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TPS922055: Leakage current issue when Driver is in OFF state

Miteshkumar Dalabhai Patel
Intellectual 2130 points
Part Number: TPS922055
Other Parts Discussed in Thread: TPS922052, TPS922054, TPS922053

Hi,

One of my customer is working on TPS922055 based LED drvier & facing strange issue. Driver is working ok in normal use casebut when driver is in off state at that time there is a leakage of 50 to 60uA current & becuase of this LED is not switching off completly.

Cusotmer has varified on EVM as well apart from their on board & in both the cases they found this leakge current. What is the solution for the same? & Is it becuase of current sense path or through MOSFET path?

Input Voltage - 16 to 33V

Output Configuration - 12V approx / 2 to 3A.

Application - Strobe light for Fire Panels.  (20mSeocnds ON & 980 mSeconds OFF)/ (flashing every 1 seconds for 20 mseconds)m when falult occurs. In normal scenario driver will be OFF state.

Issue  - In OFF state LEDs are slightly glowing becuase of leakge current.

Need help for the same.

Mitesh

  • 0
    TI__Genius 17415 points

    Hi Mitesh,

    This is due to the leakage current of UVP resistor divider (The current path is drawn in red line as below). The value of the resistor divider in the current prototype-version EVM is too low and may introduce tens of uA leakage current. We will repair this issue in the formal-release EVM.

    There are two ways to avoid this issue:

    • Use UVP resistor divider with a larger value.
    • Parallel a large resistor R_shunt (may in hundreds of kohm) with LED string and shunt the leakage current. Actually, the R_shunt, R4 and R6 act like a voltage divider when the IC is disabled, where you should set the voltage across the LED string less than the voltage that will light up the LED. An illustration graph is shown below.
    • The same rule applies to TPS922052, TPS922053, TPS922054 and TPS922055.

    BR,

    Steven