MAX881R Fast Delivery |IC PHOENIX CO.,LIMITED

MAX881R ,Low-Noise Bias Supply in µMAX with Power OK for GaAsFET PAApplications Ordering InformationCell Phones Wireless ModemsPART TEMP RANGE PIN-PACKAGEPCS Phones T ..
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MAX881R
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 (-VIN+ 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 10-pin µMAX package.
Applications
Cell PhonesWireless Modems
PCS PhonesTwo-Way Pagers
PHS PhonesMobile Radios
Wireless HandsetsWireless Computers
FeaturesSmall µMAX Package1mVp-p Output Voltage Ripple and NoisePower-OK Signal to Control GaAsFET Drain
Switch0.05µA Logic-Controlled Shutdown1ms Guaranteed Startup2.5V to 5.5V Input-0.5V to (-VIN+ 0.6V) Output at up to 4mAOperates 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
N.C.
GND
OUTPOK
N.C. = NOT INTERNALLY CONNECTED
NEGOUT
C1-
C1+
MAX881R
μMAX
TOP VIEWSHDN
MAX881ROUT
POK
C1+
C1-
NEGOUTFBGND
SHDN
CONTROLS
GaAsFET PA’s
DRAIN SWITCH
OUTPUT
-2V (OR ADJ)
4mA, 1mVp-p
RIPPLE
INPUT
2.5V TO 5.5V
OFF
Typical Operating Circuit
19-1372; Rev 2; 1/04
PART
MAX881REUB-40°C to +85°C
TEMP RANGEPIN-PACKAGE
10 µMAX
Pin Configuration
Ordering Information
EVALUATION KIT
AVAILABLE
MAX881R
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 3, VIN= +3.6V, FB = GND, RL= ∞, SHDN= IN, TA= -40°C to +85°C, unless otherwise noted. Typical values are at= +25°C.) (Note 2)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN to GND.................................................................-0.3V to +6V
SHDNto GND...........................................................-0.3V to +6V
POKto GND...........................................................-0.3V to +12V
C1+ to GND.................................................-0.3V to (VIN+ 0.3V)
C1-, NEGOUT, OUT, FB to GND....................-6V to (VIN+ 0.3V)
Continuous Power Dissipation (TA= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C)...........444mW
Operating Temperature Range...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +165°C
Lead Temperature (soldering, 10s).................................+300°C
VIN= 3V, RL= 500Ω, VSHDN= 0 to VIN,
POKgoes low
VIN≥2.5V, IOUT= 0 to 4mA
Connected to IN or GND
VIN= 2.5V
VIN ≥2.7V, IOUT= 0 to 4mA
VIN= 5.5V
VPOK= 11V
IOUT= 4mA, circuit of Figure 3b
VIN ≥2.7V, IOUT= 0 to 4mA
VIN≥2.5V, sinking 1mA
SHDN= GND
VFB= -0.5V
FB = OUT
CONDITIONS1tSTARTStartup Time10CINSHDNInput Capacitance±1ISHDNSHDNInput Current0.35VILSHDNInput Low Voltage2.2VIHSHDNInput High Voltage1POKOff Leakage Current100POKOutput Level
% of
VOUT9092.595POKThreshold
kHz80100120fOSCOscillator Frequency-(VIN- 0.6)-0.5VOUTAdjustable Output Voltage
Range-2.1-2.0-1.9VOUT2.55.5VINSupply Voltage Range
Preset Output Voltage
mVp-p1Output Ripple
mV/mA26Output Load Regulation0.051ISHUTShutdown Supply Current
VFBFB Voltage-10-100FB Input Current500950IQSupply Current (Note 3)
UNITSMINTYPMAXSYMBOLPARAMETER
Note 1:The output may be shorted to NEGOUT or GND if the package power dissipation is not exceeded. Typical short-circuit
current is 35mA.
VIN≥2.5V,
IOUT= 0 to 4mA= +25°C= 0°C to +85°C= -40°C to +85°C
Note 2:Specifications to -40°C are guaranteed by design, not production tested.
