Rainbow Electronics LM63 User Manual
May 2003
LM63
±
1˚C/
LM63
±
1˚C/±3˚C Accurate Remote Diode Digital Temperature
Sensor with Integrated Fan Control
General Description
The LM63 is a remote diode temperature sensor with integrated fan control. The LM63 accurately measures: (1) its
own temperature and (2) the temperature of a diodeconnected transistor, such as a 2N3904, or a thermal diode
commonly found on Computer Processors, Graphics Processor Units (GPU) and other ASIC’s. The LM63 remote
temperature sensor’s accuracy is factory trimmed for the
series resistance and 1.0021 non-ideality of the Intel
µm Pentium
diode. The LM63 has an offset register to correct for errors
caused by different non-ideality factors of other thermal diodes. For the latest information contact
hardware.monitor.team
The LM63 also features an integrated, pulse-widthmodulated (PWM), open-drain fan control output. Fan speed
is a combination of the remote temperature reading, the
lookup table and the register settings. The 8-step Lookup
Table enables the user to program a non-linear fan speed vs.
temperature transfer function often used to quiet acoustic
fan noise.
®
4 and Mobile Pentium 4 Processor-M thermal
@
nsc.com.
®
0.13
Features
n Accurately senses diode-connected 2N3904 transistors
or thermal diodes on-board large processors or ASIC’s
n Accurately senses its own temperature
n Factory trimmed for Intel Pentium 4 and Mobile Pentium
4 Processor-M thermal diodes
n Integrated PWM fan speed control output
n Acoustic fan noise reduction with User-programmable
8-step Lookup Table
n Multi-function, user-selectable pin for either ALERT
output, or Tachometer input, functions
n Tachometer input for measuring fan RPM
n Offset register can adjust for a variety of thermal diodes
n 10 bit plus sign remote diode temperature data format,
with 0.125˚C resolution
n SMBus 2.0 compatible interface, supports TIMEOUT
n LM86-compatible pinout
n LM86-compatible register set
n 8-pin SOIC package
Key Specifications
j
Remote Diode Temp Accuracy (with quantization
error)
Ambient
Temp
30 to 50˚C 60 to 100˚C 5 mA LM63C
30 to 50˚C 60 to 100˚C 5 mA LM63D
0 to 85˚C 25 to 125˚C 8 mA All
j
Local Temp Accuracy (includes quantization error)
Ambient Temp Max Error
25˚C to 125˚C
j
Supply Voltage 3.0 V to 3.6 V
j
Supply Current 1.3 mA (typ)
Diode
Temp
I
PWML
Max
Version
±
3.0˚C
Applications
n Computer Processor Thermal Management
(Laptop, Desktop, Workstations, Servers)
n Graphics Processor Thermal Management
n Electronic Test Equipment
n Projectors
n Office Equipment
n Industrial Controls
Max
Error
±
1.0˚C
±
3.0˚C
±
3.0˚C
±
3˚C Accurate Remote Diode Digital Temperature Sensor with Integrated Fan Control
Connection Diagram
20057001
Intel®and Pentium®are registered trademarks of Intel Corporation.
© 2003 National Semiconductor Corporation DS200570 www.national.com
Pin Descriptions
LM63
Pin Name Input/Output Function and Connection
Connect to a low-noise +3.3
1V
2 D+ Analog Input
3 D− Analog Input
4 PWM
5 GND Ground This is the analog and digital ground return.
6 ALERT/TACH
7 SMBDAT
8 SMBCLK Digital Input Digital Input. This is the SMBus clock input.
DD
Power Supply Input
Open-Drain
Digital Output
Digital I/O
Digital Input/
Open-Drain Output
with a 0.1 µF ceramic capacitor in parallel with a 100 pF ceramic capacitor.
A bulk capacitance of 10 µF needs to be in the vicinity of the LM63’s V
pin.
Connect to the anode (positive side) of the remote diode. A 2.2 nF ceramic
capacitor must be connected between pins 2 and 3.
Connect to the cathode (negative side) of the remote diode. A 2.2 nF
ceramic capacitor must be connected between pins 2 and 3.
