SN74AVCBH164245: IBHLO spec for 3.3V supply

Ella KIM

Expert 4212 points

Part Number: SN74AVCBH164245
Other Parts Discussed in Thread: SN74LVC1G34, , SN74AVCB164245, SN74AVC16T245

Hello,

Customer wants to know IBHLO spec for 3.3V supply.

Per calculation with IBHLO spec for 3.6V, Rpull-up should be <2.47kohm to drive enough current for L to H transition.

RPull-up = (VCC - VIH) / IBHLO

VCC = 3.3V

VIH = 2.0V

IBHLO = 525uA (@3.6V)

RPull-up = (3.3V - 2.0V) / 525uA = 2.47kohm

But their driver needs 4.7kohm pullup. Is there a way to increase Rpullup value than 2.47kohm?

Thanks for advice.

Sincerely,

Ella

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 317370 points

Bus-hold inputs should not be used with pull-up/-down resistors. (The bus hold circuit acts like such a resistor, so you get conflicts when the two try to pull in different directions.)

What exactly is that driver? Is that 4.7 kΩ a recommendation or a limit?

0 Ella KIM over 2 years ago in reply to Clemens Ladisch

TI__Expert 4212 points

Hi Clemens,

I'm reading An Overview of Bus-Hold Circuit and the Applications (Rev. B) to understand how it works and want to get your confirmation.

SN74AVCBH16425 can be used with open-drain type driver but there should not be pull-up resistor on the input side as internal bus hold circuitry (non-inverting buffer circuitry) acts like a pull-up resistor. Is it correct?

Sincerely,

Ella

0 Clemens Ladisch over 2 years ago in reply to Ella KIM

Guru 317370 points

Bus-hold inputs can be used with open-drain drivers only if the pull-up resistor is strong enough. Either use a 2.2 kΩ pullup, or insert a buffer (e.g., SN74LVC1G34) in front of the input.

0 Ella KIM over 2 years ago in reply to Clemens Ladisch

TI__Expert 4212 points

Hi Clemens,

Maybe I should go back to initial question.

Ella KIM said:
Customer wants to know IBHLO spec for 3.3V supply.

Can you help check IBHLO spec for 3.3V supply so that Samsung can check the min pull up resistor value that can be permitted? It does not seem to have a linear relationship between supply voltage and IBHLO.

Thanks,

Ella

+1 Clemens Ladisch over 2 years ago in reply to Ella KIM

Guru 317370 points

3.6 V is the worst case of a 3.3 V ± 0.3 V supply; you are supposed to use this value.

If you can guarantee that the supply has tighter tolerances, you can use linear interpolation: [FAQ] What method is best used for estimating specification values between those given in the datasheet?

0 Ella KIM over 2 years ago in reply to Clemens Ladisch

TI__Expert 4212 points

Hi Clemens,

Thanks! Problem solved. It looks we can interpolate IBHLO at 3.3V to be 450mA. Just FYI, I've discussed more on their requirement.

- Driver is open drain type and requires 4.7~10kohm pullup resistor to meet VOL spec based on low sink current.

- SN74AVCBH164245 does not need pull-up/down resistor or requires low pull-up resistor to make sure enough driving current.

- They would check the max resistor value based on linear interpolation and then use a buffer or find another solution.

Sincerely,

Ella

0 Ella KIM over 2 years ago in reply to Ella KIM

TI__Expert 4212 points

Hi Clemens,

Besides buffer (SN74LVC1G34) insertion solution, Samsung is looking for another device. Summary for their requirements :

- Level converting from 3.3V to 1.8V or vice versa

- External pull-up >4.7kohm is required

- # of channels : 16 or 32

- DIR/OE pin is needed

I check that SN74AVC32T245ZKER is already AVLed in Samsung system. Can you advise if you have any concern on SN74AVC32T245ZKER and if you have a better device suggestion?

Sincerely,

Ella

0 Clemens Ladisch over 2 years ago in reply to Ella KIM

Guru 317370 points

Yes, using a similar device without bus-hold inputs will work. (If the bus-hold functionality is not needed.)

0 Ella KIM over 2 years ago in reply to Clemens Ladisch

TI__Expert 4212 points

Do we have any p2p device to SN74AVCBH164245, but without bus-hold inputs?

+1 Clemens Ladisch over 2 years ago in reply to Ella KIM

Guru 317370 points

The SN74AVCB164245 is the same device without bus hold.

The SN74AVC16T245 is more modern, cheaper, and uses less power, but the control inputs are referenced to V_CCA (this still works if V_CCA < V_CCB).

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SN74AVCBH164245: IBHLO spec for 3.3V supply