LM63 datasheet(8/28 Pages) NSC

8 / 28 page

1.0 Functional Description (Continued)

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

Mobile

Pentium

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

31.25 ms. Different Conversion Rates will cause the LM63 to

draw different amounts of supply current as shown in Figure

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.

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 > LHS, when this condition is no longer true, the

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

20057006

FIGURE 2. Supply Current vs Conversion Rate

20057007

FIGURE 3. ALERT Output as Temperature Comparator

Response Diagram

LM63 Arkusz danych(PDF) 8 Page - National Semiconductor (TI)

LM63 Arkusz danych(HTML) 8 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Arkusz danych Pobierz

Link URL