Documentation/hwmon/max31827.rst

Source file repositories/reference/linux-study-clean/Documentation/hwmon/max31827.rst

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Documentation/hwmon/max31827.rst
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.. SPDX-License-Identifier: GPL-2.0

Kernel driver max31827
======================

Supported chips:

  * Maxim MAX31827

    Prefix: 'max31827'

    Addresses scanned: I2C 0x40 - 0x5f

    Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX31827-MAX31829.pdf

  * Maxim MAX31828

    Prefix: 'max31828'

    Addresses scanned: I2C 0x40 - 0x5f

    Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX31827-MAX31829.pdf

  * Maxim MAX31829

    Prefix: 'max31829'

    Addresses scanned: I2C 0x40 - 0x5f

    Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX31827-MAX31829.pdf


Authors:
	- Daniel Matyas <daniel.matyas@analog.com>

Description
-----------

The chips supported by this driver are quite similar. The only difference
between them is found in the default power-on behaviour of the chips. While the
MAX31827's fault queue is set to 1, the other two chip's fault queue is set to
4. Besides this, the MAX31829's alarm active state is high, while the other two
chip's alarms are active on low. It is important to note that the chips can be
configured to operate in the same manner with 1 write operation to the
configuration register. From here on, we will refer to all these chips as
MAX31827.

MAX31827 implements a temperature sensor with a 6 WLP packaging scheme. This
sensor measures the temperature of the chip itself.

MAX31827 has low and over temperature alarms with an effective value and a
hysteresis value: -40 and -30 degrees for under temperature alarm and +100 and
+90 degrees for over temperature alarm.

The alarm can be configured in comparator and interrupt mode from the
devicetree. In Comparator mode, the OT/UT status bits have a value of 1 when the
temperature rises above the TH value or falls below TL, which is also subject to
the Fault Queue selection. OT status returns to 0 when the temperature drops
below the TH_HYST value or when shutdown mode is entered. Similarly, UT status
returns to 0 when the temperature rises above TL_HYST value or when shutdown
mode is entered.

In interrupt mode exceeding TH also sets OT status to 1, which remains set until
a read operation is performed on the configuration/status register (max or min
attribute); at this point, it returns to 0. Once OT status is set to 1 from
exceeding TH and reset, it is set to 1 again only when the temperature drops
below TH_HYST. The output remains asserted until it is reset by a read. It is
set again if the temperature rises above TH, and so on. The same logic applies
to the operation of the UT status bit.

Annotation

Implementation Notes