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| TMC1203KLC50 |
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 CADEKA
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12 page 
TMC1203 PRODUCT SPECIFICATION 12 Figure 10. Typical Interface Circuit - High Performance + – + – + – + – LM185-1.2 1k ½ 1k ½ 1k ½ 1k ½ 10k ½ 1k ½ 75 ½ 100 20 ½ +5V +5V +5V GREEN Video Input GREEN Digital Video Output BLUE Digital Video Output RED Digital Video Output Pixel Clock 0.1 µF 65-3720-07 Gain Adjust Wideband Op-amp 1k ½ 1k ½ 10k ½ 75 ½ 100 +5V BLUE Video Input Wideband Op-amp 1k ½ 1k ½ 10k ½ 75 ½ 100 +5V RED Video Input Wideband Op-amp 2k ½ 0.1 µF 0.1 µF 0.1 µF VDDA RTA RTB RTC RBA RBB RBC VINA VINB VINC AGND DGND VDD DA7-0 OEA CLKA TMC1203 DB7-0 OEB CLKB DC7-0 OEC CLKC 0.1 µF Application Notes The circuit in Figure 10 employs a band-gap reference to generate a variable RTX reference voltages for the TMC1203 as well as a bias voltage to offset the wideband input amplifi- ers to mid-range. The operational amplifier in the reference circuitry is a standard 741-type. The voltage reference at RTX can be adjusted from 0.0 to 2.4 volts while RBX is grounded. Schottky diodes are used to restrict the wideband amplifier output to between -0.3V and VDD +0.3V. Diode protection is good practice to limit the analog input voltage at VINX to the safe operating range. Grounding The TMC1203 has separate analog and digital circuits. To keep digital system noise from the A/D converter, it is rec- ommended that power supply voltages (VDD and VDDA) come from the same source, and that ground connections (DGND and AGND) be made to the analog ground plane, and as close as possible to the device pins. Power supply pins should be individually decoupled at the pin. The digital cir- cuitry that gets its input from the TMC1203 should be referred to the system digital ground plane. Printed Circuit Board Layout Designing with high performance mixed-signal circuits demands printed circuits with ground planes. Overall system performance is strongly influenced by the board layout. Capacitive coupling from digital to analog circuits may result in poor A/D conversion. Consider the following sug- gestions when doing the layout: 1. Keep the critical analog traces (VN, RTX, RBX) as short as possible and as far as possible from all digital signals. The TMC1203 should be located close to the analog input connectors. |
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