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19-1773; Rev 2; 2/03
KIT ATION EVALU BLE AVAILA
+2.8V, Single-Supply, Cellular-Band Linear Power Amplifier
Features
o Ultra-Compact 4
4
General Description
The MAX2251 low-voltage linear power amplifier (PA) is designed for TDMA/AMPS dual-mode phone applications. 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 operation. An on-chip shutdown feature reduces operating current to 1A (typ), eliminating the need for an external supply switch. The MAX2251 does not need an external reference voltage, and requires only a few external matching components 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, thereby maintaining the highest possible efficiency at all power levels. (2.06mm
MAX2251
2.06mm) CSP
o High Efficiency--41% at +30dBm POUT (TDMA) (typ) o On-Chip Power Detector o ICC < 1A in Shutdown Mode o +2.8V to +4.5V True Single-Supply Operation o 0.9dB Gain Variation from TA = -40C to +85C o Current Adjustable with PDM or DAC Signal o No External Logic Interface Circuitry Required
________________________Applications
Cellular-Band TDMA/AMPS Dual-Mode Phones PA Modules 2-Way Pagers Cordless Phones
PART
Ordering Information
TEMP RANGE PINPACKAGE TOP MARK
2251 EBE MAX2251EBE -40C to +85C 4 x 4 UCSP _ _ _ (LOT #) _ _ _ (DATE CODE)
Typical Operating Circuit appears at end of data sheet.
Pin Configuration
TOP VIEW
PIN A1 INDICATOR
BIAS2
GND A2 POWER DETECTOR
GND A3
GND A4
MAX2251
A1
B1 PD_OUT BIAS1 C1
B2 GND GND C2
B3 OUT VCC C3
B4 OUT GND C4
LOGIC AND BIAS D1 VCC D2 IN D3 SHDN D4 MODE
________________________________________________________________ Maxim Integrated Products
1
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.
+2.8V, Single-Supply, Cellular-Band Linear Power Amplifier MAX2251
ABSOLUTE MAXIMUM RATINGS
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 = +70C) 4 4 UCSP (derate 80mW/C above +70C) ....................4W Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Thermal Resistance from Junction to Backside.................1C/W Thermal Resistance from Junction to Ambient (using MAX2251 EV kit)...............................................40C/W Storage Temperature Range .............................-65C to +150C Bump Reflow Temperature .............................................+235C Continuous Operating Lifetime ...................10 yrs 0.92(TA - 45C) (At POUT = +32dBm, for Operating Temperature, TA 45C)
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.
DC ELECTRICAL CHARACTERISTICS
(VCC = +2.8V to +4.5V, no RF signal applied, SHDN = high, TA = -40C to +85C, unless otherwise noted. Typical values are measured at VCC = +3.3V and TA = +25C.)
PARAMETER Idle Supply Current Logic High Threshold Logic Low Threshold Shutdown Supply Current Logic High Input Current Logic Low Input Current -1 SHDN = MODE = GND VCC = +2.8V to +4.0V VCC = +4.5V 0.6 60 MODE = high 2.0 0.8 10 120 5 +1 CONDITIONS MIN TYP 205 MAX 255 UNITS mA V V A A A
2
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+2.8V, Single-Supply, Cellular-Band Linear Power Amplifier MAX2251
AC CHARACTERISTICS, TDMA OPERATION
(MAX2251 EV kit, fIN = 824MHz to 849MHz, VCC = VMODE = V SHDN = +3.3V, 50 system, NADC modulation, duty cycle = 100%, TA = +25C, unless otherwise noted. Typical values are at fIN = 836MHz, TA = +25C.) (Note 1)
