General Description
The MAX2251 low-voltage linear power amplifier (PA) is
designed for TDMA/AMPS dual-mode phone applica-
tions. The device is packaged in an ultra-compact
(2.06mm ✕2.06mm) chip-scale package (CSP), and
delivers over +30dBm of linear power in TDMA opera-
tion. An on-chip shutdown feature reduces operating
current to 1µA (typ), eliminating the need for an external
supply switch.
The MAX2251 does not need an external reference volt-
age, and requires only a few external matching compo-
nents and no bias circuitry. Another feature of this
device is the use of external bias resistors, eliminating
wasted “safety-margin” current. This feature also allows
current throttleback at lower output power levels, there-
by maintaining the highest possible efficiency at all
power levels.
________________________Applications
Cellular-Band TDMA/AMPS Dual-Mode Phones
PA Modules
2-Way Pagers
Cordless Phones
Features
♦Ultra-Compact 4 ✕ 4 (2.06mm ✕2.06mm) CSP
♦High Efficiency—41% at +30dBm POUT (TDMA)
(typ)
♦On-Chip Power Detector
♦ICC < 1µA in Shutdown Mode
♦+2.8V to +4.5V True Single-Supply Operation
♦±0.9dB Gain Variation from TA= -40°C to +85°C
♦Current Adjustable with PDM or DAC Signal
♦No External Logic Interface Circuitry Required
MAX2251
+2.8V, Single-Supply,
Cellular-Band Linear Power Amplifier
________________________________________________________________ Maxim Integrated Products 1
PIN A1
INDICATOR
POWER
DETECTOR
LOGIC AND
BIAS
A1 A2
GND
A3
GND
A4
GND
PD_OUT
B1
GND
B2
OUT
B3
OUT
B4
D1
VCC
C2
GND
D2
IN
C3
VCC
D3
SHDN
C4
GND
D4
MODE
BIAS1
C1
TOP VIEW
BIAS2
MAX2251
Pin Configuration
19-1773; Rev 2; 2/03
EVALUATION KIT
AVAILABLE
Ordering Information
PART TEMP
RANGE
PIN-
PACKAGE
TOP MARK
MAX2251EBE
- 40°C to + 85° C 4 × 4 U C S P
2251
EBE
_ _ _ (LOT #)
_ _ _ (D ATE CODE)
Typical Operating Circuit appears at end of data sheet.
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX2251
+2.8V, Single-Supply,
Cellular-Band Linear Power Amplifier
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
VCC to GND ..........................................................-0.3V to +4.5V
SHDN, MODE to GND ................................-0.3V to (VCC + 0.3V)
BIAS_ to GND.............................................-0.3V to (VCC + 0.3V)
RF Input Power ...............................................................+10dBm
Continuous Power Dissipation (TA= +70°C)
4 ✕4 UCSP (derate 80mW/°C above +70°C) ....................4W
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Thermal Resistance from Junction to Backside.................1°C/W
Thermal Resistance from Junction to Ambient
(using MAX2251 EV kit)...............................................40°C/W
Storage Temperature Range .............................-65°C to +150°C
Bump Reflow Temperature .............................................+235°C
Continuous Operating Lifetime ...................10 yrs ✕ 0.92(TA- 45°C)
(At POUT = +32dBm, for Operating Temperature, TA≥45°C)
PARAMETER CONDITIONS
MIN
TYP
MAX
Idle Supply Current MODE = high
205 255
Logic High Threshold 2.0 V
Logic Low Threshold 0.8 V
VCC = +2.8V to +4.0V
0.6 10
Shutdown Supply Current SHDN = MODE =
GND VCC = +4.5V 60
120
µA
Logic High Input Current 5µA
Logic Low Input Current -1 +1 µA
DC ELECTRICAL CHARACTERISTICS
(VCC = +2.8V to +4.5V, no RF signal applied, SHDN = high, TA= -40°C to +85°C, unless otherwise noted. Typical values are mea-
sured at VCC = +3.3V and TA= +25°C.)
MAX2251
+2.8V, Single-Supply,
Cellular-Band Linear Power Amplifier
_______________________________________________________________________________________ 3
AC CHARACTERISTICS, TDMA OPERATION
(MAX2251 EV kit, fIN = 824MHz to 849MHz, VCC = VMODE = V SHDN = +3.3V, 50Ωsystem, NADC modulation, duty cycle = 100%,
TA= +25°C, unless otherwise noted. Typical values are at fIN = 836MHz, TA= +25°C.) (Note 1)
Note 1: Guaranteed by design and characterization.
