_______________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 V
IN
> 2.7V.
These circuits can operate with small capacitors, as low
as 0.22F.
An internal linear regulator reduces the MAX840's out-
put voltage ripple to 1mVp-p. With a well-filtered control
voltage (V
CTRL
), the MAX843/MAX844 also achieve less
than 1mVp-p typical output ripple. Supply current is
750A, and reduces to less than 1A 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
____________________________Features
o
Fixed -2V or Adjustable -0.5V to -9.4V Output
at 4mA (MAX840)
o
2.5V to 10V Input Voltage Range
o
Operate with Small Capacitors (as low as 0.22F)
o
1mVp-p Output Voltage Ripple
o
Charge-Pump Switching Frequency:
100kHz in Normal Operation
20kHz in Shutdown Mode (MAX844)
o
1A Max Logic-Level Shutdown Over Temp.
(MAX840/MAX843)
o
Small 8-Pin SO Package
MAX840/MAX843/MAX844
Low-Noise, Regulated, -2V GaAsFET Bias
________________________________________________________________
Maxim Integrated Products
1
( ) ARE FOR MAX843/MAX844
1
2
3
4
8
7
6
5
IN
GND
OUT
FB (CONT)
SHDN
NEGOUT
C1-
C1+
MAX840
MAX843
MAX844
SO
TOP VIEW
__________________Pin Configuration
MAX840
FB
OUT
SHDN
NEGOUT
C1-
C1+
IN
GND
V
IN
= 2.5V to 10.0V
(3 CELLS)
0.22
F
V
OUT
= -2.0V
(V
GG
of GaAsFET)
4.7
F
0.22
F
0.22
F
ON/OFF
__________Typical Operating Circuit
19-0388; Rev 1; 3/96
PART
MAX840
C/D
MAX840ISA
MAX840ESA
-40C to +85C
-25C to +85C
0C to +70C
TEMP. RANGE
PIN-PACKAGE
Dice*
8 SO
8 SO
EVALUATION KIT MANUAL
FOLLOWS DATA SHEET
______________Ordering Information
* Dice are specified at T
A
= +25C only.
MAX843
C/D
0C to +70C
Dice*
MAX843ISA
-25C to +85C
8 SO
MAX843ESA
-40C to +85C
8 SO
MAX844
C/D
0C to +70C
Dice*
MAX844ISA
-25C to +85C
8 SO
MAX844ESA
-40C to +85C
8 SO
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX840/MAX843/MAX844
Low-Noise, Regulated, -2V GaAsFET Bias
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Figures 2a and 2c, 2.5V
V
IN
10V, V
OUT
= -2V, GND = 0V, R
L
=
, SHDN = V
IN
, T
A
= T
MIN
to T
MAX
, unless otherwise noted.
Typical values are measured at V
IN
= 3.6V and T
A
= +25C.)
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.
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.
Supply Voltage, V
IN
to GND ..................................-0.3V to 10.5V
V
NEGOUT
to GND ...................................................-10.5V to 0.3V
V
IN
to V
NEGOUT
.........................................................-0.3V to 21V
V
OUT
to GND (Note 1).......................................V
NEGOUT
to 0.3V
V
SHDN
to GND ............................................-0.3V to (V
IN
+ 0.3V)
Continuous Power Dissipation (T
A
= +70C)
SO (derate 5.88mW/C above +70C) .........................471mW
Operating Temperature Ranges
MAX84_I_ _A ...................................................-25C to +85C
MAX84_E_ _A ..................................................-40C to +85C
Storage Temperature Range .............................-65C to +150C
Lead Temperature (soldering, 10sec) .............................+300C
C4 = 10F
V
IN
= 3.6V,
R
L
=
or 500
MAX844, V
IN
3.6V, SHDN = 0V
MAX844, V
IN
= 10V, SHDN = 0V
MAX840/MAX843, V
IN
= 10V, SHDN = 0V
MAX843/MAX844, V
CONT
= 0V
MAX843/MAX844,
V
CTRL
= 2V
MAX840, V
FB
= 0V
MAX840, V
FB
= -0.5V
MAX840, no load
CONDITIONS
mVp-p
1
V
OUT
Ripple
mV/mA
2
8
V
OUT
Load Regulation
3
8
A
175
300
I
SHUT
Shutdown Supply Current
940
1
nA
1
100
I
CONT
CONT Leakage Current
nA
1
100
I
FB
FB Leakage Current
V
-0.516 -0.5
-0.484
V
FB
FB Voltage
-2.1
-2.0
-1.9
V
2.5
10
V
IN
Supply Voltage Range
-0.5 to
(V
IN
- 0.6)
V
OUT
Output Voltage Adjust Range
V
-2.05
-2.0
-1.95
V
OUT
Output Voltage
-2.1
-2.0
-1.9
-2.05
-2.0
-1.95
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
80
100
120
Oscillator Frequency
F
OSC
V
IN
= 3.6V,
T
A
= +25C
14
20
26
kHz
Input High Voltage
V
IH
SHDN
2.2
V
V
IN
2.7V,
I
OUT
= 0mA to 4mA
V
IN
2.5V,
I
OUT
= 0mA to 3mA
V
IN
2.5V,
I
OUT
= 0mA to 3mA
V
IN
2.7V,
I
OUT
= 0mA to 4mA
V
MAX840, V
FB
= 0V
MAX843/MAX844,
V
CTRL
= 2V
Input Low Voltage
V
IL
SHDN
0.35
V
Input Current
I
IN
SHDN
-1
1
A
Input Capacitance
C
IN
SHDN
10
pF
MAX840/MAX843/
MAX844
MAX844, SHDN = 0V
No load, V
IN
3.6V
I
Q
Supply Current
A
750
1300
MAX840/MAX843/MAX844
Low-Noise, Regulated, -2V GaAsFET Bias
_______________________________________________________________________________________
3
-2.040
0
10
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
-2.050
MAX840-01
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
6
-2.070
-2.060
2
4
8
1
3
5
7
9
-2.040
OUTPUT VOLTAGE vs. INPUT VOLTAGE
OVER TEMPERATURE
-2.050
-2.045
MAX840-02
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
-2.065
-2.060
-2.055
10
6
2
4
8
3
5
7
9
T
A
= +85C
T
A
= +25C
T
A
= -40C
20
0
10
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
60
40
MAX840-03
INPUT VOLTAGE (V)
MAXIMUM OUTPUT CURRENT (mA)
6
120
100
80
2
4
8
3
5
7
9
V
OUT
< -1.95V
(CIRCUIT OF FIG 2a)
V
OUT
< -1.95V
(CIRCUIT OF FIG 2d)
V
OUT
< 2mVp-p RIPPLE
(CIRCUIT OF FIG 2d)
V
OUT
< 2mVp-p RIPPLE
(CIRCUIT OF FIG 2a)
High-current operation not
recommended for extended
periods of time.
