19-1093; Rev 2; 1/98 UAL MAN ET KIT E N H O S I T A LUA DAT EVA LOWS L O F Low-Voltage, Silicon RF Power Amplifier/Predriver ____________________________Features The MAX2430 is a versatile, silicon RF power amplifier that operates directly from a 3V to 5.5V supply, making it suitable for 3-cell NiCd or 1-cell lithium-ion battery applications. It is designed for use in the 800MHz to 1000MHz frequency range and, at 915MHz, can produce +21dBm (125mW) of output power with greater than 32dB of gain at VCC = 3.6V. A unique shutdown function provides an off supply current of typically less than 1µA to save power during “idle slots” in time-division multiple-access (TDMA) transmissions. An external capacitor sets the RF output power envelope ramp time. External power control is also possible over a 15dB range. The amplifier’s input is matched on-chip to 50Ω. The output is an open collector that is easily matched to a 50Ω load with few external components. The MAX2430 is ideal as a driver amplifier for portable and mobile telephone systems, or as a complete power amplifier for other low-cost applications, such as those in the 915MHz spread-spectrum ISM band. It is fabricated with Maxim’s high-frequency bipolar transistor process and is available in a thermally enhanced, 16-pin narrow SO and miniature 16-pin PwrQSOP packages with heat slug. ♦ Operates Over the 800MHz to 1000MHz Frequency Range ♦ Delivers 125mW at 915MHz from +3.6V Supply (100mW typical from +3.0V supply) ♦ Operates Directly from 3-Cell NiCd or 1-Cell Lithium-Ion Battery ♦ Over 32dB Power Gain ♦ RF Power Envelope Ramping is Programmable with One External Capacitor ♦ Input Matched to 50Ω (VSWR < 2:1) ♦ 15dB Output Power Control Range ♦ 1µA Typical Shutdown Current Ordering Information TEMP. RANGE PIN-PACKAGE MAX2430IEE PART -20°C to +85°C 16 PwrQSOP MAX2430ISE -20°C to +85°C 16 Narrow SO ________________________Applications Digital Cordless Phones 915MHz ISM-Band Applications Two-Way Pagers Wireless LANs Cellular Phones AM and FM Analog Transmitters Pin Configuration Functional Diagram VCC1 7 SHDN GND1 RFIN VCC2 8 TOP VIEW BIAS 10 2 MASTER BIAS OUTPUT BIAS 6 4 RFOUT DRIVER GAIN GND2 1, 15, 16 GND3 NOTE: MAX2430IEE (PwrQSOP PACKAGE) UNDERSIDE METAL SLUG MUST BE SOLDERED TO PCB GROUND PLANE. 16 GND3 SHDN 2 15 GND3 GND2 3 9 MAX2430 3, 5 GND3 1 11, 12, 13, 14 GND4 RFIN 4 14 GND4 MAX2430 13 GND4 GND2 5 12 GND4 GND1 6 11 GND4 VCC1 7 10 BIAS VCC2 8 9 RFOUT Narrow SO/PwrQSOP ________________________________________________________________ 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. MAX2430 ________________General Description MAX2430 Low-Voltage, Silicon RF Power Amplifier/Predriver ABSOLUTE MAXIMUM RATINGS VCC1, VCC2 ..........................................................................+6V SHDN, BIAS...................................................-0.3V, (VCC + 0.3V) RFIN.............................................................................-0.3V, +2V PRFIN ..................................................................................-3dBm Continuous Power Dissipation (TA = +70°C) PwrQSOP (derate 20mW/°C above +70°C) ......................1.6W Narrow SO (derate 20mW/°C above +70°C) ....................1.6W Operating Temperature Range ...........................-20°C to +85°C Storage Temperature Range .............................