9.2.2 OPA192 Buffered Multiplexer Output (MXO)

The use of a buffer relaxes the R_SOURCE requirements to an extent. Charge from the sample-and-hold capacitor no longer dominates as a residual charge from a previous channel. Although having good performance is possible with a larger impedance using the OPA192, the output capacitance of the MXO also holds the previous channel charge and cannot be isolated, which limits how large the input impedance can finally be for good performance. In this configuration, the 1xV_REF range allows slightly higher impedance because the OPA192 (20 V/µs) slews approximately 2.5 V in contrast to the 2xV_REF range that requires the OPA192 to slew approximately 5 V.

A. Restriction on the source impedance exists. R_(SOURCE) ≤ 500 Ω for a 12-bit settling at 1 MSPS with both 1xV_REF and 2xV_REF ranges.

Figure 66. Application Diagram for an OPA192 Buffered MXO