FEATURES Wide RF Frequency Range:.7GHz to.ghz 7.dBm Typical Input IP at GHz On-Chip RF Output Transformer On-Chip 5Ω Matched LO and RF Ports Single-Ended LO and RF Operation Integrated LO Buffer: 5dBm Drive Level Low LO to RF Leakage: dbm Typical Noise Figure:.dB Wide IF Frequency Range: MHz to MHz Enable Function with Low Off-State Leakage Current Single 5V Supply Small -Lead QFN Plastic Package APPLICATIO S U Wireless Infrastructure Cable Downlink Infrastructure Point-to-Point and Point-to-Multipoint Data Communications High Linearity Frequency Conversion DESCRIPTIO LT559.7GHz to.ghz High Linearity Upconverting Mixer U The LT 559 mixer is designed to meet the high linearity requirements of wireless and cable infrastructure transmission systems. A high speed, internally 5Ω matched, LO amplifier drives a double-balanced mixer core, allowing the use of a low power, single-ended LO source. An RF output transformer is integrated, thus eliminating the need for external matching components at the RF output, while reducing system cost, component count, board area and system-level variations. The IF port can be easily matched to a broad range of frequencies for use in many different applications. The LT559 mixer delivers +7.dBm typical input rd order intercept point at GHz with IF input signal levels of dbm. The input db compression point is typically +5.5dBm. The IC requires only a single 5V supply., LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO U 5V DC µf pf 9nH RF Output Power, IM and IM vs IF Input Power (Two Input Tones) BPF : pf LO INPUT 5dBm pf Ω pf Ω (OPTIONAL) EN V CC V CC V CC BIAS LT559 IF + IF 5pF 5Ω 5pF LO + LO pf RF + RF 559 Fa BPF PA P OUT, IM, IM (dbm/tone) 5 7 9 P OUT f RF = MHz P LO = 5dBm f LO = MHz f IF = MHz f IF = MHz IM IM IF INPUT POWER (dbm/tone) 559 Fb Figure. Frequency Conversion in Wireless Infrastructure Transmitter
ABSOLUTE AXI U RATI GS W W W (Note ) Supply Voltage... 5.5V Enable Voltage....V to (V CC +.V) LO Input Power (Differential)... +dbm LO + to LO Differential DC Voltage... ±V LO + and LO DC Common Mode Voltage... V to V CC IF Input Power (Differential)... +dbm IF + and IF DC Currents... 5mA RF + to RF Differential DC Voltage... ±.V RF + and RF DC Common Mode Voltage... V to V CC Operating Temperature Range... C to 5 C Storage Temperature Range... 5 C to 5 C Junction Temperature (T J )... 5 C U U U W PACKAGE/ORDER I FOR ATIO IF + IF TOP VIEW LO LO + 5 5 7 EN 7 VCC V CC VCC RF + RF 9 UF PACKAGE -LEAD (mm mm) PLASTIC QFN T JMAX = 5 C, θ JA = 7 C/W EXPOSED PAD (PIN 7) IS MUST BE SOLDERED TO PCB ORDER PART NUMBER LT559EUF UF PART MARKING 559 Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS PARAMETER CONDITIONS MIN TYP MAX UNITS IF Input Frequency Range to MHz LO Input Frequency Range to MHz RF Output Frequency Range 7 to MHz GHz Application: V CC = 5V DC, EN = High,, IF input = MHz at dbm, LO input =.GHz at 5dBm, RF output measured at GHz, unless otherwise noted. (Test circuit shown in Figure ) (Notes, ) PARAMETER CONDITIONS MIN TYP MAX UNITS IF Input Return Loss Z O = 5Ω, with External Matching db LO Input Return Loss Z O = 5Ω 7 db RF Output Return Loss Z O = 5Ω db LO Input Power to dbm Conversion Gain. db Input rd Order Intercept dbm/tone, f = MHz 7. dbm Input nd Order Intercept dbm, Single Tone dbm LO to RF Leakage dbm LO to IF Leakage dbm Input db Compression 5.5 dbm IF Common Mode Voltage Internally Biased.77 V DC Noise Figure Single-Side Band. db
