SLVSDR2B November 2018 – March 2021 ADC12DJ3200QML-SP
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
Most applications can be narrowed down into two categories: those that need DC coupling and those that do not need DC coupling. The needs and interface recommendations for each category are different. In most cases, the driving circuit will need to perform a conversion from single-ended signaling at the signal source to differential signaling for the ADC12DJ3200QML-SP inputs.
Applications that require DC coupling will need to use a DC coupled amplifier to drive the ADC. DC coupling is often more difficult due to the need for matched common-mode voltage (VCM) between the driver amplifier and ADC12DJ3200QML-SP. ADC12DJ3200QML-SP makes this easy for many applications due to the 0-V input common-mode voltage (VICM). A 0-V VICM allows a split supply differential amplifier to drive the ADC directly with no VCM shift which in turn allows the amplifier to operate at its optimal operating point, typically with an output common-mode voltage (VOCM) equal to the midpoint of the two supplies. If the differential amplifier has a pin to set its VOCM then that pin can be tied directly to GND. An example amplifier that is capable of driving ADC12DJ3200QML-SP is the LMH5401-SP which is capable of converting from single-ended to differential signaling and has a high gain-bandwidth product to match the ADC12DJ3200QML-SP bandwidth capabilties.
The second category, applications that do not require DC coupling, will often find that best performance can be achieved using transformers or baluns to convert from single-ended to differential signaling. These transformers can also perform impedance conversion such that a 50-Ω, single-ended source is well matched to the 100-Ω, differential termination inside the ADC12DJ3200QML-SP. For instance, a 1:2 impedance ratio transformer can provide both single-ended to differential conversion and proper impedance matching. The transformer outputs can be either AC-coupled, or directly connected to the ADC differential inputs, which are terminated internally to GND on each input pin through a 50-Ω resistor. Baluns must be selected to cover the needed frequency range, have a 1:2 impedance ratio, and have acceptable gain and phase balance over the frequency range of interest. Poor gain and phase balance will result in degraded 2nd-harmonic distortion performance. Table 8-1 lists a number of recommended baluns for different frequency ranges, but is not fully inclusive.
PART NUMBER | MANUFACTURER(1) | MINIMUM FREQUENCY (MHz) | MAXIMUM FREQUENCY (MHz) |
---|---|---|---|
BAL-0009SMG | Marki Microwave | 0.5 | 9000 |
BAL-0208SMG | Marki Microwave | 2000 | 8000 |
TCM2-43X+ | Mini-Circuits | 10 | 4000 |
TCM2-33WX+ | Mini-Circuits | 10 | 3000 |
B0430J50100AHF | Anaren | 400 | 3000 |