DC1464A Analog Devices

DEMO CIRCUIT 1464 DEMO CIRCUIT DC1464 QUICK START GUIDE FOR LTC6412 QUICK START GUIDE LTC6412 800MHz, 31dB Range Analog-Controlled VGA DESCRIPTION Demonstration circuit 1464 features the LTC6412 ana- The demo board is easily configured to access the +V G log-controlled VGA. The demo board incorporates a va- control mode and EN/SHDN features. Other simple PCB riety of passive components to allow for direct connec- modifications can accommodate differential input/output tion to a 2-port network analyzer or other single-ended signals and shunt tuning elements for bread-boarding 50 test system for simplified evaluation. into larger systems. The 1464 demo board factory default configuration is set Design files for this circuit board are available. Call for V control mode in the power-on and amplifier- the LTC factory. G enabled state (SHDN=1, EN=0). L, LTC, LTM, and LT are trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products. QUICK START PROCEDURE Demonstration circuit 1464 is easy to set up to evaluate the performance of the LTC6412. Refer to Figure 1 for This procedure contains only one critical sequence order. proper measurement equipment setup and follow the The user must apply supply voltage before applying the procedure below: control signal voltage and remove or turn-down the con- 1. Connect SMA cables to the +IN and +OUT ports. trol signal voltage before turning down the supply volt- Applied signal should be less than +10dBm peak RF age. This proper sequence will prevent excessive current power to avoid damage in the power-off state. through the ESD diodes from the V pins to the positive G supply, V . CC 2. Apply +3.3V between +V and GND turrets. Limit CC supply current to approximately 150mA. Table 1 shows the function of each SMA connector on the board. Only J1 and J2 are used in the default evalua- 3. Apply the desired control signal to either the V G tion configuration. Other connectors provide flexibility turret or the V SMA to access the V pin of the G G for fast control signals, differential input/output signals, LTC6412. For this V control mode, an increase in G and balun loss calibration. control signal voltage produces a decrease in ampli- fier gain. 1 DEMO CIRCUIT DC1464 QUICK START GUIDE FOR LTC6412 Table 1. DC1464 SMA Connector Descriptions CONNECTOR FUNCTION Differential input connected to input balun for single-ended operation. J1 (+IN) Drive from a 50 Ohm signal source. No external termination needed. Differential output connected to output balun for single-ended operation. J2 (+OUT) Impedance matched to 50 Ohms for direct connection to a 50 Ohm network/spectrum analyzer input. J3 (-IN) Differential input. Not connected by default. Resistor R9 can be removed to drive the input balun differentially. J4 (-OUT) Differential output. Not connected by default. Capacitor at C21 can be moved to C9 to drive the differential outputs. SMA terminal. Default connected in parallel with VG turret to the VG pin of LTC6412. Used to apply fast control J5 (VGAIN) signals. Move jumper R15 to location R14 and jumper R19 to location R18 to configure for +V control. G J6 (TEST IN) Cascaded 1:1 balun thru connection. Used to estimate the loss of the input balun at the frequency of interest. J7 (TEST OUT) Figure 1. Picture of DC1464 Top Silkscreen with recommended default measurement setup connections shown in maroon. 2