MAX1735 200mA, Negative-Output, Low-Dropout Linear Regulator in SOT23 General Description

MAX1735 200mA, Negative-Output, Low-Dropout Linear Regulator in SOT23 General Description

19-1783; Rev 1; 11/03

200mA, Negative-Output, Low-Dropout

Linear Regulator in SOT23

General Description

The MAX1735 negative-output, low-dropout linear regulator operates from a -2.5V to -6.5V input and delivers a guaranteed 200mA with a low 80mV dropout. The highaccuracy (±1%) output voltage is preset or can be adjusted from -1.25V to -5.5V with an external resistive voltage-divider.

An internal N-channel MOSFET allows for a low 85µA quiescent current virtually independent of the load, making this device ideal for battery-powered portable equipment, such as PDAs, mobile phones, cordless phones, and wireless data modems.

The device is available in several preset output voltage versions: -5.0V, -3.0V, and -2.5V. All versions offer a

1nA low-power shutdown mode, short-circuit protection, and thermal overload protection. The device is offered in a tiny 5-pin SOT23 package.

Applications

Disk Drives

Modems

Instrumentation Amplifiers

Notebook Computers

Mobile and Cordless Telephones

PCMCIA Cards

GaAsFET Bias

Mobile Wireless Data Modems

PDAs and Palmtop Computers

Guaranteed 200mA Output Current

Low 80mV Dropout Voltage at 200mA

Low 85µA Quiescent Supply Current

Low 1nA Current Shutdown Mode

Stable with 1µF C

OUT

PSRR >60dB at 100Hz

Thermal Overload Protection

Short-Circuit Protection

-5.0V, -3.0V, or -2.5V Output Voltage

or Adjustable (-1.25V to -5.5V)

Tiny SOT23-5 Package

Features

PART

MAX1735EUK50-T

MAX1735EUK30-T

MAX1735EUK25-T

Ordering Information

TEMP RANGE

-40°C to +85°C

-40°C to +85°C

-40°C to +85°C

PIN-

PACKAGE

5 SOT23-5

5 SOT23-5

5 SOT23-5

Output-Voltage Selector Guide

PART

MAX1735EUK50-T

MAX1735EUK30-T

MAX1735EUK25-T

PRESET OUTPUT

VOLTAGE

-5.0V or adj

-3.0V or adj

-2.5V or adj

SOT TOP

MARK

ADOZ

ADOY

ADOX

-6.5V TO -2.5V

INPUT

C

IN

Typical Operating Circuit

IN OUT

-5V, -3V, OR -2.5V

OUTPUT

UP TO 200mA

C

OUT

GND

ON

OFF

ON

SHDN

MAX1735

GND

SET

TOP VIEW

Pin Configuration

GND 1

IN 2

MAX1735

5 OUT

SHDN 3 4 SET

SOT23-5

________________________________________________________________ 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.

200mA, Negative-Output, Low-Dropout

Linear Regulator in SOT23

ABSOLUTE MAXIMUM RATINGS

IN, SET to GND .................................................... -7.0V to +0.3V

SHDN to GND ............................................ (V

IN

- 0.3)V to +7.0V

OUT to GND ...............................................(V

IN

- 0.3)V to +0.3V

Output Short-Circuit Duration ........................................Indefinite

Continuous Power Dissipation (T

A

= +70

°C)

5-Pin SOT23 (derate 7.1mW/

°C above +70°C)........... 571mW

Operating Temperature Range ...........................-40

Storage Temperature Range ............................ -65

°C to +85°C

Junction Temperature ......................................................+150

°C

°C to +150°C

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

°C

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

(Circuit of Figure 2, V

IN

= V

OUT

- 1V, V

SHDN

= V

IN

, T

A

= -40

°C to +85°C, unless otherwise noted. Typical values are at T

A

(Note 1)

= +25

°C.)

