MAX8581_V01_技术文档

19-0593; Rev 1; 1/07

2.5MHz/1.5MHz Step-Down Converters

with 60m Bypass in TDFN for CDMA PA Power

General Description

Features

The MAX8581/MAX8582 high-frequency step-down con-

verters are optimized for dynamically powering the power

amplifier (PA) in CDMA handsets. They integrate a high-

efficiency PWM step-down converter for medium- and

low-power transmission and a 60m (typ) bypass mode

to power the PA directly from the battery during high-

power transmission. They use an analog input driven by

an external DAC to control the output voltage linearly for

continuous PA power adjustment. The MAX8581/

MAX8582 use an internal feedback network, and the

switching frequency is internally set to 2.5MHz and

1.5MHz, respectively.

♦ 600mA Step-Down Converter

♦ 60m (typ) Bypass Mode with Integrated FET

♦ Dynamically Adjustable Output from 0.4V to V

♦ 2.5MHz and 1.5MHz Switching Frequency

IN

♦ Small LC Components: 1.5µH to 3.3µH and 2.2µF

♦ Up to 94% Efficiency

♦ Low Output Ripple at All Loads

♦ 2.7V to 5.5V Input

Fast switching (up to 2.5MHz) and fast soft-start allow

the use of ceramic 2.2µF input and output capacitors

while maintaining low voltage ripple. The small 1.5µH to

3.3µH inductor size can be optimized for efficiency.

♦ 0.1µA Shutdown Mode

♦ Output Short-Circuit Protection

♦ Thermal Shutdown

The MAX8581/MAX8582 are available in 10-pin, 3mm x

3mm TDFN packages (0.8mm max height).

♦ 10-Pin, 3mm x 3mm TDFN Packages

Applications

Ordering Information

WCDMA/NCDMA Cell Phones

PIN-

PACKAGE

TOP

MARK

PKG

CODE

PART*

Wireless PDAs, Smartphones

MAX8581ETB+

MAX8582ETB+

10 TDFN-EP**

ACT

ACU

T1033-1

*All devices are specified in the -40°C to +85°C extended

temperature range.

**EP = Exposed pad.

+Denotes a lead-free package.

Typical Operating Circuit

Pin Configuration

OUTPUT

INPUT

Li+ BATTERY

TOP VIEW

0.4V TO V

BATT

IN

OUT

LX

1.5 H OR 3.3 H

10

9

8

7

6

MAX8581

MAX8582

2.2 F

GND

2.2 F

MAX8581/

MAX8582

SHDN

REFIN

ON/OFF

ANALOG

CONTROL

FORCED BYPASS

HP

+

2

3

5

1

4

________________________________________________________________ Maxim Integrated Products

1

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

2.5MHz/1.5MHz Step-Down Converters

with 60m Bypass in TDFN for CDMA PA Power

ABSOLUTE MAXIMUM RATINGS

IN, SHDN, HP, REFIN to GND...............................-0.3V to +6.0V

LX, OUT, IC to GND.....................................-0.3V to (V + 0.3V)

Continuous Power Dissipation (T = +70°C)

A

10-Pin TDFN (derate 24.4mW/ C above +70°C).........1951mW

°

IN

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range.............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

OUT Short Circuit to GND ..........................................Continuous

LX Current ......................................................................0.7A

IN, OUT Current..............................................................2.5A

RMS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional

operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to

absolute maximum rating conditions for extended periods may affect device reliability.

