SMSC MON35W42 Datasheet

MON35W42

Hardware Monitoring IC with Thermal Diode

Interface

FEATURES

Monitoring Items

!"

- 3 Thermal Inputs From Remote
Thermistors or 2N3904 NPN-type
Transistors or Pentium
Thermal Diode Output

- 9 Voltage Inputs - Typical for Vcore,
+3.3V, +12V, -12V, +5V, -5V, +5V Vsb,
Vbat, and One Reserved

- 3 Fan Speed Monitoring Inputs

- Case Open Detection Input

- WATCHDOG Comparison of all

Monitored Values

- Programmable Hysteresis and Setting
Points (Alarm Thresholds) for all
Monitored Items

Action Enabling

!"

- Beep Tone Warning

- 4 PWM (Pulse Width Modulation)

Outputs for Fan Speed Control (3 are
MUX Optional); Up to 3 sets of fan
Speed Monitoring and Control.

- Issue nSMI, nOVT, nGPO Signals to
Activate System Protection

- Warning Signal Pop-Up for Application
Software

®

II (Deschutes)

General

!"

- ISA and I

- 5 VID Input Pins for CPU Vcore

Identification (for Pentium® II)

- Initial Power Fault Beep (for +3.3V,
Vcore)

- Master Reset Input to MON35W42

- Independent Power Plane of Digital Vcc

and Analog Vcc (Inputs to IC)

- 3 Pins (IA0, IA1, IA2) to Provide
Selectable Address Setting for
Application of Multiple Devices (up to 8
Devices) Wired Through I

- Intel

- Acer ADM (DMI Driver 2.0) Support

- SMSC Hardware Monitoring Application

Software (Hardware Doctor) Support,
for Both Windows 95/98 and Windows
NT 4.0/5.0

- Input Clock Rate Optional for 24, 48,

14.318 MHz

- 5V Vcc Operation

Package

!"

- 48 Pin TQFP

2

C Serial Bus Interface

®

LDCM (DMI Driver 2.0) Support

2

C Interface

GENERAL DESCRIPTION

The MON35W42 is an enhanced version of the
MON35W41 hardware status monitoring IC. The
MON35W42 can be used to monitor several
critical hardware parameters of the system,
including power supply voltages, fan speeds,
and temperatures, which are very important for
the stability and proper operation of high-end
computer systems. MON35W42 provides both
ISA and I

An 8-bit analog-to-digital converter (ADC) is
contained within the MON35W42. The
MON35W42 can simultaneously monitor 9
analog voltage inputs, 2 fan tachometer inputs, 3
remote temperature and 1 case-open detection
signal. The remote temperature sensing can be
performed by thermistors, or 2N3904 NPN-type
transistors, or directly from Intel
CPU thermal diode output. The MON35W42
provides: 4 PWM (pulse width modulation)
outputs for the fan speed control; beep tone
output for audio warning and nSMI, nOVT, and
nGPO signals for system protection events.

2

C serial bus interface.

®

Deschutes

With application software such as the Intel

®

LDCM (LANDesk Client Managemet software,
the user can read all the monitored parameters
of system from time to time. And a pop-up
warning can also be activated when the
monitored item drifts out of the proper/preset
range. Also the user can set the upper and lower
limits (alarm thresholds) of these monitored
parameters and activate programmable and
maskable interrupts. An optional beep tone can
be used as a warning signal when the monitored
parameter is out of the preset range.

Additionally, 5 VID inputs are provided to read
the VID of CPU (i.e. Pentium

®

II) if applicable.
This provides automatic correction of the Vcore
voltage. The MON35W42 uniquely provides an
optional feature: early stage (before BIOS is
loaded) beep warning. This is to detect if a fatal
condition is present --- Vcore or +3.3V voltage
fail, and the system can not boot up. There are
3 specific pins to provide selectable address
settings for applications using multiple devices
(up to 8 devices) wired through the I

2

C interface.

