19-1463; Rev 0; 5/99 ANUAL N KIT M EET IO T A U EVAL TA SH WS DA FOLLO +3.6V, 1W Autoramping Power Amplifier for 900MHz Applications Features 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 1µA. ♦ 800MHz to 1000MHz Operation 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. ♦ 47% Efficiency ♦ High Output Power at 836MHz +32.5dBm at +5.0V +30dBm at +3.6V +29dBm at +3.0V +28dBm at +2.7V ♦ +2.7V to +5.5V Single-Supply Operation ♦ Automatic Power-Up/Power-Down Ramp ♦ Direct On/Off Keying (OOK) without Intersymbol Interference or VCO Pulling ♦ 37dB Power-Control Range ♦ <1µA Supply Current in Shutdown Mode ♦ Small 20-Pin TSSOP Package with Heat Slug Ordering Information PART MAX2235EUP TEMP. RANGE PIN-PACKAGE -40°C to +85°C 20 TSSOP-EP Applications 900MHz ISM-Band Applications Two-Way Pagers TOP VIEW Analog Cellular Phones Microcellular GSM (Power Class 5) Wireless Data Networks Functional Diagram RAMP REF SHDN GC RFIN VCC VCC VCC 4 3 5 8, 9 11 19 MAX2235 BIAS RFIN 1 20 GC GND 2 19 SHDN VCC 3 18 GND VCC 4 VCC 5 VCC 12 Pin Configuration 20 RFOUT 15, 16 1 17 GND MAX2235 16 RFOUT GND 6 15 RFOUT GND 7 14 GND VCC 8 13 GND VCC 9 12 REF GND 10 11 RAMP TSSOP-EP VGA 2 GND 6, 7, 10 GND 13, 14, 17, 18, SLUG NOTE: THE GROUND OF THE OUTPUT STAGE IS CONNECTED TO THE UNDERSIDE METAL SLUG. GND NOTE: SOLDER UNDERSIDE OF METAL SLUG TO BOARD GND PLANE. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX2235 General Description MAX2235 +3.6V, 1W Autoramping Power Amplifier for 900MHz Applications 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 = +70°C) TSSOP (derate 80mW/°C above TA = +70°C) ..................6.4W Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10sec) .............................+300°C 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 = -40°C to +85°C, unless otherwise noted. Typical values are at VCC = +3.6V and TA = +25°C.) PARAMETER SYMBOL SHDN Logic High VIH SHDN Logic Low VIL CONDITIONS MIN TYP MAX 2.0 V 0.5 SHDN = GND 0.5 ISHDN 2.7V < VCC < 3.4V, SHDN = GND, TA = +55°C Standby Supply Current ISTBY VGC < 0.4 20 V SHDN = 2.0V 0.5 GC Input Current GC Open-Circuit Voltage 2 IINSHDN IGC VGCNOM 1 V SHDN < 0.5V -0.5 0.5 V SHDN < 0.5V, VGC < 0.4V -0.5 0.5 V SHDN > 2.3V, VGC > 0.6V -10 1.0 2.0 2.2 _______________________________________________________________________________________ V 10 Shutdown Supply Current SHDN Input Current UNITS 2.4 µA mA µA µA V +3.6V, 1W Autoramping Power Amplifier for 900MHz Applications (MAX2235 Evaluation Kit, GC = unconnected, PRFIN adjusted to give PRFOUT = +30dBm, fRFIN = 836MHz, VCC = V SHDN = +3.6V, TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER Operational Frequency Range (Note 2) SYMBOL CONDITIONS MIN 800 fRFIN VCC = 5.0V PRFOUT Average Supply Current 27.0 VCC = 3.0V, TA = TMIN to TMAX 25.5 Power Gain 28.7 47 PRFOUT = +30dBm 610 PRFIN adjusted to give PRFOUT = +24dBm 315 PRFIN = 0dBm, VGC adjusted to give PRFOUT = 24dBm 305 GP Gain-Control Range (Note 3) 1000 MHz dBm 28.0 PAE ICC UNITS 30.3 VCC = 3.0V (Note 2) VCC = 2.7V Power Added Efficiency MAX 32.5 VCC = 3.6V Minimum Output Power TYP 24 0.6V < VGC < 2.3V % mA 26 dB 37 dB Auto-Power Ramping-Up Maximum Slope (Note 4) dP/dt 1.6 mW/µs Auto-Power Ramping-Down Minimum Slope (Note 4) dP/dt -1.3 mW/µs Input VSWR VSWR Standby Mode Input VSWR Change ∆VSWR 50Ω source impedance 1.5:1 Input VSWR relative to input impedance in operating mode 1.5:1 Maximum Nonharmonic Spurious Output Due to Load Mismatch VCC = 2.7V to 5.5V, 6:1 VSWR at any phase angle Noise Power 30kHz BW at offset = 45MHz Harmonic Suppression (Note 5) PRFIN = +7dBm Off-Isolation PRFIN = 0dBm -60 dBc -90 dBm 30 38 dBc V SHDN = 0.5V 40 48 GC = GND 25 36 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. 0.068µF 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: _______________________________________________________________________________________ 3 MAX2235 AC ELECTRICAL CHARACTERISTICS Typical Operating Characteristics (MAX2235 Evaluation Kit, GC = unconnected, fRFIN = 836MHz, VCC = V SHDN = +3.6V, TA = +25°C, unless otherwise noted.) OUTPUT POWER vs. VOLTAGE AT GC PIN 300 200 TA = +25°C 20 TA = +85°C 10 0 100 -10 0 -20 10 15 20 25 30 35 0 0.5 1.0 MAX2235 toc03 VCC = +2.7V 20 15 10 0 -25 2.5 TA = +85°C 15 10 -20 -15 -10 -5 0 5 2nd -20 3rd -30 -40 -15 -10 5 20 PRFIN = -13dBm 15 10 PRFIN = -21dBm -5 0 5 0 820 10 825 830 835 840 845 850 INPUT POWER (dBm) INPUT FREQUENCY (MHz) EFFICIENCY vs. OUTPUT POWER POWER GAIN vs. OUTPUT POWER POWER GAIN vs. OUTPUT POWER AND TEMPERATURE VCC = +5.0V 35 POWER GAIN (dB) VCC = +2.7V VCC = +3.0V 30 20 VCC = +5.0V 10 10 15 20 35 30 40 5 40 25 OUTPUT POWER (dBm) 30 35 TA = -40°C 30 VCC = +3.6V 25 20 VCC = +2.7V VCC = +3.0V 15 25 TA = +25°C 20 TA = +85°C 15 10 10 5 5 0 855 MAX2235 toc09 50 40 MAX2235 toc07 VCC = +3.6V 10 MATCHED AT 836MHz INPUT POWER (dBm) 60 0 -20 0 PRFIN = -5dBm 25 5 -60 -25 10 -5 PRFIN = +3dBm 30 POWER GAIN (dB) 0 -25 -10 OUTPUT POWER vs. FREQUENCY -50 5 -15 35 MAX2235 toc05 -10 HARMONIC POWER (dBm) 25 -20 INPUT POWER (dBm) 0 MAX2235 toc04 TA = +25°C 20 2.0 SECOND AND THIRD HARMONICS vs. INPUT POWER TA = -40°C 30 1.5 VGC (V) 35 OUTPUT POWER (dBm) 25 MAX2235 toc06 5 OUTPUT POWER (dBm) 0 OUTPUT POWER vs. INPUT POWER AND TEMPERATURE 4 VCC = +3.6V VCC = +3.0V 5 OUTPUT POWER (dBm) 0 VCC = +5.0V 30 MAX2235 toc08 ICC (mA) 400 TA = -40°C 30 OUTPUT POWER (dBm) TA = +85°C 500 PRFIN = 0dBm OUTPUT POWER vs. INPUT POWER 35 OUTPUT POWER (dBm) TA = -40°C TA = +25°C 600 40 MAX2235 toc01 700 MAX2235 toc02 SUPPLY CURRENT vs. OUTPUT POWER EFFICIENCY (%) MAX2235 +3.6V, 1W Autoramping Power Amplifier for 900MHz Applications 0 5 10 15 20 25 OUTPUT POWER (dBm) 30 35 0 0 5 10 15 20 25 OUTPUT POWER (dBm) _______________________________________________________________________________________ 30 35 +3.6V, 1W Autoramping Power Amplifier for 900MHz Applications FALL TIME vs. RAMPING CAPACITANCE RISE TIME vs. RAMPING CAPACITANCE FULL POWER = +30dBm 1000 FULL POWER = +20dBm FALL TIME (µs) 1000 RISE TIME (µs) MAX2235 toc11 FULL POWER = +10dBm 1200 1200 MAX2235 toc10 1400 800 600 800 FULL POWER = +10dBm 600 400 400 FULL POWER = +20dBm FULL POWER = +30dBm 200 200 0 0 0 20 40 60 80 100 0 120 20 40 60 80 100 120 CAPACITANCE (nF) CAPACITANCE (nF) Pin Description PIN NAME FUNCTION 1 RFIN RF Input. A DC blocking capacitor in series with RFIN is required. The value of the capacitor depends on the operating frequency. 