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Original question:

TIDA-01093: BOM designation is missing, Please help to get complete BOM

TIDA-01093: TIDA-01093 schematic understanding, U8 pin-6 voltage

smash Micheal
Intellectual 1000 points

Part Number: TIDA-01093

Dear Texas / All,

I have one query for TIDA-010193 U8 chip pin-6 'TS1' , please help to understand, voltage available at pin-6 of U8 when a switch 'S1' is pressed ?

Limit for that pin 'TS!' is 5vdc as per datasheet.

Rohit

  • 0
    Intellectual 1000 points

    Hello Texas  & team members,

    I have one query for TIDA-010193 U8 chip pin-6 'TS1' , please help to understand, voltage available at pin-6 of U8 when a switch 'S1' is pressed ?

    Limit for that pin 'TS!' is 5vdc as per datasheet.

    Rohit

  • 0 in reply to smash Micheal
    TI__Guru 54715 points

    Hi Rohit,

    When S1 is pressed, Cell 1 voltage is divided with R57, D17 and the thermistor, the voltage to the gate of Q18 should turn it on causing Q51 to turn on.

    With Q51 turning on the source of Q49 will be about 2V below the cell 11 voltage.  D58 may drop another 0.5V to the TS1 pin (U8 pin 6).  So if the cells are at 3V U8 may not boot.  Consider the operating range of your cells, you may need to select Schottky diode for D58 and a lower Vgsth FET for Q51.

  • 0 in reply to WM5295
    Intellectual 1000 points

    Hi,

    Thanks for reply.

    How is the voltage of 2vdc present @ source of Q49 &Q51 respectively ? Even if 2vdc is present, Drain voltage should be available @ source of Q49 ,which is equal to = approx 80vdc.

    If i consider 2 vdc @ D58 , than @ TS1 pin[ U8-pin-6] voltage will be 0.25 only , as 1.25 is getting dropped @ D58 ,2-1.25 = 0.25vdc only, will this voltage will be used to detect wake up signal ?

    Also when will D55 be active?

    Rohit

  • 0 in reply to smash Micheal
    TI__Guru 54715 points

    Hi Rohit,

    The 2V mentioned is a value in the range of Vgsth for the Q49.  If BAT+ and the drain of Q49 is 80V, GND_U is about 40V, C11 is about 44V.  See source follower or common drain amplifier in your favorite electronics reference.  The Q49 source would be about 42V, or 2V above GND_U and sufficient to boot the U8 if Q51 is on after the D58 diode voltage drop.  D58 will have little current once the capacitor is charged, perhaps 0.5 or 0.6 V drop.

    D55 will be active when Q18 is on.  R63 will limit the current in the path, with a 1.7V typical Vgsth of Q18, about 515 uA will flow, this current through R130 would be a large voltage, so D55 will conduct most of the current with approximately 13V/6.2M = 2.2 uA in R130.