PARAMETER

Input Voltage

Output Voltage Accuracy

SET Regulation Set Point

Maximum Output Current

Current Limit

Ground-Pin Current

Dropout Voltage (Note 2)

Line Regulation

SYMBOL

I

I

V

IN

OUT

LIM

I

Q

CONDITIONS MIN

-6.5

TYP MAX UNITS

-2.5

T

A

= +25

°C, I

OUT

= -100µA

I

OUT

= -100µA, T

A

= 0°C to +85°C

-1

-2

+1

+2

I

LOAD

= -100µA to -200mA -3 +2

Circuit of Figure 3, T

A

= +25

°C, I

OUT

= -100µA -1.2625

-1.25

-1.2375

V

%

Circuit of Figure 3, I

OUT

= -100µA,

T

A

= 0°C to +85°C

Circuit of Figure 3,

V

IN

from -6.5V to -2.5V, V

OUT

= -1.25V

-1.275

Circuit of Figure 3, I

LOAD

= -100µA to -200mA -1.275

-200

V

OUT

= 0

I

OUT

= -100µA

I

OUT

= -200mA

I

OUT

= -100mA

I

OUT

= -200mA

-1020

-180

-0.15

-515

-85

-125

40

80

0

-1.225

-1.2125

-250

240

+0.15

V mA mA

µA mV

%/V

Load Regulation

Output Voltage Noise

Power-Supply Rejection Ratio

Shutdown Supply Current

SHDN Input High Threshold

(Note 3)

SHDN Input Low Threshold

(Note 3)

Set Input Bias Current

SHDN Input Bias Current

PSRR

I

SET

I

OUT

from 0mA to -200mA

10Hz to 1MHz, C

OUT

= 1µF f = 100Hz

V

SHDN

= 0

T

A

= +25

°C

T

A

= +85

°C

Positive voltage at

SHDN

Negative voltage at

SHDN

Positive voltage at

SHDN

Negative voltage at

SHDN

V

SET

= -1.25V, T

A

= +25

°C

T

A

= +25

°C

V

SHDN

= +6.5V

V

SHDN

= 0, -6.5V

-1

-1.6

+0.4

-100

-0.5

0.004

160

60

-0.001

-1

-15

+1.6

-0.4

3.5

+0.5

%/mA

µV

RMS dB

µA

V

V nA

µA

Thermal Shutdown Junction

Temperature

Hysteresis = 15

°C (typ)

160

°C

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

Note 2: The dropout voltage is defined as VOUT - VIN, when VOUT is 100mV above the nominal value of VOUT.

Note 3: The SHDN logic input can be driven by either a positive voltage or a negative voltage. | V SHDN | < 0.4V puts the device in shutdown, while | V

SHDN | > 1.6V enables the device.

2 _______________________________________________________________________________________

200mA, Negative-Output, Low-Dropout

Linear Regulator in SOT23

Typical Operating Characteristics

(Circuit of Figure 2, V

IN

= -4.0V, V

OUT

= -3.0V, T

A

= +25°C, unless otherwise specified.)

180

160

140

120

100

80

60

40

20

0

-40

SUPPLY CURRENT vs. SUPPLY VOLTAGE

180

160

140

120

100

80

60

40

20

0

0

I

LOAD

= 200mA

-1 -2 -3 -4 -5

SUPPLY VOLTAGE (V)

-6

-7

SUPPLY CURRENT vs. TEMPERATURE

I

LOAD

= 200mA

NO LOAD

-15 10 35

TEMPERATURE (

°C)

60 85

SUPPLY CURRENT vs. LOAD CURRENT

140

130

120

110

100

90

80

70

0 20 40 60 80 100 120 140

LOAD CURRENT (mA)

160 180 200

DROPOUT VOLTAGE vs. LOAD CURRENT

100

V

OUT

= -2.9V

80

T

A

= +25

°C

60

T

A

= +85

°C

40

T

A

= -40

°C

20

0

0 25 50 75 100 125 150 175 200

LOAD CURRENT (mA)