2 GND GND connection for the input stage (variable-gain amplifier). Connect to the circuit board ground plane with a separate low-inductance path (via). 3 VCC Supply Voltage Input for the Input Stage. Bypass with its own 100pF low-inductance capacitor to GND. 4 VCC 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. 5 VCC Supply Voltage Input for the Input Stage. Bypass with its own 22pF low-inductance capacitor to pins 6 and 7. 6, 7, 10 GND GND Connection for the Second-Stage Amplifier (driver). Connect to the circuit board ground plane with a separate low-inductance path (via). 8 VCC Supply Voltage Input for the Second Stage. Bypass with its own 220pF and 1000pF low-inductance capacitors to GND. 9 VCC Supply Voltage Input for the Second Stage. Connect to pin 8. 11 RAMP Power Ramp Pin. Connect a capacitor between RAMP and REF to provide a gradual linear power-up/down ramp. See Detailed Description. 12 REF Reference Voltage for RAMP Capacitor. The reference is internally set to 1.9V. 13, 14, 17, 18, SLUG GND 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. 15 RFOUT 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. 16 RFOUT Power Amplifier Output. Connect to pin 15. 19 SHDN 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. 20 GC 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 MAX2235 Typical Operating Characteristics (continued) (MAX2235 Evaluation Kit, GC = unconnected, fRFIN = 836MHz, VCC = V SHDN = +3.6V, TA = +25°C, unless otherwise noted.) +3.6V, 1W Autoramping Power Amplifier for 900MHz Applications MAX2235 Typical Operating Circuit JU2 470pF 8.2nH 100pF J1 1 SMA 2 3 VCC 4 1000pF 5 22pF 100pF 100pF 6 7 8 VCC 100pF 1000pF RFIN GC GND SHDN VCC VCC GND MAX2235 GND VCC RFOUT GND RFOUT GND GND VCC GND VCC 1000pF 20 3 2 19 17 16 VCC 1500pF * 68pF J2 15 14 JU1 1000pF 1 470pF 18 SMA 47pF 11pF 13 9 V CC REF 12 10 GND RAMP 11 0.068µF J3 VCC J4 0.01µF 1µF * 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 Second- and Third-Stage Matching 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 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. 6 _______________________________________________________________________________________ +3.6V, 1W Autoramping Power Amplifier for 900MHz Applications 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. Table 1. Operating Modes SHDN GC >2.0V >0.6V On >2.0V <0.4V Standby <0.5V Don’t care Shutdown MODE 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. 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. _______________________________________________________________________________________ 7 MAX2235 Third Stage (Power Stage) This last stage delivers 30dBm to a 50Ω 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. +3.6V, 1W Autoramping Power Amplifier for 900MHz Applications TSSOP.EPS MAX2235 Package Information 8 _______________________________________________________________________________________