TPS61169; control of CTRL pin and efficiency

Takao Yamamoto

Genius 4135 points

Other Parts Discussed in Thread: TPS61169

Dear all,

Could you teach me two questions?

Q1; Can I control CTRL pin by ON/OFF from MCU I/O pin?

Is there no care point?

Q2;Can I consider the efficiency as about 85% at following situation?

I set ILED=102mA (RSET=2ohm, Vin=3.5-4.2V).

*I did not guess the efficiency because the efficiency characteristic is under ILED=20mA at data sheet.

**I attached my application circuit.

aplication_circuit.pdf

Best regards,

over 9 years ago

0 Randy Dahl over 9 years ago

TI__Intellectual 2090 points

Q1) Yes the CTRL pin can be used as an enable to turn on/off the LED string.

There is a 300 kohm pulldown on this pin and you need to ensure the VIH/VIL levels.

Q2) 85% efficiency is okay for estimation.

Best regards,

Randy

0 Iker Caballero over 9 years ago in reply to Randy Dahl

Prodigy 50 points

Hello,

We need to use a 50Hz signal to enable/disable the driver, but not for analog dimming. Just to switch on the LEDs at max current, 30% duty at 40-50Hz. Would it be possible with this driver?

We are going to use a string of 14 LEDs at 100mA (Vf=1,5V).

Regards,

Iker.

0 Randy Dahl over 9 years ago in reply to Iker Caballero

TI__Intellectual 2090 points

Hi Iker

In the configuration you are describing the LED will be on for ~3 to 6 ms and off for ~19 to 22 msec which will result in some flicker of the LEDs. The startup and shutdown times of the TPS61169 are not the same which causes the shift in on/off times.

Regards,

Randy

0 Iker Caballero over 9 years ago in reply to Randy Dahl

Prodigy 50 points

Yes, flickering does not matter. But I've seen the soft-start is not valid for our application.

Thanks Randy!
Iker.

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TPS61169; control of CTRL pin and efficiency