www.fairchildsemi.com
FMS2701
Temperature and Power Supply Voltage Monitor
Features
•
•
•
•
•
•
•
•
•
Remote diode temperature sensing
Ambient (on-chip) temperature sense
Dual 3.3 volt supply monitoring
SMBus interface to internal registers
Status registers
Thermal trip output
Interrupt output
Fan speed control output
ACPI Thermal Management compliant
Description
The FMS2701 is a temperature- and voltage-monitoring
device that can be interrogated and controlled through an
SMBus serial interface. Outputs are an analog fan control
voltage, thermal alarm and interrupts.
Preliminary Information
Applications
• PCs and Servers, Workstations
• Office Equipment
• Test and Measurement Instruments
Remote (DIODE+ and DIODE-) and ambient diode temper-
ature sensor inputs are selected in sequence at a 1Hz rate by
a multiplexer that drives an A/D converter. Digitized diode
temperatures are stored in registers. Violation of a program-
mable limit or trip point will set an interrupt register bit and/
or assert a digital output.
Power supply voltages are monitored through two pins:
VCCAUX3 monitors the power to the FMC2701; VCC3 is a
separate 3.3 volt sense voltage input. AUXRST and RST out-
puts indicate the status of voltage monitoring.
Analog output, FAN_SPD can be used as an input to a fan
speed control circuit while THERM, INT and FAN_OFF are
additional digital control outputs.
Power is derived from a +3.3V supply. Package is 16-lead
Quad Small Outline Pack (QSOP).
Block Diagram
VCC3AUX
Oscillator
INTRST
VCC3
Timing
and Control
Current
Generators
Main Reset
MR
RST
Aux Reset
AUXRST
D/A
Register
Low-pass
Filter
Mux
On-chip
Bias &
Diode
A/D
Converter
DSP
Limit
Comparators
D/A
Converter
FAN_SPD
DIODE+
DIODE-
Interrupt
Status
Registers
THERM
Value & Limit
Registers
ADD
Interrupt
Mask
Register
SDA
SCL
GPI
SMBus
Interface
Internal Bus
Mask
Gating
INT
Configuration
Register
Lit. No. 600402-001
FAN_OFF
Rev. 1.0.3
PRELIMINARY INFORMATION
describes products that are not in full production at the time of printing. Specifications are based on design goals
and limited characterization. They may change without notice. Contact Fairchild Semiconductor for current information.
PRODUCT SPECIFICATION
FMS2701
Architectural Overview
Overall operation of the FMS2701 is controlled by the
SMBus which sets register values and interrupt masking.
Four sensing inputs are monitored:
1. Remote temperature diode voltage
2. Ambient temperature sensing diode voltage
3. Remote 3.3 volt power supply voltage
4. Local 3.3 volt power supply
Following comparisons against either preset or programma-
ble thresholds, the following hardware outputs are set:
1. Master reset
2. Auxiliary reset
3. Temperature trip point violated (THERM)
4. Interrupt (INT)
Also set are the following register bits:
1. GPI active (General Purpose Input)
2. Remote Temperature limit exceeded
3. THERM input asserted
4. Remote diode fault
Fan Speed control voltage, FAN_SPD is set in the range
0–2.5V by loading the D/A Register through the SMBus.
External THERM = L forces FAN_SPD = 2.5V. A Master
Reset clears the D/A Register.
Following the A/D converter is a DSP block which averages
digitized temperature over several samples.
Upper and lower temperature limits are loaded into the limit
registers. If a limit is violated, an interrupt is generated. Remote
diode open or short circuit fault condition is also sensed.
Power Supply Voltage Monitors
Two Voltage Monitors operating over a 1.0 to 3.8 volt
supply range, sense VCC3 and VCC3AUX voltages. If
input VCC3 < 2.93 volt or master reset input, MR = L, then
RST= L until 140 msec after sensing the fault condition.
If the FMS2701 supply, VCC3AUX < 2.93 volt, AUXRST = L
until 140 msec. after sensing the fault condition, and the main
reset RST = L until 180 msec. after AUXRST is cleared.
When AUXRST = L, internal reset, INTRST =L. AUXRST
is bi-directional, accepting a hard reset input.
Preliminary Information
SMBus Interface
FMS2701 Registers are accessed through the SMBus inter-
face located at the address 0x2C + n; where n = 0, 1, 2
depending upon the state of ADD, a tri-level input. Within
the FMS2701, registers are accessed through an 8-bit bus.