0

-0.2

-0.4

-0.6

-0.8

-1.0

OUTPUT VOLTAGE CHANGE vs. LOAD CURRENT

V

OUT

= -3V

T

A

= +85

°C

T

A

= -40

°C

T

A

= +25

°C

-1.2

0 25 50 75 100 125 150 175 200

LOAD CURRENT (mA)

OUTPUT VOLTAGE CHANGE vs. TEMPERATURE

1.00

0.75

0.50

0.25

0

-0.25

-0.50

-0.75

-1.00

-40

I

LOAD

NO LOAD

-15

= 200mA

10 35

TEMPERATURE (

°C)

60 85

_______________________________________________________________________________________

3

200mA, Negative-Output, Low-Dropout

Linear Regulator in SOT23

Typical Operating Characteristics (continued)

(Circuit of Figure 2, V

IN

= -4.0V, V

OUT

= -3.0V, T

A

= +25°C, unless otherwise specified.)

30

20

10

0

1

70

60

50

40

POWER-SUPPLY REJECTION RATIO vs. FREQUENCY

10

C

OUT

= 1.0

µF

C

OUT

= 10

µF

100 1k 10k 100k

FREQUENCY (Hz)

1M

100

REGION OF STABLE ESR vs. LOAD CURRENT

C

OUT

= 1

µF

10

10

1

0.1

0.01

10

OUTPUT NOISE DENSITY vs. FREQUENCY

1k

FREQUENCY (Hz)

100k

500

µV/div

C

OUT

= 1

µF

I

LOAD

= 50mA

OUTPUT NOISE

(10Hz TO 1MHz)

TIME (1ms/div)

LINE-TRANSIENT RESPONSE

MAX1735 toc11

1

V

OUT

50mV/div

0.1

0.01

REGION OF STABILITY

0.001

0 20 40 60 80 100 120 140 160 180 200

LOAD CURRENT (mA)

LOAD-TRANSIENT RESPONSE

(NORMAL OPERATION)

MAX1735 toc12

I

LOAD STEP

0 to 50mA

TIME (100

µs/div)

LOAD-TRANSIENT RESPONSE

(NEAR DROPOUT)

MAX1735 toc13

V

IN

1V/div

I

LOAD STEP

0 to 50mA

V

OUT

10mV/div

V

OUT

10mV/div

TIME (100

µs/div)

TIME (100

µs/div)

4 _______________________________________________________________________________________

200mA, Negative-Output, Low-Dropout

Linear Regulator in SOT23

Typical Operating Characteristics (continued)

(Circuit of Figure 2, V

IN

= -4.0V, V

OUT

= -3.0V, T

A

= +25°C, unless otherwise specified.)

SHUTDOWN RESPONSE

(DRIVEN FROM A POSITIVE VOLTAGE)

MAX1735 toc14a

SHUTDOWN RESPONSE

(DRIVEN BY A NEGATIVE VOLTAGE)

MAX1735 toc14b

SHUTDOWN-PIN BIAS CURRENT vs. SHUTDOWN-PIN VOLTAGE

2.0

TIME (200

µs/div)

V

SHDN

2V/div

0

0

V

OUT

2V/div

TIME (200

µs/div)

0

V

SHDN

2V/div

0

V

OUT

2V/div

1.5

1.0

0.5

0

-0.5

-6.5

-5.0 -3.5

-2.0 -0.5

1.0 2.5 4.0 5.5

SHUTDOWN-PIN VOLTAGE (V)

Pin Description

PIN

1

2

3

4

5

NAME

GND

IN

SHDN

SET

OUT

FUNCTION

Ground

Regulator Input. Supply voltage can range from -2.5V to -6.5V. Bypass with a 1

µF capacitor to GND

(see Capacitor Selection and Regulator Stability). This pin also functions as a heatsink. Solder to a large PC board pad or directly to the PC board power plane to maximize thermal dissipation.

Shutdown Input. Drive

SHDN to GND to turn the regulator off, reducing the input current to less than

1nA. Drive

SHDN above +1.6V or below -1.6V to enable the regulator. Connect SHDN to IN for always-on operation.

