Rainbow Electronics MAX844 User Manual

19-0388; Rev 1; 3/96

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

Low-Noise, Regulated, -2V GaAsFET Bias

_______________General Description

The MAX840/MAX843/MAX844 low-noise, inverting
charge-pump power supplies are ideal for biasing
GaAsFETs in cellular telephone transmitter amplifiers.
They operate with inputs down to 2.5V.

The MAX840 offers both a -2V preset output and a -0.5V
to -9.4V adjustable output. The MAX843/MAX844 use
an external positive control voltage to set the negative
output voltage. Input voltage range for all the devices is

2.5V to 10V, and output current is 4mA with VIN> 2.7V.
These circuits can operate with small capacitors, as low
as 0.22µF.

An internal linear regulator reduces the MAX840’s out­put voltage ripple to 1mVp-p. With a well-filtered control
voltage (V

), the MAX843/MAX844 also achieve less

CTRL

than 1mVp-p typical output ripple. Supply current is
750µA, and reduces to less than 1µA in shutdown
(MAX840/MAX843). The MAX844’s unregulated output
is active in shutdown, with the charge pump switching at
20kHz. It provides a low-power LCD supply.

________________________Applications

Cellular Phones
GaAsFET Power Amplifier Modules
Personal Communicators, PDAs
Wireless Data Loggers
Continuously Adjustable GaAsFET Bias
LCD-Bias Contrast Control
Regulated Negative Power Supplies

__________Typical Operating Circuit

VIN = 2.5V to 10.0V

(3 CELLS)

____________________________Features

♦ Fixed -2V or Adjustable -0.5V to -9.4V Output

at 4mA (MAX840)

♦ 2.5V to 10V Input Voltage Range
♦ Operate with Small Capacitors (as low as 0.22µF)
♦ 1mVp-p Output Voltage Ripple
♦ Charge-Pump Switching Frequency:

100kHz in Normal Operation
20kHz in Shutdown Mode (MAX844)

♦ 1µA Max Logic-Level Shutdown Over Temp.

(MAX840/MAX843)

♦ Small 8-Pin SO Package

______________Ordering Information

PART

MAX840C/D

MAX840ISA
MAX840ESA -40°C to +85°C
MAX843C/D
MAX843ISA -25°C to +85°C 8 SO
MAX843ESA -40°C to +85°C 8 SO
MAX844C/D
MAX844ISA -25°C to +85°C 8 SO
MAX844ESA -40°C to +85°C 8 SO

* Dice are specified at TA= +25°C only.

TEMP. RANGE PIN-PACKAGE

0°C to +70°C

-25°C to +85°C

0°C to +70°C Dice*

0°C to +70°C Dice*

Dice*
8 SO
8 SO

MAX840/MAX843/MAX844

__________________Pin Configuration

TOP VIEW

1

C1+

2

C1-

NEGOUT

3

SHDN

4

( ) ARE FOR MAX843/MAX844

MAX840
MAX843
MAX844

SO

Maxim Integrated Products

8
7
6
5

IN
GND
OUT

FB (CONT)

1

0.22µF

0.22µF

ON/OFF

0.22µF

C1+

C1-

NEGOUT

SHDN


________________________________________________________________

IN

MAX840

GND

OUT

= -2.0V

V

OUT

of GaAsFET)

(V

GG

4.7µF

FB

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone]

Low-Noise, Regulated, -2V GaAsFET Bias

ABSOLUTE MAXIMUM RATINGS

Supply Voltage, V
V

NEGOUT

V

IN

V

OUT

V

SHDN

to GND...................................................-10.5V to 0.3V

to V

NEGOUT

to GND (Note 1).......................................V

to GND ............................................-0.3V to (VIN+ 0.3V)

Continuous Power Dissipation (T

to GND ..................................-0.3V to 10.5V

IN

.........................................................-0.3V to 21V

to 0.3V

= +70°C)

A

NEGOUT

SO (derate 5.88mW/°C above +70°C).........................471mW

Note 1: The output may be shorted to NEGOUT or GND if the package power dissipation is not exceeded. Typical short-circuit

current from 4V to GND is 40mA.

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

(Figures 2a and 2c, 2.5V ≤ VIN≤ 10V, V
Typical values are measured at VIN= 3.6V and TA= +25°C.)

