19-1372; Rev 1; 6/98
IT
TION K
VALUA
E
BLE
AVAILA
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
General Description
Features
o
Small µMAX Package
o
1mVp-p Output Voltage Ripple and Noise
o
Power-OK Signal to Control GaAsFET Drain
Switch
o
0.05µA Logic-Controlled Shutdown
o
1ms Guaranteed Start-Up
o
2.5V to 5.5V Input
o
-0.5V to (-V
IN
+ 0.6V) Output at up to 4mA
o
Operates with One 4.7µF and Three 0.22µF
Capacitors (no inductors needed)
MAX881R
The MAX881R low-noise, inverting power supply is
designed for biasing GaAsFET power amplifiers in
portable wireless applications. This device is a charge-
pump inverter followed by a negative linear regulator.
The input voltage range is 2.5V to 5.5V. The output is
preset at -2.0V or can be set, using two resistors, to any
voltage from -0.5V to (-V
IN
+ 0.6V). It can deliver up to
4mA. The internal linear regulator also filters the output
to 1mVp-p ripple and noise.
Other features include a power-OK (POK) output that sig-
nals when the negative voltage is within 7.5% of its set
point. It protects the GaAsFET by not allowing power to
be applied to the GaAsFET’s drain until it is properly
biased. The signal can be routed either to a microcon-
troller or directly to a switch at the GaAsFET drain. The
MAX881R is available in a space-saving 10-pin µMAX
package.
Applications
Cell Phones
PCS Phones
PHS Phones
Wireless Handsets
Wireless Modems
Two-Way Pagers
Mobile Radios
Wireless Computers
PART
MAX881REUB
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
10 µMAX
Typical Operating Circuit
TOP VIEW
INPUT
2.5V TO 5.5V
IN
OUT
C1+
1
OUTPUT
-2V (OR ADJ)
4mA, 1mVp-p
RIPPLE
Pin Configuration
10
IN
9
N.C.
GND
OUT
FB
MAX881R
ON
OFF
SHDN
C1-
NEGOUT
2
3
4
5
MAX881R
8
7
6
C1+
POK
C1-
NEGOUT
FB
GND
CONTROLS
GaAsFET PA’s
DRAIN SWITCH
POK
SHDN
µMAX
N.C. = NOT INTERNALLY CONNECTED
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