Dual Mode™ Regulator Feedback Input. Connect SET to GND for the preset output voltage. Use a resistive voltage-divider from OUT to SET to set the output voltage between -1.25V and -5.5V.

Regulation setpoint is -1.25V.

Regulator Output. OUT supplies up to 200mA in regulation. Bypass to GND with a 1

µF ceramic capacitor.

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

_______________________________________________________________________________________ 5

200mA, Negative-Output, Low-Dropout

Linear Regulator in SOT23

GND

ON

OFF

ON

C

IN

IN

SHDN

SHUTDOWN

LOGIC

THERMAL

SENSOR

ERROR

AMPLIFIER

MAX1735

NMOS

PASS

TRANSISTOR

OUT

C

OUT

R1

V

REF

-1.25V

SET

Dual Mode

COMPARATOR

R2

-270mV

GND

Figure 1. Functional Diagram

Detailed Description

The MAX1735 is a low-dropout negative linear voltage regulator. It features Dual Mode operation, allowing a fixed -5.0V, -3.0V, or -2.5V output voltage or an adjustable output from -1.25V to -5.5V. The regulator is guaranteed to supply 200mA of output current. It features 60dB power-supply rejection for noise-sensitive applications and a low 85µA operating current that optimizes it for battery-operated devices.

As Figure 1 illustrates, the device consists of an internal

-1.25V reference, an error amplifier, an N-channel

MOSFET, an internal precision-trimmed feedback voltage-divider, and a Dual Mode comparator.

The -1.25V reference is connected to the inverting input of the error amplifier. The error amplifier compares the reference voltage with the selected feedback voltage and amplifies the difference. The error amplifier drives the MOSFET to control the output voltage.

The feedback voltage for regulation is generated by either an internal or external resistive voltage-divider connected from OUT to SET. The internal Dual Mode comparator selects the feedback path based on V

SET

.

Connect SET to GND to use the internal feedback path, setting the output voltage to the preset value. If an external voltage-divider is used, see Output Voltage

Selection.

Internal N-Channel MOSFET

The MAX1735 features an N-channel MOSFET pass transistor. Unlike similar designs using NPN bipolar pass transistors, N-channel MOSFETs require extremely low drive currents, reducing overall quiescent current. Also, NPN-based regulators consume still more base current in dropout conditions when the pass transistor saturates. The MAX1735 does not suffer from these problems, consuming only 125µA total current at full load and in dropout.

Output Voltage Selection

The MAX1735 features Dual Mode operation, allowing for a preset or adjustable output voltage. In preset voltage mode, the output of the MAX1735 is set to -5.0V, -3.0V, or

-2.5V (see Ordering Information). Select this mode by connecting SET to GND (Figure 2).

6 _______________________________________________________________________________________

200mA, Negative-Output, Low-Dropout

Linear Regulator in SOT23

-6.5V TO -2.5V

INPUT

C

IN

1

µF CERAMIC

GND

ON

OFF

ON

IN

MAX1735

OUT

-5.0V,-3.0V, OR -2.5V

FIXED

OUTPUT

C

OUT

1

µF CERAMIC

SHDN

SET

GND

Figure 2. Typical Application Circuit with Preset Output Voltage

In adjustable mode, an output voltage between -5.5V and

-1.25V is selected using two external resistors connected as a voltage-divider from OUT to SET (Figure 3). The output voltage is determined by the following equation:

V

OUT

=

V

SET

1

R 1

R 2



 where V

SET

= V

REFERENCE

= -1.25V when in regulation.

Since the input bias current at SET is <100nA, use large resistance values for R1 and R2 to minimize power consumption in the feedback network. A typical value of 100k

Ω for R2 is acceptable for most applications. Higher values consume less current at the expense of output voltage accuracy. The above equation solved for R1 is:

R 1

=

R 2



V

OUT

V

SET



1

For preset output voltage mode, connect SET directly to GND.

