SNVS480J January 2007 – July 2020 LM5022
Parasitic circuit capacitance, inductance, and gate drive current create a spike in the current sense voltage at the point where Q1 turns on. To prevent this spike from terminating the on-time prematurely, every circuit must have a low-pass filter that consists of CCS and RS1, shown in Figure 14. The time constant of this filter must be long enough to reduce the parasitic spike without significantly affecting the shape of the actual current sense voltage. The recommended range for RS1 is between 10 Ω and 500 Ω, and the recommended range for CCS is between 100 pF and 2.2 nF. For this example, the values of RS1 and CCS is 100 Ω and 1 nF, respectively.