19-0388; Rev 1; 3/96
UAL
IT MAN
TION K
A
HEET
EVALU
DATA S
LOWS
FOL
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 V
IN
> 2.7V.
These circuits can operate with small capacitors, as low
as 0.22µF.
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
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.
____________________________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 0.22µF)
o
1mVp-p Output Voltage Ripple
o
Charge-Pump Switching Frequency:
100kHz in Normal Operation
20kHz in Shutdown Mode (MAX844)
o
1µA Max Logic-Level Shutdown Over Temp.
(MAX840/MAX843)
o
Small 8-Pin SO Package
MAX840/MAX843/MAX844
______________Ordering Information
PART
MAX840C/D
MAX840ISA
MAX840ESA
MAX843C/D
MAX843ISA
MAX843ESA
MAX844C/D
MAX844ISA
MAX844ESA
TEMP. RANGE
0°C to +70°C
-25°C to +85°C
-40°C to +85°C
0°C to +70°C
-25°C to +85°C
-40°C to +85°C
0°C to +70°C
-25°C to +85°C
-40°C to +85°C
PIN-PACKAGE
Dice*
8 SO
8 SO
Dice*
8 SO
8 SO
Dice*
8 SO
8 SO
________________________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
V
IN
= 2.5V to 10.0V
(3 CELLS)
* Dice are specified at T
A
= +25°C only.
0.22µF
IN
C1+
0.22µF
C1-
V
OUT
= -2.0V
(V
GG
of GaAsFET)
OUT
4.7µF
NEGOUT
0.22µF
__________________Pin Configuration
TOP VIEW
MAX840
C1+ 1
C1- 2
NEGOUT 3
SHDN 4
8
IN
GND
OUT
FB (CONT)
MAX840
MAX843
MAX844
7
6
5
ON/OFF
SHDN
GND
FB
SO
( ) ARE FOR MAX843/MAX844
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
Low-Noise, Regulated, -2V GaAsFET Bias
MAX840/MAX843/MAX844
ABSOLUTE MAXIMUM RATINGS
Operating Temperature Ranges
Supply Voltage, V
IN
to GND ..................................-0.3V to 10.5V
V
NEGOUT
to GND ...................................................-10.5V to 0.3V
MAX84_I_ _A ...................................................-25°C to +85°C
V
IN
to V
NEGOUT
.........................................................-0.3V to 21V
MAX84_E_ _A ..................................................-40°C to +85°C
V
OUT
to GND (Note 1).......................................V
NEGOUT
to 0.3V
Storage Temperature Range .............................-65°C to +150°C
V
SHDN
to GND ............................................-0.3V to (V
IN
+ 0.3V)
Lead Temperature (soldering, 10sec) .............................+300°C
Continuous Power Dissipation (T
A
= +70°C)
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
≤
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
= +25°C.)
PARAMETER
Supply Voltage Range
SYMBOL
V
IN
V
IN
≥
2.5V,
I
OUT
= 0mA to 3mA
V
IN
≥
2.7V,
I
OUT
= 0mA to 4mA
V
IN
≥
2.5V,
I
OUT
= 0mA to 3mA
V
IN
≥
2.7V,
I
OUT
= 0mA to 4mA
CONDITIONS
MIN
2.5
-2.1
-2.1
-2.05
-2.05
-2.0
-2.0
-2.0
-2.0
-0.5 to
(V
IN
- 0.6)
MAX840, no load
MAX840, V
FB
= -0.5V
MAX843/MAX844, V
CONT
= 0V
No load, V
IN
≤
3.6V
MAX840/MAX843, V
IN
= 10V, SHDN = 0V
Shutdown Supply Current
I
SHUT
MAX844, V
IN
= 10V, SHDN = 0V
MAX844, V
IN
≤
3.6V, SHDN = 0V
V
OUT
Load Regulation
V
OUT
Ripple
Oscillator Frequency
Input High Voltage
Input Low Voltage
Input Current
Input Capacitance
2
F
OSC
V
IH
V
IL
I
IN
C
IN
V
IN
= 3.6V,
R
L
=
∞
or 500Ω
C4 = 10µF
V
IN
= 3.6V,
T
A
= +25°C
SHDN
SHDN
SHDN
SHDN
-1
10
MAX840/MAX843/
MAX844
MAX844, SHDN = 0V
80
14
2.2
0.35
1
MAX840, V
FB
= 0V
MAX843/MAX844,
V
CTRL
= 2V
940
175
3
2
1
100
20
120
26
V
V
µA
pF
300
8
8
mV/mA
mVp-p
kHz
-0.516
-0.5
±1
±1
750
-0.484
±100
±100
1300
1
µA
TYP
MAX
10
-1.9
-1.9
V
-1.95
-1.95
V
V
nA
nA
µA
UNITS
V
MAX840, V
FB
= 0V
Output Voltage
V
OUT
MAX843/MAX844,
V
CTRL
= 2V
Output Voltage Adjust Range
FB Voltage
FB Leakage Current
CONT Leakage Current
Supply Current
V
OUT
V
FB
I
FB
I
CONT
I
Q
_______________________________________________________________________________________
Low-Noise, Regulated, -2V GaAsFET Bias
__________________________________________Typical Operating Characteristics
(Circuit of Figure 2a, V
IN
= 3.6V, T
A
= +25°C, unless otherwise noted.)
