MAXIM MAX8887, MAX8888 User Manual

Page 1

General Description

The MAX8887/MAX8888 low-dropout linear regulators operate from a 2.5V to 5.5V input and deliver up to 300mA continuous (500mA pulsed) current. The MAX8887 is optimized for low-noise operation, while the MAX8888 includes an open-drain POK ouput flag. Both regulators feature exceptionally low 100mV dropout at 200mA. These devices are available in a variety of preset output voltages in the 1.5V to 3.3V range.

An internal PMOS pass transistor allows the low 55µA supply current to remain independent of load, making these devices ideal for portable battery-powered equipment such as personal digital assistants (PDAs), cellular phones, cordless phones, and notebook computers. Other features include a micropower shutdown mode, short-circuit protection, thermal shutdown protection, and an active-low open-drain power-OK (POK) output that indicates when the output is out of regulation. The MAX8887/MAX8888 are available in a thin 5-pin SOT23 package that is only 1mm high.

________________________Applications

Notebook Computers

Wireless Handsets

PDAs and Palmtop Computers

Digital Cameras

PCMCIA Cards

Hand-Held Instruments

Features

♦ Guaranteed 300mA Output Current (500mA for

Pulsed Loads)

♦ Low 100mV Dropout at 200mA Load

♦ POK Output (MAX8888)

♦ 42µV

RMS

Output Noise (MAX8887)

♦ Preset Output Voltages (1.5V, 1.8V, 2.85V, and

3.3V)

♦ 55µA No-Load Supply Current

♦ Thermal Overload and Short-Circuit Protection

♦ Foldback Output Current-Limit Protection

♦ 60dB PSRR at 1kHz

♦ 0.1µA Shutdown Current

♦ Thin 5-Pin SOT23 Package, 1mm High

MAX8887/MAX8888

Low-Dropout, 300mA Linear Regulators in SOT23

________________________________________________________________ Maxim Integrated Products 1

Pin Configurations

MAX8887 MAX8888

OFF

INPUT

2.5V TO 5.5V IN

SHDN

GND

(BP)

POK

OUT

300mA

2.2μF

OUT

2.2μF

0.01μF

( ) ARE FOR MAX8887 ONLY.

Typical Operating Circuit

19-1859; Rev 3; 11/06

Ordering Information

*Other versions (xy) between +1.5 and +3.3V are available in

100mV increments. Contact factory for other versions. Minimum order quantity is 25,000 units.

+Denotes lead-free availability.

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.

查询MAX8887EZK15供应商

PART

M A X8 8 8 7 E Z K15+ T -40°C to +85°C 5 SOT23-5 ADQD

MAX8887EZK18+ T -40°C to +85°C 5 SOT23-5 ADPX

MAX8887EZK29+ T -40°C to +85°C 5 SOT23-5 ADPY

MAX8887EZK33+ T -40°C to +85°C 5 SOT23-5 ADPZ

MAX8887EZKxy+ T* -40°C to +85°C 5 SOT23-5 —

M A X8 8 8 8 E Z K15+ T -40°C to +85°C 5 SOT23-5 ADQE

MAX8888EZK18+ T -40°C to +85°C 5 SOT23-5 ADQA

MAX8888EZK29+ T -40°C to +85°C 5 SOT23-5 ADQB

MAX8888EZK33+ T -40°C to +85°C 5 SOT23-5 ADQC

MAX8888EZKxy+ T* -40°C to +85°C 5 SOT23-5 —

TEMP

RANGE

PINPACKAGE

MARK

TOP

TOP VIEW

15OUTIN

MAX8887

GND

BPSHDN

15OUTIN

MAX8888

GND

POKSHDN

Page 2

MAX8887/MAX8888

Low-Dropout, 300mA Linear Regulators in SOT23

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= V

OUT

+ 1V, SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 1)

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.