ELECTRICAL CHARACTERISTICS

(V = V

IN

= 3.6V, V

= 0.9V, V

= V = 0V, T = -40°C to +85°C, typical values are at T = +25°C, unless otherwise

HP IC A A

SHDN

REFIN

noted.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

SUPPLY

Supply Voltage Range

UVLO Threshold

V

2.7

5.5

V

IN

UVLO

V

rising, 180mV hysteresis

2.55

2.63

4000

0.1

2.70

IN

I

= 0A, switching at 1.5MHz

LOAD

Supply Current

OUT

I

Shutdown, T = +25 C

10

µA

IN

A

Shutdown, T = +85 C

1.0

A

V

= 4.2V, V

= 3.6V

= 1.7V

REFIN

3.33

1.75

0.75

3.40

1.80

0.80

360

558

3.47

1.85

0.85

IN

OUT Voltage Accuracy

V

R

V

k

V

= 0.9V

= 0.4V

OUT

REFIN

MAX8581

MAX8582

OUT Input Resistance

V

= V

LX OUT

OUT

REFIN

REFIN Common-Mode Range

REFIN to OUT Gain

0

2.2

V

V/V

k

2.00

518

REFIN Input Resistance

0.45 x 0.463 x 0.475 x

REFIN Dual Mode Threshold

LOGIC INPUTS

rising, 77mV hysteresis

V

REFIN

V

IN

V

= 2.7V to 5.5V

1.4

IH

IN

Logic Input Level

V

= 2.7V to 5.5V

0.4

1

IL

T

= +25 C

= +85 C

0.01

0.1

A

Logic Input Bias Current

I

, I

IH IL

V

= 0V or V

IN

µA

INPUT

A

Dual Mode is a trademark of Maxim Integrated Products, Inc.

2

_______________________________________________________________________________________

2.5MHz/1.5MHz Step-Down Converters

with 60m Bypass in TDFN for CDMA PA Power

ELECTRICAL CHARACTERISTICS (continued)

(V = V

= 3.6V, V = 0.9, V = V = 0V, T = -40°C to +85°C, typical values are at T = +25°C, unless otherwise noted.)

REFIN HP IC A A

IN

SHDN

(Note 1)

PARAMETER

SYMBOL

CONDITIONS

p-channel MOSFET switch, I = -40mA

MIN

TYP

MAX

UNITS

LX

R

ONP

0.2

0.18

0.1

1

0.4

0.35

5

LX

On-Resistance

R

n-channel MOSFET rectifier, I = 40mA

LX

ONN

T

A

T

A

= +25 C

= +85 C

V

= 5.5V,

IN

LX Leakage Current

I

µA

mA

LXLKG

LX = GND

p-Channel MOSFET Peak

Current Limit

I

700

790

1077

985

1400

1150

LIMP

LIMN

n-Channel MOSFET Valley

Current Limit

I

t

70

114

112

1.02

2.5

150

1.13

ON(MIN)

Minimum On- and Off-Times

ns

s/s

t

OFF(MIN)

t

/t

Ratio

t

/ t

0.90

ON OFF

ON(MIN) OFF(MIN)

MAX8581

MAX8582

Switching Frequency

MHz

1.5

BYPASS

p-channel MOSFET bypass,

= -400mA, T = +25 C

0.06

0.1

I

On-Resistance

R

ONBYP

OUT

A

p-channel MOSFET bypass, I

= -400mA

0.12

OUT

Bypass Current Limit

1.0

2.1

A

Step-Down Current Limit in

Bypass

700

1077

1400

mA

GENERAL

Thermal Shutdown

Thermal-Shutdown Hysteresis

Power-Up Delay

+160

20

C

V

rising to V rising

50

130

µs

SHDN

LX

Note 1: All devices are 100% production tested at T = +25°C. Limits over the operating temperature range are guaranteed by design.

A

_______________________________________________________________________________________

3

2.5MHz/1.5MHz Step-Down Converters

with 60m Bypass in TDFN for CDMA PA Power

Typical Operating Characteristics

(V = 3.6V, V

= 1.2V, MAX8582 EV Kit, T = +25°C, unless otherwise noted.)