-65°C to +160°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 = VCC1 = VCC2 = RFOUT = 3V to 5.5V, GND1 = GND2 = GND3 = GND4 = 0V, SHDN = 2.2V, BIAS = open, RFIN = open, TA = -20°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL Supply Voltage Range VCC Supply Current ICC Shutdown Supply Current ICC(OFF) BIAS Pin Voltage VBIAS SHDN High Input VSHDN(HI) SHDN Low Input VSHDN(LO) SHDN Bias Current ISHDN CONDITIONS MIN TYP 3 No RF input applied, VCC = 5.5V SHDN = low BIAS pin open MAX UNITS 5.5 V 52 70 mA 1 10 µA 2.2 2.2 V VCC SHDN = VCC V 0.4 V 18 µA AC ELECTRICAL CHARACTERISTICS (MAX2430 EV kit, f = 915MHz, VCC = 3.6V, SHDN = VCC, RFOUT matched to 50Ω resistive load, output measurements taken after matching network, TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL Frequency Range POUT at 1dB Compression P1dB Power Gain GP Output IM3 OIM3 CONDITIONS MIN TYP (Note 2) 800 VCC = 3.6V 20 21.4 VCC = 3.0V 19 20.4 MAX2430ISE 32 34 MAX2430IEE 31 33 PRFIN = -20dBm MAX UNITS 1000 MHz dBm dB f1 = 915MHz, f2 = 916MHz, POUT per tone = 14dBm -30 dBc 2nd Harmonic POUT = P1dB -26 dBc 3rd Harmonic POUT = P1dB -40 dBc Efficiency Supply Current η POUT = P1dB 24 % ICCRF POUT = P1dB 160 mA RFIN connected to 50Ω source 2:1 Maximum Input VSWR VSWRIN Maximum Output Load Mismatch VSWROUT VCC = 3V to 5.5V, PRFIN ≤ -10dBm (Note 3) 8:1 Maximum Output Load Mismatch for Stability VSWROUT VCC = 3V to 5.5V, PRFIN ≤ -12dBm (Note 4) 6:1 Noise Figure 2 NF 7 _______________________________________________________________________________________ dB Low-Voltage, Silicon RF Power Amplifier/Predriver MAX2430 AC ELECTRICAL CHARACTERISTICS (continued) (MAX2430 EV kit, f = 915MHz, VCC = 3.6V, SHDN = VCC, output matched to 50Ω resistive load, output measurements taken after matching network, TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS SHDN = 0.4V, PIN = -10dBm RFIN to RFOUT Isolation Turn-On/Off Times MIN TYP MAX UNITS MAX2430ISE 50 dB MAX2430IEE 47 dB BIAS pin capacitor C1 = 120pF 1 BIAS pin capacitor C1 = 2.2nF 10 µs Note 1: Minimum and maximum parameters are guaranteed by design. Note 2: For optimum performance at a given frequency, output matching network must be designed for maximum output power. See Applications Information section. Operation outside this frequency range is possible but has not been characterized. Note 3: No damage to the device. Note 4: All non-harmonically related outputs are more than 60dB below the desired signal for any electrical phase. __________________________________________Typical Operating Characteristics (MAX2430EVKIT-SO, f = 915MHz, VCC = 3.6V, SHDN = VCC, output matched to 50Ω resistive load, output measurements taken after matching network, TA = +25°C, unless otherwise noted.) POUT @ PIN = -12dBm 200 20 ICC 5 50 0 0 -25 -20 -15 PIN (dBm) -10 ICC @ PIN = -17dBm 10 5 -20 -5 -5.5V 3.6V 3V 0 OUTPUT POWER AND GAIN vs. TEMPERATURE (NORMAL OPERATING MODE) 3.6V 15 5 -25 INPUT IMPEDANCE (Ω) VSWR 3V 2.5 5V 1.5 15 40 60 TEMPERATURE (°C) 80 100 -10 -5 50 0 IMAG -50 -100 1.0 20 -15 PIN (dBm) REAL 100 20 -20 150 MAX2430-05 4.0 2.0 0 3V RF INPUT IMPEDANCE vs. FREQUENCY 3.0 PIN = -12dBm POUT -20 POUT 10 3.5 5.5V 3.6V 3.0V 5.5V 20 50 100 GAIN 30 25 POUT (dBm) 80 100 3.6V 25 INPUT VSWR vs. FREQUENCY MAX1691-4a GAIN (dB) 35 20 40 60 TEMPERATURE (°C) 150 5.5V 3V 30 ICC (mA) 100 10 ICC @ PIN = -12dBm 15 GAIN 35 POUT @ PIN = -17dBm 150 POUT (dBm) POUT 15 40 200 20 3.6V 3V ICC (mA) 5.5V POUT (dBm) 250 25 MAX2430-03 250 3.6V 3V GAIN (dB) 5.5V POUT (dBm) 25 OUTPUT POWER AND GAIN vs. INPUT POWER OUTPUT POWER AND CURRENT vs. TEMPERATURE MAX2430-06 OUTPUT POWER AND CURRENT vs. INPUT POWER -150 400 600 800 1000 1200 1400 FREQUENCY (MHz) 1600 400 800 1200 1600 FREQUENCY (MHz) _______________________________________________________________________________________ 2000 3 _____________________________Typical Operating Characteristics (continued) (MAX2430EVKIT-SO, f = 915MHz, VCC = 3.6V, SHDN = VCC, output matched