We are using the device for following in/out specification:
- Vin = 10V
- Vout = 13.5V
- Iout ca. 1-1.5A
We are using the design with external current sense resistor and disconnect MOSFET. We have used in our design a Mosfet with 2-4V Vgs threshold (e.g. BSZ440N10 from Infineon). According datasheet page 20 below figure 4 a Vgsth value below 1.5V is required:
“Gate-to-source threshold voltage: The
threshold should be below 1.5V. A 1V to
1.2V range across the overall temperature
range is recommended.“
The internal charge pump seems to be able to boost the Gate ~4.4V above the input voltage (~10V). The voltage drop across the Mosfet is ca. 60-70mV at ca. 0.6A load current, which is basically fine.
Q1: Can we stick with higher Gate source threshold voltages or what would be negative impacts?
Remark: There seems to be different OCP modes according table 3, which implies that for current limit during power up Vgate < Vin+1.6V
Q2: What is the maximum Gate output voltage above input voltage the internal charge pump can generate?
Remark: Actually we have measured \~4.4V but not sure if this can be guaranteed over the complete temperature range.
Thanks in advance!
BR Andreas N.