A

IN

OUT

BYPASS MODE DROPOUT VOLTAGE

vs. LOAD CURRENT

EFFICIENCY

EFFICIENCY vs. OUTPUT VOLTAGE

vs. LOAD CURRENT (V

= 1.8V)

OUT

100

95

90

85

80

75

70

65

60

0.08

0.07

0.06

0.05

0.04

0.03

0.02

0.01

0

100

90

80

70

60

V

= 3.2V

OUT

50

40

30

20

10

0

V

= 3.6V

OUT

R

= 7.5

2.8

LOAD

0.8

1.2

1.6

2.0

2.4

3.2

0

0.2

0.4

0.6

0.8

1.0

10

100

1000

OUTPUT VOLTAGE (V)

LOAD CURRENT (A)

LOAD CURRENT (mA)

EFFICIENCY

NO-LOAD SUPPLY CURRENT

vs. SUPPLY VOLTAGE

vs. LOAD CURRENT (V

= 1.2V)

vs. LOAD CURRENT (V

= 0.6V)

OUT

100

90

80

70

60

50

40

30

20

10

0

9

8

7

6

5

4

3

2

1

0

80

70

60

50

40

30

20

10

0

10

100

1000

10

100

1000

2.5

3.0

3.5

4.0

4.5

5.0

5.5

LOAD CURRENT (mA)

SUPPLY VOLTAGE (V)

OUTPUT VOLTAGE vs. LOAD CURRENT

OUTPUT VOLTAGE vs. REFIN VOLTAGE

1.210

1.200

1.190

4.5

V

= 4.2V

IN

4.0

3.5

V

= 3.6V

IN

3.0

2.5

V

= 3.0V

IN

1.180

1.170

1.160

2.0

1.5

1.0

0.5

R

= 7.5

LOAD

1.150

0

100

200

300

400

500

600

0

0.3

0.6

0.9 1.2 1.5 1.8 2.1

LOAD CURRENT (mA)

REFIN VOLTAGE (V)

4

_______________________________________________________________________________________

2.5MHz/1.5MHz Step-Down Converters

with 60m Bypass in TDFN for CDMA PA Power

Typical Operating Characteristics (continued)

(V = 3.6V, V

= 1.2V, MAX8582 EV Kit, T = +25°C, unless otherwise noted.)

A

IN

OUT

LIGHT-LOAD SWITCHING WAVEFORMS

HEAVY-LOAD SWITCHING WAVEFORMS

MAX8581/2 toc09

MAX8581/2 toc10

I

= 50mA

LOAD

600mA

I

LX

100mA/div

0A

I

LX

400mA

200mA

I

= 500mA

LOAD

V

20mV/div

AC-COUPLED

20mV/div

AC-COUPLED

OUT

V

OUT

2V/div

0V

2V/div

0V

V

LX

V

LX

200ns/div

LINE-TRANSIENT WAVEFORMS

LOAD TRANSIENT

SOFT-START WAVEFORMS

MAX8581/2 toc12

MAX8581/2 toc13

MAX8581/2 toc11

R

= 7.5

LOAD

2V

2V/div

V

4V

3V

SHDN

V

IN

50mV/div

AC-COUPLED

1V/div

0V

V

OUT

V

OUT

V

OUT

I

IN

50mV/div

AC-COUPLED

100mA/div

0A

I

OUT

I

LX

500mA/div

0A

200mA/div

0A

I

LX

100mA/div

0A

20 s/div

HP TRANSIENT RESPONSE

WITH FORCED AUTOBYPASS

REFIN TRANSIENT RESPONSE

REFIN TRANSIENT WITH AUTOBYPASS

MAX8581/2 toc15

MAX8581/2 toc14

MAX8581/2 toc16

R

= 7.5

R

= 7.5

LOAD

R

V

= 7.5

= 0.6V

LOAD

REFIN

V

OUT

V

OUT

2V

1V

2V/div

0V

V

2V/div

0V

OUT

V

REFIN

1V/div

0V

1V/div

V

HP

1V

0V

V

REFIN

I

LX

0.5V

I

LX

500mA/div

0A

500mA/div

0A

I

LX

200mA/div

0A

500mA/div

0A

500mA/div

0A

I

OUT

20 s/div

_______________________________________________________________________________________

5

2.5MHz/1.5MHz Step-Down Converters

with 60m Bypass in TDFN for CDMA PA Power

Pin Description

NAME

FUNCTION

1

GND

Ground

Supply Voltage Input. 2.7V to 5.5V. Bypass with a 2.2µF ceramic capacitor as close as possible to IN

and GND.