Addressable Memory
Within the FMS2701, there are three sections of addressable
memory which implement the following functions.
Temperature Channel
There are two temperature sense inputs: one for remote sens-
ing; the other for measuring ambient temperature. Both
inputs utilize the thermal variation of the voltage drop across
a diode, to derive the diode temperature.
Instead of sensing the change in V
D
at one current, which is
approximately –2mV/°C, V
D
is sampled at two currents
(I
MAX
= 10 and I
MIN
= 100 µA) to cancel out common error
voltages. Difference voltage between the two currents is
proportional to absolute temperature:
Command Register (5 locations)
•
•
•
•
•
Configuration
Interrupt status
Interrupt mask
Interrupt status mirror
Extended function
Read only RAM (2 locations)
• Company ID
• Revision No.
nkT
I
∆
V
D
=
q
⋅
ln
MAX
I
MIN
Where:
n = PN junction ideality factor, typically 1.0065 for the
Pentium II thermal diode. Nominal diode sensitivity is
199.7 µV/°C.
Value RAM (13 locations)
•
•
•
•
Diode temperature, °C
THERM temperature trip points, °C
INT temperature limits, °C
Analog output D/A converter
Write accessible locations have default values that may be
overridden by programming through the SMBus interface.
2
FMS2701
PRODUCT SPECIFICATION
Pin Assignment
FAN_OFF
MR
AUXRST
GND
VCC3AUX
VCC3
RST
FAN_SPD/NTEST_IN
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
SDA
SCL
INT
ADD/NTESTOUT
GPI
THERM
DIODE(+)
DIODE(-)
Pin Descriptions
Pin No.
Pin Name
Reset
7
RST
Type/Value
Output
Pin Function Description
Reset.
Output pulse from Main Reset Generator, which
is tripped by either MR =L or Internal Reset or VCC3 <
2.93 V. When active, RST = L and register D
7-0
is
cleared.
Auxiliary Reset Input/Output.
As an output, AUXRST =
L pulse is triggered by VCC3AUX < 2.93 V. As an input,
AUXRST = L trips Internal Reset. NAND test input,
NTEST_IN is sampled by trailing edge of AUXRST pulse.
Manual Reset.
Input to Master Reset Generator. If MR =
L, a master reset cycle is initiated. MR pin has a 20 kΩ
pull-up to VCC3AUX.
Positive diode sense input.
Current source to remote
temperature sensing diode anode and upper voltage
sense input.
Negative diode sense input.
Current sink from remote
temperature sensing diode cathode and lower voltage
sense input.
Fan speed control voltage output/NAND Test Input.
Proportional to the value in register 0x19, output is
0–2.5V. External THERM = L forces a 2.5 volt output. If
NTEST_IN = H, the NAND tree test input is enabled for
ATE.
Data.
SMBus data to/from FMS2701
Clock.
SMBus clock into FMS2701
SMBus Address Input/NAND Test Output.
Lowest two
bits of serial port address with three states: 00, 01 and
10, corresponding to H, L and Z inputs. If NTEST_IN is
sampled HIGH, the NAND tree test output is enabled.
Thermal Overload.
THERM = L indicates that a
temperature trip point has been exceeded. Input THERM
= L sets the THERM bit in the Interrupt Status Register.
System interrupt.
INT = L when a voltage, temperature
limit or temperature trip point is violated and bit 1 of the
Configuration Register is set H.
3
Preliminary Information
3
AUXRST
Bi-directional
2
MR
Input
Analog I/O
10
DIODE+
Voltage input/
current source
Voltage input/
current sink
Analog output/
digital input
9
DIODE-
8
FAN_SPD/NTEST_IN
Serial Port
16
SDA
15
SCL
13
ADD/NTEST_OUT
Bi-directional
Input
Tri-level
Digital I/O
11
THERM
I//O (Open drain)
14
INT
Open drain
PRODUCT SPECIFICATION
FMS2701
Pin No.
Pin Name
12
GPI
Type/Value
Input
1
FAN_OFF
Open Drain Output
Pin Function Description
General Purpose Input.
Sets a bit in the interrupt
registers. Assertion polarity is set by the GPI_INV bit.
(default is GPI = H causes interrupt)
Fan off request.
FAN_OFF reflects the state of the
Configuration Register FAN_OFF bit. FAN_OFF = L is a
request to shut the fan off.