2

TABLE OF CONTENTS

FEATURES............................................................................................................................................ 1

GENERAL DESCRIPTION....................................................................................................................2

TABLE OF CONTENTS.........................................................................................................................3

Key Specifications...............................................................................................................................5

PIN CONFIGURATION.......................................................................................................................... 5

PIN DESCRIPTION................................................................................................................................ 6

DESCRIPTION OF PIN FUNCTIONS....................................................................................................6

Functional Description........................................................................................................................9

General Description ........................................................................................................................... 9

Access Interface ................................................................................................................................ 9

Analog Inputs................................................................................................................................... 16

FAN Speed Count and FAN Speed Control..................................................................................... 19

Temperature Measurement Machine............................................................................................... 21

REGISTERS AND RAM....................................................................................................................... 25

Address Register (Port x5h)............................................................................................................. 25

Data Register (Port x6h) .................................................................................................................. 26

Configuration Register ! Index 40h................................................................................................ 27

Interrupt Status Register 1! Index 41h........................................................................................... 28

Interrupt Status Register 2 ! Index 42h.......................................................................................... 28

nSMI Mask Register 1 ! Index 43h................................................................................................. 29

nSMI Mask Register 2 ! Index 44h................................................................................................. 29

Reserved Register ! Index 45h...................................................................................................... 30

Chassis Clear Register -- Index 46h................................................................................................ 30

VID/Fan Divisor Register ! Index 47h............................................................................................ 30

Serial Bus Address Register ! Index 48h....................................................................................... 31

Value RAM ! Index 20h- 3Fh or 60h - 7Fh (auto-increment)......................................................... 31

Voltage ID (VID4) & Device ID -- Index 49h..................................................................................... 32

Temperature 2 and Temperature 3 Serial Bus Address Register--Index 4Ah.................................. 33

Pin Control Register -- Index4Bh ..................................................................................................... 33

nIRQ/nOVT Property Select -- Index 4Ch........................................................................................ 34

FAN IN/OUT and BEEP/nGPO Control Register -- Index 4Dh......................................................... 35

Register 50h ~ 5Fh Bank Select -- Index 4Eh.................................................................................. 36

SMSC Vendor ID -- Index 4Fh......................................................................................................... 36

SMSC Test Register -- Index 50h - 55h (Bank 0)............................................................................ 37

BEEP Control Register 1-- Index 56h (Bank 0)................................................................................ 37

BEEP Control Register 2-- Index 57h (Bank 0)................................................................................ 38

Chip ID -- Index 58h (Bank 0) .......................................................................................................... 38

Reserved Register -- Index 59h (Bank 0)........................................................................................ 39

PWMOUT2 Control -- Index 5Ah (Bank 0)....................................................................................... 39

PWMOUT1 Control -- Index 5Bh (Bank 0)....................................................................................... 40

PWMOUT1/2 Clock Select -- Index 5Ch (Bank 0)............................................................................ 41

VBAT Monitor Control Register -- Index 5Dh (Bank 0)..................................................................... 41

PWMOUT3 Control -- Index 5Eh (Bank 0)....................................................................................... 42

PWMOUT4 Control -- Index 5Fh (Bank 0)....................................................................................... 42

Temperature Sensor 2 Temperature (High Byte) Register - Index 50h (Bank 1)............................. 43

3

Temperature Sensor 2 Temperature (Low Byte) Register - Index 51h (Bank 1).............................. 43

Temperature Sensor 2 Configuration Register - index 52h (Bank 1)............................................... 44

Temperature Sensor 2 Hysteresis (High Byte) Register - Index 53h (Bank 1).................................44

Temperature Sensor 2 Hysteresis (Low Byte) Register - Index 54h (Bank 1).................................. 45

Temperature Sensor 2 Over-temperature (High Byte) Register - Index 55h (Bank 1)..................... 45

