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19-1463; Rev 0; 5/99
NUAL KIT MA UATION TA SHEET EVAL WS DA FOLLO
+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications
Features
o 800MHz to 1000MHz Operation o High Output Power at 836MHz +32.5dBm at +5.0V +30dBm at +3.6V +29dBm at +3.0V +28dBm at +2.7V o +2.7V to +5.5V Single-Supply Operation o Automatic Power-Up/Power-Down Ramp o Direct On/Off Keying (OOK) without Intersymbol Interference or VCO Pulling o 37dB Power-Control Range o 47% Efficiency o <1A Supply Current in Shutdown Mode o Small 20-Pin TSSOP Package with Heat Slug
General Description
The MAX2235 low-voltage, silicon RF power amplifier (PA) is designed for use in the 900MHz frequency band. It operates directly from a single +2.7V to +5.5V supply, making it suitable for use with 3-cell NiCd or 1-cell Li-Ion batteries. The device delivers +30dBm (1W) typical output power from a +3.6V supply or +28dBm from a +2.7V supply. The MAX2235's gain is adjustable over a 37dB range. A power-control pin controls gain and bias to maintain optimum efficiency, even at lower output power levels, thus extending the operating life of the battery. At +30dBm output power, efficiency is typically 47%. An additional power-saving feature is a shutdown mode that typically reduces supply current below 1A. A key feature of this PA is its autoramping capability. During turn-on and turn-off periods, the RF envelope is controlled to approximate a raised cosine on the rising and falling edge, thereby minimizing transient noise and spectral splatter. The ramp time is set by selecting the value of an external capacitor. The MAX2235 is intended for use in constant envelope applications such as AMPS, two-way paging, or FSKbased communications in the 900MHz ISM band. The device is available in a thermally enhanced 20-pin TSSOP package with a heat slug.
MAX2235
Ordering Information
PART MAX2235EUP TEMP. RANGE -40C to +85C PIN-PACKAGE 20 TSSOP-EP
Applications
900MHz ISM-Band Applications Two-Way Pagers Analog Cellular Phones Microcellular GSM (Power Class 5) Wireless Data Networks
TOP VIEW
RFIN 1 GND 2 VCC 3
Pin Configuration
20 GC 19 SHDN 18 GND 17 GND
Functional Diagram
VCC 4 RAMP REF SHDN GC 11 12 19 20 BIAS VCC VCC 3 5 VCC 8, 9
VCC 4 VCC 5 GND 6 GND 7
MAX2235
16 RFOUT 15 RFOUT 14 GND 13 GND 12 REF 11 RAMP
MAX2235
VCC 8 VCC 9
RFOUT 15, 16
GND 10
RFIN
1 VGA 2 GND 6, 7, 10 GND 13, 14, 17, 18, SLUG GND
TSSOP-EP
NOTE: THE GROUND OF THE OUTPUT STAGE IS CONNECTED TO THE UNDERSIDE METAL SLUG.
NOTE: SOLDER UNDERSIDE OF METAL SLUG TO BOARD GND PLANE.