to 50Ω resistive load, output measurements taken after matching network, TA = +25°C, unless otherwise noted.) -10 -20 -30 – -54.0 dBm -40 – -50 – -60 1 2 3 4 5 TA = -20°C -30 TA = +25°C -35 TA = +85°C IM5 -40 -45 -50 TA = -20°C -55 TA = +25°C -60 TA = +85°C -10 HARMONIC NUMBER -5 0 5 10 15 -55 -60 100 5.5V -65 IM5 -70 -5 0 25 -15 0V SHDN 0V 3V 1V/div 2.0 0 2.4 VCC = 3.0V BIAS CAPACITOR = 1nF POUT = 20.4dBm (110mW) tON ≈ tOFF = 5µs 5µs/div BIAS PIN VOLTAGE (V) 4 5 10 15 OUTPUT POWER PER TONE (dBm) 75 50 1.6 IM3 125 TA = +85°C 1.2 3.0V 3.6V -50 150 -5 0.8 -45 -10 3V 175 ICC (mA) OUTPUT POWER (dBm) ICC 5.5V -40 RF OUTPUT ENVELOPE CHARACTERISTICS vs. SHUTDOWN CONTROL POUT 200 PIN = -12dBm VCC = 3.6V 20 TA = +85°C 15 TA = -20°C 10 TA = +25°C 5 TA = -20°C 0 TA = +25°C 0.4 -35 20 OUTPUT POWER AND SUPPLY CURRENT vs. EXTERNAL CONTROL VOLTAGE -10 -30 OUTPUT POWER PER TONE (dBm) 25 3.0V 3.6V -25 -75 -65 -15 6 -20 MAX2430-09 -25 IM3 _______________________________________________________________________________________ MAX2430-10 0 VCC = 3.6V f1 = 915MHz f2 = 916MHz INTERMODULATION DISTORTION (dBc) 10 -20 MAX2430-08 VCC = 3.0V +20.4dBm f1 = 915MHz POUT = +20.4dBm VCC = 3.6V VCC = 4.5V VCC = 5.5V – -4.93dBm – -16.7dBm -47.6 – dBm – -35.3dBm 20 – INTERMODULATION DISTORTION (dBc) MAX2430-07 30 INTERMODULATION DISTORTION vs. OUTPUT POWER AND VCC INTERMODULATION DISTORTION vs. OUTPUT POWER AND TEMPERATURE OUTPUT POWER AND HARMONICS OUTPUT SPECTRUM (dBm) MAX2430 Low-Voltage, Silicon RF Power Amplifier/Predriver 20 Low-Voltage, Silicon RF Power Amplifier/Predriver PIN NAME FUNCTION 1, 15, 16 GND3 Driver Stage Ground. Connect directly to ground plane. 2 SHDN Shutdown Input (TTL/CMOS) 3, 5 GND2 Input Stage Ground. Connect directly to ground plane. 4 RFIN RF Input. Internally matched to 50Ω. Requires series DC-blocking capacitor. 6 GND1 Bias Circuitry Ground. Connect directly to ground plane. 7 VCC1 Bias Circuitry Supply. Connect to supply. Bypass with 1000pF capacitor. 8 VCC2 Driver Stage Output. Connect to supply through inductor (see Applications Information). 9 RFOUT 10 BIAS Output Stage Bias Pin. Connect capacitor to GND to control start-up power envelope. Drive directly for power control (see Applications Information). 11–14 GND4 Output Stage Ground. Connect directly to ground plane. Output Transistor. Open Collector. Note: MAX2430IEE (PwrQSOP package) underside metal slug must be soldered to PCB ground plane. Detailed Description The MAX2430 consists of a large power output transistor driven by a capacitively coupled driver stage (see Functional Diagram ). The driver and front-end gain stages are DC-connected and biased on-chip from the master bias cell. The master bias cell also controls the output stage bias circuit. The input impedance at the RFIN pin is internally matched to 50Ω, while the output stage must be tuned and filtered externally for any narrow-band frequency range of interest between 800MHz and 1000MHz. The driver amplifier requires an external inductor at the VCC2 pin to provide DC bias and proper matching to the output stage. This inductor’s value depends on the package type and frequency range of operation; typically it will vary between 5nH and 22nH. The output transistor at the RFOUT pin requires an external RF choke inductor connected to the supply for DC bias, and a matching network to transform the desired external load impedance to the optimal internal load impedance of approximately 15Ω. The MAX2430 includes a unique shutdown feature. The TTL/CMOS-compatible SHDN input allows the device to be shut down completely without the use of any external components. Also, the RF output power envelope