Temperature Sensor 2 Over-temperature (Low Byte) Register - Index 56h(Bank 1)....................... 46

Temperature Sensor 3 Temperature (High Byte) Register - Index 50h (Bank 2)............................. 46

Temperature Sensor 3 Temperature (Low Byte) Register - Index 51h (Bank 2).............................. 46

Temperature Sensor 3 Configuration Register - Index 52h (Bank 2)............................................... 47

Temperature Sensor 3 Hysteresis (High Byte) Register - Index 53h (Bank 2).................................47

Temperature Sensor 3 Hysteresis (Low Byte) Register - Index 54h (Bank 2).................................. 48

Temperature Sensor 3 Over-temperature (High Byte) Register - Index 55h (Bank 2)..................... 48

Temperature Sensor 3 Over-temperature (Low Byte) Register - Index 56h(Bank 2)....................... 49

Interrupt Status Register 3 -- Index 50h (BANK4)............................................................................ 49

nSMI Mask Register 3 -- Index 51h (BANK 4)................................................................................. 50

BEEP Control Register 3-- Index 53h (Bank 4)................................................................................ 50

Reserved Register -- Index 54h--58h............................................................................................... 51

Real Time Hardware Status Register I -- Index 59h (Bank 4).......................................................... 51

Real Time Hardware Status Register II -- Index 5Ah (Bank 4)......................................................... 52

Real Time Hardware Status Register III -- Index 5Bh (Bank 4)........................................................ 52

PWMOUT3/4 Clock Select -- Index 5Ch (Bank 4)............................................................................ 53

Value RAM 2! Index 50h - 5Ah (auto-increment) (BANK 5).......................................................... 53

SMSC Test Register - Index 50h (Bank 6)....................................................................................... 53

SPECIFICATIONS............................................................................................................................... 54

Absolute Maximum Ratings ............................................................................................................. 54

DC Characteristics........................................................................................................................... 54

AC CHARACTERISTICS..................................................................................................................56

ISA Read/Write Interface Timing ..................................................................................................... 56

PACKAGE DIMENSIONS.................................................................................................................... 58

4

KEY SPECIFICATIONS

"# Voltage monitoring accuracy $1% (Max)
"# Monitoring Temperature Range and Accuracy

- 40%C to +120%C $ 3%C (Max)
"# Supply Voltage 5V
"# Operating Supply Current 5 mA typ.
"# ADC Resolution 8 Bits

PIN CONFIGURATION

VCOREA

VINR0

+3.3VIN

+5VIN

+12VIN

-12VIN

VBAT

5VSB

-5VIN

GNDA

BEEP/nGPO

VID3

VREF

VTIN3/PIITD3

VTIN2PIITD2
VTIN1PIITD1

VID0

nOVT

ARDMSEL

nSMI
SA2/IA2
SA1/IA1
SA0/IA0

nCS

3635343332313029282726

37
38
39
40
41
42

MON35W42

43
44
45
46
47
48

1234567891011

nIOR

D7D6D5D4D3

nIOW

CLKIN

D2

25

24
23
22
21
20
19
18
17
16
15
14
13

12

VID1

D1/PWMOUT4

D0/PWMOUT3

VID2
PWMTOUT1
SDA
SCL
FAN1IO
FAN2IO
FAN3I0/PWMOUT2
VID4
CASEOPEN
MR
GNDD
VCC

5

PIN DESCRIPTION

I/O

- TTL level bi-directional pin with 12 mA source-sink capability

12t

I/O

- TTL level and schmitt trigger

12ts

OUT

- Output pin with 12 mA source-sink capability

12

AOUT - Output pin (Analog)
OD

- Open-drain output pin with 12 mA sink capability

12

IN

- TTL level input pin

t

IN

- TTL level input pin and schmitt trigger

ts

AIN - Input pin (Analog)

DESCRIPTION OF PIN FUNCTIONS

PIN NAME PIN NO. TYPE DESCRIPTION

nIOR 1 INts An active low standard ISA bus I/O Read

Control.

nIOW 2 INts An active low standard ISA bus I/O Write

Control.

