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Can TXB0106 work with DRV8833?

Tim Baker
Intellectual 540 points
Other Parts Discussed in Thread: TXB0106, DRV8833

Hi,

I am posting a question on the compatibility between TXB0106 and motor driver DRV833. The question has been posted in Motor Drivers Forum yesterday as Can DRV8833 work with TXB0106 and Motor Drive Application Manager Ryan Kehr suggested yes because DRV8833's input pin has pull-down resistor ≥150K which is larger than the minimum pull-down impedance of 50kohm (datasheet page 10: Pullup or Pulldown Resistors on I/O Lines) of TXB0106.

I would like to confirm again with experts here in voltage level translator forum: from the above reasoning, do we know for sure that TXB0106 can work with DRV8833?

 

Original Question in Motor Driver Forum

DRV8833 has four input control pins: AIN1, AIN2, BIN1, BIN2, nSLEEP. According to ELECTRICAL CHARACTERISTICS, AIN1, AIN2, BIN1, BIN2 require VIH > 2, and nSLEEP require VIH > 2.5.

 

If a processor uses 1.8V I/O voltage, then a voltage level translator is required. I found that TXB0106 which has six pins on both A and B side might be an ideal choice.

However, TXB0106 is an auto-sensing translator which has different architecture as traditional unidirectional translators. The primary concern here is its weak output. It employs one-shot modules to translate rising and falling edges with relatively strong current, but after a short-period the one-shot modules would be shut off, and the high-or-low logic level will be maintained weakly via 4K resistors connected in parallel.

Compatibility

I.

If DRV8833 detects rising/falling edges as what is flip-flop does, then since at the rising/falling edges one-shot module turns on T1 and T3 and there is very small impedance, the current would then be strong enough to drive DRV8833 to trigger the change. And also since flip-flops registers change only at edges, this means the weak input through 4K resistor after one-shot has turned T1/T3 off would have no impact on DRV8833, just as if there is without these 4K resistors.

II.

However, if DRV8833 requires constant input current to maintain input status, it might turns out that TXB0106is not a good idea after a short period the current would be limited by 4K resistors.

But would 4K resistor limit the current to the extent that DRV8833 would fail to work? From DRV8833'sELECTRICAL CHARACTERISTICS, page 6, the input current is on the order of µA. Assuming 3.3V VIH, this implies that there are equivalent resistor of MΩ resistance internally at input pins to limit the current. Since MΩ >> 4K, it seems that this 4K resistor would have little effect on the IIH AND IIL, and this suggests thatDRV8833 could work with TXB0106.

 

Is this reasoning correct? Could TI employees in this motor forum confirm with people in the logic level translator group?

 

Tim