Note 2: Operation outside the frequency range is possible, but has not been characterized.
Note 3: Time when V SHDN transitions to VCC until POUT is within 1dB of its final mean power.
Note 4: Harmonics are measured on the MAX2251 EV kit. The output matching provides some harmonic attenuation in addition to the
rejection provided by the IC. The combined suppression is specified.
Note 5: The range is defined by the difference between the rated linear output power and the output power that corresponds to
VPD = 0.57V.
Note 6: Time from when V SHDN transitions high until detector output reaches within 10% of its final value.
PARAMETER CONDITIONS
MIN
-4.5σ
TYP
4.5σ
MAX
UNITS
Frequency Range (Note 2) VMODE = VCC or GND 824
849
MHz
Power Gain POUT = +30dBm
25.7 26.1 27.8
dB
E xtr em e C ondi ti on P ow er Gai nT
A = -40°C to +85°C, POUT = +30dBm
24.8 25.2
dB
Output Power VCC = +3.3V, meets ACPR
specifications 30
dBm
TA = +25oC-29.3/
-47.5
-27.4/
-45.4
-27/
-44.6
Adjacent/Alternate-Channel
Power Ratio
fOFFSET = 30/60kHz in
25kHz bandwidth
TA = +85°C
-28/
-48
dBc
AMPS Output Power
VMODE = VCC
,
PIN = +8dBm single tone 31.8
32
dBm
Power-Added Efficiency POUT = +30dBm
41.2
%
AM P S P ow er - Ad d ed E ffi ci ency PIN = +8dBm single tone at 836MHz 51 %
Turn-On Time (Note 3) 25µs
Input VSWR
1.2:1 1.76:1
Maximum Nonharmonic
Spurious Due to Load
Mismatch
VCC = +2.8V to +4.5V, all input power
levels, VSWR = 4:1 all phase angle,
TA = -40°C to +85°C
-55
dBc
Noise Power fRF = 849MHz, noise measured at
869MHz, POUT = +30dBm
-121
dBm/
Hz
AMPS Noise Power fRF = 836MHz, noise measured at
881MHz, POUT = +31dBm
-141
dBm/
Hz
H ar m oni c S up p r essi on ( N ote 4)
45
dBc
Power Detector Range (Note 5) 27
29.4
dB
Power Detector Settling Time
( N ote 6) CDET = 4700pF 2 3 µs
MAX2251
+2.8V, Single-Supply,
Cellular-Band Linear Power Amplifier
4 _______________________________________________________________________________________
0
10
5
20
15
35
30
25
40
2.8 3.6 4.5
SHUTDOWN vs. SUPPLY VOLTAGE
MAX2251-01
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT (nA)
TA = +25°C
TA = -40°C
TA = +85°C
VSHDN = VMODE = GND
NO INPUT DRIVE
0
100
50
200
150
350
300
250
400
2.8 3.6 4.5
MAX2251-02
SUPPLY VOLTAGE (V)
QUIESCENT CURRENT (mA)
QUIESCENT CURRENT
vs. SUPPLY VOLTAGE
NO INPUT DRIVE
TA = +85°C
TA = +25°C
TA = -40°C
0
200
100
400
300
700
600
500
800
2.8 3.6 4.5
MAX2251-03
SUPPLY VOLTAGE (V)
QUIESCENT CURRENT (mA)
QUIESCENT CURRENT
vs. SUPPLY VOLTAGE
VMODE = GND
NO INPUT DRIVE
TA = +25°C
TA = +85°C
TA = -40°C
0
50
150
100
250
200
300
-10 -5 0 5 10
SUPPLY CURRENT
vs. OUTPUT POWER
MAX2251-04
OUTPUT POWER (dBm)
SUPPLY CURRENT (mA)
WITHOUT THROTTLEBACK
WITH THROTTLEBACK (MAINTAIN
ACPR = -29dBc, ALT <-50dBc)
20
22
28
26
24
30
10 15 20 25 30
GAIN vs. OUTPUT POWER
MAX2251-05
OUTPUT POWER (dBm)
GAIN (dB)
TA = +25°C TA = -40°C
TA = +85°C
20
22
28
26
24
30
10 15 20 25 30
GAIN vs. OUTPUT POWER
MAX2251-06
OUTPUT POWER (dBm)
GAIN (dB)
VCC = +3.3V VCC = +4.5V
VCC = +2.8V
20
22
24
28
26
30
824 829 834 839 844 849
GAIN vs. FREQUENCY
MAX2251-07
FREQUENCY (MHz)
GAIN (dB)
POUT = +30dBm
TA = +25°CTA = -40°C
TA = +85°C
20
22
24
28
26
30
824 829 834 839 844 849
GAIN vs. FREQUENCY
MAX2251-08
FREQUENCY (MHz)
GAIN (dB)
VCC = VMODE = VSHDN = +2.8V
POUT = +28dBm
20
22
24
26
32
28
30
34
824 829 834 839 844 849
GAIN vs. FREQUENCY AMPS
MAX2251-09
FREQUENCY (MHz)
GAIN (dB)
VMODE = GND
VMODE = VCC
POUT = +31dBm
Typical Operating Characteristics
(MAX2251 EV kit, VCC = VMODE = VSHDN = +3.3V, fIN = 836MHz, TDMA modulation, TA= +25°C, unless otherwise noted.)
