19-1372; Rev 2; 1/04
IT
TION K
VALUA
E
BLE
AVAILA
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
General Description
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 10-pin µMAX package.
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 Startup
♦
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)
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
INPUT
2.5V TO 5.5V
IN
OUT
OUTPUT
-2V (OR ADJ)
4mA, 1mVp-p
RIPPLE
Pin Configuration
TOP VIEW
C1+
1
10
IN
9
N.C.
GND
OUT
FB
MAX881R
ON
OFF
SHDN
C1+
POK
C1-
NEGOUT
FB
GND
CONTROLS
GaAsFET PA’s
DRAIN SWITCH
C1-
NEGOUT
POK
SHDN
2
3
4
5
MAX881R
8
7
6
µMAX
N.C. = NOT INTERNALLY CONNECTED
________________________________________________________________
Maxim Integrated Products
1
For pricing delivery, and ordering information please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
MAX881R
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V
SHDN
to GND...........................................................-0.3V to +6V
POK
to GND ...........................................................-0.3V to +12V
C1+ to GND .................................................-0.3V to (V
IN
+ 0.3V)
C1-, NEGOUT, OUT, FB to GND ....................-6V to (V
IN
+ 0.3V)
Continuous Power Dissipation (T
A
= +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
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.
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.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 3, V
IN
= +3.6V, FB = GND, R
L
=
∞,
SHDN
= IN,
T
A
= -40°C to +85°C,
unless otherwise noted. Typical values are at
T
A
= +25°C.) (Note 2)
PARAMETER
Supply Voltage Range
Preset Output Voltage
Adjustable Output Voltage
Range
FB Voltage
FB Input Current
Supply Current (Note 3)
Shutdown Supply Current
Output Load Regulation
Output Ripple
Oscillator Frequency
POK
Threshold
POK
Output Level
POK
Off Leakage Current
SHDN
Input High Voltage
SHDN
Input Low Voltage
SHDN
Input Current
SHDN
Input Capacitance
Startup Time
V
IH
V
IL
I
SHDN
C
IN
t
START
V
IN
= 3V, R
L
= 500Ω, V
SHDN
= 0 to V
IN
,
POK
goes low
f
OSC
FB = OUT
V
IN
≥
2.5V, sinking 1mA
V
POK
= 11V
V
IN
= 5.5V
V
IN
= 2.5V
Connected to IN or GND
10
1
2.2
0.35
±1
I
Q
I
SHUT
SHDN
= GND
V
IN
≥
2.7V, I
OUT
= 0 to 4mA
I
OUT
= 4mA, circuit of Figure 3b
80
90
SYMBOL
V
IN
V
OUT
V
OUT
V
IN
≥
2.7V, I
OUT
= 0 to 4mA
V
IN
≥
2.5V, I
OUT
= 0 to 4mA
V
IN
≥
2.5V,
I
OUT
= 0 to 4mA
V
FB
= -0.5V
T
A
= +25°C
T
A
= 0°C to +85°C
T
A
= -40°C to +85°C
CONDITIONS
MIN
2.5
-2.1
-(V
IN
- 0.6)
-0.515
-0.525
-0.535
-10
500
0.05
2
1
100
92.5
120
95
100
1
-0.5
-2.0
TYP
MAX
5.5
-1.9
-0.5
-0.485
-0.475
-0.465
-100
950
1
6
nA
µA
µA
mV/mA
mVp-p
kHz
% of
V
OUT
mV
µA
V
V
µA
pF
ms
V
UNITS
V
V
V
V
FB
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.
2
_______________________________________________________________________________________
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
MAX881R
Typical Operating Characteristics
(Circuit of Figure 3, V
IN
= 3.6V, T
A
= +25°C, unless otherwise noted.)
