SPRZ506C October 2022 – May 2024 TMS320F2800132 , TMS320F2800133 , TMS320F2800135 , TMS320F2800137
CMPSS: A CMPSS Glitch can Occur if Comparator Input Pin has AGPIO Functionality and ADC is Sampling the Input Pin
0, A, B, C
The combinations of use cases for a specific analog input pin that need special considerations are shown in Table 3-2. As shown in this table, special considerations or workarounds need to be used for the combination of CMPSS Input, ADC Sampling, and AGPIO.
FUNCTION USED ON A SPECIFIC ANALOG PIN | COMPONENT USED | ||||
---|---|---|---|---|---|
CMPSS Comparator Input | Yes | - | Yes | - | Yes |
ADC Sampling | Yes | Yes | - | Yes | Yes |
AGPIO Analog Pin Type | Yes | Yes | Yes | - | - |
AIO Analog Pin Type | - | - | - | Yes | Yes |
Result | Workaround needed | No special analysis or workaround needed |
The AGPIO analog pin path contains an extra series switch of 53Ω. This creates a low-capacitance isolated node shared by the ADC and CMPSS comparator, as shown in Figure 3-1. This node can be disturbed when the ADC samples the channel (depending on the prior voltage stored on the ADC sample-and-hold capacitor), and this disturbance can cause a false CMPSS event of up to 50ns. To accommodate this potential disturbance, the workarounds below can be implemented.