LT6600-20 APPLICATIONS INFORMATIONInterfacing to the LT6600-20 output voltage is 1.65V, and the differential output voltage is 2V The LT6600-20 requires two equal external resistors, R P-P for frequencies below 20MHz. The common mode IN, output voltage is determined by the voltage at Pin 2. Since to set the differential gain to 402Ω/RIN. The inputs to the Pin 2 is shorted to Pin 7, the output common mode is the fi lter are the voltages V + – IN and VIN presented to these mid-supply voltage. In addition, the common mode input external components, Figure 1. The difference between voltage can be equal to the mid-supply voltage of Pin 7 V + – IN and VIN is the differential input voltage. The aver- (see the Distortion vs Input Common Mode Level graphs age of V + – IN and VIN is the common mode input voltage. in the Typical Performance Characteristics section). Similarly, the voltages V + – OUT and VOUT appearing at Pins 4 and 5 of the LT6600-20 are the fi lter outputs. The Figure 2 shows how to AC couple signals into the difference between V + – OUT and VOUT is the differential LT6600-20. In this instance, the input is a single-ended output voltage. The average of V + – OUT and VOUT is the signal. AC coupling allows the processing of single-ended common mode output voltage. or differential signals with arbitrary common mode levels. The 0.1μF coupling capacitor and the 402Ω gain setting Figure 1 illustrates the LT6600-20 operating with a single resistor form a high pass fi lter, attenuating signals below 3.3V supply and unity passband gain; the input signal is 4kHz. Larger values of coupling capacitors will proportion- DC coupled. The common mode input voltage is 0.5V, and ally reduce this highpass 3dB frequency. the differential input voltage is 2VP-P. The common mode 3.3V 0.1μF V V 3 402Ω 3 – 1 3 VIN – 4 + 7 + V + OUT V 2 2 OUT LT6600-20 2 V + – IN 0.01μF – V 1 OUT + 8 – VOUT 1 V 5 IN + 402Ω 6 0 t 0 t – 66002 F01 VIN Figure 1 3.3V 0.1μF V V 0.1μF 402Ω 3 2 1 – 3 + 7 + 4 VOUT V + OUT 1 LT6600-20 2 2 V + 0.1μF IN 0.01μF – – VOUT 0 t + 8 – VOUT 1 V 5 IN + 402Ω 6 –1 0 66002 F02 Figure 2 62pF 5V 0.1μF V V 100Ω 3 – 1 3 3 VIN – + + 7 + 4 VOUT VOUT 2 LT6600-20 2 2 0.01μF – – VOUT 500mVP-P (DIFF) + 8 – VOUT 1 1 V 5 IN + V + 100Ω IN 6 0 t – + 0 t V 66002 F03 IN – 2V 62pF Figure 3 66002fb 7