2, 3

4

IN

SHDN

HP

Active-Low Shutdown Input. Connect to IN or logic-high for normal operation. Connect to GND or

logic-low for shutdown mode.

High-Power Mode Set Input. Drive HP high to invoke bypass mode. Bypass mode connects IN

directly to OUT with the internal bypass MOSFET.

5

DAC-Controlled Input. Output regulates to 2 x V

threshold at 0.465 V enables bypass mode.

IN

for the MAX8581 and MAX8582. Dual-mode

REFIN

6

7

REFIN

IC

Internally Connected. Connect to ground.

Output Voltage Connection for Bypass Mode. Internally connected to IN using the internal bypass

MOSFET during bypass mode. Connects to the internal feedback network.

8, 9

OUT

Inductor Connection. Connect inductor to the drains of the internal p-channel and n-channel

MOSFETs. Connects to the internal feedback network.

10

—

LX

EP

Exposed Paddle. Connect to GND.

Voltage-Positioning Load Regulation

The MAX8581/MAX8582 utilize a unique feedback net-

Detailed Description

The MAX8581/MAX8582 step-down converters deliver

over 600mA to dynamically power the PA in CDMA

handsets. The hysteretic PWM control scheme switches

with nearly fixed frequency at 1.5MHz (MAX8582) to

2.5MHz (MAX8581), allowing efficiency and tiny external

components. A 60m bypass mode connects the PA

directly to the battery during high-power transmission.

work. By taking feedback from the LX node, the usual

phase lag due to the output capacitor is removed, mak-

ing the loop exceedingly stable and allowing the use of

very small ceramic output capacitors. This configura-

tion yields load regulation equal to half the inductor’s

series resistance multiplied by the load current. This

voltage-positioning load regulation greatly reduces

overshoot during load transients or when changing

Control Scheme

A hysteretic PWM control scheme ensures high effi-

ciency, fast switching, fast transient response, low out-

put ripple, and physically tiny external components.

This control scheme is simple: When the output voltage

is below the regulation voltage, the error comparator

begins a switching cycle by turning on the high-side

switch. This switch remains on until the minimum on-

time expires and the output voltage is in regulation or

the current-limit threshold is exceeded. Once off, the

high-side switch remains off until the minimum off-time

expires and the output voltage falls out of regulation.

During this period, the low-side synchronous rectifier

turns on and remains on until the high-side switch turns

on again. The internal synchronous rectifier eliminates

the need for an external Schottky diode.

V

from one voltage to another. However, when cal-

OUT

culating REFIN voltage, the load regulation should be

considered. Because inductor resistance is typically

well specified and the typical PA is a resistive load, the

V

to V

gain is slightly less than 2V/V for the

OUT

REFIN

MAX8581/MAX8582.

Bypass Mode

During high-power transmission, the bypass mode’s

low on-resistance provides low dropout, long battery

life, and high output-current capability. Bypass mode

connects IN directly to OUT with the internal 60m

(typ) bypass FET, while the step-down converter is

forced into 100% duty-cycle operation to slightly lower

total on-resistance to less than 60m (typ).

6

_______________________________________________________________________________________

2.5MHz/1.5MHz Step-Down Converters

with 60m Bypass in TDFN for CDMA PA Power

Applications Information

The MAX8581/MAX8582 are optimized for use with a tiny

V

= 3.2V TO 3.66V

IN

inductor and small ceramic capacitors. The correct

selection of external components ensures high efficiency,

low output ripple, and fast transient response.

200mV/div

Setting the Output Voltage

The MAX8581/MAX8582 output voltages are set by the

voltage applied to REFIN. The output voltage is 2 V

REFIN

minus half the IR voltage drop caused by the inductor’s

DC resistance for the MAX8581/MAX8582.

V

OUT

= 3V

200mV/div

Inductor Selection

The MAX8581/MAX8582 use 1.5µH and 3.3µH, respec-

tively. Low inductance values are physically smaller

but require faster switching, which results in some effi-

ciency loss (see the Typical Operating Characteristics

for efficiency).