ramp time can be programmed with a single external capacitor connected between the BIAS pin and ground. Pulling the shutdown pin (SHDN) high powers on the master bias circuit, which in turn charges the external capacitor tied to the BIAS pin using a controlled current. The voltage at BIAS controls the output power level, which ramps until the BIAS pin is internally clamped to approximately 2.2V. The envelope rampdown time is controlled in a similar manner when the SHDN pin is pulled low. Variable output power control over a 15dB range is also possible by forcing the voltage on the BIAS pin externally from 0.6V to 2.4V. During the on state (SHDN = high), the power-supply bias current is typically 52mA with no RF applied to the input. During the off state (SHDN = low), the supply current is typically reduced to less than 1µA. _______________________________________________________________________________________ 5 MAX2430 _____________________Pin Description MAX2430 Low-Voltage, Silicon RF Power Amplifier/Predriver VCC VCC 1nF 2.2nF 1nF L2* VCC1 ON OFF VCC2 LC 47nH BIAS 9 SHDN OUTPUT BIAS MASTER BIAS 5nH RFOUT GND1 CIN 1nF RF INPUT CO RF OUTPUT GAIN GND2 GND3 RL ˜50Ω ˜15Ω THREE-ELEMENT MATCHING NETWORK DRIVER 50Ω L1 8nH CSH MAX2430 RFIN RC 470Ω CO AND CSH TUNED FOR MAXIMUM POWER OUTPUT AT THE DESIRED FREQUENCY BETWEEN 800MHz AND 1000MHz. GND4 MAX2430IEE (PwrQSOP) UNDERSIDE METAL SLUG MUST BE SOLDERED TO PCB GROUND PLANE. * L2 = 8nH FOR NARROW SO PACKAGE (MAX2430ISE) L2 = 12nH FOR PwrQSOP PACKAGE (MAX2430IEE) Figure 1. Typical Application Circuit __________Applications Information Output Matching The optimum internal load impedance seen by RFOUT is approximately 15Ω. This on-chip low drive impedance provides maximum power transfer and best efficiency under low (3V) supply conditions where the voltage-swing headroom is limited. For example, driving an output power of 21.3dBm (135mW) into 50Ω translates to a 7.35Vp-p swing at the output. An RF amplifier would require at least a 4.5V supply to drive a 50Ω load directly. However, driving 21.3dBm into 15Ω translates to 4.02Vp-p. The MAX2430 can achieve a voltage swing of 4.02Vp-p or 2.01Vp from a 3V supply voltage without saturating the output transistor. Figure 1 shows the MAX2430 configured for 800MHz to 1000MHz operation. The output matching circuitry converts the desired 50Ω load impedance to the 15Ω optimal load seen by the output transistor’s collector. This configuration uses a low-loss, controlled-Q inductor network. Starting from the RFOUT pin, this network consists of a series L (which includes the 5nH package parasitic inductance), series C, and shunt C. The design equations for this network are as follows: R1 = Output resistance as seen by the collector ~15Ω RL = Desired load resistance 6 The controlled-Q inductor network requires that ( ) RL / R1 − 1 . Choose Q and comRL > R1 and Q > pute matching components as given below: Let (R A = L x R1 − R12 ) XL = Q x R1 XCo = XL − A XCsh = RL x R1 / A L1 = XL / ω - 5nH of package inductance 1 CO = ωXCo CSH = 1 ωXCsh where ω equals the center frequency in radians/second. Recommended starting values for L1 and L2 are given in Table 1. Table 1. Recommended L1 and L2 Starting Values f = ω / 2π (MHz) L1(nH) 400 to 600* 22 12 18 600 to 800* 15 8 12 800 to 1000 8 8 12 MAX2430ISE MAX2430IEE L2(nH) L2(nH) *Not characterized _______________________________________________________________________________________ Low-Voltage, Silicon RF Power Amplifier/Predriver Forcing the BIAS pin directly in this manner disrupts the RF envelope timing function. To avoid this, place a diode in series with the BIAS pin control circuit, as