Open-Drain Digital Output. Connect to fan drive circuitry. The power-on
default for this pin is low (pin 4 pulled to ground).
Depending on how the LM63 is programmed, this pin is either an
open-drain ALERT output or a tachometer input for measuring fan speed.
The power-on default for this pin is the ALERT function.
This is the bi-directional SMBus data line.
±
0.3 VDC power supply, and bypass to GND
Simplified Block Diagram
DD
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20057002
Typical Application
LM63
Ordering Information
Part Description Top Mark Order Number Transport Media
LM63C (
LM63C (
LM63D (
LM63D (
With Software and User’s Guide
±
1˚C) 8-pin SOIC LM63CIMA LM63CIMAX 2500 Units in Tape and Reel
±
1˚C) 8-pin SOIC LM63CIMA LM63CIMA 95 Units in Rail
±
3˚C) 8-pin SOIC LM63DIMA LM63DIMAX 2500 Units in Tape and Reel
±
3˚C) 8-pin SOIC LM63DIMA LM63DIMA 95 Units in Rail
LM63 Evaluation Board
20057003
N/A LM63EVAL Packaged
www.national.com3
Absolute Maximum Ratings (Notes 1,
LM63
2)
Supply Voltage, V
DD
Voltage on SMBDAT, SMBCLK,
ALERT/Tach, PWM Pins −0.5 V to 6.0 V
Voltage on Other Pins −0.3 V to (V
Input Current, D− Pin
−0.3 V to 6.0 V
+0.3V)
DD
±
1mA
ESD Susceptibility (Note 4)
Human Body Model 2000 V
Machine Model 200 V
Soldering Information, Lead Temperature
SOIC-8 Package (Note 6)
Vapor Phase (60 seconds) 215˚C
Infrared (15 seconds) 220˚C
Input Current at All Other Pins (Note 3) 5 mA
Package Input Current (Note 3) 30 mA
Package Power Dissipation (Note 5)
SMBDAT, ALERT, PWM pins
Output Sink Current 10 mA
Storage Temperature −65˚C to +150˚C
Operating Ratings (Notes 1, 2)
Specified Temperature Range T
LM63CIM, LM63DIM 0˚C ≤ TA≤ +85˚C
Remote Diode Temperature Range 0˚C ≤ T
Supply Voltage Range (V
) +3.0 V to +3.6 V
DD
MIN
≤ TA≤ T
≤ +125˚C
A
DC Electrical Characteristics
TEMPERATURE-TO-DIGITAL CONVERTER CHARACTERISTICS The following specifications apply for VDD= 3.0 VDC to
3.6 VDC, and all analog source impedance R
T
A=TMIN
to T
; all other limits TA= +25˚C.
MAX
Parameter Conditions Version
Temperature Error Using the Remote
Thermal Diode of an Intel Pentium 4
or Mobile Pentium 4 Processor-M
T
I
PWML
with typical non-ideality of 1.0021.For
other processors e-mail
@
hardware.monitor.team
nsc.com to
obtain the latest data.
Temperature Error Using the Local
T
I
PWML
T
Diode
Remote Diode Resolution All
Local Diode Resolution All
Conversion Time, All Temperatures Fastest Setting All 31.25 34.4 ms (max)
D− Source Voltage All 0.7 V
(V
Diode Source Current
Low Current All 13
=50Ω unless otherwise specified in the conditions. Boldface limits apply for
S
T
= +30 to +50˚C
A
≤ 5mA
= +0 to +85˚C
A
≤ 8mA
= +25 to +125˚C (Note 10)
A
T
Junction Temperature
T
= +60 to +100˚C
D
= Remote Diode
D
= +25 to +125˚C All
D
LM63C
LM63D
All
Typical
(Note 7)
±
Limits
(Note 8)
1
11 Bits
0.125 ˚C
8 Bits
1˚C
D+−VD−
) = +0.65 V; High Current All 160
±
1 ˚C (max)
±
3 ˚C (max)
±
3 ˚C (max)
±
3 ˚C (max)
315 µA (max)
110 µA (min)
20 µA (max)
7 µA (min)
MAX
Units
(Limits)
Operating Electrical Characteristics
Parameter
Conditions
Typ
(Note 7)
ALERT and PWM Output Saturation Voltage ALERT PWM
I
I
OUT
OUT
4mA 5mA 0.4
6 mA 0.55
Power-On-Reset Threshold Voltage 2.4 V (max)
Supply Current (Note 9) SMBus Inactive, 16 Hz
Conversion Rate
1.1 2.0 mA (max)
STANDBY Mode 300 µA
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Limits
(Note 8)
V (max)
1.8 V (min)
Units
AC Electrical Characteristics
The following specifications apply for VDD= 3.0 VDC to 3.6 VDC, and all analog source impedance RS=50Ω unless other-
wise specified in the conditions. Boldface limits apply for T
A=TMIN
Symbol Parameter Conditions
to T
; all other limits TA= +25˚C.