Voltage Monitor Input.
Voltage monitor input to Main
Reset Generator. If VCC3 drops below 2.93V. a Main
Reset cycle is initiated.
Ground.
Return for 3.3 volt supply, VCC3AUX.
Auxiliary 3.3 volt.
Power source for FMS2701. If
VCC3AUX drops below 2.93 volt, an Auxiliary Reset
cycle is initiated.
Power and Ground
6
VCC3
+3.3 V Input
4
5
GND
VCC3AUX
0V
+3.3 V Power
Preliminary Information
Addressable Memory
Addressable memory is divided into two sections:
1. Command, consisting of five registers
2. Value RAM, consisting of thirteen locations, of which: eleven are used to store temperature data, limits and trip points;
two are used to store the company ID, version and revision number.
Table 1. Addressable Memory Map
Name
Configuration Register
Interrupt Status Register
Interrupt Mask Register
Interrupt Status Register Mirror
PTA
7-0
PTR
7-0
FTA
7-0
FTR
7-0
DAC
7-0
TR
7-0
TA
7-0
TRHI
7-0
TRLO
7-0
TAHI
7-0
TALO
7-0
Manufacturer ID
Version, Revision
Address
0x40
0x41
0x43
0x4C
0x13
0x14
0x17
0x18
0x19
0x26
0x27
0x37
0x38
0x39
0x3A
0x3E
0x3F
Power-up Value, [7:0]
0x25
0x00
0x00
0x00
0x46
0x64
0x46
0x64
0x00
0x46
0x3C
0x50
0x3C
0x46
0x32
0xFC
0xCn
Register Definitions
Configuration Register (0x40)
BIT#
0
Name
START
Type
R/W
Description
Start Temperature and Voltage Monitoring
0:
Standby mode. (INT is not cleared)
1:
Run (Power-up default). All limit and trip values should be entered into
FMS2701 registers prior to setting START = 1.
4
FMS2701
PRODUCT SPECIFICATION
BIT#
1
Name
INT_EN
Type
R/W
Description
Interrupt Enable
0:
Disabled (Power-up default)
1:
Enables the INT output.
Interrupt Clear
0:
INT output unaffected.
1:
Clears the INT output. Contents of the Interrupt Status Register
preserved. (Power-up default = 1)
Temperature Trip Point Lock
0:
THERM trip points set by fixed value registers FTA
7-0
and FTR
7-0
.
Writes to programmable registers PTA
7-0
and PTR
7-0
are enabled.
(Power-up default = 0)
1:
THERM trip points set by values preserved in programmable registers
PTA
7-0
and PTR
7-0
, while RST = H.
Soft Reset
0:
Power-up default restored by SOFT_RST cycle.
1:
Restore power-up values to the Configuration, Interrupt Status,
Interrupt Status Mirror and Interrupt Mask registers.
Fan Off
0:
Set output pin FAN_OFF = L. (fan-off)
1:
Set output pin FAN_OFF = Z. (Power-up default, fan-on)
If pin THERM = L, then FAN_OFF = H.
GPI Polarity Invert
0:
GPI input passed to Interrupt registers. (Power-up default)
1:
Invert the GPI input passed to Interrupt registers
Reserved (Default=0)
2
INT_CLR
R/W
3
TRIP_LOCK
R/(W-once)
Preliminary Information
4
SOFT_RST
R/W
5
FAN_OFF
R/W
6
GPI_INV
R/W
7
Reserved
R/W
Interrupt Status Register
1
(0x41)
BIT#
0
Name
ATV
Type
R
Description
Ambient Temperature Violation
0:
On-chip temperature within limits.
1:
On-chip temperature limit violated
Reserved for Remote Thermal Diode 2 temp error
Reserved for Remote Thermal Diode 2 fault
Undefined
General Purpose Input Status.
GPI is set according to the following truth table:
GPI pin
0
1
0
1
GPI_INV
0
0
1
1
GPI bit
0
1
1
0
1
2
3
4
Reserved
Reserved
Reserved
GPI
R
R
R
R
5
RTV
R
6
THERM
R
Reading this register will not clear the GPI bit.
Remote Temperature Violation.
0:
Remote temperature within limits.
1:
Remote temperature limit violated
THERM input status.
0:
THERM input negated. (THERM = H)
1:
THERM input asserted. (THERM = L)
5
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