MAX840/MAX843/MAX844
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX840-01
OUTPUT VOLTAGE vs. INPUT VOLTAGE
OVER TEMPERATURE
MAX840-02
-2.070
-2.065
-2.060
OUTPUT VOLTAGE (V)
-2.060
OUTPUT VOLTAGE (V)
-2.055
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
-2.050
-2.050
-2.045
-2.040
0
1
2
3
4
5
6
7
8
9
10
OUTPUT CURRENT (mA)
-2.040
2
3
4
5
6
7
8
9
10
INPUT VOLTAGE (V)
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
MAX840-03
NEGOUT CURRENT vs. INPUT VOLTAGE
V
NEGOUT
= 0.9 x V
NEGOUT(NO LOAD)
25
NEGOUT CURRENT (mA)
20
15
10
5
0
SHUTDOWN
(MAX844)
MAX840-04
120
MAXIMUM OUTPUT CURRENT (mA)
100
80
60
40
20
0
2
3
4
5
6
7
8
9
V
OUT
< -1.95V
(CIRCUIT OF FIG 2a)
V
OUT
< -1.95V
(CIRCUIT OF FIG 2d)
30
High-current operation not
recommended for extended
periods of time.
V
OUT
< 2mVp-p RIPPLE
(CIRCUIT OF FIG 2a)
V
OUT
< 2mVp-p RIPPLE
(CIRCUIT OF FIG 2d)
10
2
3
4
5
6
7
8
9
10
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
N0-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX840-05
SUPPLY CURRENT vs. TEMPERATURE
MAX840-06
START-UP TIME vs. INPUT VOLTAGE
MAX840-07
5
NO-LOAD SUPPLY CURRENT (mA)
7
6
SUPPLY CURRENT (mA)
5
V
IN
= 10V
4
3
2
1
V
IN
= 3.6V
2.8
2.4
START-UP TIME (ms)
2.0
1.6
1.2
0.8
0.4
4
3
2
1
0
2
3
4
5
6
7
8
9
10
INPUT VOLTAGE (V)
0
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
2
3
4
5
6
7
8
9
10
INPUT VOLTAGE (V)
_______________________________________________________________________________________
3
Low-Noise, Regulated, -2V GaAsFET Bias
MAX840/MAX843/MAX844
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, V
IN
= 3.6V, T
A
= +25°C, unless otherwise noted.)
OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
MAX840-17
MAX844
OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
29
27
25
T
A
= -40°C
23
21
19
17
15
10
SHDN = LOW
T
A
= +25°C, +85°C
MAX840-18
150
OSCILLATOR FREQUENCY (kHz)
140
130
120
110
100
90
80
70
2
3
4
5
6
7
8
9
SUPPLY VOLTAGE (V)
SHDN = HIGH
T
A
= +25°C, +85°C
T
A
= -40°C
31
OSCILLATOR FREQUENCY (kHz)
2
3
4
5
6
7
8
9
10
SUPPLY VOLTAGE (V)
MAX840 OUTPUT NOISE AND RIPPLE
(C1 = C2 = C3 = 1µF, C4 = 10µF)
MAX840 OUTPUT NOISE AND RIPPLE
(C1 = C2 = C3 = 0.22µF, C4 = 4.7µF)
V
OUT
500µV/div
V
OUT
1mV/div
10µs/div
V
IN
= 3.6V, V
OUT
= -2V, I
OUT
= 4mA, AC COUPLED
10µs/div
V
IN
= 3.6V, V
OUT
= -2V, I
OUT
= 4mA, AC COUPLED
MAX843/MAX844 OUTPUT NOISE AND RIPPLE
(C1 = C2 = C3 = 1µF, C4 = 10µF)
MAX843/MAX844 OUTPUT NOISE AND RIPPLE
(C1 = C2 = C3 = 0.22µF, C4 = 4.7µF)
V
OUT
500µV/div
V
OUT
1mV/div
10µs/div
V
IN
= 3.6V, V
OUT
= -2V, I
OUT
= 4mA, AC COUPLED
10µs/div
V
IN
= 3.6V, V
OUT
= -2V, I
OUT
= 4mA, AC COUPLED
4
_______________________________________________________________________________________
Low-Noise, Regulated, -2V GaAsFET Bias
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, V
IN
= 3.6V, T
A
= +25°C, unless otherwise noted.)
MAX840/MAX843/MAX844
MAX840 NOISE SPECTRUM
(C1 = C2 = C3 = 1µF, C4 = 10µF)
40
V
IN
= 3.6V,
I
OUT
= 4mA
30
NOISE (dBµV)
20
10
0
-10
0.1
1
10
FREQUENCY (kHz)
100
1000
MAX840 NOISE SPECTRUM
(C1 = C2 = C3 = 0.22µF, C4 = 4.7µF)
50
V
IN
= 3.6V,
I
OUT
= 4mA
40
NOISE (dBµV)
30
20
10
0
0.1
1
10
FREQUENCY (kHz)
100
1000
MAX843/MAX844 NOISE SPECTRUM
(C1 = C2 = C3 = 1µF, C4 = 10µF)
40
V
IN
= 3.6V,
I
OUT
= 4mA
30
NOISE (dBµV)
20
10
0
V
OUT
NOTE: dBµV = 20 LOG ______
1µV
-10
0.1
1
10
FREQUENCY (kHz)
100
1000
_______________________________________________________________________________________
5