MAX
Typical
(Note 7)
Limits
(Note 8)
Units
(Limit)
TACHOMETER ACCURACY
Fan Control Accuracy
±
10 % (max)
Fan Full-Scale Count 65535 (max)
Fan Counter Clock Frequency 90 kHz
Fan Count Update Frequency 1.0 Hz
FAN PWM OUTPUT
Frequency Accuracy
±
10 % (max)
Digital Electrical Characteristics
Symbol Parameter Conditions
V
V
I
IH
I
IL
C
Logical High Input Voltage 2.1 V (min)
IH
Logical Low Input Voltage 0.8 V (max)
IL
Logical High Input Current VIN=V
DD
Logical Low Input Current VIN= GND −0.005 −10 µA (max)
Digital Input Capacitance 20 pF
IN
Typical
(Note 7)
0.005 +10 µA (max)
Limits
(Note 8)
Units
(Limit)
LM63
SMBus Logical Electrical Characteristics
The following specifications apply for VDD= 3.0 VDC to 3.6 VDC, and all analog source impedance RS=50Ω unless other-
wise specified in the conditions. Boldface limits apply for T
A=TMIN
to T
Symbol Parameter Conditions
SMBDAT OPEN-DRAIN OUTPUT
V
I
OH
Logic Low Level Output Voltage IOL=4mA 0.4 V (max)
OL
High Level Output Current V
OUT=VDD
SMBDAT, SMBCLK INPUTS
V
V
V
HYST
Logical High Input Voltage 2.1 V (min)
IH
Logical Low Input Voltage 0.8 V (max)
IL
Logic Input Hysteresis Voltage 320 mV
; all other limits TA= +25˚C.
MAX
Typical
(Note 7)
0.03 10 µA (max)
Limits
(Note 8)
Units
(Limit)
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SMBus Digital Switching Characteristics
LM63
Unless otherwise noted, these specifications apply for VDD= +3.0 VDC to +3.6 VDC, CL(load capacitance) on output lines =
80 pF. Boldface limits apply for T
A=TJ;TMIN
≤ TA≤ T
; all other limits TA=TJ= +25˚C, unless otherwise noted. The
MAX
switching characteristics of the LM63 fully meet or exceed the published specifications of the SMBus version 2.0. The following
parameters are the timing relationships between SMBCLK and SMBDAT signals related to the LM63. They adhere to but are
not necessarily the same as the SMBus bus specifications.
Symbol Parameter Conditions
f
SMB
SMBus Clock Frequency 10
Limits
(Note 8)
100
t
t
LOW
HIGH
SMBus Clock Low Time From V
SMBus Clock High Time From V
IN(0) max
IN(1) min
to V
to V
IN(0) max
IN(1) min
4.7 µs (min)
4.0
50
t
R
t
F
t
OF
t
TIMEOUT
t
SU:DAT
t
HD:DAT
SMBus Rise Time (Note 11) 1 µs (max)
SMBus Fall Time (Note 12) 0.3 µs (max)
Output Fall Time CL= 400 pF, IO=3mA 250 ns (max)
SMBData and SMBCLK Time Low for Reset
of Serial Interface See (Note 13)
25
35
Data In Setup Time to SMBCLK High 250 ns (min)
Data Out Hold Time after SMBCLK Low 300
930
t
HD:STA
t
SU:STO
t
SU:STA
t
BUF
Hold Time after (Repeated) Start Condition.