Shutdown

In shutdown, the N-channel MOSFET, control circuitry, reference, and all internal circuits are turned off, reducing supply current to typically 1nA. SHDN can be driven by either a positive or negative voltage. Drive

SHDN above +1.6V or below -1.6V to turn the regulator on. To turn the regulator off, drive SHDN to GND. For always-on operation, connect SHDN to IN. By including a positive threshold at SHDN, it can be driven by a standard 5V TTL level without needing level-shifting circuitry.

-6.5V TO -2.5V

INPUT

C

IN

1

µF CERAMIC

GND

ON

OFF

ON

IN OUT

R1

-5.5V TO -1.25V

ADJUSTABLE

OUTPUT

C

OUT

1

µF

CERAMIC

MAX1735

SHDN

GND

SET

R2

V

OUT

= V

SET

(

1 + R1

)

R2

Figure 3. Typical Application Circuit with Adjustable Output

Voltage

Current Limiting

The MAX1735 features a current limit that protects the regulator. Short-circuit output current is typically

515mA. The output will withstand a short to ground indefinitely; however, if the increased power dissipation heats the die to +160°C, the thermal overload protection will shut off the regulator, preventing damage to the

IC.

Thermal Overload Protection

The thermal overload protection circuit protects the regulator against overheating due to prolonged overload conditions. When the die temperature exceeds +160°C, an on-chip thermal sensor disables the pass transistor, allowing the IC to cool. The thermal sensor reenables the pass MOSFET once the die temperature drops

15°C. A continuous short-circuit fault condition results in a cyclical enabling and disabling of the output.

Thermal overload protection is designed to safeguard the MAX1735 in the event of overload fault conditions.

For normal operation, do not exceed the absolute maximum junction temperature rating of +150°C. Junction temperature is greater than ambient by an amount depending on package heat dissipation and the thermal resistance from the junction to ambient (

θ

JA

):

T

JUNCTION

= T

AMBIENT

+ (

θ

JA

)(P

DISSIPATION

) where

θ

JA for the 5-pin SOT23 is about 0.140°C/mW.

_______________________________________________________________________________________ 7

200mA, Negative-Output, Low-Dropout

Linear Regulator in SOT23

250

MAXIMUM OUTPUT CURRENT vs. INPUT-OUTPUT VOLTAGE DIFFERENTIAL

200

150

100

50

MAXIMUM CONTINUOUS CURRENT

AT MAXIMUM

JUNCTION TEMP

(T

J

= +150

°C)

T

A

T

A

= +85

T

A

= +70

°C

= +50

°C

°C

0

0 1 2 3 4 5

INPUT-OUTPUT VOLTAGE DIFFERENTIAL (V)

6

Figure 4. Output Current and In-Out Voltage Differential

Operating Region Bounded by Available Power Dissipation at

Selected Ambient Temperatures

selected ambient temperatures. The working principle is that the SOT23-5 package is small enough that in a typical application circuit at room temperature, the package cannot dissipate enough power to allow -6.5V to be regulated to -1.25V at -200mA output (more than 1200mW).

As ambient temperature falls, the available power dissipation increases to allow for a greater operating region.

The equation for the family of curves follows:

|

I

OUT

|

=

P

|

MAX

T

A

70

θ

JA

V

OUT

V

IN

| where

|

I

OUT

| is in mA,

|

V

OUT

- V

IN

| in V, P

MAX

(571mW) is the absolute maximum rated power dissipation at

+70°C for the SOT23-5, and

θ

JA

(0.140°C/mW) is the approximate junction-to-ambient thermal resistance of the SOT23-5 in a typical application.

A key to reducing

θ

CA

, thereby increasing thermal conductivity to the PC board, is to provide large PC board pads and traces for IN.