Note 3:MAX881R may draw high supply current during startup, up to the minimum operating supply voltage. To guarantee proper
startup, the input supply must be capable of delivering 90mA more than the maximum load current.
MAX881R
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX881R TOC01
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
CIRCUIT OF FIGURE 3a
VIN = 2.5V
VIN ≥ 3.6V
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX881R TOC02
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
CIRCUIT OF FIGURE 3b
VIN = 2.5V
VIN ≥ 3.6V
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
MAX881R TOC03
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
ILOAD = 4mA
Typical Operating Characteristics
(Circuit of Figure 3, VIN= 3.6V, TA= +25°C, unless otherwise noted.)
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
MAX881r TOC04
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
VOUT < 2mVp-p RIPPLE
CIRCUIT OF FIGURE 3b
VOUT < 2mVp-p RIPPLE
CIRCUIT OF FIGURE 3a
VOUT ≤ -1.8V
CIRCUIT OF FIGURE 3a
VOUT ≤ -1.8V
CIRCUIT OF FIGURE 3b
MAXIMUM NEGOUT CURRENT
vs. INPUT VOLTAGE
MAX881R TOC05
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
VNEGOUT = 0.9 x VNEGOUT(NO LOAD)
CIRCUIT OF FIGURE 3b
CIRCUIT OF FIGURE 3a
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX881R TOC06
INPUT VOLTAGE (V)
SUPPLY CURRENT (
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
MAX881R TOC07
TEMPERATURE (°C)
SUPPLY CURRENT (
VIN = 5.5V
VIN = 3.6V
VIN = 2.5V
STARTUP TIME
vs. INPUT VOLTAGE
MAX881R TOC08
INPUT VOLTAGE (V)
START-UP TIME (
CIRCUIT OF FIGURE 3a
NO LOAD
SHDN TO POK DELAY
OSCILLATOR FREQUENCY
vs. INPUT VOLTAGE
MAX881R TOC09
INPUT VOLTAGE (V)
FREQUENCY (kHz)
TA = -40°C
TA = +25°C
TA = +85°C
MAX881R
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
Typical Operating Characteristics (continued)
(Circuit of Figure 3, VIN= 3.6V, TA= +25°C, unless otherwise noted.)
100μs/div
STARTUP FROM SHUTDOWN
(NO LOAD)
+5V
VOUT
POK
SHDN
MAX881R-TOC10
-2V
VINVIN = 3.6V
CIRCUIT OF FIGURE 3b
5μs/div
OUTPUT NOISE AND RIPPLE
(CIRCUIT OF FIGURE 3a)
VOUT
1mV/div
AC-COUPLED
MAX881R-TOC11
VIN = 3.6V
VOUT = -2V
IOUT = 2.5mA
10μs/div
OUTPUT NOISE AND RIPPLE
(CIRCUIT OF FIGURE 3b)
VOUT = 0
VIN = 0
1mV/div
AC-COUPLED
VOUT = -2V
VIN = 3.6V
1mV/div
AC-COUPLED
MAX881R-TOC12
RL = 500Ω
NOISE FLOOR
OUTPUT NOISE
OUTPUT NOISE SPECTRUM
(CIRCUIT OF FIGURE 3a)
MAX881R TOC13
FREQUENCY (kHz)
NOISE (dB
VIN = 3.6V
VOUT = -2V
IOUT = 2.5mA
OUTPUT NOISE SPECTRUM
(CIRCUIT OF FIGURE 3b)
MAX881R TOC14
FREQUENCY (kHz)
NOISE (dB
VIN = 3.6V
VOUT = -2V
IOUT = 4mA
2ms/div
LINE-TRANSIENT RESPONSE
VIN
VOUT
MAX881R-TOC15
10mV/
div
3.3V
2.7V
ILOAD = 4mA
VOUT = -2V
CIRCUIT OF FIGURE 3b
100μs/div
LOAD-TRANSIENT RESPONSE
IOUT
VOUT
MAX881R-TOC16
10mV/
div
4mA
400μA
VIN = 3.6V
VOUT = -2V
CIRCUIT OF FIGURE 3b
MAX881R
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
CHARGE PUMP
NEGOUT
SHDN
0.5V0.4625V
GND
C1+C4
OUT
POK
C1-
MAX881R
Pin Description
Figure 1. Functional Diagram
Dual Mode is a trademark of Maxim Integrated Products.
