MAX881R Datasheet, PDF (1/8 Pages) Maxim Integrated Products – Low-Noise Bias Supply in μMAX with Power-OK for GaAsFET PA

19-1372; Rev 1; 6/98
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Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
General Description
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
Typical Operating Circuit
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)
PART
MAX881REUB
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
10 µMAX
Pin Configuration
INPUT
2.5V TO 5.5V
ON
OFF
IN
OUT
MAX881R
SHDN
C1+
POK
C1-
NEGOUT FB GND
OUTPUT
-2V (OR ADJ)
4mA, 1mVp-p
RIPPLE
CONTROLS
GaAsFET PA’s
DRAIN SWITCH
TOP VIEW
C1+ 1
C1- 2
NEGOUT 3
POK 4
SHDN 5
MAX881R
µMAX
10 IN
9 N.C.
8 GND
7 OUT
6 FB
N.C. = NOT INTERNALLY CONNECTED
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