After this period the first clock is generated.
Stop Condition SMBCLK High to SMBDAT
Low (Stop Condition Setup)
SMBus Repeated Start-Condition Setup Time,
SMBCLK High to SMBDAT Low
SMBus Free Time between Stop and Start
Conditions
4.0 µs (min)
100 ns (min)
4.7 µs (min)
4.7 µs (min)
Units
(Limit)
kHz (min)
kHz (max)
µs (min)
µs (max)
ms (min)
ms (max)
ns (min)
ns (max)
SMBus Timing Diagram for SMBCLK and SMBDAT Signals
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20057004
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed
specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test
conditions.
Note 2: All voltages are measured with respect to GND, unless otherwise noted.
Note 3: When the input voltage (V
components and/or ESD protection circuitry are shown below for the LM63’s pins. The nominal breakdown voltage of D3 is 6.5 V. Care should be taken not to forward
bias the parasitic diode, D1, present on pins D+ and D−. Doing so by more than 50 mV may corrupt temperature measurements. An "X" means it exists in the circuit.
) at any pin exceeds the power supplies (V
IN
IN
<
GND or V
>
V+), the current at that pin should be limited to 5 mA. Parasitic
IN
LM63
Pin Name PIN
V
DD
#
D1 D2 D3 D4 D5 D6 R1 SNP ESD CLAMP
1X X
D+ 2 XX XXX X
D− 3 XX XXX X
PWM 4 X X X X
ALERT/Tach
6X XXX
SMBDAT 7 X X X X
SMBCLK 8 X X
20057005
FIGURE 1. ESD Protection Input Structure
Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Machine model, 200 pF discharged directly into each pin. See Figure 1 above for the ESD
Protection Input Structure.
Note 5: Thermal resistance junction-to-ambient when attached to a printed circuit board with 2 oz. foil is 168˚C/W.
Note 6: See the URL “http://www.national.com/packaging/” for other recommendations and methods of soldering surface mount devices.
Note 7: “Typicals” are at T
Note 8: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 9: The supply current will not increase substantially with an SMBus transaction.
Note 10: Local temperature accuracy does not include the effects of self-heating. The rise in temperature due to self-heating is the product of the internal power
dissipation of the LM63 and the thermal resistance. See (Note 5) for the thermal resistance to be used in the self-heating calculation.
Note 11: The output rise time is measured from (V
Note 12: The output fall time is measured from (V
Note 13: Holding the SMBData and/or SMBCLK lines Low for a time interval greater than t
SMBDAT and SMBCLK pins to a high impedance state.
1.0 Functional Description
The LM63 Remote Diode Temperature Sensor with Integrated Fan Control incorporates a ∆V
sensor using a Local or Remote diode and a 10-bit plus sign
∆Σ ADC (Delta-Sigma Analog-to-Digital Converter). The
pulse-width modulated (PWM) open-drain output, with a
pull-up resistor, can drive a switching transistor to modulate
the fan. 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. 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 below.
The LM63’s two-wire interface is compatible with the SMBus
Specification 2.0 . For more information the reader is di-
= 25˚C and represent most likely parametric norm. They are to be used as general reference values not for critical design calculations.
A
IL max
IH min
- 0.15 V) to (V
+ 0.15 V) to (V
IH min
IL min
+ 0.15 V).
- 0.15 V).
will reset the LM63’s SMBus state machine, therefore setting
TIMEOUT
In the LM63 digital comparators are used to compare the
measured Local Temperature (LT) to the Local High Setpoint
-based temperature
BE
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) userprogrammable 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
rected to www.smbus.org.
www.national.com7
1.0 Functional Description (Continued)
LM63
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.
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 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.
1.1 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.
1.2.1 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 example, 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 during set-up. In order for the ALERT to be used as a temperature 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.
20057006
FIGURE 2. Supply Current vs Conversion Rate
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.
