Rainbow Electronics MAX1804 User Manual

General Description

The MAX1804 feedback integrator is designed to
improve voltage regulation in power-supply systems.
The device corrects line- and load-regulation problems,
and can be used to compensate for voltage drops in
power-management distribution lines.

The regulation set point is determined by an external
reference voltage applied at the ADJ pin. The differ­ence between that reference and MAX1804 feedback is
integrated, and a correction current is applied to the
voltage regulator’s feedback.

The MAX1804’s four inputs allow voltage monitoring in
several local and remote locations to correct for distribu­tion losses caused by long traces, connectors, and
switches. This eliminates the wasteful practice of perma­nently adjusting the regulator’s output voltage high
enough to correct for worst-case voltage drops. This is
especially helpful in systems where the load current
varies widely and portions of the load are often shut down
or disconnected (for example, in notebook computers).

If a load switch is opened and the output voltage
sensed at one input falls, the MAX1804 automatically
disables that input and adjusts the regulator’s output
voltage to the lowest of remaining active inputs. If all
inputs are disabled, the OUT pin is in a high-imped­ance state and makes no output voltage correction.

When SHDN is low, the MAX1804 draws less than 1µA
and its inputs and output are high impedance. The
MAX1804 is available in a 10-pin µMAX package, about
half the size of an 8-pin SOIC.

Features

♦ High Precision (±1% max Error)
♦ Low Power (25µA Supply Current)
♦ Automatic Input Disable
♦ Shutdown (1µA max Supply Current)
♦ Inputs and Outputs High Impedance in Shutdown

or When V+ = 0

♦ +2.7V to +5.5V Supply Range
♦ 2.8V to 5.5V Regulation Adjust Range
♦ Parallelable for More than Four Inputs
♦ 10-Pin µMAX Package

MAX1804

External Four-Input Feedback Integrator for

Power Supplies

________________________________________________________________ Maxim Integrated Products 1

19-1737; Rev 0; 7/00

For free samples and the latest literature, visit www.maxim-ic.com or phone [phone].
For small orders, phone [phone].

Ordering Information

Applications

Pin Configuration appears at end of data sheet.

Remote Feedback Regulators

High-Accuracy Regulators

Desktop/Notebook Computers

Servers and Workstations

Subnotebooks and PDAs

Typical Operating Circuit

PART TEMP. RANGE PIN-PACKAGE

MAX1804EUB -40°C to +85°C 10 µMAX

V

IN

DH

SYSTEM
SUPPLY

DL

R

TOP

FBREF

SHDN

IN1

IN2
IN3
IN4

R

BOTTOM

V+

R

OUT

OUT

ADJ

MAX1804

COMP

GND

V

A

OUT

V

B

OUT

V

C

OUT

D

V

OUT

MAX1804

External Four-Input Feedback Integrator for
Power Supplies

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(TA= 0°C to +85°C, VV+ = 3.3V, V

ADJ

= 1.2V, V

OUT

= 2V, CV+ = 0.1µF, C

COMP

= 470pF. Typical values are at TA= +25°C, unless

otherwise noted.)

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.

V+, IN1, IN2, IN3, IN4, OUT, ADJ, SHDN to GND...…-0.3V, +6V

COMP to GND ....................................................-0.3V, V+ +0.3V

Continuous Power Dissipation (T

A

= +70°C)