PARAMETER Frequency Range (Note 2) Power Gain Extreme Condition Power Gain Output Power CONDITIONS VMODE = VCC or GND POUT = +30dBm TA = -40C to +85C, POUT = +30dBm VCC = +3.3V, meets ACPR specifications TA = +25oC TA = +85C AMPS Output Power Power-Added Efficiency AMPS Power-Added Efficiency Turn-On Time (Note 3) Input VSWR Maximum Nonharmonic Spurious Due to Load Mismatch Noise Power AMPS Noise Power Harmonic Suppression (Note 4) Power Detector Range Power Detector Settling Time (Note 6) (Note 5) CDET = 4700pF 27 VCC = +2.8V to +4.5V, all input power levels, VSWR = 4:1 all phase angle, TA = -40C to +85C fRF = 849MHz, noise measured at 869MHz, POUT = +30dBm fRF = 836MHz, noise measured at 881MHz, POUT = +31dBm -121 -141 45 29.4 2 3 VMODE = VCC, PIN = +8dBm single tone POUT = +30dBm PIN = +8dBm single tone at 836MHz 31.8 32 41.2 51 2 1.2:1 5 1.76:1 -55 dBc dBm/ Hz dBm/ Hz dBc dB s MIN 824 25.7 24.8 30 -29.3/ -47.5 -28/ -48 dBm % % s -27.4/ -45.4 -27/ -44.6 dBc 26.1 25.2 27.8 -4.5 TYP 4.5 MAX 849 UNITS MHz dB dB dBm
Adjacent/Alternate-Channel Power Ratio
fOFFSET = 30/60kHz in 25kHz bandwidth
Guaranteed by design and characterization. Operation outside the frequency range is possible, but has not been characterized. Time when V SHDN transitions to VCC until POUT is within 1dB of its final mean power. 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. Note 1: Note 2: Note 3: Note 4:
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+2.8V, Single-Supply, Cellular-Band Linear Power Amplifier MAX2251
Typical Operating Characteristics
(MAX2251 EV kit, VCC = VMODE = V SHDN = +3.3V, fIN = 836MHz, TDMA modulation, TA = +25C, unless otherwise noted.)
SHUTDOWN vs. SUPPLY VOLTAGE
MAX2251-01
QUIESCENT CURRENT vs. SUPPLY VOLTAGE
MAX2251-02
QUIESCENT CURRENT vs. SUPPLY VOLTAGE
700 QUIESCENT CURRENT (mA) 600 500 400 300 200 100 0 TA = +25C TA = +85C VMODE = GND NO INPUT DRIVE
MAX2251-03
40 35 SHUTDOWN CURRENT (nA) 30 25 20 15 10 5 0 2.8
VSHDN = VMODE = GND NO INPUT DRIVE
400 350 QUIESCENT CURRENT (mA) 300
NO INPUT DRIVE
800
TA = +85C
TA = +85C 250 200 150 100 50 0 TA = -40C TA = +25C
TA = +25C
TA = -40C
TA = -40C 3.6 SUPPLY VOLTAGE (V) 4.5
2.8
3.6 SUPPLY VOLTAGE (V)
4.5
2.8
3.6 SUPPLY VOLTAGE (V)
4.5
SUPPLY CURRENT vs. OUTPUT POWER
MAX2251-04
GAIN vs. OUTPUT POWER
MAX2251-05
GAIN vs. OUTPUT POWER
MAX2251-06
300 250 SUPPLY CURRENT (mA) 200 WITHOUT THROTTLEBACK
30
30
28
28 VCC = +2.8V VCC = +4.5V
GAIN (dB)
GAIN (dB)
26
TA = +85C
150 100 50 0 -10
TA = +25C
TA = -40C
26
VCC = +3.3V
WITH THROTTLEBACK (MAINTAIN ACPR = -29dBc, ALT <-50dBc)
24
24
22
22
20 -5 0 5 10 10 15 20 25 30 OUTPUT POWER (dBm) OUTPUT POWER (dBm)
20 10 15 20 25 30 OUTPUT POWER (dBm)
GAIN vs. FREQUENCY
MAX2251-07
GAIN vs. FREQUENCY
VCC = VMODE = VSHDN = +2.8V POUT = +28dBm
MAX2251-08
GAIN vs. FREQUENCY AMPS
34 32 30 VMODE = GND POUT = +31dBm
MAX2251-09
30
POUT = +30dBm
30
28
28
GAIN (dB)
GAIN (dB)
GAIN (dB)
26 TA = +85C 24 TA = +25C TA = -40C
26
28 26 24 VMODE = VCC
24
22
22 22
20 824 829 834 839 844 849 FREQUENCY (MHz)
20 824 829 834 839 844 849 FREQUENCY (MHz)
20 824 829 834 839 844 849 FREQUENCY (MHz)
4
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+2.8V, Single-Supply, Cellular-Band Linear Power Amplifier
Typical Operating Characteristics (continued)
(MAX2251 EV kit, VCC = VMODE = V SHDN = +3.3V, fIN = 836MHz, TDMA modulation, TA = +25C, unless otherwise noted.)
