TPS929120-Q1: Multiplex Outputs

Hello Matt,

Can I connect 4 outputs together and set them for 50mA each and expect the LED to be driven at 200mA?

yes you can.

So could I shut off channel 2-4 and set channel 1 to 50mA?

Because every output has a individual current source, so you can do that.

Do you mind to offer the information of your project: )

So could I shut off channel 2-4 and set channel 1 to 50mA?

Because every output has a individual current sink, so you can't??? do that.

CH1-4 are joined at the pins of the part.

3LEDS on these joined channels

I cant set CH2-4 to 0mA and CH1 to 50mA... Then I would expect the LEDs are driven to 50mA????

But I can join the channels and set the outputs to 50mA each and expect that the LED's are driven to 200mA from your comments.

Is there a document that describes connecting these outputs is acceptable?  I would assume I have to pwm at the same rate if I would intertwine Channels  0 - 5 & 6-11 with one another.  I may not use the PWM function through the PWM0 /1 pins but I am asking ahead of time.

Thank you

sorry it's typo, i mean you can do that.

Is there a document that describes connecting these outputs is acceptable?  

We don't have a document to describe it expressly, but some customers has already used like you describe.

I would assume I have to pwm at the same rate if I would intertwine Channels  0 - 5 & 6-11 with one another. I may not use the PWM function through the PWM0 /1 pins but I am asking ahead of time.

As prior description,  each output can be controlled individually. You can also use UART communication to adjust related register to set the PWM duty cycle of each output. So if you simultaneously set related register, you can control the channels you connect together at the same time without PWM pins.

Frank

I appreciate the answers to my questions.  I need to over ride this chip and turn it off easily through external hardware.  Would I be able to short the REF pin to ground to shut the outputs off?

The chips outputs have to turn off very quickly.

Please let me know what your thoughts are.

Thank you

Matt

May I please have an answer to my question... I am trying to get a board layout completed for this to try.

Thank you

You can do that from the principle side, but i recommend you don't do that because :

1)The ref pin is used for setting the current of output. The less noise the better. 

2)when you connect the ref pin to the ground the device will detect a fault and pull down the fault pin.

Could you show me some points:

1)what's the meaning of turn off easily? You want to control the dimming with UART or the PWM input?

2)How fast you need to shunt down the output and why you need that.

Frank

I have two functions on my light.  

1st Function - Matrix Driver with a bunch of LEDs

2nd Function- Turn

Legally I cannot have both functions on at the same time and I have to prevent from exceeding a specified current draw.  I need to override the matrix driver elements by turning them off every time Function 2 is activated.  Is there another way of configuring the chip that I can shut it down externally without a software command?  I am open to suggestions.  

I was thinking of using a 2n7002 mosfet connected to the ref pin... I wont add a lot of trace length as to add a lot of noise to this pin.

Please let me know your thoughts.