10-Pin µMAX (derate 8.3mW/°C above +70°C) ..........667mW

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

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

Storage Temperature Range.……...……………-65°C to +165°C

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

PARAMETER CONDITIONS

U N IT S

Supply Voltage Range (V+) 2.7 5.5 V
Shutdown Supply Current (V+) SHDN = GND

1 µA

Quiescent Supply Current (V+) SHDN = V+ 25 35 µA

UVLO Threshold, Rising 2.5 2.6 V

UVLO Threshold, Falling 2.3 2.4 V

INTEGRATOR INPUTS IN1–IN4

IN_ Voltage Range 0 5.5 V

IN_ Offset VV+ = 2.7V to 5.5V -15 15

mV

V

ADJ

= 0.7V to 1.4V

V/V

V

IN_

= 4.75V to 4.85V, V

COMP

= 1.3V 12 30

48

µS

V

IN_

= 4.8V 1.5 2.7 µA

SHDN = GND 0.2 µA

VV+ = 0, V

SHDN

= 0 0.2 µA

IN_ Disable Threshold

V

ADJ

= 0.7V to 1.4V, V

ADJ

x 4, falling edge 87 90 93

%

V

ADJ

= 0.7V to 1.4V, rising edge 50

mV

ADJ INPUT

0.7 1.4 V

-20 20 nA

SHDN = GND 0.2 µA

VV+ = 0, V

SHDN

= 0 0.2 µA

COMP OUTPUT

V

COMP

= 1.3V, V

IN_

= 4.6V 1.6 2.0 2.4 µA

V

COMP

= 1.3V, V

IN_

= 5.0V 1.6 2.0 2.4 µA

Sink 1µA, V

IN_

= 5.0V 0.2 V

Source 1µA, V

IN_

= 4.6V 2.4 V

OUT OUTPUT

I

OUT

= 10 µA, V

IN_

= 4.6V 0.2 V

V

SHDN

= 0 0.1

VV+ = 0 0.1

V

IN_

= 5.0V 0.1

µA

V

COMP

= 1V to 2V 4 10 22 µS

IN_ Scale Factor

IN_ Transconductance

IN_ Bias Current

IN_ Shutdown Current

IN_ Leakage Current

IN_ Disable Threshold Hysteresis

ADJ Voltage Range

ADJ Bias Current

ADJ Shutdown Current

ADJ Leakage Current

COMP Source Current

COMP Sink Current

COMP Output Voltage Low

COMP Output Voltage High

OUT Output Voltage Low

OUT Output Leakage Current

OUT Transconductance

MIN TYP MAX

0.01

3.988 4.000 4.016

MAX1804

External Four-Input Feedback Integrator for

Power Supplies

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(TA= 0°C to +85°C, VV+ = 3.3V, V

ADJ

= 1.2V, V

OUT

= 2V, CV+ = 0.1µF, C

COMP

= 470pF. Typical values are at TA= 25°C, unless oth-

erwise noted.)

PARAMETER CONDITIONS

MIN

TYP

MAX

U N IT S

SHDN INPUT

Logic Input Voltage High VV+ = 2.7V to 5.5V 2.0 V

Logic Input Voltage Low VV+ = 2.7V to 5.5V 0.6 V

Logic Input Current -1 1 µA

ELECTRICAL CHARACTERISTICS

(TA= -40°C to +85°C, VV+ = 3.3V, V

ADJ

= 1.2V, V

OUT

= 2V, CV+ = 0.1µF, C

COMP

= 470pF.) (Note 1)

PARAMETER CONDITIONS

U N IT S

Supply Voltage Range (V+) 2.7 5.5 V
Shutdown Supply Current (V+) SHDN = GND 1 µA
Quiescent Supply Current (V+) SHDN = V+ 35 µA

