19-231; Rev 1; 1/6 EVALUATION KIT AVAILABLE LNAs with Step Attenuator and VGA General Description The wideband low-noise amplifier (LNA) ICs are designed for direct conversion receiver (DCR) or very low intermediate frequency (VLIF) receiver applications. They contain single-channel, single-ended LNAs with switchable attenuator and automatic gain control (AGC) intended as a low-noise gain stage. These devices provide high gain-control range (typically 6dB) at radio frequency (RF) with excellent noise and reverse isolation characteristics. The can work over the frequency range from 1MHz to 1GHz. In practice, only a narrow band is needed in each application, so different matching circuits can be applied. The devices are dynamically configured through the digital/analog control pins to select either maximum gain and low noise figure or power-saving mode. In addition, the feature high/low-current modes, high/low attenuation modes, linearly controlled gain states, and shutdown mode. Direct Conversion Receiver (DCR) Very Low IF Receiver Applications Features Low Noise Figure (1.8dB typical) High Small-Signal Gain (1dB Nominal) Wide Frequency Range of Operation (1MHz to 1GHz) 2dB Step Attenuator 4dB AGC Range Excluding Step Attenuator 2.6V to 3.3V Single-Supply Operation Shutdown Mode 3.mA Supply Current, Adjustable Down to 2.mA 4dB Reverse Isolation PART Ordering Information TEMP RANGE PIN- PACKAGE PKG CODE MAX2371EGC -4 C to +8 C 12 QFN-EP* G1233-1 MAX2371ETC -4 C to +8 C 12 TQFN-EP* T1233-3 MAX2371ETC+ -4 C to +8 C 12 TQFN-EP* T1233+3 MAX2373EGC -4 C to +8 C 12 QFN-EP* G1233-1 MAX2373ETC -4 C to +8 C 12 TQFN-EP* T1233-3 MAX2373ETC+ -4 C to +8 C 12 TQFN-EP* T1233+3 *EP = Exposed pad. +Denotes lead-free package. Pin Configuration Functional Diagram TOP VIEW LNA_IN 1 GND 12 RF_V CC RSET 11 1 9 AGC_BYP LNA_IN GND RF_V CC MAX2371 MAX2373 RSET AGC_BYP LNA_V CC LNA_E RX_EN 2 3 MAX2371 MAX2373 8 7 LNA_V CC LNA_OUT LNA_E RX_EN RF ATTENUATOR LNA EXPONENTIAL CONVERTER AGC AMP LNA_OUT 4 6 RF_ATTN AGC LNA_I QFN/TQFN RF_ATTN AGC LNA_I Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim s website at www.maxim-ic.com.
ABSOLUTE MAXIMUM RATINGS V CC to GND...-.3V to +3.6V All Pins Excluding Grounds to Pin GND...-.3V to (V CC +.3V) LNA Input Power (RX_EN = low)...dbm Continuous Power Dissipation (T A = +7 C) 12-Pin QFN (derate 11.9mW/ C above +7 C)...92mW 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 Operating Temperature Range...-4 C to +8 C Junction Temperature...+1 C Storage Temperature Range...-6 C to +16 C Soldering Temperature (1s)...+3 C (V CC = 7V, RX_EN = high, R SET = 1.1kΩ, V AGC = V CC /2, T A = -4 C to +8 C. Typical values are at T A = +2 C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage V CC 2.6 7 3.3 V RX_EN = low, V CC = 3.3V. 2 µa Supply Current I CC LNA_I = high, RF_ATTN = low 3.. ma LNA_I = low 2. 3. ma Digital Input Logic High V IH Pins LNA_I, RF_ATTN, RX_EN.7 V CC V CC V Digital Input Logic Low V IL Pins LNA_I, RF_ATTN, RX_EN.3 V CC V Logic Pin Impedance Logic pins RX_EN, RF_ATTN, LNA_I kω AGC Pin Impedance Pins AGC 1 kω AC ELECTRICAL CHARACTERISTICS ( EV Kits, V CC = 2.6V to 3.3V, RX_EN = high, R SET = 1.1kΩ, T A = -4 C to +8 C. Typical values are at V CC = 7V; for MAX2371 f RF = 1MHz, for MAX2373 f RF = 8MHz to 94MHz; T A = +2 C, unless otherwise noted.