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TPS40210: Characteristic of the current limit function

Nikolaus Ng
Intellectual 390 points
Part Number: TPS40210


Hi,

     Hope to know the behavior of the current limit function, here below is the scenario :

1) DC/DC output voltage set to 10V

2) Load is a resistive load, like a 10 ohm resistor

3) Current limit is set to 0.5A

    In this case, will the DC/DC circuit output 5V @0.5A ? 

    And if the resistive load is like a 100 ohm resistor, the circuit will output 10V, and consuming 0.1A in the load side ?

    Thanks.

  • 0
    TI__Guru**** 191445 points
    TPS40210 uses cycle by cycle valley mode over current protection. In your case if the load current is higher than the current limit, the off time will be longer than normal so the effective duty cycle is less and the output voltage will decrease as you have noted. The actual output voltage will depend on a number of additional variables, such as Vin, Lout and Fsw. If the output voltage falls below 65% (typical) of the normal regulated value, the TPS40210 will enter hiccup mode due to UVP operation. This is all explained in the datasheet.
  • 0 in reply to JohnTucker
    Intellectual 390 points
    Thanks for your explanation.
    Our application is to use 24VDC as input, to provide float charge of a 24V lead acid battery, which is 27.5VDC with current limit of 0.6A.
    1) When charging during the battery is low in capacity, it will drain more than 0.6A when applying 27.5V, so we need the circuit to limit current at 0.6A while voltage can be lesser than 27.5V and decreas accordingly
    2) When in stable floating charge, it will drain not more than 50mA, we need the circuit to output 27.5VDC

    Do you think this chip can perform this function ?
  • 0 in reply to Nikolaus Ng
    TI__Guru**** 191445 points
    I often answer general questions such as your original inquiry. I do not really support TPS40210. Also, we may have a dedicated battery management solution. Let me alert the proper application support.