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LM3648: sequence, pin connections I2C specification

Ryuji
Guru 20090 points
Part Number: LM3648

Hello,

I have questions about Lm3648.

(1) Pin connections
If we use LM3648 on the torch mode and control by I2C.
Could you please let me know the recommended pin connection of HWEN, STROBE, TORCH/TEMP, TX?

HWEN : pull up to IN with pull up resistor? If yes please let me know the recommended pull up resistor value.
STROBE, TORCH/TEMP, TX : can we connect these pins to GND if we don't used ? or can be left floating?

(2)Write Sequence of Register
If we use only torch mode, could you please let me know the write sequence of  register?

1: set the Torch Brightness Register
2: set the Enable Register,

Keep other registers as Default

(3) I2C specifications
In the datasheet, there is fewer I2C timing specifications than NXP specification.
Can we use this device on the following I2C specification which is published by NXP?
Our customer would like to use Fast Mode.

http://www.nxp.com/documents/user_manual/UM10204.pdf

Best Regards,
Ryuji

  • 0
    TI__Intellectual 1940 points

    Hello,

    1) HWEN must be high for the device to operate.  If you want to hard connect it to VIN you can or you could use a 10k resistor if a pull-up is preferred.  There is a 300kohm pull down on HWEN.  Strobe, Torch/Temp and TX can be left floating so long as they are disabled via I2C as there are built in pull-downs on the pins.

    2)  You have it correct.  Set brightness to desired level, and then enable torch mode via I2C

    3)  We are compatible with the 400kHz version of the I2C standard so it should not be a problem.

    Greg