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS LNA AND AGC AMP CHARACTERISTICS Radio Frequency Range (Note 2) Input Return Loss () (Note 3) Reverse Isolation (S12) Max Power Gain (Note 3) Low band (MAX2371) 136 1 174 High band (MAX2373) 8 9 94 LNA_I = high; MAX2371-12 -9. RF_ATTN = low MAX2373-1 -9. LNA_I = high; MAX2371-14 -1 RF_ATTN = high MAX2373-1 -6. Over AGC range MAX2371-4 -3 MAX2373-42 -3 LNA_I = high, T A = MAX2371 13 14. 16 +2 C, V CC = 7V MAX2373 14 1. 17 LNA_I = low, T A = MAX2371 1. 12 +2 C, V CC = 7V MAX2373 1. 13 Gain Variation Over Temperature T A = -4 C to +8 C, V AGC < 1.8V -2. 2. db MHz db db db 2
AC ELECTRICAL CHARACTERISTICS (continued) ( EV Kits, V CC = 2.6V to 3.3V, RX_EN = high, R SET = 1.1kΩ, T A = -4 C to +8 C. Typical values are at V CC = 7V; for MAX2371 f RF = 1MHz, for MAX2373 f RF = 8MHz to 94MHz; T A = +2 C, unless otherwise noted.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS SSB Noise Figure vs. AGC Input 1dB Compression Point Input IP3 (Notes 4, ) Input IP3 Over AGC Range AGC RESPONSE AGC Attenuation Range (Note 6) AGC Slope Over Control Range RF STEP ATTENUATOR LNA_I = high, T A = +2 C, V CC = 7V, RF_ATTN = low LNA_I = low, T A = +2 C, V CC = 7V, RF_ATTN = low V AGC = 7V 1.8 V AGC = V. 7.7 V AGC = 1.87V 11 14. V AGC = 2.17V 2 V AGC = 7V 2.1 2.6 RF_ATTN = low, LNA_I = high -21. 19. V AGC < 1.8V LNA_I = low -24-22 RF_ATTN = high, LNA_I = high -3 V AGC < 1.8V LNA_I = low -9-6. db dbm LNA_I = high -1 RF_ATTN = low, V AGC = V CC /2 LNA_I = low MAX2371 MAX2373-7 -12-4 -9 dbm RF_ATTN = high, V AGC = V CC /2 to V LNA_I = high 9 13 dbm RF_ATTN = low, LNA_I = high, MAX2371-1. -8 V AGC = V CC /2 to 1.8V MAX2373-12. -1. V CC = 7V, RF_ATTN = low, V AGC = 1.337V to V, T A = +2 C dbm 3 4 db RF_ATTN = low, V AGC = 1.62V 32 4 47 RF_ATTN = high, V AGC = 1.62V 24 33 41 RF_ATTN = high to low, MAX2371 16. 17. 19. Gain Step db LNA_I = high MAX2373 18. 19. 21. Note 1: Parameters over temperature and supply voltage range are guaranteed by design and characterization, unless otherwise noted. Note 2: Operation outside these frequency bands is possible but has not been characterized. See Typical Operating Characteristics. Note 3: Measured with external matching network. Note 4: f IN1 = 1MHz, f IN2 = 1.1MHz, P IN = -3dBm for both tones (MAX2371). Note : f IN1 = 9MHz, f IN2 = 9.1MHz, P IN = -3dBm for both tones (MAX2373). Note 6: Parameters are guaranteed by production test. db/v 3
Typical Operating Characteristics ( EV Kits, V CC = 7V, RX_EN = high, R SET = 1.1kΩ, LNA_I = high, T A = +2 C. For MAX2371, f RF = 1MHz; for MAX2373, f RF = 9MHz, unless otherwise noted.) GAIN (db) 2 1 1 T A = +8 C GAIN vs. FREQUENCY T A = +2 C -1 13 14 1 16 17 18 FREQUENCY (MHz) T A = -4 C MAX2371 toc1 GAIN (db) 2 1-1 MAX2371 GAIN vs. V AGC -2 T A = +8 C -3 T A = +2 C -4 T A = -4 C -6 1.6 2. 2.4 2.8 MAX2371 toc2 IIP3 (dbm) 2 2 1 1 IIP3 vs. V AGC T A = +8 C T A = +2 C T A = -4 C -1-1 1.3 1.4 1. 1.6 1.8 MAX2371 toc3 1.. P 1dB vs. V AGC MAX2371 toc4 3 2 NOISE FIGURE vs. V AGC MAX2371 toc -1, S22, S12 vs. FREQUENCY S22 MAX2371 toc6 P1dB (dbm). T A = -4 C -1. -1. -2. T A = +2 C T A = +8 C -2. NOSIE FIGURE (db) 2 1 1, S22, S12 (db) -1-2 -2-3 -3-4 -4 S12 13 14 1 16 17 18 FREQUENCY (MHz), S22, S12 vs. V AGC -1 MAX2371 toc7, S22, S12 (db) -2-3 -4 S22 S12-6 4