DC ELECTRICAL CHARACTERISTICS (Test Circuit Shown in Figure ) V CC = 5V DC, EN = High,, unless otherwise noted. (Note ) PARAMETER CONDITIONS MIN TYP MAX UNITS Enable (EN) Low = OFF, High = ON Turn-On Time (Note ) µs Turn-Off Time (Note ) µs Input Current V ENABLE = 5V DC µa Enable = High (ON) V DC Enable = Low (OFF).5 V DC Power Supply Requirements (V CC ) Supply Voltage.5 to 5.5 V DC Supply Current V CC = 5V DC 7 ma Shutdown Current EN = Low µa Note : Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note : External components on the final test circuit are optimized for operation at f RF = GHz, f LO =.GHz and f IF = MHz. Note : Specifications over the C to 5 C temperature range are assured by design, characterization and correlation with statistical process controls. Note : Turn-On and Turn-Off times are based on the rise and fall times of the RF output envelope from dbm to full power with an IF input power of dbm. TYPICAL PERFOR A CE CHARACTERISTICS U W (Test Circuit Shown in Figure ) Supply Current vs Supply Voltage. Shutdown Current vs Supply Voltage. SUPPLY CURRENT (ma) 5 5 5 5 T A = C SHUTDOWN CURRENT (µa).... T A = C 5.5.5.75 5 5.5 SUPPLY VOLTAGE (V) 5.5.5.5.75 5 SUPPLY VOLTAGE (V) 5.5 5.5 559 G 559 G
TYPICAL PERFOR A CE CHARACTERISTICS U W V CC = 5V DC, EN = High,, IF input = MHz at dbm, LO input =.GHz at 5dBm, RF output measured at MHz, unless otherwise noted. For -tone inputs: nd IF input = MHz at dbm. (Test Circuit Shown in Figure.) GAIN, NF (db) Conversion Gain and SSB Noise Figure vs RF Output Frequency 5 NF GAIN LOW SIDE AND 7 9 5 RF OUTPUT FREQUENCY (MHz) IIP (dbm) 5 9 7 5 5 IIP and IIP vs RF Output Frequency IIP 7 9 RF OUTPUT FREQUENCY (MHz) IIP 5 5 IIP (dbm) LO LEAKAGE (dbm) 5 5 LO-RF Leakage vs RF Output Frequency 7 9 5 RF OUTPUT FREQUENCY (MHz) 559 G 559 G 559 G5 GAIN (db) Conversion Gain and SSB Noise Figure vs LO Input Power GAIN T A = C T A = C LO INPUT POWER (dbm) NF NF (db) IIP (dbm) 9 7 5 IIP and IIP vs LO Input Power IIP T A = C T A = C LO INPUT POWER (dbm) IIP 5 IIP (dbm) LO LEAKAGE (dbm) 5 LO-RF Leakage vs LO Input Power T A = C LO INPUT POWER (dbm) 559 G 559 G7 559 G IIP (dbm) 9 7 IIP and IIP vs LO Input Power IIP IIP 5 IIP (dbm) P OUT, IM (dbm/tone) 5 7 RF Output Power and Output IM vs IF Input Power (Two Input Tones) P OUT IM T A = C T A = C P OUT, IM (dbm/tone) 5 7 RF Output Power and Output IM vs IF Input Power (Two Input Tones) P OUT IM T A = C T A = C 5 LO INPUT POWER (dbm) 9 IF INPUT POWER (dbm/tone) 9 IF INPUT POWER (dbm/tone) 559 G9 559 G 559 G
TYPICAL PERFOR A CE CHARACTERISTICS U W LT559 V CC = 5V DC, EN = High,, IF input = MHz at dbm, LO input =.GHz at 5dBm, RF output measured at MHz, unless otherwise noted. For -tone inputs: nd IF input = MHz at dbm. (Test Circuit Shown in Figure.) GAIN (db) 5 Conversion Gain vs IF Input Power (One Input Tone) T A = C IF INPUT POWER (dbm) RETURN LOSS (db) 5 5 5 IF, LO and RF Port Return Loss vs Frequency LO PORT IF PORT RF PORT 5 5 FREQUENCY (MHz) GAIN (db) Conversion Gain, IIP and IIP vs Supply Voltage IIP IIP GAIN LOW SIDE AND.5.5.75 5 5.5 5.5 SUPPLY VOLTAGE (V) 5 IIP, IIP (dbm) 559 G 559 G 559 G PI FU CTIO S U U U (Pins,, 9,,, ): Internal Grounds. These pins are used to improve isolation and are not intended as DC or RF grounds for the IC. Connect these pins to low impedance grounds on the PCB for best performance. IF +, IF (Pins, ): Differential IF Signal Inputs. A differential signal must be applied to these pins through DC blocking capacitors. The pins must be connected to ground with Ω resistors (the grounds must each be capable of sinking about ma). For best LO leakage performance, these pins should be DC isolated from each other. An impedance transformation is required to match the IF input to the desired source impedance (typically 5Ω or 75Ω). EN (Pin 5): Enable Pin. When the applied voltage is greater than V, the IC is enabled. When the applied voltage is