JAJSN49 January 2022 TPSM5D1806E
PRODUCTION DATA
The TPSM5D1806E 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.