TPS3808: TPS3808G01 vs TPS3898A

David,

1)
To start, it is very important to note that ENABLE and MR are inverses. RESET and SENSE OUT are also inverses. This means active-low RESET is the same function as active-high SENSE OUT. Active-low MR is the same as active-high ENABLE. You can tell if the pin function is "active-low" or "active-high" depending if there is a bar above the label. Active-low uses the bar above the label to signify the pin is activated when logic low.

To tell if the devices have the same function, you always refer to the TIMING DIAGRAM. TPS3808 and TPS3898 are both open-drain outputs but TPS3808 has an active-low RESET and active-low MR while TPS3898 has active-low SENSE OUT and active-low ENABLE meaning they are actually opposite function logic.

TPS3808 is functionally equivalent to TPS3897.


2) any voltage supervisor can be set to a threshold above the VIT+ minus V_hysteresis which is sometimes labeled VIT- found in the ELECTRICAL CHARACTERISTICS table. For TPS3897, VIT+ value is 500mV. The V_hys is 5mV. For the trip point for falling detection is 500mV - 5mV = 495mV.

3)

Reset point = VIT- * ((Rtop + Rbot)/Rbot)

0.81 = 495mV * ((Rtop + 10k)/10k)

Rtop = ~ 6.3kohm



Please let me know if you have any other questions or if you need any additional support. Thank you!

-Michael

Hi David,

I think you should take a look into TPS3890 (www.ti.com/.../slvsd65a.pdf)
If you can do without sense, TPS3840 (www.ti.com/.../samplebuy),

TPS3840 is being sampled right now and should be orderable around 09/19.


Let me know if either of these options are appealing and if so, we can work on a schematic review when you're ready :)

Hi David, this is good info.
One thing I liked about TPS3890 was it had a lower Vdd,min spec of 1.5V, versus , versus TPS3897 Vdd,min spec of 1.7V. Vdd,min spec of 1.7V.

If you want to trip at 900mV, a good option may be TPS3850. You can order a fixed 900mV part. This would allow you to eliminate the voltage divider you would need to "adjust" the TPS3897. Additionally, it has a lower Vdd,min spec of 1.6V, versus TPS3897 Vdd,min spec of 1.7V. This will allow for some additional headroom if powering off 1.8V.

It does come with an integrated watchdog which you can or cannot use. This might present some value to the system. Either way, it doesn't necessarily require an additional CWD capacitor. If you don't want to use it, you can disable it, and save on iQ.

TPS3850 should be pretty close in price to TPS3808. Lowest cost probably would be TPS3897A.
All seem like good options for your system requirements. Think about what product you would like to go with. Once you decide what part you would like to go with, if you would like to do a schematic review, feel free to email me at:m-beck1@ti.com