__________Applications Information

Operating Region and Power Dissipation

Maximum power dissipation of the MAX1735 depends on the thermal resistance of the case and the circuit board, the temperature difference between the die junction and ambient air, and the rate of air flow (see also Thermal Overload Protection). The maximum power that can be dissipated by the device is:

P

MAX

=

T

JMAX

T

A

θ

JC

+ θ

CA

=

T

JMAX

T

A

θ

JA where the numerator expresses the temperature difference between the maximum allowed die junction

(+150°C) and the surrounding air,

θ

JC

(junction to case) is the thermal resistance of the package, and

θ

CA

(case to ambient) is the thermal resistance from the package through the PC board, traces, and other material to the surrounding air. The former is a characteristic solely of the device in its package, and the latter is completely defined by PC board layout and airflow. It is important to note that the ability to dissipate power is as much a function of the PC board layout and air flow as the packaged part itself. Hence, a manufacturer can reliably provide a value for

θ

JC

, but not accurately provide a value for the total thermal resistance

θ

JA

.

θ

JA is the sum of

θ

JC and

θ

CA

, and the manufacturer can seldom reliably predict the thermal characteristics of the application circuit.

Figure 4 shows the estimated allowable power dissipation for a MAX1735 mounted on a typical PC board at ambient temperatures of +50°C, +70°C, and +85°C.

Figure 4 shows the maximum continuous output current for a particular input-to-output voltage differential, for

Capacitor Selection and

Regulator Stability

Capacitors are required at the input and output of the

MAX1735. Connect a 1µF or greater capacitor between

IN and GND. This input capacitor serves only to lower the source impedance of the input supply in transient conditions; a smaller value can be used when the regulator is powered from a low-impedance source, such as another regulated supply or low-impedance batteries.

For output voltages between -2.5V and -5.5V, connect a 1µF or greater capacitor between OUT and GND. For voltages between -1.25V and -2.5V, use a 2.2µF or greater output capacitor. The maximum value of the output capacitor to guarantee stability is 10µF.

The output capacitor’s value and equivalent series resistance (ESR) affect stability and output noise. To ensure stability and optimum transient response, output capacitor ESR should be 0.1

Ω or less for output voltages from -1.25V to -2.45V and 0.2

Ω or less for output voltages between -2.5V and -5.5V. Inexpensive surface-mount ceramic capacitors typically have very-low

ESR and are commonly available in values up to 10µF.

Other low-ESR capacitors, such as surface-mount tantalum, may also be used. Do not use low-cost aluminum electrolytic capacitors due to their large size and relatively high ESR. Lastly, make sure the input and output capacitors are as close to the IC as possible to minimize the impact of PC board trace impedance.

8 _______________________________________________________________________________________

200mA, Negative-Output, Low-Dropout

Linear Regulator in SOT23

Noise, PSRR, and Transient Response

MAX1735 output noise is typically 160µV

RMS

. This is suitably low for most applications. See the Output

Noise vs. Frequency plot in the Typical Operating

Characteristics.

The MAX1735 is optimized for battery-powered equipment, with low dropout voltage and low quiescent current. It maintains good transient response, AC rejection, and noise characteristics even near dropout. See

Power-Supply Rejection Ratio vs. Frequency in the

Typical Operating Characteristics. When operating from very noisy sources, supply noise rejection and transient response can be improved by increasing the input and output capacitance, and by employing passive postfiltering.

Dropout Voltage

A regulator’s minimum input-to-output voltage differential dropout voltage determines the lowest usable supply voltage for an application. In battery-powered systems, this determines the useful end-of-life battery voltage. Since the MAX1735’s pass element is an

N-channel MOSFET, dropout voltage is the product of

R

DS(ON) and the load current; see Electrical

Characteristics and Dropout Voltage vs. Load Current in the Typical Operating Characteristics for details. The

MAX1735 operating (ground pin) current typically remains below 125µA at full load in dropout.

___________________Chip Information

TRANSISTOR COUNT: 293

_______________________________________________________________________________________ 9

200mA, Negative-Output, Low-Dropout

Linear Regulator in SOT23

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, SOT-23, 5L

21-0057 E

1

1

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.

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

© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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