5ms/div

Figure 1. V and V

IN

with Automatic Entry/Exit into Bypass

OUT

Mode

The inductor’s DC current rating only needs to match the

maximum load of the application because the

MAX8581/MAX8582 feature zero current overshoot during

startup and load transients. For optimum transient

response and high efficiency, choose an inductor with

DC series resistance in the 50m to 150m range.

Forced and Automatic Bypass Mode

Invoke forced-bypass mode by driving HP high or

invoke automatic bypass by applying a high voltage to

REFIN (V

> 2.1V with a Li-ion (Li+) battery at IN).

REFIN

To prevent excessive output ripple as the step-down

converter approaches dropout, the MAX8581/MAX8582

preemptively enter bypass mode automatically when

Output Capacitor Selection

The output capacitor is required to keep the output volt-

age ripple small and to ensure regulation loop stability.

The output capacitor must have low impedance at the

switching frequency. Ceramic capacitors with X5R or

X7R dielectric are highly recommended due to their

small size, low ESR, and small temperature coefficients.

Due to the unique feedback network, the output capa-

citance can be very low. In most applications, 2.2µF

works well. For optimum load-transient performance

and very low output ripple, the output capacitor value

can be increased.

V

> 0.465 V (see Figure 1).

IN

REFIN

Shutdown Mode

Connect SHDN to GND or logic-low to place the

MAX8581/MAX8582 in shutdown mode and reduce

supply current to 0.1µA. In shutdown, the control cir-

cuitry, internal switching MOSFET, and synchronous

rectifier turn off and LX becomes high impedance.

Connect SHDN to IN or logic-high for normal operation.

Fast Soft-Start

The MAX8581/MAX8582 have internal fast soft-start cir-

cuitry that limits inrush current at startup, reducing tran-

sients on the input source. Soft-start is particularly

useful for supplies with high output impedance such as

Li+ and alkaline cells. See the Soft-Start Waveforms in

the Typical Operating Characteristics.

Input Capacitor Selection

The input capacitor reduces the current peaks drawn

from the battery or input power source and reduces

switching noise in the MAX8581/MAX8582. The imped-

ance of the input capacitor at the switching frequency

should be kept very low. Ceramic capacitors with X5R

or X7R dielectric are highly recommended due to their

small size, low ESR, and small temperature coefficients.

Due to the MAX8581/MAX8582s’ fast soft-start, the input

capacitance can be very low. In most applications,

2.2µF works well. For optimum noise immunity and low

input ripple, the input capacitor value can be increased.

Analog REFIN Control

The MAX8581/MAX8582 use REFIN to set the output

voltage and to switch to bypass mode. The output volt-

age is two times the voltage applied at REFIN minus

half the IR voltage drop caused by the inductor’s DC

resistance for the MAX8581/MAX8582. This allows the

converter to operate in applications where dynamic

voltage control is required.

_______________________________________________________________________________________

7

2.5MHz/1.5MHz Step-Down Converters

with 60m Bypass in TDFN for CDMA PA Power

Table 1. Suggested Inductors

INDUCTANCE

(µH)

ESR

( )

CURRENT

RATING (mA)

