SLOS930C November 2015 – October 2024 THS4541-Q1
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
A very common requirement is driving the capacitive load of an ADC or some other next stage device. Directly driving a capacitive load with a closed-loop amplifier such as the THS4541-Q1 can lead to an unstable response, as shown in the step response plots into a capacitive load (see Figure 6-8 and Figure 6-26). One typical remedy for this instability is to add two small series resistors (Ro in Figure 7-11) at the outputs of the THS4541-Q1. Figure 6-6 and Figure 6-24 provide parametric plots of recommended Ro values versus differential capacitive load values and gain.
Operating at higher gains requires lower Ro values to achieve a ±0.5-dB flat response for the same capacitive load. Some direct parasitic loading is acceptable with no series Ro that increases with gain setting, as illustrated in Figure 6-6 and Figure 6-24 where the Ro value is 0 Ω. Even when these plots suggest no series Ro is required, good practice is to include a place for the Ro elements in the board layout (0-Ω load initially) for later adjustment, in case the response appears unacceptable. The TINA simulation model does a good job of predicting this effect and showing the impact for different choices of capacitive load isolating resistors (Ro).