Supply Voltage Range

Output Voltage

MAX840/MAX843/MAX844

Output Voltage Adjust Range

V

V

FB Voltage
FB Leakage Current
CONT Leakage Current

CONT

Supply Current µA750 1300

Shutdown Supply Current

V

Load Regulation

OUT

Ripple

OUT

I

SHUT

Oscillator Frequency F

Input High Voltage V
Input Low Voltage V
Input Current I
Input Capacitance C

= -2V, GND = 0V, RL= ∞, SHDN = VIN, TA= T

OUT

IN

MAX840, VFB= 0V

OUT

MAX843/MAX844,
V

= 2V

CTRL

OUT

MAX840, no load

FB

FB

MAX840, VFB= -0.5V
MAX843/MAX844, V
No load, VIN≤ 3.6VI

Q

MAX840/MAX843, VIN= 10V, SHDN = 0V
MAX844, VIN= 10V, SHDN = 0V
MAX844, VIN≤ 3.6V, SHDN = 0V

VIN= 3.6V,
RL= ∞ or 500Ω

C4 = 10µF

OSC

VIN= 3.6V,
TA= +25°C

SHDN 2.2 V

IH

SHDN 0.35 V

IL

SHDN -1 1 µA

IN

SHDN 10 pF

IN

Operating Temperature Ranges

MAX84_I_ _A ...................................................-25°C to +85°C

MAX84_E_ _A ..................................................-40°C to +85°C

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

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

to T

MIN

, unless otherwise noted.

MAX

CONDITIONS

VIN≥ 2.5V,

I

= 0mA to 3mA

OUT

VIN≥ 2.7V,

I

= 0mA to 4mA

OUT

VIN≥ 2.5V,

I

= 0mA to 3mA

OUT

VIN≥ 2.7V,

I

= 0mA to 4mA

OUT

-2.1 -2.0 -1.9

-2.1 -2.0 -1.9

-2.05 -2.0 -1.95

-2.05 -2.0 -1.95

-0.5 to

- 0.6)

(V

IN

= 0V

CONT

1
940
175 300

MAX840, VFB= 0V
MAX843/MAX844,

V

= 2V

CTRL

MAX840/MAX843/
MAX844

MAX844, SHDN = 0V

80 100 120
14 20 26

38
28

UNITSMIN TYP MAXSYMBOLPARAMETER

mV/mA

mVp-p1V

V2.5 10V

V

V

V-0.516 -0.5 -0.484V
nA±1 ±100I
nA±1 ±100I

µA

kHz

2 _______________________________________________________________________________________

Low-Noise, Regulated, -2V GaAsFET Bias

__________________________________________Typical Operating Characteristics

(Circuit of Figure 2a, VIN= 3.6V, TA= +25°C, unless otherwise noted.)

OUTPUT VOLTAGE 

vs. OUTPUT CURRENT

-2.070

MAX840-01

-2.060

-2.050

OUTPUT VOLTAGE (V)

-2.040
010

24 8

13579

OUTPUT CURRENT (mA)

6

MAXIMUM OUTPUT CURRENT 

vs. INPUT VOLTAGE

120

100

80

60

V

(CIRCUIT OF FIG 2d)

(CIRCUIT OF FIG 2a)

< -1.95V

OUT

V

< -1.95V

OUT

MAX840-03

High-current operation not
recommended for extended
periods of time.

OUTPUT VOLTAGE vs. INPUT VOLTAGE

OVER TEMPERATURE

-2.065

-2.060

-2.055
T

= +85°C

A

-2.050

OUTPUT VOLTAGE (V)

-2.045

-2.040

TA = +25°C

TA = -40°C

INPUT VOLTAGE (V)

NEGOUT CURRENT vs. INPUT VOLTAGE

30

V

= 0.9 x V

NEGOUT

25

20

15

NEGOUT(NO LOAD)

MAX840-02

10624 83579

MAX840-04

MAX840/MAX843/MAX844

40

20

MAXIMUM OUTPUT CURRENT (mA)

0

24 83579

INPUT VOLTAGE (V)

N0-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE

5

4

3

2

1

NO-LOAD SUPPLY CURRENT (mA)

0

24 83579

6

INPUT VOLTAGE (V)

_______________________________________________________________________________________

V

< 2mVp-p RIPPLE

OUT

(CIRCUIT OF FIG 2a)

V

< 2mVp-p RIPPLE

OUT

(CIRCUIT OF FIG 2d)

6

10

10

NEGOUT CURRENT (mA)

5

0

24 83579

INPUT VOLTAGE (V)

SUPPLY CURRENT vs. TEMPERATURE

7

MAX840-05

SUPPLY CURRENT (mA)

10

6

5

4

3

2

1

0

VIN = 10V

VIN = 3.6V

-40 0 80-20 20 60 100
TEMPERATURE (°C)

40

MAX840-06

START-UP TIME (ms)

SHUTDOWN

(MAX844)

6

10

START-UP TIME vs. INPUT VOLTAGE

2.8

2.4

2.0

1.6

1.2

0.8

0.4
24 8357910

6

INPUT VOLTAGE (V)

MAX840-07

3