JAJSIB3D August 2017 – February 2021 THS4561
The THS4561 is principally intended to operate with a nominal single-supply voltage of 3 V to 12 V. Supply voltage tolerances are supported with the specified operating range of 2.85 V (10% low on a 3-V nominal supply) and 12.6 V (5% high on a 12-V nominal supply). Supply decoupling is required, as described in Section 8.7. Split (or bipolar) supplies can be used with the THS4561, as long as the total value across the device remains less than that specified in Section 7.3.
Using a negative supply to deliver a true swing to ground output when driving SAR ADCs can be desired. Although the THS4561 quotes a rail-to-rail output, linear operation requires approximately 200-mV headroom to the supply rails. One easy option for extending the linear output swing to ground is to provide the small negative supply voltage required using the LM7705 fixed –230-mV, negative-supply generator. This low-cost, fixed, negative-supply generator can accept a 3-V to 5-V positive supply and provides a fixed –230-mV supply for the negative power supply. Using the LM7705 provides an effective solution, as discussed in the Extending Rail-to-Rail Output Range for Fully Differential Amplifiers to Include True Zero Volts reference guide.