Team,
my customer cannot use external bias supply. How long will the SVR stay operational if Vin drops below 4V?
Nominal Vin = 5V..12V but it can drop down to 3.xV shortly (max current during drop is 1-2A)
Datasheet says lowest Vin without external bias is 4V.
UVLO for Vin and VCC are below 3V.
Is SVR running until either Vin or UVLO is triggered or Vout UVP is triggered?
Thanks
Difficult to estimate the minimum input voltage, but it will be below 4V.
It will depend on the output current, switching frequency, size of pcb traces to VIN and PGND, and where vin is measured.
The falling VIN uvlo threshold is 2.15V. The falling VCC uvlo threshold is 2.77V.
VCC is generated from VIN. The linear regulator from VIN to VCC and has a drop out voltage
The dropout voltage of the linear reg is 27mV with a load of 2mA when not switching.
The ICC current draw when is 3x to 5x of the 2mA see figure 8-13 depending on the switching frequency.
I estimated the dropout voltage as ~135mV at the 1000kHz.
The maximum falling vin voltage will be 2.77V + 135mV = ~2.9V and triggered by the VCC uvlo.
If the output voltage is 2.5V or lower, the device should work down to 2.9V, assuming the enable pin is greater than 1.27V.
UVP will disable the device for output voltages greater than the 3.3V.
