JAJSDE0A June 2017 – February 2024 TPS549B22
PRODUCTION DATA
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To properly design for 4 ms and 8 ms SS settings, additional application consideration is needed. The recommended application workaround to support the 4-ms and 8-ms soft-start settings is to ensure sufficient time delay between the VDD and EN_UVLO signals. The minimum delay between the rising maximum VDD UVLO level and the minimum turn on threshold of EN_UVLO is at least TDELAY_MIN.
where
For example, if SS setting is 4 ms and VREF = 1 V, program the minimum delay at least 9 ms; if SS setting is 8 ms, the minimum delay must be programmed at least 18 ms. See Figure 6-5 and Figure 6-6 for detailed timing requirement. Because TPS549B22 is a PMBus device, the end user has the option of programming power-on delay (POD) as another workaround. Be sure to follow the same calculation to determine the needed POD (see Section 7.18 and Table 7-17 for detailed information).
The workaround/consideration described previously is not required for SS settings of 1 ms and 2 ms.