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PSoC™ 4 Forum Discussions

MaRa_4092696
Level 1
Level 1

Can the /HI pin use a 1.8V pullup while the CY8CMBR3106 is supplied from 3.3V?

I need to power the 3106 from 3.3V, and I have 3.3V-referenced I2C. But the controller that will receive the hardware interrupt is a 1.8V device. The datasheet ("Host Interrupt" section) describes the host interrupt pin as open drain. But the very next bullet describes the VDDIO supply on the 3108 and how it enables comm at lower voltage levels.

So the datasheet is not perfectly clear. Is the '3106 host interrupt a true open drain that can be referenced to voltage levels lower than VDD?

Thanks

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1 Solution
Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Yes. The HI pin will be driven to 3.3 V.

Therefore, a circuit must be implemented to pull down the voltage to 1.8 V on the HI line so that it does not damage your host device.
Since it is an active low pin, a LOW signal on the HI line is used to initiate an I2C read from the master and this can still be detected.

Thanks and regards
Harigovind

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Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hello MaRa_4092696

The HI pin can be pulled up to 1.8V while the device is powered with 3.3V.

Care needs to be taken so that the overvoltage from MBR (3.3V) does not damage you host controller. Since HI is an output pin, MBR3 only pulls the line LOW to indicate an interrupt to the master even at 1.8V.

Thanks and regards
Harigovind

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Thanks. Can you clarify:

...the overvoltage from MBR (3.3V) does not damage you host controller...

As long as the HI pin is configured as the interrupt output, it will not drive the line to 3.3V?

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Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Yes. The HI pin will be driven to 3.3 V.

Therefore, a circuit must be implemented to pull down the voltage to 1.8 V on the HI line so that it does not damage your host device.
Since it is an active low pin, a LOW signal on the HI line is used to initiate an I2C read from the master and this can still be detected.

Thanks and regards
Harigovind

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