________________________________________________________________ Maxim Integrated Products
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+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications MAX2235
ABSOLUTE MAXIMUM RATINGS
VCC to GND ...........................................................-0.3V to +6.5V SHDN to GND.............................................-0.3V to (VCC + 0.3V) GC to GND .................................................-0.3V to (VCC + 0.3V) RF Input Power .................................................+13dBm (20mW) Maximum Load Mismatch without Damage, VCC = +2.7V to +3.4V, Any Load Phase Angle, Any Duration.......................................................................20:1 Maximum Load Mismatch without Damage, VCC = +3.4V to +5.5V, Any Load Phase Angle, Any Duration.........................................................................8:1 Continuous Power Dissipation (TA = +70C) TSSOP (derate 80mW/C above TA = +70C) ..................6.4W Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+300C
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 = +2.7V to +5.5V, GC = RAMP = REF = unconnected, no input signal applied, TA = -40C to +85C, unless otherwise noted. Typical values are at VCC = +3.6V and TA = +25C.) PARAMETER SHDN Logic High SHDN Logic Low Shutdown Supply Current Standby Supply Current SHDN Input Current GC Input Current GC Open-Circuit Voltage SYMBOL VIH VIL SHDN = GND ISHDN ISTBY IINSHDN IGC VGCNOM 2.7V < VCC < 3.4V, SHDN = GND, TA = +55C VGC < 0.4 V SHDN = 2.0V V SHDN < 0.5V V SHDN < 0.5V, VGC < 0.4V V SHDN > 2.3V, VGC > 0.6V -0.5 -0.5 -10 2.0 2.2 0.5 CONDITIONS MIN 2.0 0.5 10 1 20 0.5 0.5 0.5 1.0 2.4 A mA A A V TYP MAX UNITS V V
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+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications
AC ELECTRICAL CHARACTERISTICS
(MAX2235 Evaluation Kit, GC = unconnected, PRFIN adjusted to give PRFOUT = +30dBm, fRFIN = 836MHz, VCC = V SHDN = +3.6V, TA = +25C, unless otherwise noted.) (Note 1) PARAMETER Operational Frequency Range (Note 2) SYMBOL fRFIN VCC = 5.0V VCC = 3.6V Minimum Output Power PRFOUT VCC = 3.0V (Note 2) VCC = 3.0V, TA = TMIN to TMAX VCC = 2.7V Power Added Efficiency PAE PRFOUT = +30dBm Average Supply Current ICC PRFIN adjusted to give PRFOUT = +24dBm PRFIN = 0dBm, VGC adjusted to give PRFOUT = 24dBm 24 0.6V < VGC < 2.3V dP/dt dP/dt VSWR VSWR 50 source impedance Input VSWR relative to input impedance in operating mode VCC = 2.7V to 5.5V, 6:1 VSWR at any phase angle 30kHz BW at offset = 45MHz PRFIN = +7dBm PRFIN = 0dBm V SHDN = 0.5V GC = GND 30 40 25 27.0 25.5 28.0 47 610 315 305 26 37 1.6 -1.3 1.5:1 1.5:1 dB dB mW/s mW/s mA % CONDITIONS MIN 800 32.5 30.3 28.7 dBm TYP MAX 1000 UNITS MHz
MAX2235
Power Gain Gain-Control Range (Note 3) Auto-Power Ramping-Up Maximum Slope (Note 4) Auto-Power Ramping-Down Minimum Slope (Note 4) Input VSWR Standby Mode Input VSWR Change Maximum Nonharmonic Spurious Output Due to Load Mismatch Noise Power Harmonic Suppression (Note 5) Off-Isolation
GP
-60 -90 38 48 36
dBc dBm dBc dB
Guaranteed by design and characterization. For optimum performance at a given frequency, design the output matching network for maximum output power. Gain is monotonic with VGC. 0.068F capacitor from RAMP to REF. Time is measured from SHDN low-to-high transition to +29dBm output power, or from SHDN high-to-low transition to -25dBm output power. Note 5: Harmonics measured on the evaluation kit, which provides some harmonic attenuation in addition to the rejection provided by the IC. The combined suppression is specified. Note 1: Note 2: Note 3: Note 4:
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+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications MAX2235
Typical Operating Characteristics
(MAX2235 Evaluation Kit, GC = unconnected, fRFIN = 836MHz, VCC = V SHDN = +3.6V, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. OUTPUT POWER
MAX2235 toc01
OUTPUT POWER vs. VOLTAGE AT GC PIN
MAX2235 toc02
OUTPUT POWER vs. INPUT POWER
VCC = +5.0V VCC = +3.6V VCC = +3.0V VCC = +2.7V
MAX2235 toc03
