19-0388; Rev 1; 3/96
Lo w -No is e , Re g u la t e d , -2 V Ga As FET Bia s
03/MAX84
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
The MAX840/MAX843/MAX844 low-nois e , inve rting
c ha rg e -p ump p owe r s up p lie s a re id e a l for b ia s ing
GaAsFETs in cellular telephone transmitter amplifiers.
They operate with inputs down to 2.5V.
♦ Fixed -2V or Adjustable -0.5V to -9.4V Output
at 4mA (MAX840)
♦ 2.5V to 10V Input Voltage Range
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
♦ Operate with Small Capacitors (as low as 0.22µF)
♦ 1mVp-p Output Voltage Ripple
♦ Charge-Pump Switching Frequency:
100kHz in Normal Operation
2.5V to 10V, and output current is 4mA with V > 2.7V.
IN
These circuits can operate with small capacitors, as low
as 0.22µF.
20kHz in Shutdown Mode (MAX844)
An internal linear regulator reduces the MAX840’s out-
put voltage ripple to 1mVp-p. With a well-filtered control
♦ 1µA Max Logic-Level Shutdown Over Temp.
(MAX840/MAX843)
voltage (V ), the MAX843/MAX844 also achieve less
CTRL
♦ Small 8-Pin SO Package
than 1mVp-p typical output ripple. Supply current is
750µA, a nd re d uc e s to le s s tha n 1µA in s hutd own
(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.
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
Dice*
8 SO
________________________Ap p lic a t io n s
Cellular Phones
MAX840C/D
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
GaAsFET Power Amplifier Modules
Personal Communicators, PDAs
Wireless Data Loggers
Continuously Adjustable GaAsFET Bias
LCD-Bias Contrast Control
8 SO
Dice*
8 SO
-25°C to +85°C
-40°C to +85°C
0°C to +70°C
8 SO
Dice*
8 SO
Regulated Negative Power Supplies
-25°C to +85°C
-40°C to +85°C
8 SO
__________Typ ic a l Op e ra t in g Circ u it
* Dice are specified at T = +25°C only.
A
V
IN
= 2.5V to 10.0V
(3 CELLS)
__________________P in Co n fig u ra t io n
0.22µF
IN
C1+
C1-
TOP VIEW
V
= -2.0V
OUT
0.22µF
(V of GaAsFET)
GG
MAX840
OUT
FB
1
2
3
4
8
7
6
5
C1+
C1-
IN
4.7µF
NEGOUT
GND
OUT
MAX840
MAX843
MAX844
0.22µF
NEGOUT
SHDN
FB (CONT)
ON/OFF
SHDN
SO
GND
( ) 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