN

4 of 17

www.diodes.com

= 10µF, L = 4.7µH, 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 %

0.1 1 µA

1.2 1.5 1.8 MHz

500 kHz

January 2013

© Diodes Incorporated

A

f

Typical Performance Characteristics (@T

Product Line o

Diodes Incorporated

PAM2305

= +25°C, CIN = 10µF, CO = 10µF, L = 4.7µH, unless otherwise specified.)

A

PAM2305

Document number: DSxxxxx Rev. 2 - 6

5 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Typical Performance Characteristics (cont.) (@T

Product Line o

Diodes Incorporated

PAM2305

= +25°C, CIN = 10µF, CO = 10µF, L = 4.7µH, unless otherwise specified.)

A

PAM2305

Document number: DSxxxxx Rev. 2 - 6

6 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Typical Performance Characteristics (cont.) (@T

Product Line o

Diodes Incorporated

PAM2305

= +25°C, CIN = 10µF, CO = 10µF, L = 4.7µH, unless otherwise specified.)

A

PAM2305

Document number: DSxxxxx Rev. 2 - 6

7 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Typical Performance Characteristics (cont.) (@T

Product Line o

Diodes Incorporated

PAM2305

= +25°C, CIN = 10µF, CO = 10µF, L = 4.7µH, unless otherwise specified.)

A

PAM2305

Document number: DSxxxxx Rev. 2 - 6

8 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Typical Performance Characteristics (cont.) (@T

Product Line o

Diodes Incorporated

PAM2305

= +25°C, CIN = 10µF, CO = 10µF, L = 4.7µH, unless otherwise specified.)

A

PAM2305

Document number: DSxxxxx Rev. 2 - 6

9 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

(

)

(

)

Product Line o

Diodes Incorporated

PAM2305

Application Information

The basic PAM2305 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 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

current as shown in Equation 1. A 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 1.4A rated inductor should be enough for most applications (1A + 400mA). 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

and C

IN

Δ

I

1.2V 1.5V 1.8V 2.5V 3.3V

O

L 2.2µH 2.2µH 2.2µH 4.7µH 4.7µH

OUT

C

IN

Δ

.

OUT

1

()()

Lf

⎛
⎜

−=

1

V

OUTL

⎜
⎝

⎞

V

OUT

⎟

Equation (1)

⎟

V

IN

⎠

Selection

[]

()

−

required

OUT

is determined by:

OUT

≅

≅

II

OMAXRMS

= 2V

IN

is driven by the required effective series resistance (ESR).

⎛
⎜

+

ESR

Δ

iV

LOUT

⎜
⎝

f8

C

1

OUT

OUT

OUT

⎞
⎟
⎟
⎠

, where I

VVV

V

IN

RMS

has been met, the RMS current rating generally far exceeds the I

2/1

OUTINOUT

= I

OUT

or V

IN

= 400mA (40% of 1A).

L

. To prevent large voltage transients, a low

OUT/VIN

/2. This simple worst-case condition is commonly used for design because even

also increases the ripple

OUT

(P-P) requirement. The

RIPPLE

Where f = operating frequency, C

highest at maximum input voltage since ΔI

= output capacitance and ΔIL = 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 PAM2305. 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:

−+

is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses.

I

Q

2

I

P

OD

V

RVVRV

IN

PAM2305

Document number: DSxxxxx Rev. 2 - 6

L)ON(DSOINH)ON(DSO

t

SW

++=

www.diodes.com

VIIF

INQOS

10 of 17

January 2013

© Diodes Incorporated

A

f

Product Line o

Diodes Incorporated

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

PAM2305

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

250°C/W, DFN2X2 102°C/W, and QFN3X3 68°C/W, respectively. The maximum power dissipation at T

formula:

SOT-25 package:

P

DFN2*2 package:

P

QFN3*3 package:

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)/250°C/W = 0.4W

D

=(125°C - 25°C)/102°C/W = 0.984W

D

=(125°C - 25°C)/68°C/W = 1.47W

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 TSOT25 package is

JA

= +25°C can be calculated by following

A

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:

V

where R

= VIN – I

OUT

= P-Channel switch ON resistance, I

DS(ON)

LOAD

(R

DS(ON)

= RL)

= 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 PAM2305 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 400kHz and minimum duty cycle, therefore the average input current is typically 200mA.

PAM2305

Document number: DSxxxxx Rev. 2 - 6

11 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Product Line o

Diodes Incorporated

PAM2305

Application Information (cont.)