700 600 500 ICC (mA) 400 300 200 100 0
TA = -40C TA = +25C TA = +85C
40 30
35 30 OUTPUT POWER (dBm) 25 20 15 10 5
PRFIN = 0dBm
TA = -40C
OUTPUT POWER (dBm)
20 10 0 -10 -20 0 0.5 1.0 1.5
TA = +25C TA = +85C
0
5
10
15
20
25
30
35
2.0
2.5
OUTPUT POWER (dBm)
VGC (V)
0 -25
-20
-15
-10
-5
0
5
10
INPUT POWER (dBm)
OUTPUT POWER vs. INPUT POWER AND TEMPERATURE
MAX2235 toc04
SECOND AND THIRD HARMONICS vs. INPUT POWER
MAX2235 toc05
OUTPUT POWER vs. FREQUENCY
PRFIN = +3dBm PRFIN = -5dBm PRFIN = -13dBm MATCHED AT 836MHz
MAX2235 toc06
35 TA = -40C 30 OUTPUT POWER (dBm) 25 20 15 10 5 0 -25 TA = +85C TA = +25C
0 -10 HARMONIC POWER (dBm) 2nd -20 3rd -30 -40 -50 -60 -25
35 30 OUTPUT POWER (dBm) 25 20 15 10 5 PRFIN = -21dBm
-20
-15
-10
-5
0
5
10
-20
-15
-10
-5
0
5
10
0 820
825
830
835
840
845
850
855
INPUT POWER (dBm)
INPUT POWER (dBm)
INPUT FREQUENCY (MHz)
EFFICIENCY vs. OUTPUT POWER
MAX2235 toc07
POWER GAIN vs. OUTPUT POWER
VCC = +5.0V 35 30 POWER GAIN (dB) 25 20 15 10 VCC = +2.7V VCC = +3.6V VCC = +3.0V POWER GAIN (dB)
MAX2235 toc08
POWER GAIN vs. OUTPUT POWER AND TEMPERATURE
35 30 25 20 15 10 5 TA = +25C TA = +85C TA = -40C
MAX2235 toc09
60 50 EFFICIENCY (%) 40 VCC = +3.0V 30 20 10 0 VCC = +5.0V VCC = +3.6V VCC = +2.7V
40
40
5 0 0 5 10 15 20 25 30 35
0
0
5
10
15
20
25
30
35
0
5
10
15
20
25
30
35
OUTPUT POWER (dBm)
OUTPUT POWER (dBm)
OUTPUT POWER (dBm)
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+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications
Typical Operating Characteristics (continued)
(MAX2235 Evaluation Kit, GC = unconnected, fRFIN = 836MHz, VCC = V SHDN = +3.6V, TA = +25C, unless otherwise noted.)
FALL TIME vs. RAMPING CAPACITANCE
MAX2235 toc10
MAX2235
RISE TIME vs. RAMPING CAPACITANCE
1400 1200 1000 RISE TIME (s) 800 600 400 200 0 0 20 40 60 80 100 120 FULL POWER = +30dBm 200 0 FULL POWER = +10dBm FULL POWER = +20dBm FALL TIME (s) 800 600 400 1200 1000
FULL POWER = +30dBm
FULL POWER = +10dBm
FULL POWER = +20dBm
0
20
40
60
80
100
120
CAPACITANCE (nF)
CAPACITANCE (nF)
Pin Description
PIN 1 2 3 4 5 6, 7, 10 8 9 11 12 13, 14, 17, 18, SLUG 15 16 19 20 NAME RFIN GND VCC VCC VCC GND VCC VCC RAMP REF GND FUNCTION RF Input. A DC blocking capacitor in series with RFIN is required. The value of the capacitor depends on the operating frequency. GND connection for the input stage (variable-gain amplifier). Connect to the circuit board ground plane with a separate low-inductance path (via). Supply Voltage Input for the Input Stage. Bypass with its own 100pF low-inductance capacitor to GND. Supply Voltage Input for Bias Circuitry. Bypass with its own 100pF low-inductance capacitor and a 1000pF capacitor to GND, to minimize RF signal coupling into the bias circuits. Supply Voltage Input for the Input Stage. Bypass with its own 22pF low-inductance capacitor to pins 6 and 7. GND Connection for the Second-Stage Amplifier (driver). Connect to the circuit board ground plane with a separate low-inductance path (via). Supply Voltage Input for the Second Stage. Bypass with its own 220pF and 1000pF low-inductance capacitors to GND. Supply Voltage Input for the Second Stage. Connect to pin 8. Power Ramp Pin. Connect a capacitor between RAMP and REF to provide a gradual linear power-up/down ramp. See Detailed Description. Reference Voltage for RAMP Capacitor. The reference is internally set to 1.9V. GND Connection for the Power Stage. Solder the slug to the circuit board ground plane. Connect pins 13, 14, 17, and 18 to the slug with a straight board trace under the chip. Power Amplifier Output. See Typical Operating Circuit for an example of a matching network, which provides optimal output power at 836MHz. Connect to pin 16. Power Amplifier Output. Connect to pin 15. Shutdown Pin. Drive SHDN low to turn the device off. Drive above 2.0V to turn the device on. Drive V SHDN > 2.0V and VGC < 0.4V for standby mode. Gain-Control Pin. Apply VGC between 0.6V and 2.3V to control the output power with a monotonic dB/V relationship. See the Typical Operating Characteristics for a typical relationship. _______________________________________________________________________________________ 5