Typical Operating Characteristics (continued) ( EV Kits, V CC = 7V, RX_EN = high, R SET = 1.1kΩ, LNA_I = high, T A = +2 C. For MAX2371, f RF = 1MHz; for MAX2373, f RF = 9MHz, unless otherwise noted.) GAIN (db) 2 1 1 T A = -4 C GAIN vs. FREQUENCY T A = +2 C FREQUENCY (MHz) T A = +8 C -1 84 86 88 9 92 94 MAX2371 toc8 GAIN (db) 2 1-1 -2-3 MAX2373 T A = -4 C T A = +2 C GAIN vs. V AGC -4 T A = +8 C 1.6 2. 2.4 2.8 MAX2371 toc9 IIP3 (dbm) 2 1 1-1 IIP3 vs. V AGC T A = -4 C T A = +2 C T A = +8 C -1 1.3 1.4 1. 1.6 1.8 MAX2371 toc1 P1dB (dbm) 1... -1. -1. -2. P 1dB vs. V AGC T A = -4 C T A = +2 C T A = 8 C MAX2371 toc11 NOSIE FIGURE (db) 3 2 2 1 1 NOISE FIGURE vs. V AGC MAX2371 toc12, S22, S12 (db) -1-1 -2-2 -3-3 -4-4, S22, S12 vs. FREQUENCY S22 S12 MAX2371 toc13-2. 84 86 88 9 92 94 FREQUENCY (MHz), S22, S12 vs. V AGC -1 MAX2371 toc14, S22, S12 (db) -1-2 -2-3 -3 S22-4 -4 S12
Table 1. MAX2371 S-Parameters (V CC = 7V, RX_EN = high, LNA_I = high, RF_ATTN = low, P IN = -3dBm, T A = +2 C.) FREQUENCY LNA () LNA (S21) LNA (S12) LNA (S22) (MHz) MAGNITUDE PHASE MAGNITUDE PHASE MAGNITUDE PHASE MAGNITUDE PHASE 1.94349-4.8477.98672 171.12.2136-12.49.99883-1.1632 1.74696-29.942 2.997 12.19.221 61.149.99472-4.4481 1.728794-3.699 2.34738 89.69.389 138.79.9848-6.74 2.766-43.419 693 7.13.3238 47.793.98687-7.7399 3.74636.118 9313 8.142.4439 83.493.97973-11.118 4.71961-6.242 1.623 4.427.3346 82.612.96313-14.668.731998-73.4.9374 36.67.439 68.614.947862-18.97 6.73628-8.64.84966 28.499.61 71.99.93998-267 7.73874-8.622.8147 247.4143 6.224.9318-23.71 8.73846-89.224.796627 18.18.8 93.741.9318-2.64 9.736843-91.669.793643 14.323.39 89.871.933372-27.898 1.72668-94.26.81946 9.9632.792 99.418.941369-3.211 11.7129-96.183.8164.9889.841 122.9.9486-331 12.69343-98.6.836893 1.164.119 129.22.936774-34.629 13.6798-1.39.861113-4.3698.14966 13.2.93219-37.619 14.6683-13.2.89132-61.1962 131.44.9213-4.14 1.4-16.63.9292-16.191.23963 128.73.92667-42.8 16.469143-111.4.96677-23.14.3121 121.93942-43.783 17.37231-116.2 767-29.913.39 114.74.94946-4.298 18.267147-123.39 14-37.636.47321 19.3.966296-46.3 19.122-137.61 181-4.724.689 1.48.971-48.76 2.6478 16.47.994 3.49.63929 988.97174.836 6
Table 2. MAX2373 S-Parameters (V CC = 7V, RX_EN = high, LNA_I = high, RF_ATTN = low, P IN = -3dBm, T A = +2 C.) FREQUENCY LNA () LNA (S21) LNA (S12) LNA (S22) (MHz) MAGNITUDE PHASE MAGNITUDE PHASE MAGNITUDE PHASE MAGNITUDE PHASE 1.92248 -.8171 7.27361-178.83.2162-89.276 1.92 -.8184 1.9334-9.1461 7.7713 163.94.1346 78.684.993482-2.314 2.884179-16.67 6.2982 7.2137 32.634.991791-3.8136 3.824784-22.6.92923 139.77.2217 72.86.983762.636 4.76769-27.48.478 13.2.1332 86.32.97112-7.24.79643-3.991 4.949 12.1641 86.431.9862-8.9841 6.66682-34.84 4.431492 113.7.2297 7.617.9972-2 