Rainbow Electronics MAX881R - Manual

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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
Features
♦ Small µMAX Package
♦ 1mVp-p Output Voltage Ripple and Noise
♦ Power-OK Signal to Control GaAsFET Drain
Switch
♦ 0.05µA Logic-Controlled Shutdown
♦ 1ms Guaranteed Start-Up
♦ 2.5V to 5.5V Input
♦ -0.5V to (-V IN + 0.6V) Output at up to 4mA
♦ Operates with One 4.7µF and Three 0.22µF
Capacitors (no inductors needed)
MAX881R
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
________________________________________________________________ Maxim Integrated Products 1
1
2
3
4
5
10
9
8
7
6
IN
N.C.
GND
OUT POK
N.C. = NOT INTERNALLY CONNECTED
NEGOUT
C1-
C1+
MAX881R
µ
MAX
TOP VIEW
FB SHDN
MAX881R
IN OUT
POK
C1+
C1-
NEGOUT FB GND
SHDN
CONTROLS
GaAsFET PA’s
DRAIN SWITCH
OUTPUT
-2V (OR ADJ)
4mA, 1mVp-p
RIPPLE
INPUT
2.5V TO 5.5V
ON
OFF
Typical Operating Circuit
19-1372; Rev 1; 6/98
PART
MAX881REUB -40°C to +85°C
TEMP. RANGE PIN-PACKAGE
10 µMAX
EVALUATION KIT
AVAILABLE
Pin Configuration
Ordering Information