CLKIN 3 INt System clock input. Can select 48MHz or 24MHz

or 14.318MHz. The default is 24MHz.

D7~D2 4-9 I/O

D1/

10 I/O

PWMOUT4
D0/

11 I/O

PWMOUT3
VID1 12 INt Voltage Supply readouts from P6. This value is

VCC (+5V) 13 POWER +5V VCC power. Bypass with the parallel

GNDD 14 DGROUND Internally connected to all digital circuitry.
MR 15 INts Master reset input.
nCASEOPEN 16 INt CASE OPEN detection. An active low input from

VID4 17 INt Voltage Supply readouts from P6. This value is

FAN3IO/

18 I/O

PWMOUT2

Bi-directional ISA bus Data lines. D0

12t

corresponds to the low order bit, with D7 the
high order bit. These pins are activated if pin
ADRMSEL=0.

Bi-directional ISA bus Data lines. This pin is
activated if pin ADRMSEL=0. /Fan speed control
PWM output. This pin is activated if pin
ADRMSEL=1.

Bi-directional ISA bus Data lines. This pin is
activated if pin ADRMSEL=0. /Fan speed control
PWM output. This pin is activated if pin
ADRMSEL=1.

OUT

OUT

12t

12t

12t

12t

read in the VID/Fan Divisor Register.

combination of 10&F (electrolytic or tantalum)
and 0.1&F (ceramic) bypass capacitors.

an external device when the case is opened.
This signal can be latched if VBAT is connect to
a battery, even if the MON35W42 is power off.

read in the bit <0> of Device ID Register.

0V to +5V amplitude fan tachometer input. /

12t

Fan speed control PWM output.

6

PIN NAME PIN NO. TYPE DESCRIPTION

FAN2IO-FAN1IO

19-20 I/O

0V to +5V amplitude fan tachometer input /

12t

Fan on-off control output. These multi-functional

pins can be programmable input or output.
SCL 21 INts Serial Bus Clock.
SDA 22 I/O
PWMOUT1 23 OUT

Serial Bus bi-directional Data.

12ts

Fan speed control PWM output.

12t

VID2 24 INt Voltage Supply readouts from P6. This value is

read in the VID/Fan Divisor Register.
VID3 25 INt Voltage Supply readouts from P6. This value is

read in the VID/Fan Divisor Register.
BEEP/nGPO 26 OD48 Beep (Default) / General purpose output

This multi-functional pin is programmable.
GNDA 27 AGROUND Internally connected to all analog circuitry. The

ground reference for all analog inputs.

-5VIN 28 AIN 0V to 4.096V FSR Analog Inputs.
5VSB 29 AIN 0V to 4.096V FSR Analog Inputs.
VBAT 30 AIN 0V to 4.096V FSR Analog Inputs. (This pin

should be connected to a 3V BATTERY.)

-12VIN 31 AIN 0V to 4.096V FSR Analog Inputs.
+12VIN 32 AIN 0V to 4.096V FSR Analog Inputs.
+5VIN 33 AIN This pin is Analog Vcc and connects internal

monitor channel IN3 with fixed scale.
+3.3VIN 34 AIN 0V to 4.096V FSR Analog Inputs.
VINR0 35 AIN 0V to 4.096V FSR Analog Inputs.
VCOREA 36 AIN 0V to 4.096V FSR Analog Inputs.
VREF 37 AOUT Reference Voltage.
VTIN3 /
PIITD3

38 AIN Thermistor 3 terminal input.(Default) /

Pentium

®

II diode 3 input.

This multi-functional pin is programmable.
VTIN2 /
PIITD2

39 AIN Thermistor 2 terminal input. (Default)/

Pentium

®

II diode 2 input.