MAX2251
POWER-ADDED EFFICIENCY vs. OUTPUT POWER
MAX2251-10
POWER-ADDED EFFICIENCY vs. FREQUENCY
MAX2251-11
POWER-ADDED EFFICIENCY vs. FREQUENCY, AMPS
POUT = +31dBm VMODE = VCC 48 46 44 PAE (%) 42 40 38 36 VMODE = GND
MAX2251-12
50 45 40 35 PAE (%)
50 48 46 44 PAE (%) 42 40 38 36 34 32 30
50
POUT = +30dBm
30 25 20 15 10 5 0 20 22 24 26 28 30 OUTPUT POWER (dBm)
TA = +85C
TA = -40C
TA = +25C
VCC = +2.8V PO = +28dBm TA = +25C 824 829 834 839 844 849
34 32 30 824 829 834 839 844 849
FREQUENCY (MHz)
FREQUENCY (MHz)
POWER-ADDED EFFICIENCY vs. OUTPUT POWER, AMPS
MAX2251-13
ACPR/ALT vs. FREQUENCY
MAX2251-14
ACPR/ALT vs. FREQUENCY
VSHDN = VCC = +2.8V POUT = +28dBm
MAX2251-15
60 50 40 PAE (%) 30 20 10 0 20
VMODE = VCC
-25 -30 -35 -40 -45 -50 -55
POUT = +30dBm ACPR TA = +25C
-25 -30 -35 -40 -45 -50 -55
ACPR/ALT (dBc)
ACPR/ALT (dBc)
ACPR TA = +85C
ACPR
ALT TA = +85C
ALT TA = +25C
ALT
22
24
26
28
30
32
824
829
834
839
844
849
824
829
834
839
844
849
OUTPUT POWER (dBm)
FREQUENCY (MHz)
FREQUENCY (MHz)
ACPR/ALT vs. OUTPUT POWER
MAX2251-16
NOISE POWER vs. FREQUENCY
POUT = +30dBm TA = -40C fIN = 836MHz fIN = 849MHz
MAX2251-17
NOISE POWER vs. FREQUENCY AMPS
POUT = +32dBm TA = -40C
MAX2251-18
-20 fIN = 836MHz -25 -30 ACPR/ALT (dBc) -35 -40 -45 -50 -55 -60 20 22 24 26 28 ALT ACPR
-100 -110 NOISE POWER (dBm/Hz) -120 -130 -140 -150 -160 -170
-100 -110 NOISE POWER (dBm/Hz) -120
fIN = 849MHz -130 -140 fIN = 836MHz -150 -160 -170 fIN = 824MHz
fIN = 824MHz
30
869
874
879
884
889
894
869
874
879
884
889
894
OUTPUT POWER (dBm)
FREQUENCY (MHz)
FREQUENCY (MHz)
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+2.8V, Single-Supply, Cellular-Band Linear Power Amplifier MAX2251
Typical Operating Characteristics (continued)
(MAX2251 EV kit, VCC = VMODE = V SHDN = +3.3V, fIN = 836MHz, TDMA modulation, TA = +25C, unless otherwise noted.)
