LM96194CISQ/NOPB National Semiconductor, LM96194CISQ/NOPB Datasheet - Page 29

• Manufacturer Part Number: LM96194CISQ/NOPB
• Description: IC TRUTHERM HDWR MONITOR 48-LLP
• Manufacturer: National Semiconductor
• Series: PowerWise®, TruTherm®r

Specifications of LM96194CISQ/NOPB

• Function: Fan Control, Temp Monitor
• Topology: ADC (Sigma Delta), Comparator, Fan Control, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 85°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-LLP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM96194CISQTR

range of concern through use of software calibration. Typical
non-ideality specification differences cause a gain variation of
the transfer function, therefore the center of the temperature
range of interest should be the target temperature for calibra-
tion purposes. The following equation can be used to calcu-
late the temperature correction factor (T
compensate for a target non-ideality differing from that sup-
ported by the LM96194.
where
•
•
•
The correction factor of
to the temperature reading produced by the LM96194. For
example when using the LM96194, with the 3904 mode se-
lected, to measure a AMD ™ Athlon processor, with a typical
non-ideality of 1.008, for a temperature range of 60 °C to 100
°C the correction factor would calculate to:
Therefore, 1.75°C should be subtracted from the temperature
readings of the LM96194 to compensate for the differing typ-
ical non-ideality target.
15.9.2 PCB Layout for Minimizing Noise
In the following guidelines, Remote+ and Remote -− refer to
the REMOTE1a+, Remote 1b+, REMOTE1−, REMOTE2a+,
Remote2b+ and REMOTE2− pins.
In a noisy environment, such as a power supply, layout con-
siderations are very critical. Noise induced on traces running
between the remote temperature diode sensor and the
LM96194 can cause temperature conversion errors.
The following guidelines should be followed:
1.
2.
3.
4.
5.
η
η
T
S
T
CR
Place a 0.1 µF and 100 pF LM96194 power bypass
capacitors as close as possible to the V
100pF capacitor being the closest. Place 10 µF capacitor
in the near vicinity of the LM96194 power pin.
Place a 100 pF capacitor as close as possible to the
LM96194 thermal diode Remote+ and Remote− pins.
Make sure the traces to the 100 pF capacitor are
matched and as short as possible. This capacitor is
required to minimize high frequency noise error.
Thermal diodes that share one Remote− pin must have
a separate trace from the LM96194 Remote− pin run to
each diode cathode. Do not "daisy chain" these
connections.
Ideally, the LM96194 should be placed within 10 cm of
the thermal diode pins with the traces being as straight,
short and identical as possible. Trace resistance of 1Ω
can cause as much as 1°C of error.
Diode traces should be surrounded by a GND guard ring
to either side, above and below, if possible. This GND
guard should not be between the Remote+ and Remote
− lines. In the event that noise does couple to the diode
lines, it would be ideal if it is coupled to both identically,
i.e. common mode. That is, equally to the Remote+ (D+)
and Remote−(D-) lines. (See figure below):
= LM96194 non-ideality for accuracy specification
= target thermal diode typical non-ideality
T
T
CF
= center of the temperature range of interest in °C
CF
=[(1.003−1.008)÷1.003]×(80+273) =−1.75°C
= [(η
S
−η
Processor
Equation 12
) ÷ η
S
] × (T
should be directly added
CR
+ 273 K)
DD
CF
) required to
pin, with the
(12)
29
6.
7.
8.
9.
10. Leakage current between Remote+ and GND should be
15.10 FAN CONTROL
15.10.1 Automatic Fan Control Methods
The LM96194 fan speed control method is optimized for fan
noise reduction, fan power efficiency, fan reliability and mini-
mum cost. The PWMx outputs can be filtered using an exter-
nal switching regulator type output stage that provides 5V to
12V DC for fan power. A high PWM frequency is required to
minimize the size and cost of the inductor and other compo-
nents used in the output stage. The PWM outputs of the
LM96194 can operate up to 22.5 kHz with a variable step size
depending on the fan control mode of operation. The
LM96194 supports LUT (Lookup Table) and PI (Proportional
Integral) fan control methods. These methods can function
interactively or independently as controlled by the PWM bind-
ing registers.
these fan control methods. The mapping/binding of the tem-
perature zones to the LUTs is completely independent of the
PI loops. The temperature zones can be first independently
bound to the LUTs and/or PI loops then each LUT or PI loop
can be bound to either PWM Output. The LUT parameters are
independent of the temperature zone binding. The PI loop
controller is a proportional-integral feedback controller. It gen-
erates a 9-bit PWM duty cycle and uses temperature feed-
back from the processor thermal zones (Zones 1 and 2). The
PWM output controls the airflow over the processors and thus
the temperature of the processors is adjusted by the PI loop
to maintain the hottest temperature reading between the val-
ues Tcontrol and Tcontrol - hysteresis. The LM96194 sup-
ports 2 processors and each processor can have two thermal
sub-zones. The hottest of each processor temperature is re-
ported to the Zone selectors and PI loop inputs. Each pro-
cessor has an independent Tcontrol setting.
Avoid routing diode traces in close proximity to any power
supply switching or filtering inductors.
Avoid running diode traces close to or parallel to high
speed digital and bus lines. Diode traces should be kept
at least 2 cm apart from the high speed digital traces.
If it is necessary to cross high speed digital traces, the
diode traces and the high speed digital traces should
cross at a 90 degree angle.
The ideal place to connect the LM96194’s GND pin is as
close as possible to the Processors GND associated with
the sense diode. In the case of two processors pick a
node in between the two that has the least noise.
kept to a minimum. Error in the diode temperature
reading may reach 0.4°C with 30 nA of leakage current.
Keeping the printed circuit board as clean as possible
minimizes leakage current. The residue from some
freeze spray can induce high leakage current.
Recommended Diode Trace Layout
Figure 6
shows the high level block diagram for
www.national.com
20194420