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
CIRCUIT OF FIGURE 3a
-1.86
-1.88
OUTPUT VOLTAGE (V)
1.90
-1.92
-1.94
-1.96
-1.98
-2.00
-2.02
0
1
2
3
4
5
6
7
8
9
10
OUTPUT CURRENT (mA)
V
IN
≥
3.6V
V
IN
= 2.5V
MAX881R TOC01
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
-1.86
-1.88
OUTPUT VOLTAGE (V)
-1.90
-1.92
-1.94
-1.96
-1.98
-2.00
-2.02
0
2
4
6
8
10
12
14
16
OUTPUT CURRENT (mA)
V
IN
≥
3.6V
V
IN
= 2.5V
CIRCUIT OF FIGURE 3b
MAX881R TOC02
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
-1.96
OUTPUT VOLTAGE (V)
-1.97
-1.98
-1.99
-2.00
-2.01
-2.02
-2.03
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
INPUT VOLTAGE (V)
I
LOAD
= 4mA
MAX881R TOC03
-1.84
-1.84
-1.95
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
MAX881r TOC04
MAXIMUM NEGOUT CURRENT
vs. INPUT VOLTAGE
MAX881R TOC05
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX881R TOC06
45
40
OUTPUT CURRENT (mA)
35
30
25
20
15
10
5
0
V
OUT
≤
-1.8V
CIRCUIT OF FIGURE 3b
24
20
OUTPUT CURRENT (mA)
16
12
8
4
0
V
NEGOUT
= 0.9 x V
NEGOUT(NO LOAD)
900
800
SUPPLY CURRENT (µA)
700
600
500
400
300
V
OUT
≤
-1.8V
CIRCUIT OF FIGURE 3a
V
OUT
< 2mVp-p RIPPLE
CIRCUIT OF FIGURE 3b
V
OUT
< 2mVp-p RIPPLE
CIRCUIT OF FIGURE 3a
CIRCUIT OF FIGURE 3b
CIRCUIT OF FIGURE 3a
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
MAX881R TOC07
STARTUP TIME
vs. INPUT VOLTAGE
MAX881R TOC08
OSCILLATOR FREQUENCY
vs. INPUT VOLTAGE
T
A
= -40°C
102
FREQUENCY (kHz)
101
100
99
98
97
T
A
= +25°C
T
A
= +85°C
MAX881R TOC09
900
800
SUPPLY CURRENT (µA)
700
600
500
400
V
IN
= 2.5V
300
-60
-40
-20
0
20
40
60
80
V
IN
= 3.6V
800
700
START-UP TIME (µs)
600
500
400
300
200
100
CIRCUIT OF FIGURE 3a
NO LOAD
SHDN TO POK DELAY
103
V
IN
= 5.5V
100
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
TEMPERATURE (°C)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
_______________________________________________________________________________________
3
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
MAX881R
Typical Operating Characteristics (continued)
(
Circuit of Figure 3, V
IN
= 3.6V, T
A
= +25°C, unless otherwise noted.
)
STARTUP FROM SHUTDOWN
(NO LOAD)
MAX881R-TOC10
OUTPUT NOISE AND RIPPLE
(CIRCUIT OF FIGURE 3a)
MAX881R-TOC11
OUTPUT NOISE AND RIPPLE
(CIRCUIT OF FIGURE 3b)
MAX881R-TOC12
SHDN
+5V
0
V
IN
= 3.6V
V
OUT
= -2V
I
OUT
= 2.5mA
R
L
= 500Ω
V
OUT
= 0
V
IN
= 0
1mV/div
AC-COUPLED
V
OUT
= -2V
V
IN
= 3.6V
1mV/div
AC-COUPLED
NOISE FLOOR
V
OUT
0
-2V
POK
V
IN
= 3.6V
CIRCUIT OF FIGURE 3b
100µs/div
V
IN
0
V
OUT
1mV/div
AC-COUPLED
OUTPUT NOISE
5µs/div
10µs/div
OUTPUT NOISE SPECTRUM
(CIRCUIT OF FIGURE 3a)
MAX881R TOC13
OUTPUT NOISE SPECTRUM
(CIRCUIT OF FIGURE 3b)
50
40
30
NOISE (dBµV)
20
10
0
-10
-20
-30
-40
V
IN
= 3.6V
V
OUT
= -2V
I
OUT
= 4mA
MAX881R TOC14
60
50
40
30
NOISE (dBµV)
20
10
0
-10
-20
-30
-40
1
10
100
V
IN
= 3.6V
V
OUT
= -2V
I
OUT
= 2.5mA
60
1000
1
10
100
1000
FREQUENCY (kHz)
FREQUENCY (kHz)
LINE-TRANSIENT RESPONSE
MAX881R-TOC15
LOAD-TRANSIENT RESPONSE
MAX881R-TOC16
4mA
3.3V
V
IN
2.7V
I
OUT
400µA
V
OUT
I
LOAD
= 4mA
V
OUT
= -2V
CIRCUIT OF FIGURE 3b
2ms/div
10mV/
div
V
OUT
V
IN
= 3.6V
V
OUT
= -2V
CIRCUIT OF FIGURE 3b
100µs/div
10mV/
div
4
_______________________________________________________________________________________
Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA
Pin Description
PIN
1
2
3
4
5
NAME
C1+
C1-
NEGOUT
POK
SHDN
FB
OUT
GND
N.C.
IN
Positive Terminal for C1
Negative Terminal for C1
Negative 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 Voltage
Ground
No Connection. Not internally connected.
Positive Power-Supply Input
FUNCTION
MAX881R
6
7
8
9
10
Dual Mode is a trademark of Maxim Integrated Products.
SHDN
C1+
C1
C1-
CHARGE PUMP
IN
C3
NEGOUT
C2
FB
OUT
C4
MAX881R
0.5V
0.4625V
POK
GND
Figure 1. Functional Diagram
_______________________________________________________________________________________
5
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
