LM63CIMAX National Semiconductor, LM63CIMAX Datasheet - Page 8

• Manufacturer Part Number: LM63CIMAX
• Description: IC,Motor Controller,MOS,SOP,8PIN
• Manufacturer: National Semiconductor

Specifications of LM63CIMAX

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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1.0 Functional Description
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 Section 4.1
Thermal Diode Non-Ideality.
1.1 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
2.
1.2 THE ALERT/TACH PIN AS ALERT OUTPUT
The ALERT/Tach pin is a multi-use pin. In this section we will
address the ALERT active-low open-drain output function.
When the ALERT/Tach Select bit is written as a zero in the
Configuration Register the ALERT output is selected. Also,
when the ALERT Mask bit in the Configuration register is
written as zero the ALERT interrupts are enabled.
The LM63’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 LM63.
FIGURE 2. Supply Current vs Conversion Rate
(Continued)
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The remote temperature (RT) reading is associated with a
T_CRIT Setpoint Register, and both local and remote tem-
perature (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 Open, 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.
The three different ALERT modes will be discussed in the
following sections.
1.2.1 ALERT Output as a Temperature Comparator
When the LM63 is used in a system in which does not
require temperature-based interrupts, the ALERT output
could be used as a temperature comparator. In this mode,
once the condition that triggered the ALERT to go low is no
longer present, the ALERT is negated (Figure 3). For ex-
ample, if the ALERT output was activated by the comparison
of LT
ALERT will return HIGH. This mode allows operation without
software intervention, once all registers are configured dur-
ing set-up. In order for the ALERT to be used as a tempera-
ture comparator, the Comparator Mode bit in the Remote
Diode Temperature Filter and Comparator Mode Register
must be asserted. This is not the power-on default state.
1.2.2 ALERT Output as an Interrupt
The LM63’s ALERT output can be implemented as a simple
interrupt signal when it is used to trigger an interrupt service
routine. In such systems it is desirable for the interrupt flag to
repeatedly trigger during or before the interrupt service rou-
tine has been completed. Under this method of operation,
during the read of the ALERT Status Register the LM63 will
set the ALERT Mask bit in the Configuration Register if any
bit in the ALERT Status Register is set, with the exception of
Busy and Open. This prevents further ALERT triggering until
the master has reset the ALERT Mask bit, at the end of the
interrupt service routine. The ALERT Status Register bits are
FIGURE 3. ALERT Output as Temperature Comparator
>
LHS, when this condition is no longer true, the
Response Diagram
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