how do i sequence two voltage from one power supply ?

[Mohamed Adam]

Hi guys, i have a problem with power sequencing please help me the problem is , i have DSP processor have three voltages 1.05(core), 1.8(IO), and 1.8(DDR2 controller) i want to generate 1.8V for IOs and DDR2 controller from one regulator the problem is in sequencing between IOs and controller , IOs must power up before DDR2 controller , how i can do this without drop in power (1.8)




thanks

 

[barry]

You could use a mosfet switch with a delayed turn on. Or you could use two regulators with different turn-on delays.

 

[Mohamed Adam]

thanks barry for ur reply , but i don't want do use two regulators because i have no size for this but i can use MOSFET switch with delayed turn on as u said , but can i do this without drop in power (1.8)? i mean for delay

 

[barry]

thanks barry for ur reply , but i don't want do use two regulators because i have no size for this but i can use MOSFET switch with delayed turn on as u said , but can i do this without drop in power (1.8)? i mean for delay

It depends on your current and your MOSFET on-resistance. You can get mosfets with very low Rds.