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TCA9517: I2C buffer and load switch

Shlomi Yehezkia
Mastermind 6150 points
Part Number: TCA9517
Other Parts Discussed in Thread: PCA9306, TCA9509, PCA9515B, , PCA9517,

Hi Team,

 

I considering adding protections for off board I2C sensor

One of the options is using I2C buffer and load switch

The goal is to protect and have disconnected option for malfunction sensor (over current and/or I2C short circuit from the sensor side)

I learn little about the option, attached is what I found, please review it and tell me if I am on the right track

Please advise regards the longevity and potential MP cost (I put the Web numbers…)

I can notice that PCA9306 (level translator with enable) can be cost effective? Is it good for isolate the I2C?

 

 

I2C Buffer

P/N

Brand

Features

ESD protection

Operation Voltage A

Operation Voltage B

I2C speed

Enable

FP

Cost MP

Longevity

Comments

TCA9509

TI

I2C Buffer, ReDriver,
Open Drain I2C,
isolate two halves of a bus for voltage
and capacitance.

Yes, JESD 22, 2KV Human

0.9-5.5V

2.7- 5.5V

Support 400KHZ I2C

Active High

VSSOP (3x3mm)
X2QFN (1.6x1.6mm)

<0.33$

 

 

PCA9515B

TI

I2C Buffer, ReDriver,
isolate malfunctioning slaves on power-up reset

Yes, JESD 22, 2KV Human

2.3-3.6V

Non

Support 100KHz & 400KHZ I2C

Active High

VSSOP (3x3mm)

<0.65$

 

 

PCA9515B

TI

 

 

 

 

 

 

 

 

 

 

TCA9517

TI

I2C  bidirectional buffer isolates capacitance

Yes,

0.9-5.5V

2.7- 5.5V

Support 400KHZ I2C

Active High

VSSOP (3x3mm)

<0.34$

 

 

PCA9517

NXP

I2C  bidirectional buffer isolates capacitance

PCA9517- 2kV
PCA9517A- 5.5kV

0.9-5.5V

2.7- 5.5V

Support 400KHZ I2C

Active High

8-TSSOP,
HWSON8 (2x3mm)

<0.54$

 

 

PCA9306

TI

2-Bit Bidirectional Translator, isolate a 400-kHz bus from a 100-kHz
busby controlling the EN pin, and disconnecting the
slower bus during fast-mode communication

Yes, JESD 22, 2KV Human

>5.5V

>5.5V

Support 400KHZ I2C

Active High

SSOP (3x3mm),
VSSOP (2.3x2mm),
X2SON (1.4x1mm)

<0.2$

 

 

 

 

About the load switch, I familiar with MIC2090/1, please advise your option

I would like 50 to 100mA current limit with Latch- off and Flag option

 

 

Switch load

P/N

Brand

Features

ESD protection

Operation Voltage

Over current Behaviour

Fault Flag

Cost MP

Longevity

Comments

MIC2090/1

Microchip

High side power switch, general porpose 50ma or 100mA over current circuit protection

Yes, 3kV

1.8-3.3V

2 options-
auto-retry or latchoff

Yes

<0.15$

 

2090-50mA,
2091-100mA,
2YM5- Latch-Off,
1YM5- Auto- Retry

 

 

Thanks,

Shlomi

  • 0
    TI__Guru 74741 points
    Hey Shlomi,

    I'd like to point out that PCA9306 is not a "true buffer" but rather you can think of it as a switch with level shifting capabilities. You can use PCA9306 to disconnect the I2C bus on the sensor side from the main I2C bus.

    The only device I do not like from your list is PCA9515B as it is a very old buffer and uses has a static voltage offset on both sides. TCA9509 requires VccB to be larger than VccA by atleast 1V.

    It also looks like our TCA9517 is cheaper than PCA9517 from NXP according to your chart. They have the same functionality so using the cheaper of the two makes better sense if you were to choose that device.

    From your list I would choose either TCA9517 or PCA9306. PCA9306 if you do not need a true buffer and TCA9517 if you do need true buffering. If you disable both devices, the I2C bus will be separated from each other.

    Now if you need TRUE ISOLATION (isolation of Vcc and GND) then ISO154x can provide that.

    "About the load switch, I familiar with MIC2090/1, please advise your option"
    This is a micrel device so I am not famillar with this. You may want to contact their support if you have further questions.

    From MY OPINION, this device looks like it allows for high side switching and monitors (1) over current, (2) thermal, (3) undervoltage. It looks like the Ron of the FET is around 1 ohm which will have some drop off on your overall voltage. (worst case: 100mA * 1.2 ohm is 120mV drop) You have to ask how much of a drop on Vcc is okay with you.

    Thanks,
    -Bobby
  • 0 in reply to BOBBY
    Mastermind 6150 points

    Hi Bobby,

    Thank you for the detailed answer, some more things:

    1. I can notice there is TCA9517 and TCA9517A with different DS, is it the same for my propose? Can I use both?

    2. I think it clear but just to be sure I will provide both side the same 3.3V to the buffer, here is the BD please advise.

    Thanks,

    Shlomi

    I2C Buffer.docx

  • 0 in reply to Shlomi Yehezkia
    TI__Guru 74741 points
    Hey Shlomi,

    "1. I can notice there is TCA9517 and TCA9517A with different DS, is it the same for my propose? Can I use both?"
    The only difference between A version and non A is the ViLc spec is changed. TCA9517 has ViLc = 0.4V and TCA9517A has ViLc = 0.45V; This essentially means TCA9517 (non A) has a more strict ViLc but better noise immunity because ViLc-VoLB is larger.

    i usually recommend the non A version to customers.

    "2. I think it clear but just to be sure I will provide both side the same 3.3V to the buffer, here is the BD please advise."
    TCA9517 and PCA9306 both work at 3.3V on both sides.

    You need pull up resistors on A side of your buffer in the block diagram, other wise the pin is floating and if the device is enabled then you could drive B side low unintentionally. It's okay to have pull up resistors on both the main board on A side and on the off board sensor as they will just be two parallel resistors.

    Thanks,
    -Bobby