IN, SHDN, POK, to GND...........................................-0.3V to +7V

OUT, BP to GND ............................................-0.3 to (V

+ 0.3V)

Output Short-Circuit Duration.....................................Continuous

Continuous Power Dissipation (T

= +70°C)

5-Pin SOT23 (derate 9.1mW/°C above +70°C)............727mW

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

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

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

Lead Temperature (soldering, 10s) .................................+500°C

Input Voltage V

Input Undervoltage Lockout

Output Voltage Accuracy

Maximum Output Current

Current Limit

Ground-Pin Current

Dropout Voltage (Note 2) V

Line Regulation

Output Noise

PSRR

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

rising

(2% typical hysteresis)

TA = +25°C, I

= 100µA to 300mA,

OUT

= 0°C to +85°C

= 100µA to 300mA -3 +3

OUT

Continuous 300

10ms pulse 500

= 0

OUT

> 93% of nominal value 420

OUT

No load 55 100

= 300mA 65

OUT

= +3.3V

OUT

= 2.5V or (V

= 5mA

OUT

MAX8887

MAX8888

MAX8887

MAX8888

2.5 5.5 V

2.15 2.4 V

= 100mA -1.2 +1.2

OUT

-2 +2

300

= 1mA

OUT

= 200mA 100 200

OUT

= 300mA 150

OUT

+ 0.4V) to 5.5V,

OUT

10Hz to 100kHz, C C

= 2.2µF, ESR

OUT

10Hz to 100kHz, C ESR

f < 1kHz, C C

OUT

f < 1kHz, C ESR

< 0.1Ω

COUT

= 0.01µF,

= 4.7µF, ESR

OUT

< 0.1Ω

COUT

= 2.2µF,

= 0.01µF,

COUT

= 2.2µF,

OUT

COUT

-0.15 0 0.15 %/V

< 0.1Ω

0.5

360

µV

µA

RMS

Page 3

MAX8887/MAX8888

Low-Dropout, 300mA Linear Regulators in SOT23

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= V

OUT

+ 1V, SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 1)

Note 1: All parts are 100% tested at T

= +25°C. Limits over the operating temperature range are guaranteed by design.

Note 2: Typical and maximum dropout voltage for different output voltages are shown in the Typical Operating Characteristics

curve.

Typical Operating Characteristics

(Typical Operating Circuit, TA = +25°C, unless otherwise noted.)

1.0

0.5

2.0

1.5

3.0

2.5

3.5

2.0 3.0 3.52.5 4.0 4.5 5.0 5.5

OUTPUT VOLTAGE vs. INPUT VOLTAGE

MAX8887/8 toc01

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

OUT

= 0

OUT

= 300mA

-1.0

-0.6

-0.8

0.0

-0.2

-0.4

0.2

0.4

0.8

0.6

1.0

10050 150 200 250 300

OUTPUT VOLTAGE ACCURACY

vs. LOAD CURRENT

MAX8887/8 toc02

LOAD CURRENT (mA)

% DEVIATION (%)

-0.05

-0.02

-0.03

-0.04

-0.01

0.0

0.01

0.02

0.03

0.04

0.05

-40 10-15 35 60 85

OUTPUT VOLTAGE ACCURACY

vs. TEMPERATURE

MAX8887/8 toc03

TEMPERATURE (°C)

% DEVIATION

OUT

= 0

= V

OUT

+ 500mV

SHUTDOWN

Shutdown Supply Current SHDN = GND, VIN = 5.5V 0.1 2 µA

SHDN Input Threshold

SHDN Input Bias Current SHDN = IN or GND 10 100 nA

OUT Discharge Resistance in Shutdown

POK (MAX8888 ONLY)

POK Trip Level, Referred to OUT Set Point

Operating IN Voltage Range for Valid POK

POK Output Voltage Low V

POK Output Leakage Current V

THERMAL PROTECTION

Thermal Shutdown Temperature 170 °C

Thermal Shutdown Hysteresis 20 °C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

2.5V ≤ VIN ≤ 5.5V 1.6

2.5V ≤ VIN ≤ 5.5V 0.6

SHDN = GND 650 1100 Ω

falling

OUT

(1% typical hysteresis)

90 92.5 95 %

1.0 5.5 V

= 1mA 0.1 V

SINK

= 5.5V, SHDN = IN 100 nA

POK

Page 4

MAX8887/MAX8888

Low-Dropout, 300mA Linear Regulators in SOT23

4 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Typical Operating Circuit, TA = +25°C, unless otherwise noted.)