0
10
N0-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
2
1
MAX840-05
INPUT VOLTAGE (V)
NO-LOAD SUPPLY CURRENT (mA)
6
5
4
3
2
4
8
3
5
7
9
0
10
NEGOUT CURRENT vs. INPUT VOLTAGE
10
5
MAX840-04
INPUT VOLTAGE (V)
NEGOUT CURRENT (mA)
6
30
25
20
15
2
4
8
3
5
7
9
V
NEGOUT
= 0.9 x V
NEGOUT(NO LOAD)
SHUTDOWN
(MAX844)
0
SUPPLY CURRENT vs. TEMPERATURE
3
2
1
MAX840-06
TEMPERATURE (C)
SUPPLY CURRENT (mA)
40
7
6
5
4
-40
0
80
-20
20
60
100
V
IN
= 10V
V
IN
= 3.6V
0.4
START-UP TIME vs. INPUT VOLTAGE
1.6
1.2
0.8
MAX840-07
INPUT VOLTAGE (V)
START-UP TIME (ms)
6
2.8
2.4
2.0
2
4
8
3
5
7
9
10
__________________________________________Typical Operating Characteristics
(Circuit of Figure 2a, V
IN
= 3.6V, T
A
= +25C, unless otherwise noted.)
MAX840/MAX843/MAX844
Low-Noise, Regulated, -2V GaAsFET Bias
4
_______________________________________________________________________________________
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, V
IN
= 3.6V, T
A
= +25C, unless otherwise noted.)
MAX840 OUTPUT NOISE AND RIPPLE
(C1 = C2 = C3 = 1
F, C4 = 10
F)
V
IN
= 3.6V, V
OUT
= -2V, I
OUT
= 4mA, AC COUPLED
10
s/div
V
OUT
500
V/div
MAX840 OUTPUT NOISE AND RIPPLE
(C1 = C2 = C3 = 0.22
F, C4 = 4.7
F)
V
IN
= 3.6V, V
OUT
= -2V, I
OUT
= 4mA, AC COUPLED
10
s/div
V
OUT
1mV/div
MAX843/MAX844 OUTPUT NOISE AND RIPPLE
(C1 = C2 = C3 = 1
F, C4 = 10
F)
V
IN
= 3.6V, V
OUT
= -2V, I
OUT
= 4mA, AC COUPLED
10
s/div
V
OUT
500
V/div
MAX843/MAX844 OUTPUT NOISE AND RIPPLE
(C1 = C2 = C3 = 0.22
F, C4 = 4.7
F)
V
IN
= 3.6V, V
OUT
= -2V, I
OUT
= 4mA, AC COUPLED
10
s/div
V
OUT
1mV/div
70
10
OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
90
80
MAX840-17
SUPPLY VOLTAGE (V)
OSCILLATOR FREQUENCY (kHz)
6
150
140
120
130
110
100
2
4
8
3
5
7
9
T
A
= +25C, +85C
T
A
= -40C
SHDN = HIGH
15
10
MAX844
OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
19
17
MAX840-18
SUPPLY VOLTAGE (V)
OSCILLATOR FREQUENCY (kHz)
6
31
29
25
27
23
21
2
4
8
3
5
7
9
T
A
= +25C, +85C
T
A
= -40C
SHDN = LOW
MAX840/MAX843/MAX844
Low-Noise, Regulated, -2V GaAsFET Bias
_______________________________________________________________________________________
5
MAX840 NOISE SPECTRUM
(C1 = C2 = C3 = 0.22
F, C4 = 4.7
F)
50
0
0.1
1
10
100
1000
10
FREQUENCY (kHz)
NOISE (dB
V)
20
30
40
V
IN
= 3.6V,
I
OUT
= 4mA
MAX843/MAX844 NOISE SPECTRUM
(C1 = C2 = C3 = 1
F, C4 = 10
F)
40
-10
0.1
1
10
100
1000
0
FREQUENCY (kHz)
NOISE (dB
V)
10
20
30
V
IN
= 3.6V,
I
OUT
= 4mA
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, V
IN
= 3.6V, T
A
= +25C, unless otherwise noted.)
MAX840 NOISE SPECTRUM
(C1 = C2 = C3 = 1
F, C4 = 10
F)
40
-10
0.1
1
10
100
1000
0
FREQUENCY (kHz)
NOISE (dB
V)
10
20
30
V
IN
= 3.6V,
I
OUT
= 4mA
V
OUT
NOTE: dBV = 20 LOG ______
1V
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