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Long time reset IC

Other Parts Discussed in Thread: TPS3808, TPS3899

Hi,

I'm finding a reset IC.

VDD : 4V

reset time : 10s

I saw the TPS3808 but it doesn't support 4V supply voltage.

  • Hi,

    You can use the TPS3808G01 to support a monitored rail of 4V.

    Ben

  • Hi, 

    Which part can I use?

    Nominal supply voltage has not include 4V in the table. 

    If the condition I want is supply voltage is 4V and threshold voltage is 2.79V, can i use tps3808?

    which part should i choose?

  • Hi, 

    Please use TPS3808G30 for your application.  The "nominal supply voltage" means the monitored voltage should be 3V or higher and does not represent the max VDD voltage the part can handle.  The VDD range for the TPS3808 is 1.7V to 6.5V.  Please see below. 

    Ben

  • Hello SY,

    When using TPS3808G01, you need to use an external divider to monitor the voltage as shown below.

    Doe TPS3808G01, the SENSE pin comparator voltage threshold is 0.405V. You can design R1 & R2 such that for Vin > 4V, the RESETz is not asserted. When Vin goes below 4V, the SENSE pin voltage goes below 0.405V and then the RESETz is asserted.

    The RESET delay can be programmed by connecting a suitable capacitor on CT pin. Refer section 8.3.2 of datasheet for capacitor selection.

    Apart from TPS3808, following other options may be useful to you.

    1. TPS3899DL01DSER - This device also needs external resistance divider similar to TPS3808G01. It's internal threshold for SENSE pin is 0.505V. Additional benefit with TPS3899 device is, it allows programmability for SENSE delay as well as RESET delay using capacitance.

    2. TPS3840DL40DBVR - This device will monitor the VDD voltage. It does not need resistance divider. When VDD goes below 4V, the RESETz will be asserted. The RESET delay can be programmed by external capacitor on CT pin.

    Thanks & Regards,

    Shridhar.

  • Hello SY,

    Somehow the external resistance divider image does not show up in my previous reply.

    Please refer Figure 8-1 in TPS3808 datasheet for the image.

    Thanks & Regards,

    Shridhar

  • Hi SY,

    Below is the figure that Shridhar was referring to.