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19-1093; Rev 2; 1/98
UAL MAN ET KIT ION TA SHE T LUA DA EVA LOWS OL F
Low-Voltage, Silicon RF Power Amplifier/Predriver
____________________________Features
o Operates Over the 800MHz to 1000MHz Frequency Range o Delivers 125mW at 915MHz from +3.6V Supply (100mW typical from +3.0V supply) o Operates Directly from 3-Cell NiCd or 1-Cell Lithium-Ion Battery o Over 32dB Power Gain o RF Power Envelope Ramping is Programmable with One External Capacitor o Input Matched to 50 (VSWR < 2:1) o 15dB Output Power Control Range o 1A Typical Shutdown Current
________________General Description
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 1A 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 50. The output is an open collector that is easily matched to a 50 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.
MAX2430
Ordering Information
PART MAX2430IEE MAX2430ISE TEMP. RANGE -20C to +85C -20C to +85C PIN-PACKAGE 16 PwrQSOP 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 2 MASTER BIAS 6 4 OUTPUT BIAS VCC2 8 BIAS 10
TOP VIEW
GND3 1 SHDN 2 GND2 3 9 RFOUT RFIN 4 GND2 5 GND1 6 16 GND3 15 GND3 14 GND4
GND1 RFIN
MAX2430
DRIVER GAIN 3, 5 GND2 1, 15, 16 GND3
MAX2430
13 GND4 12 GND4 11 GND4 10 BIAS 9 RFOUT
11, 12, 13, 14 GND4
VCC1 7 VCC2 8
NOTE: MAX2430IEE (PwrQSOP PACKAGE) UNDERSIDE METAL SLUG MUST BE SOLDERED TO PCB GROUND PLANE.
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.
Low-Voltage, Silicon RF Power Amplifier/Predriver MAX2430
ABSOLUTE MAXIMUM RATINGS
VCC1, VCC2 ..........................................................................+6V SHDN, BIAS...................................................-0.3V, (VCC + 0.3V) RFIN.............................................................................-0.3V, +2V PRFIN ..................................................................................-3dBm Continuous Power Dissipation (TA = +70C) PwrQSOP (derate 20mW/C above +70C) ......................1.6W Narrow SO (derate 20mW/C above +70C) ....................1.6W Operating Temperature Range ...........................-20C to +85C Storage Temperature Range .............................-65C to +160C 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 = VCC1 = VCC2 = RFOUT = 3V to 5.5V, GND1 = GND2 = GND3 = GND4 = 0V, SHDN = 2.2V, BIAS = open, RFIN = open, TA = -20C to +85C, unless otherwise noted.) PARAMETER Supply Voltage Range Supply Current Shutdown Supply Current BIAS Pin Voltage SHDN High Input SHDN Low Input SHDN Bias Current SYMBOL VCC ICC ICC(OFF) VBIAS VSHDN(HI) VSHDN(LO) ISHDN SHDN = VCC No RF input applied, VCC = 5.5V SHDN = low BIAS pin open 2.2 CONDITIONS MIN 3 52 1 2.2 VCC 0.4 18 TYP MAX 5.5 70 10 UNITS V mA A V V V A
AC ELECTRICAL CHARACTERISTICS
(MAX2430 EV kit, f = 915MHz, VCC = 3.6V, SHDN = VCC, RFOUT matched to 50 resistive load, output measurements taken after matching network, TA = +25C, unless otherwise noted.) (Note 1) PARAMETER Frequency Range POUT at 1dB Compression Power Gain Output IM3 2nd Harmonic 3rd Harmonic Efficiency Supply Current Maximum Input VSWR Maximum Output Load Mismatch Maximum Output Load Mismatch for Stability Noise Figure 2 ICCRF VSWRIN VSWROUT VSWROUT NF P1dB GP OIM3 SYMBOL (Note 2) VCC = 3.6V VCC = 3.0V PRFIN = -20dBm MAX2430ISE MAX2430IEE CONDITIONS MIN 800 20 19 32 31 21.4 20.4 34 33 -30 -26 -40 24 160 2:1 8:1 6:1 7 dB TYP MAX 1000 UNITS MHz dBm dB dBc dBc dBc % mA
f1 = 915MHz, f2 = 916MHz, POUT per tone = 14dBm POUT = P1dB POUT = P1dB POUT = P1dB POUT = P1dB RFIN connected to 50 source VCC = 3V to 5.5V, PRFIN -10dBm (Note 3) VCC = 3V to 5.5V, PRFIN -12dBm (Note 4)
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Low-Voltage, Silicon RF Power Amplifier/Predriver
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2430 EV kit, f = 915MHz, VCC = 3.6V, SHDN = VCC, output matched to 50 resistive load, output measurements taken after matching network, TA = +25C, unless otherwise noted.) (Note 1) PARAMETER RFIN to RFOUT Isolation Turn-On/Off Times SYMBOL SHDN = 0.4V, PIN = -10dBm CONDITIONS MAX2430ISE MAX2430IEE MIN TYP 50 47 1 10 MAX UNITS dB dB s
MAX2430
BIAS pin capacitor C1 = 120pF BIAS pin capacitor C1 = 2.2nF
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 50 resistive load, output measurements taken after matching network, TA = +25C, unless otherwise noted.)
