DC1250A-AD Analog Devices

DEMO CIRCUIT 1250 16-BIT HIGH PERFORMANCE ADC DRIVERS QUICK START GUIDE LTM9001 16-bit Receiver Subsystem DESCRIPTION Demonstration circuit 1250 is an evaluation board featur- rating LVDS outputs for evaluation of the part with ing Linear Technology Corporations LTM9001 16-bit LVDS outputs, obtain DC1241. DC1250 plugs into the Receiver Subsystem. DC1250 demonstrates good circuit DC890 Data Acquisition demo board and the output can layout techniques and recommended external circuitry be easily analyzed with Linear Technologys PScope data for optimal system performance. processing software, which is available for no charge on our website at LTM9001 16- BIT RECEIVER SUBSYSTEM Power Supply (3.8V-6V 1.0A) NOTE. Even a high-quality signal synthesizer will still have noise and harmonics that should be attenuated with a low-pass or band-pass filter. For good-quality high order filters, see TTE, Lark Engineering, or equivalent. To DC890 Signal Generator BPF HP 8644B or equiv. RF Signal Generator (HP 8644B) or other low phase noise BPF clock source (e.g. DC1216) Figure 1. Proper Evaluation Equipment Setup ADDITIONAL INFORMATION Although the DC1250 demo board is ready to use on de- el-shifted to within the input common-mode limits in the livery, it has additional flexibility built in for various types datasheet. of input networks. Below is some information about con- Table 2: DC1250 Input Configuration Guide figuring DC1250 to meet the specific needs of your eval- CONFIGURATION COMPONENTS NECESSARY uation. Single-Ended Input No change. Transformer T1 acts as a balun for differential drive. AC-Coupled APPLYING INPUT SIGNALS (Default Setup) Single-Ended Input Remove T1, replace with 0 jumpers. May need The input network consists of various components de- to install impedance-matching resistor at R4 No Transformer signed to allow either single-ended or differential inputs, or R1/R7. AC-Coupled AC-coupled or DC-coupled. Table 2 shows some possi- Single-Ended Input Same as above. Change C1 and C8 to 0 jum- ble input configurations, and which components to in- pers. Inputs must be within the common- No Transformer mode voltage limits of LTM9001. stall. LTM9001 is designed for excellent performance DC-Coupled Differential Inputs Remove R7 and install R5. T1 and C1/C8 can be with both single-ended and differential input drive, with replaced with 0 for DC coupling. little difference in distortion performance. When using NOTE. When driving the ADC driver with a direct DC-coupled path, increased DC-coupled inputs, the inputs to DC1250 need to be lev- input bias currents may occur due to the amplifiers input impedance. See the LTM9001 datasheet for more details. 2