MANUFACTURER

SERIES

DIMENSIONS

1.5

3.3

1.5

3.3

1.5

3.3

2.2

1.5

3.3

2.2

1.5

3.3

2.2

1.5

1.3

0.10

0.16

0.11

0.10

0.17

0.07

0.10

0.12

0.05

0.10

0.13

0.20

0.09

0.13

0.08

0.14

0.08

0.11

0.17

1400

950

Coilcraft

LP03310

SD3110

SD3112

3.3 x 3.3 x 1.0 = 11mm³

3.1 x 3.1 x 1.05 = 10mm³

3.1 x 3.1 x 1.2 = 12mm³

970

Cooper

1090

840

1500

1200

1000

680

FDK

MIPF2520D

2.5 x 2.0 x 1.0 = 5mm³

3.2 x 3.2 x 1.2 = 12mm³

Panasonic

Sumida

ELC3FN

CDRH2D09

CDRH2D11

CB2016

450

510

2.0 x 1.25 x 1.45 = 3.6mm³

CBC2016

CB2518

750

510

2.0 x 1.6 x 1.8 = 5.8mm³

2.5 x 1.8 x 2.0 = 9mm³

Taiyo Yuden

TOKO

CBC2518

890

1200

840

NR3010

MDT2520-CR

D2812C

3.2 x 3.2 x 1.2 = 12mm³

2.5 x 2.0 x 1.0 = 5mm³

2.8 x 2.8 x 1.2 = 9.4mm³

700

900

730

PCB Layout

Checklist

L1 = FDK MIPF2520 SERIES

High switching frequencies and relatively large peak cur-

rents make the PCB layout a very important part of

design. Good design minimizes excessive EMI on the

feedback paths and voltage gradients in the ground

plane, both of which can result in instability or regulation

errors. Connect the input capacitor close to IN and GND.

Connect the inductor and output capacitor as close to

the IC as possible and keep their traces short, direct,

and wide. Keep noisy traces, such as the LX node, as

short as possible. Connect GND to the exposed paddle

directly under the IC. Figure 2 illustrates an example

PCB layout and routing scheme.

1.5 H FOR MAX8581

3.3 H FOR MAX8582

C1, C2 = TAIYO YUDEN JMK105BJ225MV-B

L1

GND

OUT

GND

C1

IN

C2

SHDN

HP

REFIN

Chip Information

PROCESS: BiCMOS

Figure 2. Example PCB Layout and Routing Scheme

8

_______________________________________________________________________________________

2.5MHz/1.5MHz Step-Down Converters

with 60m Bypass in TDFN for CDMA PA Power

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information

go to www.maxim-ic.com/packages.)

PACKAGE OUTLINE, 6,8,10 & 14L,

TDFN, EXPOSED PAD, 3x3x0.80 mm

1

H

21-0137

2

_______________________________________________________________________________________

9

2.5MHz/1.5MHz Step-Down Converters

with 60m Bypass in TDFN for CDMA PA Power

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information

go to www.maxim-ic.com/packages.)

PACKAGE VARIATIONS

COMMON DIMENSIONS

MIN. MAX.

SYMBOL

PKG. CODE

T633-1

N

6

D2

1.50±0.10 2.30±0.10 0.95 BSC

1.50±0.10 2.30±0.10

E2

e

JEDEC SPEC

MO229 / WEEA

MO229 / WEEC

b

[(N/2)-1] x e

1.90 REF

1.95 REF

2.00 REF

2.40 REF

0.40±0.05

0.30±0.05

A

0.70

2.90

0.00

0.20

0.80

3.10

0.05

0.40

T633-2

6

D

E

0.95 BSC

T833-1

8

1.50±0.10 2.30±0.10 0.65 BSC

T833-2

8

A1

L

T833-3

8

T1033-1

T1033-2

T1433-1

T1433-2

10

14

1.50±0.10 2.30±0.10 0.50 BSC MO229 / WEED-3 0.25±0.05

k

0.25 MIN.

0.20 REF.

1.50±0.10 2.30±0.10

0.25±0.05

0.20±0.05

A2

0.50 BSC MO229 / WEED-3

1.70±0.10 2.30±0.10 0.40 BSC

- - - -

PACKAGE OUTLINE, 6,8,10 & 14L,

TDFN, EXPOSED PAD, 3x3x0.80 mm

2

-DRAWING NOT TO SCALE-

H

21-0137

2

Revision History

Pages changed at Rev 1: 1, 3, 8, 9, 10

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 10

is a registered trademark of Maxim Integrated Products, Inc.


型号：	MAX8581_V01
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	2.5MHz/1.5MHz Step-Down Converters with 60mÎ© Bypass in TDFN for CDMA PA Power CD
文件：	总10页 (文件大小：562K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

MAX8581_V01 [MAXIM]

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