less than.5v, the IC is disabled and the DC current drops to about µa. V CC (Pin ): Power Supply Pin for the Bias Circuits. Typical current consumption is about ma. This pin should be externally connected to V CC and have appropriate RF bypass capacitors. V CC (Pin 7): Power Supply Pin for the LO Buffer Circuits. Typical current consumption is about ma. This pin should have appropriate RF bypass capacitors as shown in Figure. The pf capacitor should be located as close to the pins as possible. V CC (Pin ): Power Supply Pin for the Internal Mixer. Typical current consumption is about ma. This pin should be externally connected to V CC through an inductor. A 9nH inductor is shown in Figure, though the value is not critical. RF, RF + (Pins, ): Differential RF Outputs. One pin may be DC connected to a low impedance ground to realize a 5Ω single-ended output. No external matching components are required. A DC voltage should not be applied across these pins, as they are internally connected through a transformer winding. LO +, LO (Pins, 5): Differential Local Oscillator Inputs. The LT559 works well with a single-ended source driving the LO + pin and the LO pin connected to a low impedance ground. No external 5Ω matching components are required. An internal resistor is connected across these pins; therefore, a DC voltage should not be applied across the inputs. Exposed Pad (Pin 7): DC and RF ground return for the entire IC. This must be soldered to the printed circuit board low impedance ground plane. 5
BLOCK DIAGRA W EXPOSED PAD RF + RF 7 9 LO + LO 5 5pF 5Ω 5pF HIGH SPEED LO BUFFER DOUBLE- BALANCED MIXER BIAS pf 5 V CC V CC EN 7 V CC IF + IF 559 BD TEST CIRCUIT LO IN MHz IF IN MHz T 5 C C R C 5 LO LO + IF + RF + LT559 IF RF RF OUT MHz."."." ER =. RF DC R EN 5 EN V CC C5 V CC V CC V CC 7 C 559 F L 9 7 REF DES VALUE SIZE PART NUMBER C, C pf AVX CKATA C pf AVX AKATA C pf AVX AKATA C5 µf Taiyo Yuden LMK7BJ5MA L 9nH Toko LL5-FH9NJ R, R Ω,.% IRC PFC-WR--R-B T : SM- M/A-COM ETC-- Figure. Test Schematic for the LT559
APPLICATIO S I FOR ATIO U W U U The LT559 consists of a double-balanced mixer, a high performance LO buffer and bias/enable circuits. The RF and LO ports may be driven differentially; however, they are intended to be used in single-ended mode by connecting one input of each pair to ground. The IF input ports must be DC-isolated from the source and driven differentially. The IF input should be impedance-matched for the desired input frequency. The LO input has an internal broadband 5Ω match with return loss better than db at frequencies up to MHz. The RF output band ranges from 7MHz to MHz, with an internal RF transformer providing a 5Ω impedance match across the band. Low side or high side LO injection can be used. IF Input Port The IF inputs are connected to the emitters of the doublebalanced mixer transistors, as shown in Figure. These pins are internally biased and an external resistor must be connected from each IF pin to ground to set the current through the mixer core. The circuit has been optimized to work with Ω resistors, which will result in approximately ma of DC current per side. For best LO leakage performance, the resistors should be well matched; thus resistors with.% tolerance are recommended. If LO leakage is not a concern, then lesser tolerance resistors can be used. The symmetry of the layout is also important for achieving optimum LO isolation. The capacitors shown in Figure, C and C, serve two purposes. They provide DC isolation between the IF + and IF ports, thus preventing DC interactions that could cause unpredictable variations in LO leakage. They also IF IN 5Ω T : C C C Ω.% Ω.