MAX2251
+2.8V, Single-Supply,
Cellular-Band Linear Power Amplifier
_______________________________________________________________________________________ 5
0
15
45
30
5
10
20
40
25
35
50
20 22 24 26 28 30
POWER-ADDED EFFICIENCY
vs. OUTPUT POWER
MAX2251-10
OUTPUT POWER (dBm)
PAE (%)
30
36
48
42
32
34
38
46
40
44
50
824 829 834 839 844 849
POWER-ADDED EFFICIENCY
vs. FREQUENCY
MAX2251-11
FREQUENCY (MHz)
PAE (%)
TA = +25°C
VCC = +2.8V
PO = +28dBm
TA = +25°C
TA = -40°C
TA = +85°C
POUT = +30dBm
30
36
48
42
32
34
38
46
40
44
50
824 829 834 839 844 849
POWER-ADDED EFFICIENCY
vs. FREQUENCY, AMPS
MAX2251-12
FREQUENCY (MHz)
PAE (%)
VMODE = GND
VMODE = VCC
POUT = +31dBm
0
20
10
50
30
40
60
20 24 2622 28 3230
POWER-ADDED EFFICIENCY
vs. OUTPUT POWER, AMPS
MAX2251-13
OUTPUT POWER (dBm)
PAE (%)
VMODE = VCC
-55
-45
-50
-30
-40
-35
-25
824 829 834 839 844 849
ACPR/ALT vs. FREQUENCY
MAX2251-14
FREQUENCY (MHz)
ACPR/ALT (dBc)
POUT = +30dBm
ACPR
TA = +25°C
ACPR
TA = +85°C
ALT
TA = +85°C
ALT
TA = +25°C
-55
-45
-50
-30
-40
-35
-25
824 829 834 839 844 849
ACPR/ALT vs. FREQUENCY
MAX2251-15
FREQUENCY (MHz)
ACPR/ALT (dBc)
VSHDN = VCC = +2.8V
POUT = +28dBm
ACPR
ALT
-60
-40
-45
-50
-55
-25
-35
-30
-20
20 22 24 26 28 30
ACPR/ALT vs. OUTPUT POWER
MAX2251-16
OUTPUT POWER (dBm)
ACPR/ALT (dBc)
fIN = 836MHz
ACPR
ALT
-170
-140
-150
-160
-110
-130
-120
-100
869 874 879 884 889 894
NOISE POWER vs. FREQUENCY
MAX2251-17
FREQUENCY (MHz)
NOISE POWER (dBm/Hz)
POUT = +30dBm
TA = -40°C
fIN = 849MHz
fIN = 836MHz
fIN = 824MHz
-170
-140
-150
-160
-110
-130
-120
-100
869 874 879 884 889 894
NOISE POWER vs. FREQUENCY AMPS
MAX2251-18
FREQUENCY (MHz)
fIN = 849MHz
fIN = 836MHz
fIN = 824MHz
NOISE POWER (dBm/Hz)
POUT = +32dBm
TA = -40°C
Typical Operating Characteristics (continued)
(MAX2251 EV kit, VCC = VMODE = VSHDN = +3.3V, fIN = 836MHz, TDMA modulation, TA= +25°C, unless otherwise noted.)