DROPOUT VOLTAGE vs. LOAD CURRENT

160

(mV)

140

120

100

TA = +85°C

TA = +25°C

MAX8887/8 toc04

DROPOUT

TA = -40°C

0 10050 150 200 250 300

LOAD CURRENT (mA)

GROUND-PIN CURRENT vs. LOAD CURRENT

100

VIN = 5.5V

VIN = 3.8V

GROUND-PIN CURRENT (μA)

0 10050 150 200 250 300

LOAD CURRENT (mA)

MAX8887/8 toc07

DROPOUT VOLTAGE vs. OUTPUT VOLTAGE

300

250

200

MAXIMUM

(mV)

150

DROPOUT

100

TYPICAL

2.5 2.7 2.9 3.1 3.3 V

OUT

(V)

OUT

GROUND-PIN CURRENT vs. TEMPERATURE

= 0

OUT

= V

+ 500mV

OUT

TEMPERATURE (°C)

GROUND-PIN CURRENT (μA)

-40 10-15 35 60 85

= 200mA

MAX8887/8 toc05

MAX8887/8 toc08

GROUND-PIN CURRENT vs. INPUT VOLTAGE

150

125

100

= 300mA

LOAD

GROUND-PIN CURRENT (μA)

LOAD

0 1.0 2.0 3.0 4.0 5.0

INPUT VOLTAGE (V)

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

= 2.2μF

OUT

= 0.01μF

PSRR (dB)

= 3.30V

OUT

= 30mA

LOAD

0.01 0.1 1 10 100 1000

MAX8887 ONLY

FREQUENCY (kHz)

MAX8887/8 toc06

= 0

MAX8887/8 toc09

MAX8887

OUTPUT NOISE DC TO 1MHz

= 1.8V, VIN = 3.8V, I

OUT

LOAD

40ms/div

= 15mA

MAX8887/8 toc10

OUT

50μV/div

OUT

LOAD-TRANSIENT RESPONSE

MAX8887/8 toc11

OUT

10μs/div

= 3.3V = 3.8V

300mA

10mA

50mV/div AC-COUPLED

Page 5

MAX8887/MAX8888

Low-Dropout, 300mA Linear Regulators in SOT23

_______________________________________________________________________________________ 5

Pin Description

Typical Operating Characteristics (continued)

(Typical Operating Circuit, TA = +25°C, unless otherwise noted.)

LOAD-TRANSIENT RESPONSE

OUT

SHDN

NEAR DROPOUT

10μs/div

SHUTDOWN WAVEFORM

OUT

MAX8887/8 toc12

OUT

MAX8887/8 toc14

= 3.3V = 3.4V

300mA

10mA

50mV/div AC-COUPLED

2V/div

LINE-TRANSIENT RESPONSE

OUT

100μs/div

POK WAVEFORM

= 3.3V, R

OUT

LOAD

MAX8887/8 toc13

= 3.3V

OUT

= 100mA

MAX8887/8 toc15

= 100Ω

4.5V

20mV/div AC-COUPLED

2V/div

OUT

= 3.3V, R

LOAD

= 10Ω

20μs/div

1V/div DC-COUPLED

POK

20ms/div

MAX8887 MAX8888 NAME FUNCTION

11IN

Regulator Input. Supply voltage can range from 2.5V to 5.5V. Bypass with 2.2µF capacitor to GND (see the Capacitor Selection and Regulator Stability section).

2 2 GND Ground

33SHDN

Active-Low Shutdown Input. A logic low reduces the supply current to below 0.1µA. In shutdown, POK and OUT are driven low. Connect to IN for normal operation.

