DC1164A Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1164 SIGNAL SOURCE High Speed ADC Signal Source DESCRIPTION Demonstration circuit 1164 is a signal source to By replacing a few components and a jumper, this use to demonstrate high speed ADCs. Each as- demo board becomes a complete IF strip for use sembly will include a 70.56MHz crystal which can with spread spectrum signals. By feeding this be used with any high speed ADC as a clean signal board with an external spread spectrum signal, the source. signal chain becomes a means to provide a clean low noise signal, with programmable amplitude, to Functionally, the DC1164 uses a crystal oscillator as the ADC. a precision clock source. The output of the crystal is then directed through a signal chain which pro- This circuit also is a model for designing complex IF vides proper filtering to produce a low distortion, strips which require SAW filtering and multiple am- low noise signal tone signal for high speed ADCs. plifiers. Design files for this circuit board are A programmable step attenuator allows for 32dB of available. Call the LTC factory. dynamic range on the output signal. LTC is a trademark of Linear Technology Corporation Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE The board has LT1763 LDOs Supply Voltage to provide power to the vari- 6V-9V ous parts of the circuit. Crystal frequency 70.56MHz Saw Filter Bandwidth 20MHz Saw Filter Center Fre- 70MHz quency 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1164 SIGNAL SOURCE QUICK START PROCEDURE Demonstration circuit 1152 is easy to set up to evaluate measurement equipment setup and follow the procedure the performance of most members of the LTC2246H below: family of A/D converters. Refer to Figure 1 for proper SETUP - + 6-9V Signal Output To ADC Demo Board Clock Output Signal Input SW1 - A rotary switch that controls attenuation in JUMPERS: 1 dB steps. The 0 setting is 0dB of attenuation, Signal Path/Xtal Selects which element is active. and F is 16dB of attenuation. Xtal supplies the crystal with 5 volts, producing a 70.56MHz signal at the output. Signal path removes PORTS: the 5 volts on the crystal and redirects it to the gain J1: Signal input When using the DC1164 as an IF block to amplify the external signal presented at J1. strip J1 is where to input the signal -0dB/-16dB Provides an additional 16dB of at- J2: Signal Output Outputs the filtered signal. Con- tenuation. Selecting 0dB provides attenuation from nect this port to the analog input of the ADC demo 0dB to 16dB, and -16 provide attenuation from16dB board. to 32dB. J3: Clock Output For applications where a clock sig- nal is required, use this port as a reference clock. This is not to be used as a clock for the ADC. 2