MAX2251
+2.8V, Single-Supply,
Cellular-Band Linear Power Amplifier
6 _______________________________________________________________________________________
0
2
1
4
3
5
20 22 24 26 28 30
EVM vs. OUTPUT POWER
MAX2251-19
OUTPUT POWER (dBm)
EVM (% RMS)
0
3
1
2
4
5
824 829 834 839 844 849
EVM vs. FREQUENCY
MAX2251-20
FREQUENCY (MHz)
EVM (% RMS)
POUT = +30dBm
VSHDN = VMODE = VCC = +3.3V
TA = +25°CTA = +85°C
0
1.0
1.5
0.5
2.5
2.0
3.0
0 5 10 15 2520 30
POWER DETECTOR vs. OUTPUT POWER
MAX2251-21
OUTPUT POWER (dBm)
POWER DETECTOR VOLTAGE (V)
TA = -40°C
TA = +25°C
TA = +85°C
0
1.0
1.5
0.5
2.5
2.0
3.0
0 5 10 15 2520 30
POWER DETECTOR vs. OUTPUT POWER
MAX2251-22
OUTPUT POWER (dBm)
POWER DETECTOR VOLTAGE (V)
VMODE = GND
fIN = 836MHz SINGLE-TONE SINE WAVE
TA = +85°C
TA = -40°C
TA = +25°C
0
1.0
1.5
0.5
2.5
2.0
3.0
0 5 10 15 2520 30
POWER DETECTOR vs. OUTPUT POWER
MAX2251-23
OUTPUT POWER (dBm)
POWER DETECTOR VOLTAGE (V)
fIN = 836MHz SINGLE-TONE SINE WAVE
VSHDN = VCC = +3.3V
VMODE = VCC
TA = +85°C
TA = -40°C
TA = +25°C
Typical Operating Characteristics (continued)
(MAX2251 EV kit, VCC = VMODE = VSHDN = +3.3V, fIN = 836MHz, TDMA modulation, TA= +25°C, unless otherwise noted.)
MAX2251
+2.8V, Single-Supply,
Cellular-Band Linear Power Amplifier
_______________________________________________________________________________________ 7
Detailed Description
The MAX2251 is a linear PA intended for TDMA/AMPS
dual-mode applications. The PA is fully characterized in
the 824MHz to 849MHz U.S. cellular band. The PA con-
sists of a driver stage and an output stage; both are
independently biased using external resistors. The
MAX2251 also features an integrated power detector.
Bias Control
External resistors connected to C1 and A1 indepen-
dently set the bias currents of the driver and output
stages, respectively. An internal bandgap reference
fixes the voltages at C1 and A1. RBIAS1 is typically
47.5kΩand RBIAS2 is typically 11kΩ. The bias current
can be dynamically adjusted by summing a current into
the bias pin of interest with an external source such as
a DAC. See the Typical Operating Circuit. The Typical
Operating Characteristics graph, Supply Current vs.
Output Power, demonstrates the current saving with
throttleback at low-output power levels.
Power Detector
The on-chip power detector monitors the output power.
The power detector outputs a voltage proportional to
the output power. Connect a filter capacitor from
PD_OUT to GND to set the power detector time con-
stant. The integrated power detector eliminates the
need for an external detector circuit.
Applications Information
External Matching
The MAX2251 requires input, interstage, and output
matching circuits for proper operation. See the Typical
Operating Circuit for suggested component values.
Use high-quality components for L2 and C12 in the out-
put-matching circuit for highest efficiency. The
MAX2251 EV kit uses a trace as a pullup inductor
(approximately 2nH) for the interstage matching.
Mode Selection
MAX2251 features two modes of operation: high-linear
mode and high-gain mode. For TDMA operation, drive
MODE high or connect to VCC. For AMPS operation,
drive MODE high for best PAE, or drive MODE low for
best gain.
Layout and Thermal Management Issues
The MAX2251 EV kit serves as a layout guide. Use con-
trolled impedance lines on all high-frequency inputs
and outputs. Connect GND to the PC board ground
plane with as low inductance path as possible. The
GND pins also serve as heat sinks. Connect all GND
PIN NAME FUNCTION
A1 BIAS2 Second Stage Bias Control. Connect an 11kΩ resistor to GND to set the bias current for the second
stage of the PA.