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20057007
FIGURE 3. ALERT Output as Temperature Comparator
Response Diagram
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 routine 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
1.0 Functional Description (Continued)
cleared only upon a read command from the master (see
Figure 4 ) and will be re-asserted at the end of the next
conversion if the triggering condition(s) persist(s). In order
for the ALERT to be used as a dedicated interrupt signal, the
Comparator Mode bit in the Remote Diode Temperature
Filter and Comparator Mode Register must be set low. This
is the power-on default state. The following sequence describes the response of a system that uses the ALERT
output pin as an interrupt flag:
1. Master senses ALERT low.
2. Master reads the LM63 ALERT Status Register to determine what caused the ALERT.
3. LM63 clears ALERT Status Register, resets the ALERT
HIGH and sets the ALERT Mask bit in the Configuration
Register.
4. Master attends to conditions that caused the ALERT to
be triggered. The fan is started, setpoint limits are adjusted, etc.
5. Master resets the ALERT Mask bit in the Configuration
Register.
20057008
FIGURE 4. ALERT Output as an Interrupt Temperature
Response Diagram
1.2.3 ALERT Output as an SMBus ALERT
An SMBus alert line is created when the ALERT output is
connected to: (1) one or more ALERT outputs of other
SMBus compatible devices, and (2) to a master. Under this
implementation, the LM63’s ALERT should be operated using the ARA (Alert Response Address) protocol. The SMBus
2.0 ARA protocol, defined in the SMBus specification 2.0, is
a procedure designed to assist the master in determining
which part generated an interrupt and to service that interrupt.
The SMBus alert line is connected to the open-drain ports of
all devices on the bus, thereby AND’ing them together. The
ARA method allows the SMBus master, with one command,
to identify which part is pulling the SMBus alert line LOW. It
also prevents the part from pulling the line LOW again for the
same triggering condition. When an ARA command is received by all devices on the bus, the devices pulling the
SMBus alert line LOW: (1) send their address to the master
and (2) release the SMBus alert line after acknowledgement
of their address.
LM63
The SMBus Specifications 1.1 and 2.0 state that in response
to and ARA (Alert Response Address) “after acknowledging
the slave address the device must disengage its ALERT
pulldown”. Furthermore, “if the host still sees ALERT low
when the message transfer is complete, it knows to read the
ARA again.” This SMBus “disengaging ALERT requirement
prevents locking up the SMBus alert line. Competitive parts
may address the “disengaging of ALERT” differently than the
LM63 or not at all. SMBus systems that implement the ARA
protocol as suggested for the LM63 will be fully compatible
with all competitive parts.
The LM63 fulfills “disengaging of ALERT” by setting the
ALERT Mask Bit in the Configuration Register after sending
out its address in response to an ARA and releasing the
ALERT output pin. Once the ALERT Mask bit is activated,
the ALERT output pin will be disabled until enabled by
software. In order to enable the ALERT the master must read
the ALERT Status Register, during the interrupt service routine and then reset the ALERT Mask bit in the Configuration
Register to 0 at the end of the interrupt service routine.
The following sequence describes the ARA response protocol.
1. Master senses SMBus alert line low
2. Master sends a START followed by the Alert Response
Address (ARA) with a Read Command.
3. Alerting Device(s) send ACK.
4. Alerting Device(s) send their address. While transmitting
their address, alerting devices sense whether their address has been transmitted correctly. (The LM63 will
reset its ALERT output and set the ALERT Mask bit once
its complete address has been transmitted successfully.)
5. Master/slave NoACK
6. Master sends STOP
7. Master attends to conditions that caused the ALERT to
be triggered. TheALERT Status Register is read and fan
started, setpoints adjusted, etc.
8. Master resets the ALERT Mask bit in the Configuration
Register.
The ARA, 000 1100, is a general call address. No device
should ever be assigned to this address.
The ALERT Configuration bit in the Remote Diode Temperature Filter and Comparator Mode Register must be set low in
order for the LM63 to respond to the ARA command.
The ALERT output can be disabled by setting the ALERT
Mask bit in the Configuration Register. The power-on default
is to have the ALERT Mask bit and the ALERT Configuration
bit low.
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