RFOUT RFOUT SHDN GC
MAX2235 toc11
+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications MAX2235
Typical Operating Circuit
JU2 J1 SMA 100pF 8.2nH 1 2 VCC 1000pF 100pF 100pF 22pF 3 4 5 6 7 8 VCC 1000pF J3 VCC J4 0.01F 1F 100pF RFIN GND VCC VCC VCC GND GND VCC GC SHDN GND 20 19 18 17 16 15 14 13 47pF 11pF 470pF 3 2 1000pF 1 VCC JU1 470pF 1000pF VCC
MAX2235
GND RFOUT RFOUT GND GND
*
1500pF
68pF J2 SMA
9V CC 10 GND
REF 12 RAMP 11 0.068F
* VALUE OF OUTPUT INDUCTOR DEPENDS ON APPLICATION.
Detailed Description
The MAX2235 power amplifier (PA) operates over a wide frequency range of 800MHz to 1000MHz. The signal path consists of three stages: the input stage, the driver stage, and the power stage. There are matching circuits between the first and second stages, and between the second and third stages. The bias circuits process external commands to control the device's power-up/down and the gain of the PA.
stage operates in class A and remains on in standby mode to ensure that the VSWR at the input does not vary more than 1.5:1 compared with normal operation. The input stage typically requires an external inductor to achieve an optimum input VSWR.
Second Stage (Driver)
The driver produces a signal large enough to drive the power stage into saturation. The driver stage operates in Class C and is off during standby.
Input Stage
The first stage is a variable-gain amplifier with 37dB gain-control range. The input transistor acts as a transconductor with constant bias current. Gain control is achieved by steering the signal current from the input transistor to the first output matching network (to drive the second stage) or to a separate supply pin. This
Second- and Third-Stage Matching
The interstage matching networks provide optimal loading and power transfer. The circuits are on-chip to save board space. The bandwidths of the matching networks allow the PA to operate over a wide frequency range.
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+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications
Third Stage (Power Stage)
This last stage delivers 30dBm to a 50 load. It operates in Class E to achieve a high power-added efficiency (PAE). Proper output matching is required for optimal output power. The output of the power stage requires a low-series-resistance pull-up inductor with a minimum current rating of 1.5A. See the Typical Operating Circuit for an example of an output matching circuit.
Table 1. Operating Modes
SHDN >2.0V >2.0V <0.5V GC >0.6V <0.4V Don't care MODE On Standby Shutdown
MAX2235
Board Assembly Precaution
Solder the underside metal slug evenly to the board ground plane for optimal performance. Fill all vias in the area under the slug. For maximum power gain and saturated output power, ensure that the entire slug makes contact with the board ground.
Biasing and Power Control
SHDN, GC, RAMP, and REF are bias and power-control pins. Drive SHDN below 0.5V to turn off the entire chip, and drive SHDN above 2.0V to turn on the device. When SHDN is high, a VGC from 0.6V to 2.3V continuously controls the gain in the first stage (VGA) and the output power. Drive GC below 0.4V to put the device in standby mode with only the first stage on. If GC is unconnected and V SHDN > 2.0V, the device is set to maximum gain. Table 1 summarizes these operating modes.
Chip Information
TRANSISTOR COUNT: 668
Power Ramping Control
A capacitor connected between RAMP and REF controls the output power rise/fall time to reduce transient noise when SHDN turns the device on and off. Because the ramp is approximately a raised cosine, this device can be used in direct On/Off Keying (OOK) applications with minimum intersymbol interference. The value of the ramping capacitor is determined from the Rise/Fall Time vs. Ramping Capacitance curves in the Typical Operating Characteristics.
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+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications MAX2235
Package Information
TSSOP.EPS
8
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