% LT559 ma IF + Figure. IF Input with External Matching IF ma V CC 559 F improve the impedance match by canceling excess inductance in the package and transformer. The input capacitor value required to realize an impedance match at desired frequency, f, can be estimated as follows: C = C = ( π f ) ( L + L ) IN EXT where; f is in units of Hz, L IN and L EXT are in Henry, and C, C are in Farad. L IN is the differential input inductance of the LT559, and is approximately.7nh. L EXT represents the combined inductances of differential external components and transmission lines. For the evaluation board shown in Figure, L EXT =.nh. Thus, for f = MHz, the above formula gives C = C = pf. Table lists the differential IF input impedance and reflection coefficient for several frequencies. A : balun can be used to transform the impedance up to about 5Ω. Table. IF Input Differential Impedance FREQUENCY DIFFERENTIAL DIFFERENTIAL S (MHz) INPUT IMPEDANCE MAG ANGLE. + j.7.. + j.7. 79 7. + j.75. 7. + j.7. 77 7. + j.7. 7. + j.5. 7. + j.. 7 5. + j5.. 7 LO Input Port The simplified circuit for the LO buffer input is shown in Figure. The LO buffer amplifier consists of high speed limiting differential amplifiers, optimized to drive the mixer quad for high linearity. The LO + and LO ports can be driven differentially; however, they are intended to be driven by a single-ended source. An internal resistor connected across the LO + and LO inputs provides a broadband 5Ω impedance match. Because of the resistive match, a DC voltage at the LO input is not recommended. If the LO signal source output is not AC coupled, then a DC blocking capacitor should be used at the LO input. 7
APPLICATIO S I FOR ATIO U W U U LT559 LO IN LO + 5Ω 5pF LT559 RF + Ω V CC 5Ω V CC LO 5 5pF Ω pf RF RF OUT 5Ω Figure. LO Input Circuit 559 F 559 F5 V CC Figure 5. RF Output Circuit Though the LO input is internally matched to 5Ω, there may be some cases, particularly at higher frequencies or with different source impedances, where a further optimized match is desired. Table includes the single-ended input impedance and reflection coefficient vs frequency for the LO input for use in such cases. Table. Single-Ended LO Input Impedance FREQUENCY INPUT S (MHz) IMPEDANCE MAG ANGLE 7. j.... j..5.7. j7.5. 9..9 j..9..7 j..5.7. j7.. 5.5. j9.5... j..55 7.. j... RF Output Port An internal RF transformer, shown in Figure 5, reduces the mixer-core impedance to provide an impedance of 5Ω across the RF + and RF pins. The LT559 is designed and tested with the outputs configured for single-ended operation, as shown in the Figure 5; however, the outputs can be used differentially as well. A center tap in the transformer provides the DC connection to the mixer core and the transformer provides DC isolation at the RF output. The RF + and RF pins are connected together through the secondary windings of the transformer; thus a DC voltage should not be applied across these pins. The impedance data for the RF output, listed in Table, can be used to develop matching networks for different load impedances. Table. Single-Ended RF Output Impedance FREQUENCY OUTPUT S (MHz) IMPEDANCE MAG ANGLE 7 7. + j..5 9.7 + j..5. 9 5.9 + j.5.7 7.7 5.5 + j..5 5.5. + j... j..9 57. j..59. j..7 7 Operation at Different Input Frequencies On the evaluation board shown in Figure, the input of the LT559 can be easily matched for different frequencies by changing the capacitors, C, C and C. Capacitors C and C set the input matching frequency while C improves the LO to RF leakage performance. Decreasing the value of C at higher input frequencies reduces its impact on conversion gain. Table lists some actual values used at selected frequencies.
