Datasheet

LM96163
SNAS433D JUNE 2008REVISED MAY 2013
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FUNCTIONAL DESCRIPTION
The LM96163 Remote Diode Temperature Sensor with Integrated Fan Control incorporates a ΔV
BE
-based
temperature sensor utilizing a Local or Remote diode and a 10-bit plus sign ΔΣ ADC (Delta-Sigma Analog-to-
Digital Converter). The LM96163 includes TruTherm BJT beta compensation technology that allows precision
temperature sensing of remote diodes found in sub-micron processes. The pulse-width modulated (PWM) open-
drain output, with a pull-up resistor, is driven by a 12-point temperature to duty cycle look-up table (LUT) and can
directly drive a PWM input of a 4-pin fan in order to modulate it's speed enabling optimum system acoustic
performance. The LM96163 LUT fan control algorithm also includes a smoothing function that allows the PWM
duty cycle to gradually change over a programmed time interval when switching from one level to the next in the
LUT. When running at a frequency of 22.5kHz the PWM output resolution is 0.39%. The LM96163 includes a
TACH input that can measure the speed of a fan using the pulses from a 3 or 4 pin fan’s tachometer output. The
LM96163 includes a smart-tach measurement mode to accommodate the corrupted tachometer pulses when
using switching transistor power drive to modulate the fan speed. The LM96163 has an ALERT open-drain
output that will be pulled low when the measured temperature exceeds certain programmed limits when enabled.
Details are contained in the sections below.
The LM96163's two-wire interface is compatible with the SMBus Specification 2.0 . For more information the
reader is directed to www.smbus.org.
In the LM96163 digital comparators are used to compare the measured Local Temperature (LT) to the Local
High Setpoint user-programmable temperature limit register. The measured Remote Temperature (RT) is digitally
compared to the Remote High Setpoint (RHS), the Remote Low Setpoint (RLS), and the Remote T_CRIT
Setpoint (RCS) user-programmable temperature limits. An ALERT output will occur when the measured
temperature is: (1) higher than either the High Setpoint or the T_CRIT Setpoint, or (2) lower than the Low
Setpoint. The ALERT Mask register allows the user to prevent the generation of these ALERT outputs. A TCRIT
output will occur when the measured temperature is higher than the T_CRIT Setpoint.
The TCRIT function and the look-up table temperature hysteresis can be set separately. The hysteresis value
associated with the TCRIT output is set in the Remote T_CRIT Hysteresis Register. The value associated with
the look-up table function is set in the Lookup Table Hysteresis Register.
The LM96163 may be placed in a low power Standby mode by setting the Standby bit found in the Configuration
Register. In the Standby mode continuous conversions are stopped. In Standby mode the user may choose to
allow the PWM output signal to continue, or not, by programming the PWM Disable in Standby bit in the
Configuration Register.
The Local Temperature reading and setpoint data registers are 8-bits wide. The format of the 11-bit remote
temperature data is a 16-bit left justified word. Two 8-bit registers, high and low bytes, are provided for each
setpoint as well as the temperature reading. A digital filter may be invoked for remote temperature readings that
increases the resolution from 11-bits to 13-bits. The temperature readings are also available in an unsigned
format allowing resolution above 127°C. Two Remote Temperature Offset (RTO) Registers: High Byte and Low
Byte (RTOHB and RTOLB) may be used to correct the temperature readings by adding or subtracting a fixed
value based on a different non-ideality factor and series resistance of the thermal diode if different from the
thermal diode found in the Intel processors on 45 nm process. See section DIODE NON-IDEALITY.
ALERT and TCRIT OUTPUTS
In this section we will address the ALERT and TCRIT active-low open-drain output functions. When the ALERT
Mask bit in the Configuration register is written as zero the ALERT interrupts are enabled.
The LM96163's ALERT pin is versatile and can produce three different methods of use to best serve the system
designer: (1) as a temperature comparator (2) as a temperature-based interrupt flag, and (3) as part of an
SMBus ALERT System. The three methods of use are further described below. The ALERT and interrupt
methods are different only in how the user interacts with the LM96163.
The remote temperature (RT) reading is associated with a T_CRIT Setpoint Register, and both local and remote
temperature (LT and RT) readings are associated with a HIGH setpoint register (LHS and RHS). The RT is also
associated with a LOW setpoint register (RLS). At the end of every temperature reading a digital comparison
determines whether that reading is above its HIGH or T_CRIT setpoint or below its LOW setpoint. If so, the
corresponding bit in the ALERT Status Register is set. If the ALERT mask bit is low, any bit set in the ALERT
Status Register, with the exception of Busy or RDFA, will cause the ALERT output to be pulled low. Any
temperature conversion that is out of the limits defined in the temperature setpoint registers will trigger an
ALERT. Additionally, the ALERT Mask Bit must be cleared to trigger an ALERT in all modes.
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