UVDM40SC DC to 40 GHz MMIC Medium Power Voltage Controlled Attenuator Data Sheet Application The UVDM40SC MMIC voltage controlled attenuator is ideal for high frequency and broadband applications in test equipment, commercial and military systems. The attenuator is especially suited for applications needing a moderate amount of adjustable attenuation and fast attenuation control from DC to millimeter frequencies. The device is also useful as a general purpose building block in communications systems. Features * Wideband operation: DC to 40 GHz * Low Insertion Loss (<3 dB) * Good Input/Output Match * Medium Attenuation (max. 18 dB) * Size: 1640 x 920 m Description The UVDM40SC is a mediumpower DC-40 GHz PHEMT FET attenuator. The performance of the device is controlled by two bias voltages, Vseries and Vshunt. The bias voltages control the match and attenuation of the device when varied between -1V and +0.5V DC. Please refer to the tables of recommended bias settings optimized for flat insertion loss and flat attenuation for additional information. Key Specifications Zo=50 Parameter Description Minimum Typical Maximum Attenuation (dB) Flatness (dB) DC to 40 GHz DC to 40 GHz 0 -- -- 1.0 18 -- Insertion Loss (dB) DC to 40 GHz 3 -- 20 S11 (dB) S22 (dB) DC to 50 GHz DC to 50 GHz -- -- -10 -10 -8 -8 P-1dB (dBm) 1dB Gain Compression 0 to 15 dB Attenuation 10 12 -- Centellax Inc. 451 Aviation Blvd., Suite 101, Santa Rosa, CA 95403-1069 * Email sales@centellax.com * Tel 866.522.6888 * Fax 707.568.7647 Specifications subject to change without notice. Copyright (c) 2003 Centellax Inc. Printed in USA Rev 1001-0001 Optimized for Flat Attenuation (Typical) 18 16 14 12 10 8 6 4 Vseries(V) Vshunt (V) -0.625 -0.625 -0.625 -0.616 -0.608 -0.601 -0.595 -0.569 -0.550 0.500 0.343 -0.287 -0.400 -0.456 -0.501 -0.544 -0.583 -0.622 -0.700 -1.000 Att. (dB)* 18.3 15.9 13.6 11.6 9.6 7.5 5.7 3.8 1.8 0 2 0 Figure 1: Typical on wafer measured performance. Optimized for Flat Insertion Loss (Typical) 19 17 15 12 10 9 7 5 3 1 Vseries(V) Vshunt (V) -0.650 -0.650 -0.650 -0.650 -0.641 -0.618 0.595 -0.568 -0.550 0.500 0.000 -0.312 -0.413 -0.475 -0.513 -0.549 -0.583 -0.624 -0.700 -1.000 Loss (dB)* 19.2 16.9 14.6 12.4 10.7 8.9 7.1 5.1 3.3 1.4 Figure 2: Typical on wafer measured performance. Figure 3: Typical on wafer measured performance. Figure 4: Typical on wafer measured performance. Note: S-parameter measurement files are available upon request. Email: support@centellax.com for more information. (*) Midband Centellax Inc. 451 Aviation Blvd., Suite 101, Santa Rosa, CA 95403-1069 * Email sales@centellax.com * Tel 866.522.6888 * Fax 707.568.7647 Supplemental Specifications Parameter Description Minimum Typical Maximum Vseries Vshunt Attenuation Control Voltage Attenuation Control Voltage -2 V -2 V -- -- 0.5 V 0.5 V DCin DCout DC feedback circuit input DC feedback circuit output 0V 0V 0.25 V 0.25 V 1V 1V GND Tch ch Backside Ground Plane Channel Temperature Thermal Resistance (Tcase=25oC) -- -- -- 60 C/Watt 150oC -- o Typical Pin(-1dB) vs Attenuation 26 2GHz 4GHz 6GHz 8GHz 10GHz 12GHz 14GHz 16GHz 18GHz 20GHz 22GHz Input Referred P1dB (dBm) 24 22 20 18 16 14 12 10 8 6 0 5 10 Attenuation (dB) 15 20 Pick up and Chip Handling: The chip has exposed air bridges on the top surface. Do not pick up chip with vacuum on the die center; handle at edges or with a custom collet. ESD Handling and Bonding: This MMIC is ESD sensitive and preventive measures should be taken during handling, die attach and bonding. Epoxy die attach is recommended. Please visit our website for more handling, die attach and bonding information. (www.centellax.com) Figure 5: Typical on evaluated package measured performance. Figure 6: UVDM40SC Simplified Schematic Diagram Centellax Inc. 451 Aviation Blvd., Suite 101, Santa Rosa, CA 95403-1069 * Email sales@centellax.com * Tel 866.522.6888 * Fax 707.568.7647 DC Feedback Circuit for Variable Attenuator The following feedback circuit does a good job of providing the series and shunt biases to the variable attenuator for a user-selected amount of attenuation. The circuit references a 1/3 scale version of the microwave attenuator, which is used for the DC feedback loop. Because the devices are 1/3 the size of the unscaled attenuator, the reference impedence is 3 times larger (150 instead of 50). The circuit uses two ordinary opamps to provide the bias control voltages to the attenuator. Opamp OA1 senses the input impedance of the attenuator and adjusts the series FET gate voltage Vseries so that the impedance looking into the attenuator is 150. The input impedance can be adjusted with the potentiometer shown in the schematic (Figure 7). When this feedback loop is at DC equilibrium the voltage at DCin will be Vref/2. The second opamp OA2 adjusts the shunt FET gate voltage so that the DC output voltage DCout is equal to the voltage at the opamp negative input terminal. When 0V is applied to the negative input terminal of OA2, the attenuation is maximized. Conversely, if Vref/2 is applied at the negative input of OA2 then the attenuation is minimized. A voltage divider with the shunt resistor terminated by the voltage Vref makes for a convienient conversion of voltage to attenuation. If the input to the divider Vatten is set to 0 volts then the negative input of OA2 will have a value of Vref/2 and the attenuator will have minimum attenuation. Conversely, if Vatten is set to -Vref then the negative input of OA2 is set 0V and the attenuator will have maximum attenuation. This makes the calculation of Vatten easy and requires a minimum number of parts. Figure 7: Scaled DC Attenuator Circuit (1/3 scale attenuator) Figure 8: The DC feedback circuit to adjust the attenuator Centellax Inc. 451 Aviation Blvd., Suite 101, Santa Rosa, CA 95403-1069 * Email sales@centellax.com * Tel 866.522.6888 * Fax 707.568.7647 Assembly Diagram of UVDM40SC Chip size: 1640 x 920 m Chip size Tolerance: 5 m Chip Thickness: 100 10 m Pad Dimensions: 80 x 80 m Physical Characteristics of UVDM40SC Centellax Inc. 451 Aviation Blvd., Suite 101, Santa Rosa, CA 95403-1069 * Email sales@centellax.com * Tel 866.522.6888 * Fax 707.568.7647 Specifications subject to change without notice. Copyright (c) 2003 Centellax Inc. Printed in USA Rev 1001-0001