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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX844 Datasheet

GaAsFET Bias

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19-0388; Rev 1; 3/96
EVFAOLLULAOTWIOSNDKAITTAMSAHNEUEATL
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 (VCTRL), the MAX843/MAX844 also achieve less
than 1mVp-p typical output ripple. Supply current is
750µA, and reduces to less than 1 µA 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)
0.22µF
0.22µF
IN
C1+
C1- MAX840 OUT
NEGOUT
0.22µF
VOUT = -2.0V
(VGG of GaAsFET)
4.7µF
ON/OFF
SHDN
GND
FB
____________________________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
______________Ordering Information
PART
MAX840C/D
TEMP. RANGE
0°C to +70°C
MAX840ISA
MAX840ESA
MAX843C/D
MAX843ISA
MAX843ESA
MAX844C/D
MAX844ISA
MAX844ESA
-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
* Dice are specified at TA = +25°C only.
PIN-PACKAGE
Dice*
8 SO
8 SO
Dice*
8 SO
8 SO
Dice*
8 SO
8 SO
__________________Pin Configuration
TOP VIEW
C1+ 1
C1- 2
NEGOUT 3
SHDN 4
MAX840
MAX843
MAX844
( ) ARE FOR MAX843/MAX844
SO
8 IN
7 GND
6 OUT
5 FB (CONT)
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX844 Datasheet

GaAsFET Bias

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Low-Noise, Regulated, -2V GaAsFET Bias
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VIN to GND ..................................-0.3V to 10.5V
VNEGOUT to GND ...................................................-10.5V to 0.3V
VIN to VNEGOUT.........................................................-0.3V to 21V
VOUT to GND (Note 1).......................................VNEGOUT to 0.3V
V SHDN to GND ............................................-0.3V to (VIN + 0.3V)
Continuous Power Dissipation (TA = +70°C)
SO (derate 5.88mW/°C above +70°C) .........................471mW
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
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, VOUT = -2V, GND = 0V, RL = , SHDN = V IN, T A = T MIN to T MAX, unless otherwise noted.
Typical values are measured at VIN = 3.6V and TA = +25°C.)
PARAMETER
Supply Voltage Range
Output Voltage
SYMBOL
VIN
VOUT
CONDITIONS
MAX840, VFB = 0V
MAX843/MAX844,
VCTRL = 2V
VIN 2.5V,
IOUT = 0mA to 3mA
VIN 2.7V,
IOUT = 0mA to 4mA
VIN 2.5V,
IOUT = 0mA to 3mA
VIN 2.7V,
IOUT = 0mA to 4mA
MIN TYP MAX UNITS
2.5 10 V
-2.1 -2.0 -1.9
-2.1 -2.0 -1.9
-2.05 -2.0 -1.95
V
-2.05 -2.0 -1.95
Output Voltage Adjust Range
FB Voltage
FB Leakage Current
CONT Leakage Current
Supply Current
Shutdown Supply Current
VOUT Load Regulation
VOUT Ripple
Oscillator Frequency
Input High Voltage
Input Low Voltage
Input Current
Input Capacitance
VOUT
VFB
IFB
ICONT
IQ
ISHUT
FOSC
VIH
VIL
IIN
CIN
MAX840, no load
MAX840, VFB = -0.5V
MAX843/MAX844, VCONT = 0V
No load, VIN 3.6V
MAX840/MAX843, VIN = 10V, SHDN = 0V
MAX844, VIN = 10V, SHDN = 0V
MAX844, VIN 3.6V, SHDN = 0V
VIN = 3.6V,
RL = or 500
MAX840, VFB = 0V
MAX843/MAX844,
VCTRL = 2V
C4 = 10µF
VIN = 3.6V,
TA = +25°C
MAX840/MAX843/
MAX844
MAX844, SHDN = 0V
SHDN
SHDN
SHDN
SHDN
-0.5 to
(VIN - 0.6)
-0.516 -0.5 -0.484
±1 ±100
±1 ±100
750 1300
1
940
175 300
38
28
V
V
nA
nA
µA
µA
mV/mA
1 mVp-p
80 100 120
kHz
14 20 26
2.2 V
0.35 V
-1 1 µA
10 pF
2 _______________________________________________________________________________________
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Part Number MAX844
Description GaAsFET Bias
Maker Maxim
Total Page 10 Pages
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