SNVS872D August 2012 – August 2018 LMZ21700
When EN is set high for device operation the LMZ21700 starts switching after 50-μs delay and the output voltage will start rising. The VOUT rising slope is controlled by the external capacitor CSS connected to the soft-start (SS) pin. The nano module has a 2.5 μA constant current source internally connected to the SS pin to program the softstart time TSS:
The softstart capacitor voltage is reset to zero volts when EN is pulled low and when the thermal protection is active.
If tracking function is desired, the SS pin can be used to track external voltage. If the applied external tracking voltage is between 100 mV and 1.2 V, the FB voltage will follow SS according to the following relationship: