N900 Hardware Battery Charger

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The battery charger charges the battery, and supplies power when running connected to USB. It can also supply power for [[N900 Hardware USB Host|USB Host]] mode.
The battery charger charges the battery, and supplies power when running connected to USB. It can also supply power for [[N900 Hardware USB Host|USB Host]] mode.
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=Hardware=
 
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The battery charger is the [http://focus.ti.com/docs/prod/folders/print/bq24150.html bq24150] charger from TI.
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==Hardware==
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It features reverse boost mode - which enables power to be supplied to a USB device connected to the N900.
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The battery charger is the [http://focus.ti.com/docs/prod/folders/print/bq24150a.html bq24150a] charger from TI.
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When initially powered on, this chip, and the [[N900 Hardware USB PHY|USB interface]] chip enable charging from dead without any software running.
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It features reverse boost mode - which enables power of up to 200 mA@5V to be supplied to a USB device connected to the N900.
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This mode of charging respects the maximum current available without negotiation - 100mA in the case of a normal USB connection, or 1.2A in the case the charger is plugged in.
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When initially powered on, this chip, and the [[N900 Hardware USB PHY|USB interface]] chip enable charging from dead without any software running. This mode of charging respects the maximum current available without negotiation - 100 mA in the case of a normal USB connection, or 1.2 A in the case the charger is plugged in (actually max current from USB in this autonomous mode is limited to 500 mA).
It also properly supports charging very depleted batteries gently.
It also properly supports charging very depleted batteries gently.
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There are safety implications of software drivers for this chip, the chip can be configured to have an output voltage of up to 4.44V, which is higher than the absolute maximum voltage of 4.2V that li-ion batteries can be safely charged to.
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There are safety implications of software drivers for this chip, the chip can be configured to have an output voltage of up to 4.44 V, which is higher than the absolute maximum voltage of 4.2 V [citation needed] that li-ion batteries can be safely charged to.
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==Software==
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=Software=
 
There is no kernel driver for this chip - it is driven over I2C by [[N900 Software BME|BME]].
There is no kernel driver for this chip - it is driven over I2C by [[N900 Software BME|BME]].
[[N900 Software BME|BME (Battery Managment Entity)]] needs replaced with an open-source version in order to allow easy operation in [[N900 Hardware USB Host|USB host mode]].  
[[N900 Software BME|BME (Battery Managment Entity)]] needs replaced with an open-source version in order to allow easy operation in [[N900 Hardware USB Host|USB host mode]].  
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Partial third party kernel driver exists, see commits in android-n900 kernel:
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[http://gitorious.org/android-n900/kernel-ng/commit/a7aa7f049e5be547a65247b7d88f6d248929d26c] and  [http://gitorious.org/android-n900/kernel-ng/commit/9c1d036cf952134eb75adcc65936a94ac6891e89]
[[category:N900_Hardware]]
[[category:N900_Hardware]]

Latest revision as of 03:20, 15 May 2015

The battery charger charges the battery, and supplies power when running connected to USB. It can also supply power for USB Host mode.

[edit] Hardware

The battery charger is the bq24150a charger from TI.

It features reverse boost mode - which enables power of up to 200 mA@5V to be supplied to a USB device connected to the N900.

When initially powered on, this chip, and the USB interface chip enable charging from dead without any software running. This mode of charging respects the maximum current available without negotiation - 100 mA in the case of a normal USB connection, or 1.2 A in the case the charger is plugged in (actually max current from USB in this autonomous mode is limited to 500 mA).

It also properly supports charging very depleted batteries gently.

There are safety implications of software drivers for this chip, the chip can be configured to have an output voltage of up to 4.44 V, which is higher than the absolute maximum voltage of 4.2 V [citation needed] that li-ion batteries can be safely charged to.

[edit] Software

There is no kernel driver for this chip - it is driven over I2C by BME. BME (Battery Managment Entity) needs replaced with an open-source version in order to allow easy operation in USB host mode.

Partial third party kernel driver exists, see commits in android-n900 kernel: [1] and [2]

Retrieved from "http://wiki.maemo.org/N900_Hardware_Battery_Charger"