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TPS5401 as LED Driver?

Other Parts Discussed in Thread: TPS5401

I need a Step-Down DC-DC IC for driving white LEDs of LED Backlight supply of LCD Display DOGL128 manufactured by Electronics Assembly.

Currently, I am using IC CAT4238 recommended by Electronics Assembly.  This is a step-up switching regulator with Vsense feedback given by sensing the current through LEDs by passing it through a resistor. This system works.  However, my voltage sources for driving the LEDs are either 24V dc supply or a 9V battery.  So, while using CAT4238, I need to first convert the 24V or 9V to around 5V and then feed it to CAT4238.  This additional conversion involves cost as well as loss of efficiency.

The LED backlight of DOGL128 is made up of three arms of LEDs, each arm has three white LEDs in parallel.

The voltage of the white LED is 2.7-3.3V depending on the current flowing through it.  I am driving around 7mA through each LED or 20mA through each arm as this gives sufficient brightness.  Currently, I have connected the arms in series and the CAT4238 develops the required 8-9V to drive the LEDs.  The LED current is passed through a resistor of 15 ohm which develops the feedback Vsense of 300mV.

I think it would be more efficient to use a step-down converter to convert 24 or 9V to say around 3V, connect all the three LED arms in parallel, drive a total current of 60mA through them and make the current flow through a suitable resistor to give the rated feedback voltage to the step-down converter IC.  This should then act as a constant current source and would be more efficient than the current arrangement of using CAT4238.

I have searched for LED driver ICs that operate in Buck mode.  However, the only ICs for this seem to be available from Linear and these are expensive.

I am already using TPS5401 to derive 3V and 5V supplies from the 24V dc and 9V battery.

So, my question is - can I use the TPS5401 as a step-down converter that can supply 3.3V white LEDs with constant current as described above.

Please also tell me if you know suitable TI Step down DC-DC converters that can be used as constant current source for multiple white LEDs of around 3V that are connected in parallel.

My worry is whether the TPS5401 if used this way, will provide protection in case of failure of any of the LEDs connected in parallel by shorting or by open ckt?

Thanks in advance for your help.