SLOS375B August 2014 – February 2024 THS4541
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
Figure 6-8 and Figure 6-26 shows 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 can lead to an unstable response, as shown in the step response plots into a capacitive load. Figure 7-11 shows how one typical remedy for this instability is to add two small series resistors (Ro) at the outputs of the THS4541. 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. Figure 6-6 and Figure 6-24 (where the Ro value is 0 Ω) shows how some direct parasitic loading is acceptable with no series Ro that increases with gain setting. 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).