DC696A Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 696 IF RECEIVER, WIDE BB LT5546 DESCRIPTION Demonstration circuit 696 with LT5546 IC is a 40MHz reduce the out-of-band noise and spurious frequency to 500MHz monolithic integrated quadrature demodu- components. The 3dB corner frequency of the noise lator with variable gain amplifier (VGA), designed for filters is approximately 17MHz. The external 2XLO low voltage operation. It supports standards that use frequency is required to be twice the IF input fre- linear modulation format. The chip consists of a quency for the mixers. The standby mode provides VGA, quadrature down-converting mixers and 17MHz reduced supply current and fast transient response lowpass noise filters. The LO port consists of a di- into the normal operating mode when the I/Q outputs vide-by-two stage and LO buffers. The IC provides all are AC-coupled to a baseband chip. building blocks for IF down-conversion to I and Q baseband signals with a single supply voltage of 1.8V Design files for this circuit board are available. Call to 5.25V. The VGA gain has a linear-in-dB relation- the LTC factory. ship to the control input voltage. Hard-clipping am- plifiers at the mixer outputs reduce the recovery time LT is a trademark of Linear Technology Corporation from a signal overload condition. The lowpass filters Table 1. Dip-Switch Setting For Different Operating Modes EN STBY COMMENTS Low Low Shutdown Mode Low High Standby Mode High Low or High Normal Operation Mode DC POWER CONSUMPTION MEASUREMENTS 1) Connect test equipment and power supplies to the 6) Standby Mode demo board as shown in Figure 1. a) Set EN dipswitch to On position (Logic 2) Set Power Supply 1 and Power Supply 2 to Low). +3.0V. b) Set STBY dipswitch to Off position (Logic NOTE: One Power Supply can be used as well. High). 3) Set Power Supply 3 Between +4.75V and c) Measure Current in Vcc1. It should be ap- +5.25V. This is the voltage source for the two Op- proximately 3.6mA. Amps U2 and U3. 7) Normal Operation Mode 4) Set Power Supply 4 to 0V (minimum gain). a) Set EN dipswitch to Off position (Logic 5) Shutdown Mode High). a) Set dipswitches for EN and STBY to On b) Set STBY dipswitch to either On or Off. (Logic Low). c) Measure Current in Vcc1. It should be ap- b) Measure Current in Vcc1. It should be ap- proximately 27mA. proximately 0.2A. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 696 IF RECEIVER, WIDE BB Figure 1. Test and Measurement Setup 2