This multi-functional pin is programmable.
VTIN1 /
PIITD1

40 AIN Thermistor 1 terminal input. (Default)/

Pentium

®

II diode 1 input.

This multi-functional pin is programmable.
VID0 41 INt Voltage Supply readouts from P6. This value is

read in the VID/Fan Divisor Register.
nOVT 42 OD

Over temperature Shutdown Output.

12t

ADRMSEL 43 INt Pin 45--47 mode selection.

0 = The 3 lowest order bits of ISA Address

Bus.(Default, internal pull-down 47K ohm)

1 = 7 bit I

2

C address setting pin.(bit2 - bit0)

7

PIN NAME PIN NO. TYPE DESCRIPTION

nSMI 44 OD12 System Management Interrupt (open drain). This

output is enabled when Bit 1 in the Configuration

Register is set to 1. The default state is disabled.
SA2-SA0

IA2,IA1,IA0

45-47 IN

IN

t

t

The three lowest order bits of the 16-bit ISA

Address Bus. A0 corresponds to the lowest

order bit.

(Default, when ARDMSEL =0 or left open )

The hardware setting pin of 7 bit I2C serial

address bit2, bit1 and bit0. (When ARDMSEL

=1)
nCS 48 INt Chip Select input from an external decoder,

which decodes high order address bits on the

ISA Address Bus. This is an active low input.

8

FUNCTIONAL DESCRIPTION

General Description

The MON35W42 provides 7 analog positive
inputs, 3 fan speed monitors, up to 4 sets of fan
PWM (Pulse Width Modulation) control, 3
thermal inputs from remote thermistors or
2N3904 transistors or Pentium
thermal diode outputs, case open detection and
beep function output. When the monitored value
exceed the set limit value for voltage,
temperature, or fan counter, the beep output can
be generated. Once the monitor function on the
chip is enabled, the watch dog machine monitors
each function and stores the values. If the
monitored value exceeds the limit value, the
interrupt status is set to 1and an interrupt can be
generated.

®

II (Deschutes)

Access Interface

The MON35W42 provides two interfaces for the
microprocessor to read/write internal registers.

ISA interface

The ISA Bus can be used to access the internal
registers of the MON35W42. This uses an Index
register and Data register to access the internal
registers. The upper address bits of the ISA bus
(bits15:3) must be externally decoded for the
Chip Select (nCS), the recommended address is
290h-297h. The Chip then uses the lower three
ISA address bits (bits 2:0) to decode the Index
and Data Registers. These two I/O registers are
described as following:
Port 295h: Index register.
Port 296h: Data register
The register structure is shown in Figure 1.

9

ISA

ISA

Data

Address

Bus

Bus

Port 5h

Index

Register

Port 6h

Data
Register

2

I

C Interface

The second interface uses the I

FIGURE 1 – ISA INTERFACE ACCESS

2

C Serial Bus.
The MON35W42 uses three serial bus
addresses. The first address defined at CR[48h]

Configuration Register

40h

nSMI Status/Mask Registers

41h, 42h, 44h, 45h

VID<3:0>/Fan Divisor Register

Temperature 2, 3 Serial
Bus Address

Select Bank for 50h~5Fh Reg.

Temperature 2 Control/Staus
Registers

Temperature 3 Control/Staus
Registers

47h

Serial Bus Address

48h

Monitor Value Registers

20h~3Fh

and

60h~7Fh (auto-increment)

VID<4>/Device ID

49h

4Ah

Control Register

4Bh~4Dh

4Eh

Winbond Vendor ID

4Fh

BANK 0

R-T Table Value
BEEP Control Register
Winbond Test Register

50h~58h

BANK 1

50h~56h

BANK 2

50h~56h

can read/write all registers excluding Bank 1 and
Bank 2 temperature sensor 2/3 registers. The
second address defined at CR[4Ah] bit2-0 can

BANK 4

Additional Control/Staus
Registers

50h~5Ch

BANK 5

Additional Limit Value &

Value RAM

50h~57h

only be used to read/write temperature sensor 2
registers, and the third address defined at

10

CR[4Ah] bit6-4 can only be used to access
(read/write) temperature sensor 3 registers.

