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TPS737: Does the TPS73733DCQR have the ability to sink current?

Part Number: TPS737

The output voltage needs to be used as the clamping voltage. Is there a current sinking capability? how many?

  • Hi Rengui,

    Linear regulators including the TPS737 are not designed to sink current. Typically the only path capable of sinking current from OUT to GND is through large feedback resistors. In the case of the TPS737, these feedback resistors add up to 80k ohms as shown in the functional block diagram. As such, the sink current will be less than 100 uA over the entire output voltage range.

    Isink,max = Vout,max/(R1 + R2)

    TI does have a selection of LDOs that include an output discharge feature allowing them to sink larger currents. Keep in mind that these regulators must be disabled first in order to discharge the output. 

    Thanks,

    Gerard

  • Hi Gerard,

    Help recommend a chip model that can sink current? I want to know about it.

    Thanks,

    Rengui
  • Hi Rengui,

    Can you provide me more information about your application? The input voltage, output voltage, load current, and any other details about your system are necessary for me to find a good recommendation.

    For future reference, you can also do a parametric search for many LDO features including "Output Discharge" and other specifications required for any application on the TI website by clicking on the Products tab here:

    One thing to remember is that LDO's with output discharge have to be disabled before they can start sinking current. The sink current is also limited by an internal resistor. If you require a regulator that can sink large currents and maintain output regulation, TI's DDR memory power solutions are the best option. You can find more information about them here:

    Thanks,

    Gerard

  • Hi Gerard,

    The 3.3V power supply of the TPS73733 supplies power to the MCU. The internal ADC of the MCU collects signals, but the signal is powered by 12V power supply. When the signal is normal within 2.5V, the abnormality will be 18V power supply. Therefore, the 3.3V clamp voltage is used, taking into account the acquisition accuracy. R1 currently uses a 470 ohm resistor. In case of abnormality, 3.3V needs to have a current sinking capacity of 15mA.

    My previous analysis was wrong, ignoring the load of TPS73733. When abnormal, the load will sink current and not be sinked by TPS73733.
    However, there is no technical specification of the load regulation rate in the datasheet. What is the load adjustment rate of the TPS73733?

    At present, the 3.3V power supply load is much larger than 15mA. If it is far less than 15mA, what kind of power chip should I choose?


    Thanks,

    Rengui

  • Hi Rengui,

    You can find the load regulation in Figure 1 of the datasheet: 

    The output voltage is within 0.5% across the entire load range when referred to a 10 mA load. Note that the TPS737 can also regulate with load currents less than 15 mA down to no load. 

    There is no information in your diagram about the TPS737 input supply. Based on the other information you have shared about the application, this LDO will be suitable if its input supply is between (3.3 V + Vdo,max) and 5.5 V. Vdo,max is the maximum dropout voltage based on your application. The TPS737 has a maximum dropout of 500 mV @ 1 A load. From this information, Vdo,max for your application's required output current can be calculated using Ohm's law: 

    Rds,on(max) = 500 mV / 1 A = 0.5 Ohms

    Vdo,max = Iout * Rds,on(max) = Iout * 0.5 Ohms

    Thanks,

    Gerard