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PDF MAX843ISA Data sheet ( Hoja de datos )
| Número de pieza | MAX843ISA | |
| Descripción | Low-Noise / Regulated / -2V GaAsFET Bias | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-0388; Rev 1; 3/96
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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 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 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)
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
TEMP. RANGE
MAX840C/D
0°C to +70°C
MAX840ISA
-25°C to +85°C
MAX840ESA
MAX843C/D
MAX843ISA
MAX843ESA
MAX844C/D
MAX844ISA
MAX844ESA
-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
1 page  
Low-Noise, Regulated, -2V GaAsFET Bias
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, VIN = 3.6V, TA = +25°C, unless otherwise noted.)
40
VIN = 3.6V,
30 IOUT = 4mA
MAX840 NOISE SPECTRUM
(C1 = C2 = C3 = 1µF, C4 = 10µF)
20
10
0
-10
0.1
50
VIN = 3.6V,
40 IOUT = 4mA
1 10 100
FREQUENCY (kHz)
MAX840 NOISE SPECTRUM
(C1 = C2 = C3 = 0.22µF, C4 = 4.7µF)
1000
30
20
10
0
0.1
40
VIN = 3.6V,
30 IOUT = 4mA
1 10 100
FREQUENCY (kHz)
MAX843/MAX844 NOISE SPECTRUM
(C1 = C2 = C3 = 1µF, C4 = 10µF)
1000
20
10
0
NOTE: dBµV = 20 LOG _V_O_U__T_
1µV
-10
0.1
1 10 100
FREQUENCY (kHz)
1000
_______________________________________________________________________________________ 5
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet MAX843ISA.PDF ] | |
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