Diodes PAM2301 User Manual

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Description

The PAM2301 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 PAM2301 provides a power-saving Pulse-

Skipping Modulation (PSM) mode to reduce quiescent current under

light load operation to save power.

The PAM2301 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

PAM2301-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 0.1mA. Other

key features include under-voltage lockout to prevent deep battery

discharge.

The PAM2301 is available in TSOT25 package.

Features

• Efficiency up to 96%

• Only 40μA (typ) Quiescent Current

• Output Current: Up to 800mA

• Internal Synchronous Rectifier

• 1.5MHz Switching Frequency

• Soft Start

• Under-Voltage Lockout

• Short Circuit Protection

• Thermal Shutdown

• 5-Pin Small TSOT25 Package

• Pb-Free Package

Diodes Incorporated

800mA STEP-DOWN DC-DC CONVERTER

Pin Assignments

Applications

• Cellular Phone

• Portable Electronics

• Wireless Devices

• Cordless Phone

• Computer Peripherals

• Battery-Powered Widgets

• Electronic Scales

• Digital Frame

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PAM2301

TSOT25

Typical Applications Circuit

Fixed Output Voltage Adjustable Output Voltage

PAM2301

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O

1R

⎞

⎛

+×=

16.0

⎜
⎝

⎟

2R

⎠

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Pin Descriptions

Pin Number Pin Name Function

1 EN

2 GND Ground

3 SW The drains of the internal main and synchronous power MOSFET.

4 VIN Power Supply

5 VOUT/FB

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.

Functional Block Diagram

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PAM2301

PAM2301

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PAM2301

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.

= +25°C, unless otherwise specified.)

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Parameter Rating Unit

Input Voltage -0.3 to +6.0 V

EN, FB Pin Voltage

SW Pin Voltage

-0.3 to V

-0.3 to (V

IN

+ 0.3)

IN

V

V

Junction Temperature +150 °C

Storage Temperature Range -65 to +150 °C

Soldering Temperature +300, 5sec °C

Recommended Operating Conditions (@T

= +25°C, unless otherwise specified.)

A

Parameter Rating Unit

Supply Voltage 2.5 to 5.5 V

Operation Temperature Range -40 to +85

Juntion Temperature Range -40 to +125

°C

Thermal Information

Parameter Symbol Max Unit

Thermal Resistance (Junction to Case)

Thermal Resistance (Junction to Ambient)

Internal Power Dissipation

θ

JC

θ

JC

P

D

Electrical Characteristics (@T

= +25°C, VIN = 3.6V, VO = 1.8V, CIN = 10µF, L = 4.7µH unless otherwise specified.)

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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

V

IN

V

FB

ΔV

FB

V

IO = 100mA

O

I

V

PK

Output Voltage Line Regulation LNR

Output Voltage Load Regulation LDR

Quiescent Current

Shutdown Current

Oscillator Frequency

Drain-Source On-State Resistance

SW Leakage Current

I

Q

I

VEN = 0V

SD

f

OSC

R

I

DS(ON)

I

LSW

IN

V

= 2.5V to 5V, IO = 10mA

IN

I

= 1mA to 800mA

O

No load 40 70 µA

= 100%

V

O

VFB = 0V or VO = 0V

= 100mA

DS

High Efficiency η 96 %

EN Threshold High

EN Threshold Low

EN Leakage Current

V

EH

V

EL

I

EN

Over Temperature Protection OTP 150 °C

OTP Hysteresis OTH 30 °C

PAM2301

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130

250

°C/W

400 mW

= 3V,VFB = 0.5V or VO = 90%

P MOSFET 0.30 0.45 Ω
N MOSFET 0.35 0.50 Ω

2.5 5.5 V

0.588 0.600 0.612 V

0.3 %/V

-3 +3 %

1.2 A

0.2 0.5 %/V

0.5 1.5 %

0.1 1.0 µA

1.2 1.5 1.8 MHz

500 kHz

±0.01 1 µA

1.5 V

0.3 V

±0.01 µA

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Typical Performance Characteristics (@T

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PAM2301

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

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PAM2301

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Typical Performance Characteristics (cont.) (@T

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PAM2301

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

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PAM2301

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Typical Performance Characteristics (cont.) @T

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PAM2301

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

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PAM2301

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Typical Performance Characteristics (cont.) @T

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PAM2301

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

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PAM2301

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Typical Performance Characteristics (cont.) @T

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PAM2301

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

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PAM2301

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PAM2301

Application Information

The basic PAM2301 application circuit is shown on Page 1. 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 1120mA rated inductor should be enough for most applications (800mA + 320mA). 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

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

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 formulations. These dielectrics have the best

temperature and voltage characteristics of all the ceramics for a given value and size.

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.

Table 1: Resistor selection for output voltage setting.

and C

IN

Δ

I

OUT

C

IN

ν

V

O

V

O

1.2V 100k 100k

1.5V 150k 100k

1.8V 200k 100k

2.5V 380k 120k

3.3V 540k 120k

.

OUT

1

()()

Lf

⎛
⎜

−=

1

V

OUTL

⎜
⎝

⎞

V

OUT

⎟

Equation 1

⎟

V

IN

⎠

Selection

[]

()

−

VVV

required

OUT

is determined by:

OUT

≅

ν

≅

II

OMAXRMS

= 2V

IN

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

⎛
⎜

+

ESR

IV

LOUT

⎜
⎝

⎛

+×=

16.0

⎜
⎝

R1 R2

fC8

OUT

1R

⎞
⎟

2R

⎠

, where I

OUT

OUT

⎞

1

⎟
⎟

OUT

⎠

= output capacitance and ΔIL = ripple current in the inductor. For a fixed output voltage, the output ripple is

increases with input voltage.

L

OUTINOUT

V

IN

=I

RMS

OUT

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

or V

IN

= 320mA (40% of 800mA).

L

. To prevent large voltage transients, a low

OUT/VIN

2/1

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

also increases the ripple

OUT

(P-P) requirement. The

RIPPLE

PAM2301

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PAM2301

Application Information (cont.)

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 = Output Current, R = Inductor DC Resistance.

DS(ON)

UVLO AND Soft-Start

The reference and the circuit remain reset until the VIN crosses its UVLO threshold.

The PAM2301 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.

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 PAM2301. 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 CIN connect to V

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

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 and

FB

and C

IN

OUT

+×−=

RRIVV

L)ON(DSLOADINOUT

as closely as possible? This capacitor provides the AC current to the internal power MOSFETs.

IN

as close as possible.

Figure 1. PAM2301 Suggested Layout

PAM2301

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Ordering Information

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PAM2301

Part Number Output Voltage Marking Package Packaging

PAM2301CAAB330 3.3V BAKYW TSOT25 3000 Units/Tape & Reel
PAM2301CAAB280 2.8V BAHYW TSOT25 3000 Units/Tape & Reel
PAM2301CAAB250 2.5V BAGYW TSOT25 3000 Units/Tape & Reel
PAM2301CAAB180 1.8V BAEYW TSOT25 3000 Units/Tape & Reel
PAM2301CAAB150 1.5V BACYW TSOT25 3000 Units/Tape & Reel
PAM2301CAAB120 1.2V BABYW TSOT25 3000 Units/Tape & Reel

PAM2301CAABADJ ADJ BAAYW TSOT25 3000 Units/Tape & Reel

Marking Information

TSOT25

PAM2301

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Package Outline Dimensions (All dimensions in mm.)

TSOT25

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PAM2301

PAM2301

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PAM2301

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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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IMPORTANT NOTICE

LIFE SUPPORT

PAM2301

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