Datasheet LT6600-10 (Analog Devices) - 10

LT6600-10
APPLICATIONS INFORMATION
Figure 5, present the output of the LT6600-10 with a 1600Ω voltage of VMID. While the internal 11k resistors are well differential load, or the equivalent of 800Ω to ground at matched, their absolute value can vary by ±20%. This each output. The impedance seen by the network analyzer should be taken into consideration when connecting an input is still 50Ω, reducing refl ections in the cabling be- external resistor network to alter the voltage of VMID. tween the transformer and analyzer input. 20 1dB PASSBAND GAIN 1MHz 25°C 2.5V COMPRESSION POINTS 0 0.1μF 1MHz 85°C COILCRAFT COILCRAFT NETWORK NETWORK –20 TTWB-1010 TTWB-16A ANALYZER ANALYZER 3RD HARMONIC 3 SOURCE 1:1 388Ω 1 4:1 INPUT 85°C – –40 4 402Ω 3RD HARMONIC 7 + 50Ω LT6600-10 25°C –60 53.6Ω 2 50Ω 2ND HARMONIC 8 – 85°C + 5 OUTPUT LEVEL (dBV) –80 402Ω 388Ω 2ND HARMONIC 6 0.1μF 25°C 6600 F05 –100 –120 –2.5V 0 1 2 3 4 5 6 1MHz INPUT LEVEL (VP-P)
Figure 5. (S8 Pin Numbers)
6600 F06
Figure 6 Differential and Common Mode Voltage Ranges
The differential amplifi ers inside the LT6600-10 contain VOCM can be shorted to VMID for simplicity. If a different circuitry to limit the maximum peak-to-peak differential common mode output voltage is required, connect VOCM voltage through the fi lter. This limiting function prevents to a voltage source or resistor network. For 3V and 3.3V excessive power dissipation in the internal circuitry supplies the voltage at VOCM must be less than or equal to and provides output short-circuit protection. The limiting the mid-supply level. For example, voltage (VOCM) ≤1.65V function begins to take effect at output signal levels above on a single 3.3V supply. For power supply voltages higher 2V than 3.3V the voltage at VOCM can be set above mid-supply. P-P and it becomes noticeable above 3.5VP-P. This is illustrated in Figure 6; the LTC6600-10 was confi gured with The voltage on VOCM should not be more than 1V below unity passband gain and the input of the fi lter was driven the voltage on VMID. The voltage on VOCM should not be with a 1MHz signal. Because this voltage limiting takes more than 2V above the voltage on VMID. VOCM is a high place well before the output stage of the fi lter reaches the impedance input. supply rails, the input/output behavior of the IC shown The LT6600-10 was designed to process a variety of input in Figure 6 is relatively independent of the power supply signals including signals centered around the mid-supply voltage. voltage and signals that swing between ground and a The two amplifi ers inside the LT6600-10 have independent positive voltage in a single-supply system (Figure 1). control of their output common mode voltage (see the The range of allowable input common mode voltage (the + – Block Diagram section). The following guidelines will average of VIN and VIN in Figure 1) is determined by optimize the performance of the fi lter for single-supply the power supply level and gain setting (see the Electrical operation. Characteristics section). VMID must be bypassed to an AC ground with a 0.01μF or
Common Mode DC Currents
higher capacitor. VMID can be driven from a low impedance In applications like Figure 1 and Figure 3 where the source, provided it remains at least 1.5V above V– and at LT6600-10 not only provides lowpass fi ltering but also level least 1.5V below V+. An internal resistor divider sets the shifts the common mode voltage of the input signal, DC 66001fe 10