Hi ,
My name is vengat from Avnet , one of my customer is using TPS2490 Hot swap controller product in their design & they want to make a initial start up delay of 118 ms for TPS2490 device , how we can achieve the 118 ms delay in EN Pin or TPS2490/91 ? . Any calculation is required to put RC combination ? Any one has application can you shared with me ..i would really help me to move it forward .
Regards/
venagt
TPS3808 has programmable delay function through external capacitor on Ct pin. Use the RESETx output to connect to TPS2490 EN pin. You'll need an intermediate voltage supply for the TPS3808.
I possible simple solution might use a TLV809xxx operating from a resistor divider and driving the EN pin.
Since the TLV809 supply current is quite small, you can reduce its effect with a much larger bias current in the divider; compensating for teh nominal supply current yields the next level of accuracy.
The TLV809 has a fairly wide reset time tolerance, however it in in the order of magnitude the customer wants. In addition, a lot of issues of input voltage droops, recovery time etc. can be solved using a part like this.
Thanks , i will suggest to my customer & would update u.
Hi,
Above combination will support 300 ms delay with TPS2490 ? ( The output should come up after 300 ms after power on.).
Do you have any Reference schematic or in TINA Model ?
Vengat
They want to achive 300 ms delay in TPS2490 but above combination of ( TPS3808 + TPS2490 for 300 ms delay )will not work because input power start from 9 V and they do not have any other input DC rail . it is possible to achive RC combination in EN Pin ? Do you have any calculation for 300 ms ?
Rgds/vengat
TPS3808 could be powered from the 12V input using either 12V-> 3.3V LDO or simple resistor + zener diode as regulator. Alternatively, the simple R-C circuit tied to the EN pin could also be used.
R x C = 0.3s / (ln (1-Ven/Vin))
Ven is EN pin trip point (1.35V typical) and Vin is the input voltage turn on (9V). You probably want to adjust depending on Ven, Vin, R, and C tolerances too.