7.616673-37.23 4.16983 17.48.171 1..94629-12.189 8.86388-39.783 3.644182 11.82.2688 73.619.941846-13.46 9.8837-41.88 3.313218 97.239.177 143.41.933168-1.19 1.366-42.914 3.939 92.43.1617 12.1.938912-16.89 11.24439-44.43 2.878 87.484.1442 11.32.932492-18.16 12.1622-4.96 2.61427 82.687.2973 178.79.9262-2.88 13.11487-47.19 2.417436 78.482.3764-17.4.91994-23.693 14.829-47.942 3642 74.93.419-176.47.91992-2 1.428-49.12 2.921 7.61.7366-163.1.917498-27.941 16.9736.1 1.97627 66.443.82-162.62.919486-29.8 17.1 1.33 1.84129 63.336.1929-163.87.92392-32.134 18.139 2.9 19293 9.87.1327-16.3.924634-33.91 19.1994 4.61 1.974 6.38.16692-162.6.933781-36.347 2.1141.66 1.46718 3.411.18843-177.66.93339-38.824 Table 3. MAX2371 Typical Noise Parameters (V CC = 7V, RX_EN = high, LNA_I = high, RF_ATTN = low, P IN = -3dBm, T A = +2 C, data from design simulation.) FREQUENCY (MHz) NF MIN (db) Γ OPT Γ OPT R N (Ω) 13.84.34 46.4 8.8 14.83.3 49.3 8. 1.82.34 8.1 16.81.34 6.2 7.8 17.81.33 9.8 7. 18.81.32 63.4 7.1 7
Table 4. MAX2373 Typical Noise Parameters (V CC = 7V, RX_EN = high, LNA_I = high, RF_ATTN = low, P IN = -3dBm, T A = +2 C, data from design simulation.) FREQUENCY (MHz) NF MIN (db) Γ OPT Γ OPT R N (Ω) 8 1.6.3 6. 87 1.8.3 61.8 9.98 89 1.1.34 63.3 9.94 91 1.11.34 64.7 9.9 93 1.13.33 66.2 9.86 9 1.1.33 67.7 9.82 PIN NAME FUNCTION 1 LNA_IN RF Input. Requires DC-blocking capacitor and external matching network. 2 LNA_E LNA Emitter. Connect to GND with an inductor. See inductor value in Table. 3 RX_EN LNA Control. Set RX_EN high to enable LNA; set RX_EN low to disable LNA. Pin Description 4 RF_ATTN Attenuator Control. Set RF_ATTN high for low-gain mode; set RF_ATTN low for high-gain mode. AGC 6 LNA_I AGC Input Voltage. Set AGC to V CC /2 for maximum gain. Set AGC to V CC - 2mV for minimum gain. If left unconnected, the LNA will operate at maximum gain and optimum noise figure. LNA Nominal Bias-Current Setting. Set LNA_I high for high-current mode. Set LNA_I low for low-current mode. If left unconnected, the default state of the LNA is high-current mode. 7 LNA_OUT RF Output Pin. Requires a pullup inductor to LNA_V CC and external matching network. 8 LNA_V CC Supply Voltage for the AGC Amplifier 9 AGC_BYP 1 RSET AGC Bypass. Connect a capacitor to ground. The value of the capacitor is a compromise of AGC response time and blocker frequency offset. External pin for precision resistor to ground to set reference bias current for IC; typical bias current is µa to 1µA. 11 RF_V CC Supply Voltage for the LNA. Bypass with a capacitor to GND as close to the pin as possible. Do NOT connect any tuned circuits to this supply pin. 12 GND Ground EP Exposed Pad Internally connected to GND. Connect to a large ground plane to maximize thermal performance. Do not use as the sole ground connection point. Table. Inductor Selection BAND L SERIES VALUE (nh) LNA TYPE 1MHz (VHF) 33 Low Band 4MHz (UHF) 1 Low Band 4MHz (UHF) High Band 8MHz 2. High Band 1GHz 1.8 High Band Detailed Description The are single-channel, singleended, low-noise amplifiers with two gain modes and continuous automatic gain control (AGC) in both modes. The