The first serial bus address, CR[48h],

uses 3 hardware setting bits. When pin 43 is set
high, pins 47-45 are used to set the I
for register CR[48h]. The selected address is
00101[pin45][pin46][pin47]. If pin45=1, pin46=1,
pin47=0, the content of CR[48h] is 00101110.
CR[4Ah] is used to set the other two I
addresses. If CR[4Ah] bit 2-0 is XXX , the
temperature sensor 2 serial address is
1001XXXG, in which G is the read/write bit. If
CR[4Ah ] bi t 6- 4 is YYY , the tem per atu re se nso r
3 serial address is 1001YYYG, in wh ich G is the
read/write bit.

The first serial bus access timing are shown
as follows:

(a)

Serial bus write to internal address register followed by the data byte

SCL

SDA

0

0 1 0 1 1 0 1 D7 D6 D5 D4 D3 D2 D1 D0

Start By

Master

Frame 1

Serial Bus Address Byte

SCL

(Continued)

780 78

R/nW

Ack

by

MON35W42

0

Internal Index Register Byte

SDA (Continued)

D7 D6 D5 D4 D3 D2 D1 D0

Frame 3

Data Byte

FIGURE 2 – SERIAL BUS WRITE TO INTERNAL ADDRESS REGISTER

FOLLOWED BY THE DATA BYTE

Frame 2

78

Ack

by

MON35W42

2

C address

Ack

by

MON35W42

Stop

by

Master

2

C

11

(b)

Serial bus write to internal address register only

SCL

SDA

0

0 1 0 1 1 0 1 D7 D6 D5 D4 D3 D2 D1 D0

Start By

Master

Frame 1

Serial Bus Ad dr e ss By te

780 78

R/nW

Ack

MON35W42

0

by

Internal Index Register Byte

Frame 2

MON35W42

FIGURE 3 – SERIAL BUS WRITE TO INTERNAL ADDRESS REGISTER ONLY

(c)

Serial bus read from a register with the internal address register preset to desired location

SCL

0

780 78

SDA

0101101 D7D6D5D4D3D2D1D0

Start By

Master

Frame 1

Serial Bus Address Byte

R/nW

MON35W42

0

Ack
by

Internal Index Register Byte

Frame 2

FIGURE 4 – SERIAL BUS WRITE TO INTERNAL ADDRESS REGISTER

The serial bus timing of the temperature 2 and 3 is shown as follow:
(a) Typical 2-byte read from preset pointer location (Temp, T

OS

, T

HYST

)

SCL

SDA

0

0101101 D7 D1D0

Start By

Master

Frame 1

Serial Bus Address Byte

780 78

R/nW

MON35W42

... ...

...

Ack

by

Frame 2

MSB Data Byte

07

D7 D1 D0

Ack

by

Master

...

LSB Data By te

Frame 3

FIGURE 5 – TYPICAL 2-BYTE READ FROM PRESENT POINTER LOCATION

Ack

by

Ack

by

Master

Ack

by

Master

Stop by

Master

Stop by

Master

Stop by

Master

12

Typical pointer set followed by immediate read for 2-byte register (Temp, TOS, T

(b)

HYST

)

SCL

SDA

0

1001A2A1A0

Start By

Master

Frame 1

Serial Bus Address Byte

780

MON35W42

Ack

by

R/nW

000000

Frame 2

Pointer Byte

4

D1 D0

MON35W42

Ack

by

... ...

...

D7 D1 D0

Ack

by

Frame 4

MSB Data Byte

07

...