A2, A3, A4,
B2, C2, C4 GND Ground. Connect to the PC board ground plane with as low an inductance path as possible.
B1 PD_OUT Power Detector Output. This output is a DC voltage indicating the PA output power. Connect a
capacitor to set time constant. The settling time is typically 2µs with a 4700pF capacitor.
B3, B4 OUT RF Output. Connect a pullup high-Q inductor to VCC. Requires matching network. Connect B3 and
B4 together.
C1 BIAS1 First Stage Bias Control. Connect an external 47.5kΩ resistor to ground to set the bias current for
the driver stage.
C3 VCC Driver Stage Supply Voltage. Connect a pullup inductor to VCC. The pullup inductor can be a PC
board trace.
D1 VCC Supply Voltage. Bypass to ground with 100pF and 0.01µF capacitors.
D2 IN RF Input. Requires a highpass L-section impedance matching network.
D3 SHDN Shutdown Input. Drive logic low to place the device in shutdown mode. Drive logic high for normal
operation.
D4 MODE Mode Selection Input. Drive logic high for TDMA/AMPS mode. Drive logic low for higher gain AMPS
operation.
Pin Description
MAX2251
+2.8V, Single-Supply,
Cellular-Band Linear Power Amplifier
8 _______________________________________________________________________________________
pins directly to the topside RF ground. On boards
where the ground plane is not on the component side,
connect all GND pins to the ground plane with plated
through holes, close to the package. PC board traces
connecting the GND pins also serve as heat sinks.
Make sure that the traces are sufficiently wide.
UCSP Reliability
The ultra-chip-scale package (UCSP) represents a
unique packaging form factor that may not perform
equally to a packaged product through traditional
mechanical reliability tests. CSP reliability is integrally
linked to the user’s assembly methods, circuit board
material, and usage environment. The user should closely
review these areas when considering use of a CSP.
Performance through Operating Life Test and Moisture
Resistance remains uncompromised as it is primarily
determined by the wafer-fabrication process.
Mechanical stress performance is a greater consideration
for a CSP. CSPs are attached through direct solder con-
tact to the user’s PC board, foregoing the inherent stress
relief of a packaged-product lead frame. Solder joint con-
tact integrity must be considered. Testing done to char-
acterize the CSP reliability performance shows that it is
capable of performing reliably through environmental
stresses. Users should also be aware that, as with any
interconnect system there are electro-migration-based
current limits that, in this case, apply to the maximum
allowable current in the bumps. Reliability is a function of
this current, the duty cycle, lifetime, and bump tempera-
ture. See the Absolute Maximum Ratings section of the
data sheet for any specific limitations, listed under
Continuous Operating Lifetime. Results of environmental
stress tests and additional usage data and recommenda-
tions are detailed in the UCSP application note, which
can be found on Maxim’s website at www.maxim-ic.com.
MAX2251
+2.8V, Single-Supply,
Cellular-Band Linear Power Amplifier
_______________________________________________________________________________________ 9
R4
11k
R3
47.5k
C9
4700pF
RTB2RTB1
DAC
L2
7.15nH
W = 85
L = 315
W = 3
L = 76
C13
220pF RFOUT
W = 12
L = 125
W = 18
L = 150
W = 18
L = 80
C12
10pF
C14
4.7pF
C5
100pF
TOP VIEW
ALL TRANSMISSION LINE UNITS ARE IN MILS.
SHUTDOWN
LOGIC INPUT
MODE SELECT
INPUT
POWER
DETECTOR
LOGIC AND
BIAS
A1 A2
GND
A3
GND
A4
GND
PD_OUT
B1
GND
B2
OUT
B3
OUT
B4
BIAS1
D1
VCC
C2
GND
D2
IN
C3
VCC
D3
SHDN
C4
GND
D4
MODE
VCC
RFIN
VCC
C6
100pF
C3
9pF
C7
0.01µF
L1
4.7nH
VCC
C11
100pF
C10
0.01µF
C4
0.01µF
W = 35
L = 187
FERRITE
BEAD
C1
PIN A1
INDICATOR
OPTIONAL BIAS CURRENT
THROTTLEBACK CONTROL
BIAS2
MAX2251
Typical Operating Circuit
MAX2251
+2.8V, Single-Supply,
Cellular-Band Linear Power Amplifier
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
16L,UCSP.EPS
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)