UVLO Threshold, Rising 2.6 V

UVLO Threshold, Falling 2.3 V

INTEGRATOR INPUTS IN1–IN4

IN_ Voltage Range 0 5.5 V

IN_ Offset VV+ = 2.7V to 5.5V -20 20

mV

V

ADJ

= 0.7V to 1.4V

V/V

V

IN_

= 4.75V to 4.85V, V

COMP

= 1.3V 12

60

µS

V

IN_

= 4.8V 2.7 µA

SHDN = GND 0.2 µA

VV+ = 0, V

SHDN

= 0 0.2 µA

IN_ Disable Threshold

V

ADJ

= 0.7V to 1.4V, V

ADJ

x 4, falling edge 87 93

%

ADJ INPUT

0.7 1.4 V

-30 30 nA

SHDN = GND 0.2 µA

V V+ = 0, V

SHDN

= 0 0.2 µA

COMP OUTPUT

V

COMP

= 1.3V, V

IN_

= 4.6V 1.6 2.4 µA

V

COMP

= 1.3V, V

IN_

= 5.0V 1.6 2.4 µA

Sink 1µA, V

IN_

= 5.0V 0.2 V

Source 1µA, V

IN_

= 0.6V 2.4 V

I

OUT

= 10µA, V

IN_

= 4.6V 0.2 V

V

SHDN

= 0 0.1

VV+ = 0 0.1

VIN = 5.0V 0.1

µA

OUT Transconductance V

COMP

= 1V to 2V 3 23 µS

IN_ Scale Factor

IN_ Transconductance

IN_ Bias Current

IN_ Shutdown Current

IN_ Leakage Current

ADJ Voltage Range

ADJ Bias Current

ADJ Shutdown Current

ADJ Leakage Current

COMP Source Current

COMP Sink Current

COMP Output Voltage Low

COMP Output Voltage High

OUT Output Voltage Low

OUT Output Leakage Current

MIN TYP MAX

3.98 4.02

ELECTRICAL CHARACTERISTICS (continued)

(TA= -40°C to +85°C, VV+ = 3.3V, V

ADJ

= 1.2V, V

OUT

= 2V, CV+ = 0.1µF, C

COMP

= 470pF.) (Note 1)

MAX1804

External Four-Input Feedback Integrator for
Power Supplies

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VV+ = V

SHDN

= 3.3V, V

ADJ

= 1.2V, V

OUT

= 2V, C

COMP

= 470pF, TA= +25°C, unless otherwise noted.)

Note 1: Specifications to -40°C are guaranteed by design and not production tested.

PARAMETER CONDITIONS MIN TYP MAX U N IT S

SHDN INPUT

Logic Input Voltage High VV+ = 2.7V to 5.5V 2.0 V

Logic Input Voltage Low VV+ = 2.7V to 5.5V 0.6 V

Logic Input Current -1 1 µA

29.0

28.5

28.0

27.5

27.0

26.5

26.0

25.5

QUIESCENT CURRENT (µA)

25.0

24.5

24.0

-40 0-20 20 40 60 80

QUIESCENT CURRENT vs.

TEMPERATURE

VV+ = 5V

VV+ = 3.3V

TEMPERATURE (°C)

IN_REGULATION SET-POINT ERROR

vs. TEMPERATURE

0.050

V

0.045

MAX1804 toc01

0.040

0.035

0.030

0.025

0.020

0.015

0.010

IN_REGULATION SET-POINT ERROR (%)

0.005

0

-40

NOTE: Circuit of Figure 1.

= 0.7V

ADJ

V

= 1.4V

ADJ

V

= 1.2V

ADJ

0-20 20 40 60 80
TEMPERATURE (°C)

MAX1804 toc02

IN_ (TO COMP) TRANSCONDUCTANCE

34

32

30

28

26

24

IN_TRANSCONDUCTANCE (µS)

22

20

-40 0-20 20 40 60 80

vs. TEMPERATURE

V

∆

= 4.85V TO 4.75V

IN_

= 1.3V

V

COMP

TEMPERATURE (°C)

MAX1804 toc03

OUT CURRENT vs. COMP VOLTAGE

30

25

20

15

OUT CURRENT (µA)

10

5

0

0 1.5 2.00.5 1.0 2.5 3.0 3.5

COMP VOLTAGE (V)

MAX1804toc04

IN_SCALE FACTOR vs. ADJ VOLTAGE

4.05

4.00

3.95

3.90

IN_SCALE FACTOR

3.85

3.80

3.75

0.4

NOTE: Circuit of Figure 1.

ADJ VOLTAGE (V)

1.0 1.20.6 0.8 1.4

0

MAX1804toc05

-50

-100

-150

-200

CHANGE IN OUTPUT VOLTAGE (mV)

-250

-300

0.001

vs. OUTPUT CURRENT

MAX1804 OFF

V

= 5V (NOMINAL)

OUT

= 470pF

C

COMP

OUTPUT CURRENT (A)

NOTE: Application Circuit of Figure 2.

CHANGE IN OUTPUT VOLTAGE

MAX1804toc06

MAX1804 ON

1100.01 0.1