D7 D1 D0

Ack

by

Master

Frame 5

LSB Data Byte

No Ack

by

Master

Stop by

Master

SCL

SDA

0

1001A2A1A0

Start By

Master

Frame 3

Serial Bus Address Byte

780 78

R/nW

MON35W42

0

FIGURE 6 – TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FOR 2-BYTE REGISTER

(c)

Typical read 1-byte from configuration register with preset pointer

SCL

SDA

0

1001

Start By

Master

A2 A1 A0

Frame 1

Serial Bus Addr ess Byte

780

R/nW

MON35W42

D7 D2

Ack

by

Frame 2

Data Byte

7

8

D0

D1D5 D4 D3D6

No Ack

by

Master

Stop by

Master

FIGURE 7 – TYPICAL 1-BYTE READ FROM CONFIGURATION WITH RESET

13

(d) Typical pointer set followed by immediate read from configuration register

780

R/nW

Ack

by

MON35W42

4

000000

Frame 2

Pointer Byte

D1 D0

SCL

SDA

0

1001A2A1A0

Start By

Master

Frame 1

Serial Bus Address Byte

SCL (Cont..)

SDA (Cont..)

0

1001

Repea
Start

By Master

A2 A1 A0

Frame 3

Serial Bus Address Byte

780

MON35W42

Ack

by

D7 D5 D4

R/nW

D6 D3

Frame 4

MSB Data Byte

7

D2 D1 D0

FIGURE 8 – TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FROM TEMP 2/3

CONFIGURATION REGISTER

(e) Temperature 2/3 configuration register Write

4

SCL

0

780

R/nW

SDA

1 0 0 1 A2 A1 A0

Start By

Master

Frame 1

Serial Bus Address Byte

0000000

Ack

MON35W42

by

Frame 2

Pointer Byte

0

SCL (Cont...)

SDA (Cont...)

0 0 D4 D 3 D2 D10D0

FIGURE 9 – CONFIGURATION REGISTER WRITE

Frame 3

Configuration Data Byte

78

Ack

by

MON35W42

Stop

by

Master

78

MON35W42

8

No Ack

by

Master

D1 D0

...

...

Ack

by

Stop by
Master

78

Ack

by

MON35W42

14

(f)

Temperature 2/3 TOS and T

SCL

SDA

SCL (Cont...)

SDA (Cont...)

0

1001A2A1A0

Start By

Master

0

D6 D5 D4 D3 D2 D1D7 D0

write

HYST

780

0

0

0000

Frame 2

Pointer Byte

Frame 1

Serial Bus Address Byte

R/nW

Ack
by

78

0

D6 D5 D4 D3 D2 D1D7 D0

Frame 4

LSB Data Byte

Frame 3

MSB Data Byte

MON35W42

Ack

by

FIGURE 10 – CONFIGURATION REGISTER WRITE

D1 D0

78

Ack

by

MON35W42MON35W42

78

Ack

by

MON35W42

Stop

Master

by

4

15

Analog Inputs

The maximum input voltage of the analog pin is

4.096V, the 8-bit ADC has a 16mv LSB. For
most PC applications, the analog inputs are
connected to the power suppliers. The CPU V-

Positive Inputs

R1

V1

Positive Input

Negative Input

Typical Thermister Connection

V3

V4

R7

R2

R
10K, 25 C

THM

FIGURE 11

core voltage,+3.3V and battery voltage can
directly connected to these analog inputs. The
5VSB and +12V inputs should be reduced using
external resistors to obtain the proper input
range. Refer to Figure 11.

12VIN

V2

+2.5VINA
+2.5VINB

+3.3VIN

VDD(+5V)

VBAT

R3

R4

Pin 36
Pin 35
Pin 34
Pin 33
Pin 30

Pin 32

5VSB Pin 29

8-bit ADC

with

16mV LSB

R5

N12VIN

N5VIN

Pin 31

Pin 28

R

10K, 1%

R8

VREF Pin 37

VTIN3

VTIN2
VTIN1

Pin 38
Pin 39
Pin 40

R6

**The Connections of VTIN1 and VTIN2

are same as VTIN3

16

Monitor over 4.096V voltage:

The input voltage +12VIN can be expressed using the following equation.