devices are intended as low-noise gain stages for direct conversion receivers (DCR) or very low IF (VLIF) receivers. These devices provide high gain-control dynamic range (typ 6dB) at RF with excellent noise and reverse isolation characteristics. Vary the resistor at pin RSET and the inductor at LNA_E to meet a wide range of gain and linearity requirements. The ICs can be dynamically configured through pins LNA_I and RF_ATTN. When LNA_I is connected to V CC, the LNA is in high-current mode, nominally configured for maximum gain and low noise figure of the amplifier. If the LNA_I pin is grounded, the current of the LNA is reduced, and the associated gain, input IP3, and noise figure are degraded. The devices have two gain modes configured by the RF_ATTN pin. Set RF_ATTN high for low-gain mode; set RF_ATTN low for high-gain mode. The gain step between these two gain modes typically is 2dB. 8
The can be turned off in transmit or battery-save standby mode. The receive-enable pin (RX_EN) also can turn off the devices even if V CC is not removed, because multiple LNAs can be connected to the same V CC for multiband applications. The devices allow external matching networks to configure operation in a wide frequency range. Refer to the EV kit schematic for a guide to designing the matching network. Applications Information AGC The AGC of the is controlled by an external voltage at pin AGC. The amplifier is at full gain if the voltage at pin AGC is nominally V CC /2. It is at minimum gain if the voltage at pin AGC is V CC. The AGC attenuation range, which is continuously variable, is specified at 4dB. The IP3 will degrade slightly as AGC reduces the gain. The devices include two gain modes. Set RF_ATTN high to enable the low-gain mode, which reduces the gain by about 2dB. Low-gain mode will increase the system IP3 by approximately 18dB, which provides strong signal overload and IM protection. An external pin (RF_ATTN) controls switching between gain modes so this function can be combined with overall AGC control. AGC is independent of the choice of gain mode. The gain step between modes is in addition to the range of AGC, allowing a large overall gain-control range. AGC Response A linear transfer function between the AGC control signal and the AGC attenuation is realized in db. The linear relationship in db/v is maintained to ±1% over a specified attenuation range. Any compensation for gain-mode change must come from the AGC control. After reducing gain by switching the RF_ATTN pin, reduce the AGC voltage to achieve the desired overall gain. The LNA current also can be changed by toggling the LNA_I pin. This operation is independent of gain mode and AGC control. The low-current mode is intended as a second (reduced-current) quiescent point of operation for strong-signal operating environments. Matching Networks For best performance, match LNA_IN and LNA_OUT to Ω for the band of operation. Typical matching circuits for two bands (136MHz to 174MHz and 8MHz to 94MHz) are shown in the EV kit. The chip impedance changes minimally from low to high gain and with AGC. The input requires