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ocrdu
ocrdu
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Using an NPN transistor as a high side-side switch

I want to use the thermistor inside of a battery pack on the BQ25887 and on a GPIO pin on a microcontroller so that both the microcontroller and the charging IC can monitor the battery voltage. For reference, I'm using the ATMega32U4 with a 5V5 V regulator.

If the charging IC is powered, then I want the thermistor to be used on the BQ25887. If it is not, then I want the thermistor to be used on the microcontroller. I'm trying to think of a way I can use two switches to switch between the charging IC and the MCU. I can't use an optocoupler since that takes up too much space on my PCB. Here is what I have now, and here are the questions that I have.

  • Can NPN transistors be used as high side switches like this?
  • If no current is flowing through the base, will the transistors truly be open?

My concern is current backfeeding into either the LDO-5V 5 V line or the BQ25887.

enter image description here

Using an NPN transistor as a high side switch

I want to use the thermistor inside of a battery pack on the BQ25887 and on a GPIO pin on a microcontroller so that both the microcontroller and the charging IC can monitor the battery voltage. For reference, I'm using the ATMega32U4 with a 5V regulator.

If the charging IC is powered, then I want the thermistor to be used on the BQ25887. If it is not, then I want the thermistor to be used on the microcontroller. I'm trying to think of a way I can use two switches to switch between the charging IC and the MCU. I can't use an optocoupler since that takes up too much space on my PCB. Here is what I have now, and here are the questions that I have.

  • Can NPN transistors be used as high side switches like this?
  • If no current is flowing through the base, will the transistors truly be open?

My concern is current backfeeding into either the LDO-5V line or BQ25887.

enter image description here

Using an NPN transistor as a high-side switch

I want to use the thermistor inside of a battery pack on the BQ25887 and on a GPIO pin on a microcontroller so that both the microcontroller and the charging IC can monitor the battery voltage. For reference, I'm using the ATMega32U4 with a 5 V regulator.

If the charging IC is powered, then I want the thermistor to be used on the BQ25887. If it is not, then I want the thermistor to be used on the microcontroller. I'm trying to think of a way I can use two switches to switch between the charging IC and the MCU. I can't use an optocoupler since that takes up too much space on my PCB. Here is what I have now, and here are the questions that I have.

  • Can NPN transistors be used as high side switches like this?
  • If no current is flowing through the base, will the transistors truly be open?

My concern is current backfeeding into either the LDO 5 V line or the BQ25887.

enter image description here

added 5 characters in body; edited title
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JRE
JRE
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Using an NPN Transistortransistor as a High Side Switchhigh side switch

I want to use the thermistor inside of a battery pack on the BQ25887 and on a GPIO pin on a microcontroller so that both the microcontroller and the charging IC can monitor the battery voltage. For reference, I'm using the ATMega32U4 with a 5V regulator.

If the charging IC is powered, then I want the thermistor to be used on the BQ25887. If it is not, then I want the thermistor to be used on the microcontroller. I'm trying to think of a way I can use two switches to switch between the charging IC and the MCU. I can't use a Optocoupleran optocoupler since that takes up too much space on my PCB. Here is what I have now, and here are the questions that I have.

  • Can NPN transistors be used as High Sidehigh side switches like this?
  • If no current is flowing through the base, will the transistors truly be open? My concern is current backfeeding into either the LDO-5V line or BQ25887.

My concern is current backfeeding into either the LDO-5V line or BQ25887.

enter image description here

Using an NPN Transistor as a High Side Switch

I want to use the thermistor inside of a battery pack on the BQ25887 and on a GPIO pin on a microcontroller so that both the microcontroller and the charging IC can monitor the battery voltage. For reference, I'm using the ATMega32U4 with a 5V regulator.

If the charging IC is powered, then I want the thermistor to be used on the BQ25887. If it is not, then I want the thermistor to be used on the microcontroller. I'm trying to think of a way I can use two switches to switch between the charging IC and the MCU. I can't use a Optocoupler since that takes up too much space on my PCB. Here is what I have now, and here are the questions that I have.

  • Can NPN transistors be used as High Side switches like this?
  • If no current is flowing through the base, will the transistors truly be open? My concern is current backfeeding into either the LDO-5V line or BQ25887.

enter image description here

Using an NPN transistor as a high side switch

I want to use the thermistor inside of a battery pack on the BQ25887 and on a GPIO pin on a microcontroller so that both the microcontroller and the charging IC can monitor the battery voltage. For reference, I'm using the ATMega32U4 with a 5V regulator.

If the charging IC is powered, then I want the thermistor to be used on the BQ25887. If it is not, then I want the thermistor to be used on the microcontroller. I'm trying to think of a way I can use two switches to switch between the charging IC and the MCU. I can't use an optocoupler since that takes up too much space on my PCB. Here is what I have now, and here are the questions that I have.

  • Can NPN transistors be used as high side switches like this?
  • If no current is flowing through the base, will the transistors truly be open?

My concern is current backfeeding into either the LDO-5V line or BQ25887.

enter image description here

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Jay
Jay
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Using an NPN Transistor as a High Side Switch

I want to use the thermistor inside of a battery pack on the BQ25887 and on a GPIO pin on a microcontroller so that both the microcontroller and the charging IC can monitor the battery voltage. For reference, I'm using the ATMega32U4 with a 5V regulator.

If the charging IC is powered, then I want the thermistor to be used on the BQ25887. If it is not, then I want the thermistor to be used on the microcontroller. I'm trying to think of a way I can use two switches to switch between the charging IC and the MCU. I can't use a Optocoupler since that takes up too much space on my PCB. Here is what I have now, and here are the questions that I have.

  • Can NPN transistors be used as High Side switches like this?
  • If no current is flowing through the base, will the transistors truly be open? My concern is current backfeeding into either the LDO-5V line or BQ25887.

enter image description here