OUTPUT POWER AND CURRENT vs. INPUT POWER
25 5.5V 250 3.6V 3V 200 5.5V POUT (dBm) 15 POUT 3.6V 3V POUT (dBm) ICC (mA) 150 20 POUT @ PIN = -17dBm ICC (mA) 15 ICC @ PIN = -12dBm 150 200 25 POUT @ PIN = -12dBm
OUTPUT POWER AND CURRENT vs. TEMPERATURE
GAIN (dB) 250 40 35 30 25 POUT (dBm) 20 GAIN
OUTPUT POWER AND GAIN vs. INPUT POWER
MAX2430-03
20
5.5V 3V 3.6V 5.5V
10 ICC
100
3.6V 15 10 5 -25 -20 -15 PIN (dBm) -10 -5 POUT 3V
5
50
10 -5.5V 3.6V 3V 0
ICC @ PIN = -17dBm
100
0 -25 -20 -15 PIN (dBm) -10 -5
0
5 -20
20 40 60 TEMPERATURE (C)
80
50 100
OUTPUT POWER AND GAIN vs. TEMPERATURE (NORMAL OPERATING MODE)
MAX1691-4a
INPUT VSWR vs. FREQUENCY
MAX2430-05
RF INPUT IMPEDANCE vs. FREQUENCY
MAX2430-06
35 GAIN (dB)
4.0 3.5
150 100 INPUT IMPEDANCE () 50 0 IMAG -50 REAL
30 5.5V 3.6V 3.0V
GAIN PIN = -12dBm POUT 3.0 VSWR 3V 2.5 2.0
25
POUT (dBm)
20 1.5 15 -20 0 20 40 60 80 100 TEMPERATURE (C) 1.0 400 600
5V
-100 -150 800 1000 1200 1400 FREQUENCY (MHz) 1600 400 800 1200 1600 FREQUENCY (MHz) 2000
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Low-Voltage, Silicon RF Power Amplifier/Predriver MAX2430
_____________________________Typical Operating Characteristics (continued)
(MAX2430EVKIT-SO, f = 915MHz, VCC = 3.6V, SHDN = VCC, output matched to 50 resistive load, output measurements taken after matching network, TA = +25C, unless otherwise noted.)
INTERMODULATION DISTORTION vs. OUTPUT POWER AND TEMPERATURE
MAX2430-07 MAX2430-08
OUTPUT POWER AND HARMONICS
30 INTERMODULATION DISTORTION (dBc) 20 - OUTPUT SPECTRUM (dBm) 10 0 -10 -20 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 -54.0 dBm -20 -25 -30 -35 -40 -45 -50 -55 -60
INTERMODULATION DISTORTION vs. OUTPUT POWER AND VCC
INTERMODULATION DISTORTION (dBc) -25 -30 -35 -40 -45 -50 -55 -60 -65 -70 -75 -10 IM5 -5 0 5 10 15 20 IM3 5.5V 3.0V 3.6V 5.5V 3.0V 3.6V
MAX2430-09 MAX2430-10
-20
TA = -20C TA = +25C TA = +85C
VCC = 3.6V f1 = 915MHz f2 = 916MHz
IM3
IM5
-30 - -40 - -50 - -60 1 2 3 4 5
TA = -20C TA = +25C TA = +85C -10 -5 0 5 10 15 20
6
-65 -15
HARMONIC NUMBER
OUTPUT POWER PER TONE (dBm)
OUTPUT POWER PER TONE (dBm)
OUTPUT POWER AND SUPPLY CURRENT vs. EXTERNAL CONTROL VOLTAGE
25 PIN = -12dBm VCC = 3.6V 20 TA = +85C 15 TA = -20C 10 TA = +25C 5 TA = -20C 0 TA = +25C -5 -10 -15 0.4 0.8 1.2 1.6 2.0 BIAS PIN VOLTAGE (V) TA = +85C POUT 200 ICC 175 150 125 100 75 50 25 0 2.4 ICC (mA) 1V/div
RF OUTPUT ENVELOPE CHARACTERISTICS vs. SHUTDOWN CONTROL
3V 0V SHDN 0V 3V
OUTPUT POWER (dBm)
VCC = 3.0V BIAS CAPACITOR = 1nF POUT = 20.4dBm (110mW) tON tOFF = 5s 5s/div
4
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Low-Voltage, Silicon RF Power Amplifier/Predriver
_____________________Pin Description
PIN 1, 15, 16 2 3, 5 NAME GND3 SHDN GND2 FUNCTION Driver Stage Ground. Connect directly to ground plane. Shutdown Input (TTL/CMOS) Input Stage Ground. Connect directly to ground plane. RF Input. Internally matched to 50. Requires series DC-blocking capacitor. Bias Circuitry Ground. Connect directly to ground plane. Bias Circuitry Supply. Connect to supply. Bypass with 1000pF capacitor. Driver Stage Output. Connect to supply through inductor (see Applications Information). Output Transistor. Open Collector. Output Stage Bias Pin. Connect capacitor to GND to control start-up power envelope. Drive directly for power control (see Applications Information). Output Stage Ground. Connect directly to 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 50, 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 15. 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 1A.