a DC-blocking capacitor. The size of this capacitor influences the startup time and IP3. There is a trade-off between these: A large DC-blocking capacitor means a good IP3 and slow startup. The maximum startup time is determined by the equation below: MAXT START = 4 C AC R SET, where C AC = AC-coupling cap in Farads, R SET = currentsetting resistor in Ω. IP3 will improve with the separation of the interfering tones, so a wider channel system can use a smaller DCblocking capacitor and achieve a better IP3. The customer also can change the emitter inductor at LNA_E to get the desired linearity and gain. Changing this inductor value requires a change to the input match. The output is an open collector and needs a pullup inductor. A load resistor also can be connected across it. The resistor determines the trade-off between the bandwidth of the match and the gain. A small load resistor means a wider match and lower gain. Layout Issues For best performance, pay attention to power-supply issues as well as to the layout of the RFOUT matching network. The EV kit can be used as a layout example. Ground connections followed by supply bypass are the most important. Power-Supply Bypassing The have two supply pins: LNA_V CC and RF_V CC. These must be bypassed separately. It is assumed that there is a large capacitor decoupling the power supply. LNA_V CC and RF_V CC are each decoupled with 1pF (MAX2371) or 1pF (MAX2373) capacitor. Use separate paths to the ground plane for each of the bypass capacitors, and minimize trace length to reduce inductance. The exposed pad must be connected to system ground with very low impedance vias. Power-Supply Layout To minimize coupling between sections of the IC, the ideal power-supply layout is a star configuration with a large decoupling capacitor at a central V CC node. The V CC traces branch from this central node, each to a separate V CC node in the PC board. At the end of each trace is a bypass capacitor that has low ESR at the RF of operation. This arrangement provides local decoupling at each V CC pin. At high frequencies, any signal leaking out of one supply pin sees a relatively high impedance (formed by the V CC trace inductance) to the central V CC node and an even higher impedance to any other supply pin, as well as a low impedance to ground through the bypass capacitor. 9
7 V DC RF INPUT MATCH LNA_IN LNA_E RX_EN GND RF ATTENUATOR RF_V CC LNA MAX2371 MAX2373 1.1kΩ PRECISION AGC AMP RSET Typical Operating Circuits AGC_BYP LNA_V CC LNA_OUT EXPONENTIAL CONVERTER RF_ATTN AGC LNA_I Impedance-Matching Network Layout The input- and output-matching networks are sensitive to layout-related parasitic inductions. To minimize parasitic inductance, keep traces short and place components as close as possible to the chip. To minimize parasitic capacitance, minimize the area of the plane. TRANSISTOR COUNT: 36 Chip Information Revision History Pages changed at Rev 1: 1, 8, 1 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. Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA 9486 48-737-76 26 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.