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.

PCB Layout Check List

When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the PAM2305. 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

C

3. Does the (+) plat e of C

MOSFETs.

4. Keep the switching node, SW, away from the sensitive VFB node.

5. Keep the (–) plates of C

OUT

pin connect directly to the feedback resistors? The resistive divider R1/R2 must be connected between the (+) plate of

FB

and ground.

connect to VIN as closely as possible? This capacitor provides the AC current to the internal power

IN

and C

IN

as close as possible.

OUT

Figure 1. PAM2305 Suggested Layout

PAM2305

Document number: DSxxxxx Rev. 2 - 6

12 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Ordering Information

Product Line o

Diodes Incorporated

PAM2305

Part Number Output Voltage Part Marking Package Type Standard Package

PAM2305AAB330 3.3V BEKYW TSOT25 3000 Units/Tape&Reel

PAM2305AAB280 2.8V BEHYW

PAM2305AAB250 2.5V BEGYW

PAM2305AAB180 1.8V BEEYW

PAM2305AAB150 1.5V BECYW

PAM2305AAB120 1.2V BEBYW

PAM2305AABADJ ADJ BEAYW

PAM2305BJE330 3.3V P2305K QFN3x3 3000 Units/Tape&Reel
PAM2305BJE280 2.8V P2305H QFN3x3 3000 Units/Tape&Reel
PAM2305BJE250 2.5V P2305G QFN3x3 3000 Units/Tape&Reel
PAM2305BJE180 1.8V P2305E QFN3x3 3000 Units/Tape&Reel
PAM2305BJE150 1.5V P2305C QFN3x3 3000 Units/Tape&Reel
PAM2305BJE120 1.2V P2305B QFN3x3 3000 Units/Tape&Reel
PAM2305BJEADJ ADJ P2305A QFN3x3 3000 Units/Tape&Reel

PAM2305CGF330 3.3V BEKYW DFN2x2-6 3000 Units/Tape&Reel

PAM2305CGF280 2.8V BEHYW DFN2x2 3000 Units/Tape&Reel

PAM2305CGF250 2.5V BEGYW DFN2x2 3000 Units/Tape&Reel

PAM2305CGF180 1.8V BEEYW DFN2x2 3000 Units/Tape&Reel

PAM2305CGF150 1.5V BECYW DFN2x2 3000 Units/Tape&Reel

PAM2305CGF120 1.2V BEBYW DFN2x2 3000 Units/Tape&Reel

PAM2305CGFADJ ADJ BEAYW DFN2x2 3000 Units/Tape&Reel

PAM2305

Document number: DSxxxxx Rev. 2 - 6

13 of 17

www.diodes.com

TSOT25

TSOT25

TSOT25

TSOT25

TSOT25

TSOT25

3000 Units/Tape&Reel

3000 Units/Tape&Reel

3000 Units/Tape&Reel

3000 Units/Tape&Reel

3000 Units/Tape&Reel

3000 Units/Tape&Reel

January 2013

© Diodes Incorporated

A

f

Marking Information

Top View

TSOT25

Product Line o

Diodes Incorporated

PAM2305

Package Outline Dimensions (All dimensions in mm.)

TSOT25

PAM2305

Document number: DSxxxxx Rev. 2 - 6

14 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Package Outline Dimensions (cont.) (All dimensions in mm.)

Product Line o

Diodes Incorporated

PAM2305

PAM2305

Document number: DSxxxxx Rev. 2 - 6

15 of 17

www.diodes.com

January 2013

© Diodes Incorporated

A

f

Package Outline Dimensions (cont.) (All dimensions in mm.)

Product Line o

Diodes Incorporated

PAM2305

Notes: 2. Controlling dimensions are in millimeters (angles in degress).

3. Coplanarity applies to the exposed pad as well as the terminals.

4. DAP is 1.90 x 1.90mm.

PAM2305

Document number: DSxxxxx Rev. 2 - 6

16 of 17

www.diodes.com

© Diodes Incorporated

January 2013

A

f

Product Line o

Diodes Incorporated

PAM2305

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.

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 © 2013, Diodes Incorporated

www.diodes.com

IMPORTANT NOTICE

LIFE SUPPORT

PAM2305

Document number: DSxxxxx Rev. 2 - 6

17 of 17

www.diodes.com

January 2013

© Diodes Incorporated