SNVSB97A December 2018 – September 2021 LM34936-Q1
The LM34936-Q1 soft-start time is programmed using a soft-start capacitor from the SS pin to AGND. When the converter is enabled, an internal current source (ISS) charges the soft-start capacitor. When the SS pin voltage is below the feedback reference voltage VREF, the soft-start pin controls the regulated FB voltage. Once SS exceeds VREF, the soft-start interval is complete and the error amplifier is referenced to VREF. The soft-start time is given by Equation 3:
The soft-start capacitor is internally discharged when the converter is disabled because of EN/UVLO falling below the operating threshold or VCC falling below the VCC UV threshold. The soft-start pin is also discharged when the converter is in Hiccup mode current limiting or in thermal shutdown. When average input or output current limiting is active, the soft-start capacitor is discharged by the constant current loop transconductance (gm) amplifier to limit either input or output current.