ZHCSMP8B November 2020 – March 2021 TPSM5D1806
PRODUCTION DATA
The TPSM5D1806 soft start feature limits the inrush current from the input supply when the device is powered up. For dual output configuration, the soft start time is internally programmed to 1 ms. The soft start pin must be left floating in dual output configuration.
The external soft start is enabled when the device is configured in parallel output operation. In parallel output applications, if the SS pin is left open, the default soft start time is also 1 ms. Applications that deliver high load current can have a large amount of capacitance at the output and can require longer soft start time. The soft start time for such applications can be extended by connecting an external capacitor, CSS from the soft-start pin to AGND. With external CSS, the soft-start time is the longer of 1 ms or the programmed external soft start time. An internal current source (ISS = 2 μA) charges CSS and generates a ramp from 0 V to VFB (0.5 V) to control the ramp-up rate of the output voltage. The external soft-start time can be selected from Table 7-6 or calculated using Equation 3.
CSS (nF) | Open | 6.2 | 8.2 | 10 | 12 | 20 |
---|---|---|---|---|---|---|
tSS (ms) | 1 | 1.5 | 2 | 2.5 | 3 | 5 |
The soft-start capacitor is discharged when VOUT is shut down by either fault protection or when VEN is below the enable threshold.