PINFUNCTIONPositive Terminal for C1Negative Terminal for C1Negative Output Voltage (unregulated)Active-Low, Open-Drain Power-OK Output. Goes low when OUT reaches 92.5% of its set
value.Active-Low, Logic-Level Shutdown Input. Connect to IN for normal operation. Do not leave this
pin unconnected.
Dual-Mode™ Feedback Input. When FB is connected to GND, the output is preset to -2V. To
select other voltages, connect FB to an external resistor-divider (Figure 4). Do not leave this pin
unconnected.Regulated Negative Output VoltageGroundNo Connection. Not internally connected.Positive Power-Supply Input
C1+
C1-
NEGOUT
POK
SHDN
OUT
GND
N.C.
NAME
MAX881R
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
Detailed Description
The MAX881R, a low-noise, inverting, regulated charge-
pump power supply, is designed for biasing GaAsFET
devices such as power-amplifier modules in cellular
handsets.
The applied input voltage (VIN) is inverted to a negative
voltage at NEGOUT by a capacitive charge pump. This
voltage is regulated by an internal linear regulator at
OUT (Figure 1). With FB connected to GND, VOUTis
regulated at -2V. Alternatively, use a voltage-divider at
FB to adjust the output voltage between -0.5V and -(VIN
- 0.6V) (see the section Setting the Output Voltage).
The internal linear regulator reduces the ripple noise
induced by the charge-pump inverter to 1mVp-p at
OUT (circuit of Figure 3b). In addition, the excellent AC
rejection of the linear regulator attenuates noise from
the incoming supply.
Power-OK Signal
The MAX881R has an active-low, open-drain, power-OK
(POK) output. This output goes low when OUT reaches
92.5% of the regulated output voltage. POKcan be
used to drive the gate of a P-MOSFET that switches
power to the GaAsFET power amplifier (Figure 2), there-
by ensuring that the power amplifier is not powered
before the required negative bias voltage is present.
Use a 50kΩor larger pull-up resistor to signal a logic
high when POKgoes high impedance.
Shutdown Mode
The MAX881R features a shutdown mode that reduces
supply current to less than 1µA over temperature. SHDN
is an active-low, logic-level input. Start-up time coming
out of shutdown mode is typically 0.5ms. OUT and
NEGOUT are switched to GND in shutdown mode.
Applications Information
Setting the Output Voltage
Select either a fixed or adjustable output for the
MAX881R. Connect FB to GND for a fixed -2V output
(Figure 3). Select an alternative output voltage by con-
necting FB to the midpoint of a resistor-divider from
OUT to GND (Figure 4). When operating under full load
(4mA), the voltage at IN should be at least 0.6V higher
than the absolute voltage required at OUT. Note that
the minimum input voltage required for operation is
2.5V, regardless of the desired output voltage.
Choose R1 to be between 100kΩand 400kΩand cal-
culate R2. For greater accuracy, use resistors with 1%
or better tolerance.
R2 = R1 (2 x |VOUT|- 1)
POK
100k
VCC FOR
POWER AMPLIFIERTO PA
GATE BIAS
POWER
AMPLIFIER
OUT
MAX881R
Figure 2. Using the POKFunction
NEGOUT
SHDN
C1-
C1+
POK
VOUT = -2V
0.22μF
0.22μF
0.22μFC4
4.7μF
VIN
OFF
OUT
GNDFB
MAX881R
Figure 3a. Standard Application Circuit for Minimum Capacitor
Values
NEGOUT
SHDN
C1-
C1+
POK
VOUT = -2V
1μF
1μF
1μFC4
10μF
VIN
OUT
GNDFB
MAX881RON
OFF
Figure 3b. Standard Application Circuit for Minimum Output
Noise

Partno	Mfg	Dc	Qty	Available	Descript
MAX881R	MAXIM	N/a	2500	avai	Low-Noise Bias Supply in µMAX with Power OK for GaAsFET PA