MAX2430
4
RFIN
6
GND1
7
VCC1
8 9
VCC2 RFOUT
10
BIAS
11-14
GND4
Note: MAX2430IEE (PwrQSOP package) underside metal slug must be soldered to PCB ground plane.
_______________________________________________________________________________________
5
Low-Voltage, Silicon RF Power Amplifier/Predriver MAX2430
VCC 1nF L2* VCC1 ON OFF SHDN MASTER BIAS GND1 CIN 1nF RF INPUT OUTPUT BIAS 5nH VCC2 BIAS LC 47nH 9 RFOUT L1 8nH CO RF OUTPUT CSH RL 50 RC 470 2.2nF 1nF VCC
MAX2430
RFIN GAIN DRIVER
15
THREE-ELEMENT MATCHING NETWORK GND4
50
GND2
GND3
CO AND CSH TUNED FOR MAXIMUM POWER OUTPUT AT THE DESIRED FREQUENCY BETWEEN 800MHz AND 1000MHz. 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 15. 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 50 translates to a 7.35Vp-p swing at the output. An RF amplifier would require at least a 4.5V supply to drive a 50 load directly. However, driving 21.3dBm into 15 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 50 load impedance to the 15 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 ~15 RL = Desired load resistance
The controlled-Q inductor network requires that RL / R1 - 1 . Choose Q and comRL > R1 and Q > pute matching components as given below: Let A=
(
)
(R
L
x R1 - R12
)
XL = Q x R1 XCo = XL - A XCsh = RL x R1 / A L1 = XL / - 5nH of package inductance 1 CO = XCo CSH = 1 XCsh
where 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 = / 2 (MHz) 400 to 600* 600 to 800* 800 to 1000 L1(nH) 22 15 8 MAX2430ISE MAX2430IEE L2(nH) L2(nH) 12 8 8 18 12 12
6
*Not characterized _______________________________________________________________________________________
Low-Voltage, Silicon RF Power Amplifier/Predriver
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. 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.
MAX2430
SHDN 2 MASTER BIAS
MAX2430
2.2V CLAMP BIAS 10
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.
OUTPUT BIAS
CBIAS
0V TO 2.0V POWER CONTROL
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 500A 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 = 4400 x CBIAS Therefore, a 2.2nF capacitor will give approximately 10s 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 700A.
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.
_______________________________________________________________________________________
7
Low-Voltage, Silicon RF Power Amplifier/Predriver MAX2430
________________________________________________________Package Information
PSSOPPS.EPS
8
_______________________________________________________________________________________
Low-Voltage, Silicon RF Power Amplifier/Predriver
___________________________________________Package Information (continued)
SOICN.EPS
MAX2430
_______________________________________________________________________________________
9
Low-Voltage, Silicon RF Power Amplifier/Predriver MAX2430
NOTES
10
______________________________________________________________________________________

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