APPLICATIO S I FOR Table. Input Capacitor Values vs Frequency ATIO U W U U FREQUENCY CAPACITANCE (C, C) CAPACITANCE (C) (MHz) (pf) (pf) 7 5 9. 5 7.. The performance was evaluated with the input tuned for each of these frequencies and the results are summarized in Figures -. The same IF input balun transformer was used for all measurements. In each case, the LO input frequency was adjusted to maintain an RF output frequency of MHz. Low Frequency Matching of the RF Output Port Without any external components on the RF output, the internal transformer of the LT559 provides a good 5Ω impedance match for RF frequencies above approximately 5MHz. Below this frequency, the return loss drops below db and degrades the conversion gain. The addition of a single pf capacitor in series with the RF output improves the match at lower RF frequencies, shifting the db return loss point to about 7MHz, as demonstrated in Figure 9. This change also results in an improvement of the conversion gain. GAIN (db) 5 INPUT TUNED FOR EACH TEST FREQUENCY GAIN LOW SIDE SSB NF LOW SIDE V CC = 5V P LO = 5dBm 5 INPUT FREQUENCY (MHz) NF (db) LEAKAGE (dbm) 5 INPUT TUNED FOR EACH TEST FREQUENCY V CC = 5V P LO = 5dBm INPUT FREQUENCY (MHz) 5 559 F 559 F Figure. Conversion Gain and Single Sideband Noise Figure vs Tuned IF Input Frequency Figure. LO to RF Leakage vs Tuned IF Input Frequency 7 INPUT TUNED FOR EACH TEST FREQUENCY 7 IIP (dbm) 5 9 7 IIP LOW SIDE HIGH SIDE LOW SIDE 5 V CC = 5V, P LO = 5dBm 5 INPUT FREQUENCY (MHz) IIP 5 IIP (dbm) GAIN (db) NO C OUT C OUT = pf 5 C OUT = pf 7 7 5 GAIN 5 5 RETURN LOSS NO C OUT 5 9 RF OUTPUT FREQUENCY (MHz) RETURN LOSS (db) 559 F7 559 F9 Figure 7. IIP and IIP vs Tuned IF Input Frequency Figure 9. Conversion Gain and Return Loss vs Output Frequency 9
TYPICAL APPLICATIO S U (a) Top Layer Silkscreen (b) Top Layer Metal Figure. Evaluation Board Layout
PACKAGE DESCRIPTIO U UF Package -Lead Plastic QFN (mm mm) (Reference LTC DWG # 5--9).7 ±.5.5 ±.5.5 ±.5.9 ±.5 ( SIDES) PACKAGE OUTLINE. ±.5.5 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS. ±. ( SIDES).75 ±.5 R =.5 TYP BOTTOM VIEW EXPOSED PAD 5.55 ±. PIN TOP MARK.5 ±. (-SIDES). REF..5 NOTE:. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO- VARIATION (WGGC). ALL DIMENSIONS ARE IN MILLIMETERS. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED.5mm ON ANY SIDE. EXPOSED PAD SHALL BE SOLDER PLATED (UF) QFN 5. ±.5.5 BSC Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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