Open-Drain Active-Low POK Output. POK remains low while the output voltage (V

—4POK

below the reset threshold. Connect a 100kΩ pullup resistor to OUT to obtain a logic level output. POK is driven low in shutdown. If not used, leave this pin unconnected.

4 — BP Reference Bypass. Bypass with a low-leakage 0.01µF ceramic capacitor.

5 5 OUT

Regulator Output. Sources up to 300mA guaranteed. Bypass with 2.2µF (<0.2Ω typical ESR) ceramic capacitor to GND.

2V/div

) is

OUT

Page 6

Detailed Description

The MAX8887/MAX8888 are low-dropout, low-quiescent-current linear regulators designed primarily for battery-powered applications. The devices supply loads up to 300mA and are available in several fixed output voltages in the 1.5V to 3.3V range. The MAX8887 is optimized for low-noise operation, while the MAX8888 includes an open-drain POK output flag. As illustrated in Figure 1, the MAX8888 consists of a

1.25V reference, error amplifier, P-channel pass transistor, and internal feedback voltage divider.

Internal P-Channel Pass Transistor

The MAX8887/MAX8888 feature a 0.5Ω P-channel MOSFET pass transistor. Unlike similar designs using PNP pass transistors, P-channel MOSFETs require no base drive, which reduces quiescent current. PNPbased regulators also waste considerable current in dropout when the pass transistor saturates and use high base drive currents under large loads. The MAX8887/MAX8888 do not suffer from these problems and consume only 55µA of quiescent current under heavy loads as well as in dropout.

Output Voltage Selection

The MAX8887/MAX8888 are supplied with various factory-set output voltages ranging from 1.5V to 3.3V. The part number’s two-digit suffix identifies the nominal output voltage. For example, the MAX8887EZK33 has a preset output voltage of 3.3V (see the Ordering Infor- mation).

Shutdown

Drive SHDN low to enter shutdown. During shutdown, the output is disconnected from the input and supply current drops to 0.1µA. When in shutdown, POK and OUT are driven low. SHDN can be pulled as high as 6V, regardless of the input and output voltages.

Power-OK Output

The power-OK output (POK) pulls low when OUT is less than 93% of the nominal regulation voltage. Once OUT exceeds 93% of the nominal voltage, POK goes high impedance. POK is an open-drain N-channel output. To obtain a logic level output, connect a pullup resistor from POK to OUT. A 100kΩ resistor works well for most applications. POK can be used as a power-on-reset (POR) signal to a microcontroller (µC) or to drive other logic. Adding a capacitor from POK to ground creates POK delay. When the MAX8887 is shut down, POK is held low independent of the output voltage. If unused, leave POK grounded or unconnected.

Current Limit

The MAX8887/MAX8888 monitor and control the pass transistor’s gate voltage, limiting the output current to

0.8A (typ). This current limit is reduced to 500mA (typ) when the output voltage is below 93% of the nominal value to provide foldback current limiting.

Thermal Overload Protection

Thermal overload protection limits total power dissipation in the MAX8887/MAX8888. When the junction temperature exceeds T

=+170°C, a thermal sensor turns off the pass transistor, allowing the device to cool. The thermal sensor turns the pass transistor on again after the junction temperature cools by 20°C, resulting in a pulsed output during continuous thermal overload conditions. Thermal overload protection protects the MAX8887/MAX8888 in the event of fault conditions. For continuous operation, do not exceed the absolute maximum junction-temperature rating of T

=+150°C.

Operating Region and Power Dissipation

The MAX8887/MAX8888’s maximum power dissipation depends on the thermal resistance of the IC package and circuit board. The temperature difference between the die junction and ambient air, and the rate of air flow. The power dissipated in the device is P = I

OUT

(VIN-

OUT

). The maximum allowed power dissipation is

727mW or:

MAX

= (T

J(MAX)

- TA) / (θJC+ θCA)

where T

J(MAX)-TA

is the temperature difference between the MAX8887/MAX8888 die junction and the surrounding air; θ

is the thermal resistance from the junction to the case; and θ

is the thermal resistance from the case through PC board, copper traces, and other materials to the surrounding air.

