LM63 datasheet(9/44 Pages) TI2

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LM63

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SNAS190E – SEPTEMBER 2002 – REVISED MAY 2013

FUNCTIONAL DESCRIPTION

The LM63 Remote Diode Temperature Sensor with Integrated Fan Control incorporates a

ΔVBE-based

temperature sensor using a Local or Remote diode and a 10-bit plus sign

ΔΣ ADC (Delta-Sigma Analog-to-Digital

Converter). The pulse-width modulated (PWM) open-drain output, with a pullup resistor, can drive a switching

transistor to modulate fan speed. When the ALERT/Tach is programmed to the Tach mode the LM63 can

measure the fan speed on the pulses from the fan’s tachometer output. The LM63 includes a smart-tach

measurement mode to accommodate the corrupted tachometer pulses when using switching transistor drive.

When the ALERT/Tach pin is programmed to the ALERT mode the ALERT open-drain output will be pulled low

when the measured temperature exceeds certain programmed limits when enabled. Details are contained in the

sections to follow.

The LM63'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 LM63 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.

The temperature hysteresis is set by the value placed in the Hysteresis Register (TH).

The LM63 may be placed in a low-power Standby mode by setting the Standby bit found in the Configuration

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. 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 of the thermal diode if different from the 0.13 micron Intel

Pentium 4 or Mobile Pentium 4 Processor-M processor’s thermal diode. See the DIODE NON-IDEALITY section.

CONVERSION SEQUENCE

The LM63 takes approximately 31.25 ms to convert the Local Temperature (LT), Remote Temperature (RT), and

to update all of its registers. The Conversion Rate may be modified using the Conversion Rate Register. When

the conversion rate is modified a delay is inserted between conversions, the actual conversion time remains at

31.25 ms. Different Conversion Rates will cause the LM63 to draw different amounts of supply current as shown

in Figure 6.

Figure 6. Supply Current vs Conversion Rate

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