CCS/MSP430G2202: I2C bus can't work well when the battery for MSP430G2202 runs out

qiuhu liu

Part Number: MSP430G2202
Other Parts Discussed in Thread: TXS0102

Tool/software: Code Composer Studio

Hi:

In my application , there are two slaves in my I2C bus, one is MSP430G2202, ther other one is an EEPROM. The MSP430G2202 is powered by a battery. The I2C bus works well if the battary have enough power, but when the battary runs out , the I2C bus can't work correctly. the master can't communicate with the EEPROM. I hope the system will still work, even if the MSP430' battery runs out. Is there any way to avoid this situation？

Thanks!

over 6 years ago

0 Clemens Ladisch over 6 years ago

Guru 244320 points

Is the EEPROM also powered by the battery?

0 qiuhu liu over 6 years ago in reply to Clemens Ladisch

Intellectual 280 points

The EEPROM is powerd by other power source. The battery only supply power to MSP430.

0 Clemens Ladisch over 6 years ago in reply to qiuhu liu

Guru 244320 points

All devices on the I²C bus must use the same high-level voltage.

You have to put a voltage regulator behind the battery, or add a voltage-level translator between the two devices on the bus.

0 qiuhu liu over 6 years ago in reply to Clemens Ladisch

Intellectual 280 points

If I remove the battery, the MSP430 still affects the I²C bus, The master can't communicate with EEPROM. Is this normal?

0 Clemens Ladisch over 6 years ago in reply to qiuhu liu

Guru 244320 points

If you remove the battery, the MSP might be powered from the bus through the ESD protection diodes (see youtube.com/watch?v=2yFh7Vv0Paw).

0 qiuhu liu over 6 years ago in reply to Clemens Ladisch

Intellectual 280 points

Hi, Clements, thanks for your reply, Is there any way to avoid this issue?

0 Clemens Ladisch over 6 years ago in reply to qiuhu liu

Guru 244320 points

A voltage translator (e.g., TXS0102) could be used to solve both issues (different voltages, and disconnect the MSP from the bus when power is off).

0 qiuhu liu over 6 years ago in reply to Clemens Ladisch

Intellectual 280 points

Thanks, as I have to consider the power consumption, the TXS0102's datasheet says "Ioff Supports Partial-Power-Down Mode Operation
", Does this mean when the maser is power off, the TXS0102 will enter Ioff mode? In Ioff mode, the power consumption of TXS0102 is just several uA?

0 Clemens Ladisch over 6 years ago in reply to qiuhu liu

Guru 244320 points

The Ioff feature makes the I/Os high impedance to prevent current flowing in to or out of them. There is not much power consumption in any state.

(Please note that the TXS has internal pull-up resistors; you should not add external ones.)

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CCS/MSP430G2202: I2C bus can't work well when the battery for MSP430G2202 runs out