Refer to Figure 2 for the MAX8887/MAX888 valid operating region.

Noise Reduction

For the MAX8887 only, an external 0.01µF bypass capacitor at BP creates a lowpass filter for noise reduction. The MAX8887 exhibits 42µV

RMS

of output voltage

noise with C

= 0.01µF and C

OUT

= 2.2µF (see the

Typical Operating Characteristics).

Applications Information

Capacitor Selection and Regulator

Stability

Connect a 2.2µF ceramic capacitor between IN and ground and a 2.2µF ceramic capacitor between OUT and ground. The input capacitor (C

) lowers the source impedance of the input supply. Reduce noise and improve load-transient response, stability, and power-supply rejection by using a larger ceramic output capacitor such as 4.7µF.

The output capacitor’s (C

OUT

) equivalent series resis-

tance (ESR) affects stability and output noise. Use out-

MAX8887/MAX8888

Low-Dropout, 300mA Linear Regulators in SOT23

6 _______________________________________________________________________________________

Page 7

put capacitors with an ESR of 0.1Ω or less to ensure stability and optimum transient response. Surface-mount ceramic capacitors have very low ESR and are commonly available in values up to 10µF. Connect C

and

OUT

as close to the MAX8887/MAX8888 as possible to

minimize the impact of PC board trace inductance.

Noise, PSRR, and Transient Response

The MAX8887/MAX8888 are designed to operate with low dropout voltages and low quiescent currents in battery-powered systems while still maintaining excellent noise, transient response, and AC rejection. See the Typical Operating Characteristics for a plot of powersupply rejection ratio (PSRR) versus frequency. When operating from noisy sources, improved supply-noise rejection and transient response can be achieved by increasing the values of the input and output bypass capacitors and through passive filtering techniques.

Input-Output (Dropout) Voltage

A regulator’s minimum input-to-output voltage differential (dropout voltage) determines the lowest usable supply voltage at which the output is regulated. In battery-powered systems, this determines the useful end-of-life battery voltage. The MAX8887/MAX8888 use a P-channel MOSFET pass transistor. Its dropout voltage is a function of drain-to-source on-resistance (R

DS(ON)

) multiplied by the load current (see the

Typical Operating Characteristics).

DROPOUT

= VIN- V

OUT

= R

DS(ON)

OUT

Chip Information

TRANSISTOR COUNT: 620 PROCESS: BiCMOS

MAX8887/MAX8888

Low-Dropout, 300mA Linear Regulators in SOT23

_______________________________________________________________________________________ 7

Figure 1. Functional Diagram

Figure 2. Power Operating Regions: Maximum Output Current vs. Input Voltage

SHDN

SHUTDOWN

LOGIC

MAX8888

1.25V REF

GND

THERMAL

SENSOR

= +3.3V

OUT

) (V)

TA = +85°C T

= +2.85V

OUT

POK

= +70°C

= +1.8V

OUT

ERROR

AMP

95%

REF

MOS DRIVER

WITH I

LIMIT

POK

MAXIMUM OUTPUT CURRENT

(POWER DISSIPATION LIMIT)

400

MAXIMUM RECOMMENDED OUTPUT CURRENT

300

200

100

MAXIMUM OUTPUT CURRENT (mA)

0 1.0 2.0 3.00.5 1.5 2.5 3.5 4.0

vs. INPUT VOLTAGE

(VIN - V

Page 8

MAX8887/MAX8888

Low-Dropout, 300mA Linear Regulators in SOT23

8 _______________________________________________________________________________________

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

THIN SOT23.EPS

Page 9

Low-Dropout, 300mA Linear Regulators in SOT23

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.

9 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

MAX8887/MAX8888

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

Revision History

Pages changed at Rev 3: 1, 8, 9