R

2

12

VINV

'(

1

RR

12

The value of R1 and R2 can be selected as 28K Ohms and 10K Ohms, respectively, when the input
voltage V1 is 12V. The node voltage of +12VIN will be subject to less than 4.096V for the maximum
input range of the 8-bit ADC. Similarly, the node voltage of 5VSB (measured standby power VSB for
ATX power supply) also can be monitored by using two series resistors R3 and R4 which can be 5.1K
ohms and 7.5K ohms so as to obtain the 5VSB as lim ited to less than 4.096V. Pin 33 is connected to
the power supply VCC at +5V. This pin supports two functions. The first function is to supply internal
analog power in the MON35W42 and the second function is to monitor the 5V input through internal
series resistors. The values of the two series resistors are 34K ohms and 50K ohms so that input
voltage to ADC is 2.98V which is less than 4.096V of the ADC maximum input voltage. The voltage
equation can be represent as follows.

K

50

VVCC

'(

in

Monitor negative voltage:

The negative voltage should be connected to series resistors and a positive voltage VREF (equal to

3.6V). In Figure 11, the voltage V3 and V4 are two negative voltages, -12V and -5V respectively. The
voltage V3 is connected to two series resistors and is then connected to VREF which is a positive
voltage. The voltage at node N12VIN must be a positive voltage and will if the values of the two series
resistors are carefully selected. If the value of two series resistors are R5=232K ohms and R6=56K
ohm. The input voltage of node N12VIN can be calculated by the following equation.

NVIN VREF V

If V

is equal to -12V then the voltage is equal to 0.567V and the converted hexdecimal data is set to

5

35h by the 8-bit ADC with 16mV-LSB. This monitored value should be converted to the real negative
voltage and the voltage is calculated by the following equation.

Where

-

is 232K/(232K+56K). If the N2VIN is 0.567 then the V5 is approximately equal to -12V.

')(

V

5

50 34

where VCC is set to 5V.

where VREF is equal 3.6V.

NVIN VREF

12

'

+

KK

)

++

55

232 56

,(

-

1

,

)

298

K

)

-

+

V

.

*

232

KK

++

V12

)()( )

17

The other negative voltage input V6 (approximate -5V) also can be evaluated by a similar method and
the series resistors can be selected as R7=120K ohms and R8=56K ohms. The equation for a V6 of ­5V voltage is as follows.

NVIN VREF

5

V

'

6

Where
VREF=3.6V and the parameter . is 0.6818 then the negative voltage of V6 can be -5V.

Monitor temperature from thermistor:

The MON35W42 can connect to three thermistors to measure three different environment
temperatures. The specification of thermistor is: (1) - value is 3435K, (2) resistor value is 10K ohms at
25%C. In Figure 11, the themistor is connected by a series resistor to a 10K Ohms resistor, then to
VREF (Pin 37).

Monitor temperature from Pentium

The MON35W42 can monitor the temperature from the Pentium
or a 2N3904 transistor. The circuit is shown in Figure 12. The Pentium
supply ground (GND) and the D+ pin is connected to pin PIITDx in the MON35W42. The resistor
R=30K ohms is connected to VREF to supply the diode bias current and the bypass capacitor
C=3300pF is used to filter the high frequency noise. The transistor 2N3904 is to a form a diode, the
Base (B) and Collector (C) in the 2N3904 are tied together to act as a thermal diode.

.

is 120K/(120K+56K). If the monitored ADC value in the N5VIN channel is 0.8635,

®

II thermal diode or bipolar transistor 2N3904

,(

.

1

,

.

®

II (Deschutes) thermal diode interface

®

II D- pin is connected to power

18