shown in Figure 2. Note that when using the BIAS pin for power control, linearity is much degraded at the lower power levels. SHDN 2 MASTER BIAS 2.2V CLAMP Output Mismatch Considerations The MAX2430 will typically withstand an output load mismatch of VSWR = 6:1 at any electrical phase without exhibiting oscillatory behavior over the entire supply voltage range of 3V to 5.5V. Resistor RC enhances stability under load mismatch conditions and does not affect normal operation of the circuit. BIAS Pin The voltage at the BIAS pin controls the output power transistor biasing. At BIAS = 0.6V, the output transistor is biased to Class C, resulting in low gain and relatively nonlinear power. Above 2V, the output stage is biased to Class AB. Note that changing the bias voltage may degrade the output transistor’s stability. The shutdown pin (SHDN) controls the master bias circuit, which in turn provides a control current of approximately ±500µA to the external capacitor connected to the BIAS pin. When SHDN transitions from low to high, the BIAS pin capacitor charges up and clamps at approximately 2.2V. When SHDN transitions from high to low, the BIAS pin capacitor is discharged to nearly ground. This results in a power-up/power-down ramping of the RF envelope, which can be approximated by the following equation: tramp ≅ CBIAS x 2.2V / 0.5mA = 4400Ω x CBIAS MAX2430 BIAS 10 OUTPUT BIAS CBIAS 0V TO 2.0V POWER CONTROL Figure 2. Power-Control Application Using BIAS Pin Operating Frequency Range The MAX2430 has been characterized for operation in the 800MHz to 1000MHz range. Operation outside this range is possible, but the following issues must be considered: • Gain increases substantially at lower frequencies, possibly causing stability problems. • Useful gain and output power levels drop rapidly above 1000MHz. Therefore, a 2.2nF capacitor will give approximately 10µs ramp time. The BIAS pin can also be used to control the final output power and gain over a 15dB range, by forcing the BIAS pin voltage externally between 0.6V and 2.4V. Note that the BIAS pin driver must be able to source/sink 700µA. _______________________________________________________________________________________ 7 MAX2430 An overall loaded Q ≤ 5 can be achieved with readily available surface-mount components. This network absorbs the parasitic elements of the surface-mount components in such a way that they do not negatively impact the stopband characteristics; in fact, they can improve the overall stopband attenuation with properly chosen components. High-Q components (Q > 100) that have self-resonance near the 3rd harmonic of the intended output frequency should provide good passband characteristics with low loss, while offering good attenuation of the undesired 2nd and 3rd harmonics that are generated. Note that most applications will require extra filtering components and good shielding after the matching network to ensure absolute attenuation of out-of-band signals in order to meet out-of-band spurious suppression requirements. ________________________________________________________Package Information PSSOPPS.EPS MAX2430 Low-Voltage, Silicon RF Power Amplifier/Predriver 8 _______________________________________________________________________________________ Low-Voltage, Silicon RF Power Amplifier/Predriver SOICN.EPS _______________________________________________________________________________________ 9 MAX2430 ___________________________________________Package Information (continued) MAX2430 Low-Voltage, Silicon RF Power Amplifier/Predriver NOTES 10 ______________________________________________________________________________________