LM95241CIMM-2/NOPB National Semiconductor, LM95241CIMM-2/NOPB Datasheet - Page 8

• Manufacturer Part Number: LM95241CIMM-2/NOPB
• Description: IC TEMP SENS DUAL REM DIO 8-MSOP
• Manufacturer: National Semiconductor
• Series: PowerWise®, TruTherm®r

Specifications of LM95241CIMM-2/NOPB

• Function: Hardware Monitor
• Topology: ADC (Sigma Delta), Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: 0°C ~ 85°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: No
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• For Use With: LM95241EB - BOARD EVALUATION LM95241
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM95241CIMM-2; LM95241CIMM-2TR

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1.0 Functional Description
The LM95241 is a digital sensor that can sense the temper-
ature of 3 thermal zones using a sigma-delta analog-to-digital
converter. It can measure its local die temperature and the
temperature of two external transistor junctions using a
ΔV
port two external transistor types, a Intel processor on 65nm
or 90mn process thermal diode or a 2N3904 diode connected
transistor. The transistor type is register programmable and
does not require software intervention after initialization. The
LM95241 has an advanced input stage using National
Semiconductor's TruTherm technology that reduces the
spread in non-ideality found in Intel processors on 65nm or
90nm process. Internal analog filtering has been included in
the thermal diode input stage thus minimizing the need for
external thermal diode filter capacitors. In addition a digital
filter has been added. These noise immunity improvements
in the analog input stage along with the digital filtering will
allow longer trace tracks or cabling to the thermal diode than
previous thermal diode sensor devices.
The 2-wire serial interface, of the LM95241, is compatible with
SMBus 2.0 and I2C
for a detailed description of the differences between the I2C
bus and SMBus.
The temperature conversion rate is programmable to allow
the user to optimize the current consumption of the LM95241
to the system requirements. The LM95241 can be placed in
shutdown to minimize power consumption when temperature
data is not required. While in shutdown, a 1-shot conversion
mode allows system control of the conversion rate for ultimate
flexibility.
The remote diode temperature resolution is variable and de-
pends on whether the digital filter is activated. When the
digital filter is active the resolution is thirteen bits and is pro-
grammable to 13-bits unsigned or 12-bits plus sign, with a
least-significant-bit (LSb) weight for both resolutions of
0.03125°C. When the digital filter is inactive the resolution is
eleven bits and is programmable to 11-bits unsigned or 10-
bits plus sign, with a least-significant-bit (LSb) weight for both
resolutions of 0.125°C. The unsigned resolution allows the
remote diodes to sense temperatures above 127°C. Local
temperature resolution is not programmable and is always 9-
bits plus sign and has a 0.25°C LSb.
The LM95241 remote diode temperature accuracy is trimmed
for the typical thermal diode of a Intel processor on 65nm or
90nm process or a typical 2N3904 transistor and the accuracy
is guaranteed only when using either of these diodes when
selected appropriately. TruTherm mode should be enabled
when measuring a Intel processor on 65nm or 90nm process
and disabled when measuring a 3904 transistor.
Diode fault detection circuitry in the LM95241 can detect the
presence of a remote diode.
The LM95241 register set has an 8-bit data structure and in-
cludes:
1.
2.
3.
4.
5.
6.
7.
be
Most-Significant-Byte (MSB) Local Temperature
Register
Least-Significant-Byte (LSB) Local Temperature
Register
MSB Remote Temperature 1 Register
LSB Remote Temperature 1 Register
MSB Remote Temperature 2 Register
LSB Remote Temperature 2 Register
Status Register: busy, diode fault
temperature sensing method. The LM95241 can sup-
®
. Please see the SMBus 2.0 specification
8
8.
9.
10. Remote Diode Model Select
11. Remote Diode TruTherm Mode Control
12. 1-shot Register
13. Manufacturer ID
14. Revision ID
1.1 CONVERSION SEQUENCE
In the power up default state the LM95241 typically takes
77.8 ms to convert the Local Temperature, Remote Temper-
ature 1 and 2, and to update all of its registers. Only during
the conversion process is the busy bit (D7) in the Status reg-
ister (02h) high. These conversions are addressed in a round
robin sequence. The conversion rate may be modified by the
Conversion Rate bits found in the Configuration Register
(03h). When the conversion rate is modified a delay is insert-
ed between conversions, the actual maximum conversion
time remains at 88.9 ms. Different conversion rates will cause
the LM95241 to draw different amounts of supply current as
shown in
1.2 POWER-ON-DEFAULT STATES
LM95241 always powers up to these known default states.
The LM95241 remains in these states until after the first con-
version.
1.
2.
3.
4.
5.
6.
7.
FIGURE 1. Conversion Rate Effect on Power Supply
Configuration Register: resolution control, conversion
rate control, standby control
Remote Diode Filter Setting
Command Register set to 00h
Local Temperature set to 0°C until the end of the first
conversion
Remote Diode Temperature set to 0°C until the end of
the first conversion
Remote Diode digital filters are on.
Remote Diode 1 model is set to Intel processor on 65nm
or 90nm process with TruTherm Mode enabled. Remote
Diode 2 model is set to 2N3904/MMBT3904 with
TruTherm mode disabled.
Status Register depends on state of thermal diode inputs
Configuration register set to 00h; continuous conversion
Figure
1.
Current
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