Datasheet

0.01 0.1 1.0 10 100
CONVERSION RATE (Hz)
200
500
800
1100
1400
1700
2000
2300
2600
SUPPLY CURRENT (PA
LM63
www.ti.com SNAS190E –SEPTEMBER 2002–REVISED MAY 2013
FUNCTIONAL DESCRIPTION
The LM63 Remote Diode Temperature Sensor with Integrated Fan Control incorporates a ΔV
BE
-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
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. 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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