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Open Menu / Documentation / hwmon / ltc4261.rst
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Kernel driver ltc4261
=====================

Supported chips:

  * Linear Technology LTC4261

    Prefix: 'ltc4261'

    Addresses scanned: -

    Datasheet:

	http://cds.linear.com/docs/Datasheet/42612fb.pdf

Author: Guenter Roeck <linux@roeck-us.net>


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

The LTC4261/LTC4261-2 negative voltage Hot Swap controllers allow a board
to be safely inserted and removed from a live backplane.


Usage Notes
-----------

This driver does not probe for LTC4261 devices, since there is no register
which can be safely used to identify the chip. You will have to instantiate
the devices explicitly.

Example: the following will load the driver for an LTC4261 at address 0x10
on I2C bus #1::

	$ modprobe ltc4261
	$ echo ltc4261 0x10 > /sys/bus/i2c/devices/i2c-1/new_device


Sysfs entries
-------------

Voltage readings provided by this driver are reported as obtained from the ADC
registers. If a set of voltage divider resistors is installed, calculate the
real voltage by multiplying the reported value with (R1+R2)/R2, where R1 is the
value of the divider resistor against the measured voltage and R2 is the value
of the divider resistor against Ground.

Current reading provided by this driver is reported as obtained from the ADC
Current Sense register. The reported value assumes that a 1 mOhm sense resistor
is installed. If a different sense resistor is installed, calculate the real
current by dividing the reported value by the sense resistor value in mOhm.

The chip has two voltage sensors, but only one set of voltage alarm status bits.
In many many designs, those alarms are associated with the ADIN2 sensor, due to
the proximity of the ADIN2 pin to the OV pin. ADIN2 is, however, not available
on all chip variants. To ensure that the alarm condition is reported to the user,
report it with both voltage sensors.

======================= =============================
in1_input		ADIN2 voltage (mV)
in1_min_alarm		ADIN/ADIN2 Undervoltage alarm
in1_max_alarm		ADIN/ADIN2 Overvoltage alarm

in2_input		ADIN voltage (mV)
in2_min_alarm		ADIN/ADIN2 Undervoltage alarm
in2_max_alarm		ADIN/ADIN2 Overvoltage alarm

curr1_input		SENSE current (mA)
curr1_alarm		SENSE overcurrent alarm
======================= =============================