Datasheet LTC1292, LTC1297 (Analog Devices) - 21

LTC1292/LTC1297
O U U W U APPLICATI S I FOR ATIO
If VCC and VREF are not tied together, then VCC should Because a unique input protection structure is used on be turned on first, then VREF. If this sequence cannot be the digital input pins, the signal levels on these pins can met, connecting a diode from VREF to VCC is recom- exceed the device VCC without damaging the device. mended (see Figure 25). 1N4148 DIODES 1N4148 DIODES CS CS V 5V V 5V CC CC 1k +IN CLK +IN CLK LTC1292 LTC1292 LTC1297 LTC1297 –IN D –IN D OUT OUT GND V GND V REF REF LTC1292/7 F24 LTC1292/7 F23
Figure 23. Overvoltage Protection with Clamp Diodes Figure 24b. Overvoltage Protection with Diode Clamps and Current Limiting Resistor
CS V 5V CC CS V 5V CC 1k +IN CLK LTC1292 +IN CLK 250Ω LTC1297 LTC1292 1N4148 –IN DOUT LTC1297 –IN DOUT GND VREF LTC1292/7 F24a GND V 5V REF LTC1292/7 F25
Figure 24a. Overvoltage Protection with Figure 25. Separate V Current Limiting Resistors CC and VREF Supplies
+5V f/32 22µF CS VCC 0.1µF CLK VDD VIN +IN CLK EN RESET LTC1292 Q1 Q4 –IN DOUT Q2 Q3 CD4520 Q3 Q2 GND VREF Q4 Q1 RESET EN V CLK SS TO OSCILLOSCOPE LTC1292/7 F26 CLOCK IN 1MHz
Figure 26. “Quick Look” Circuit for the LTC1292
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