EVM vs. OUTPUT POWER
MAX2251-19
EVM vs. FREQUENCY
POUT = +30dBm VSHDN = VMODE = VCC = +3.3V
MAX2251-20
POWER DETECTOR vs. OUTPUT POWER
MAX2251-21
5
5
3.0 POWER DETECTOR VOLTAGE (V) 2.5 2.0 1.5 1.0 0.5 0 TA = +85C TA = -40C TA = +25C
4 EVM (% RMS) EVM (% RMS)
4
3
3 TA = +25C 2 TA = +85C
2
1
1
0 20 22 24 26 28 30 OUTPUT POWER (dBm)
0 824 829 834 839 844 849 FREQUENCY (MHz)
0
5
10
15
20
25
30
OUTPUT POWER (dBm)
POWER DETECTOR vs. OUTPUT POWER
MAX2251-22
POWER DETECTOR vs. OUTPUT POWER
fIN = 836MHz SINGLE-TONE SINE WAVE VSHDN = VCC = +3.3V VMODE = VCC
MAX2251-23
3.0 POWER DETECTOR VOLTAGE (V) 2.5 2.0 1.5 1.0 0.5 0 0
VMODE = GND fIN = 836MHz SINGLE-TONE SINE WAVE
3.0 POWER DETECTOR VOLTAGE (V) 2.5 2.0
TA = -40C TA = +25C
TA = -40C 1.5 TA = +25C 1.0 TA = +85C 0.5 0
TA = +85C
5
10
15
20
25
30
0
5
10
15
20
25
30
OUTPUT POWER (dBm)
OUTPUT POWER (dBm)
6
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+2.8V, Single-Supply, Cellular-Band Linear Power Amplifier
Pin Description
PIN A1 A2, A3, A4, B2, C2, C4 B1 B3, B4 C1 C3 D1 D2 D3 D4 NAME BIAS2 GND PD_OUT OUT BIAS1 VCC VCC IN SHDN MODE FUNCTION Second Stage Bias Control. Connect an 11k resistor to GND to set the bias current for the second stage of the PA. Ground. Connect to the PC board ground plane with as low an inductance path as possible. 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 2s with a 4700pF capacitor. RF Output. Connect a pullup high-Q inductor to VCC. Requires matching network. Connect B3 and B4 together. First Stage Bias Control. Connect an external 47.5k resistor to ground to set the bias current for the driver stage. Driver Stage Supply Voltage. Connect a pullup inductor to VCC. The pullup inductor can be a PC board trace. Supply Voltage. Bypass to ground with 100pF and 0.01F capacitors. RF Input. Requires a highpass L-section impedance matching network. Shutdown Input. Drive logic low to place the device in shutdown mode. Drive logic high for normal operation. Mode Selection Input. Drive logic high for TDMA/AMPS mode. Drive logic low for higher gain AMPS operation.
MAX2251
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 consists of a driver stage and an output stage; both are independently biased using external resistors. The MAX2251 also features an integrated power detector.
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 output-matching circuit for highest efficiency. The MAX2251 EV kit uses a trace as a pullup inductor (approximately 2nH) for the interstage matching.
Bias Control
External resistors connected to C1 and A1 independently 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 47.5k and RBIAS2 is typically 11k. 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.
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 controlled 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
7
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-
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+2.8V, Single-Supply, Cellular-Band Linear Power Amplifier MAX2251
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. Mechanical stress performance is a greater consideration for a CSP. CSPs are attached through direct solder contact to the user's PC board, foregoing the inherent stress relief of a packaged-product lead frame. Solder joint contact integrity must be considered. Testing done to characterize 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 temperature. 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 recommendations are detailed in the UCSP application note, which can be found on Maxim's website at www.maxim-ic.com.
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.
8
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+2.8V, Single-Supply, Cellular-Band Linear Power Amplifier
Typical Operating Circuit
TOP VIEW OPTIONAL BIAS CURRENT THROTTLEBACK CONTROL
MAX2251
DAC RTB1 RTB2 PIN A1 INDICATOR VCC R4 11k BIAS2 A1 POWER DETECTOR GND B1 C9 4700pF PD_OUT BIAS1 C1 R3 47.5k VCC D1 C7 0.01F C6 100pF C3 9pF RFIN L1 4.7nH W = 18 L = 80 W = 18 L = 150 SHUTDOWN LOGIC INPUT MODE SELECT INPUT GND C2 B2 B3 OUT VCC C3 B4 OUT GND C4 C14 4.7pF W = 12 L = 125 FERRITE BEAD LOGIC AND BIAS IN D2 D3 SHDN MODE D4 W=3 L = 76 W = 35 L = 187 VCC C5 100pF C4 0.01F C12 10pF GND A2 GND A3 GND A4 C11 100pF L2 7.15nH W = 85 L = 315 C13 220pF C10 0.01F
MAX2251
RFOUT
VCC
ALL TRANSMISSION LINE UNITS ARE IN MILS.
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9
+2.8V, Single-Supply, Cellular-Band Linear Power Amplifier MAX2251
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.)
16L,UCSP.EPS
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 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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