LM96194CISQ/NOPB National Semiconductor, LM96194CISQ/NOPB Datasheet - Page 16

• 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

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12.11 PROCHOT BACKGROUND INFORMATION
PROCHOT is an output from a processor that indicates that
the processor has reached a predetermined temperature trip
point. At this trip point the processor can be programmed to
lower its internal operating frequency and/or lower its supply
voltage by changing the value of the 6 bit VID that it supplies
to the VRD. The final VID setting and the rate at which it tran-
sitions to the new VID is programmable within the processor.
If PROCHOT is 100% throttled, it does not mean that the CPU
is not executing, but it may mean that the CPU is about to
encounter a thermal trip if the processor temperature contin-
ues to rise.
PROCHOT is also an input to some processors so that an
external controller can force a thermal throttle based on ex-
ternal events.
PROCHOT is no longer asserted by the processor when the
temperature drops below the predefined thermal trip point.
Oscillation around the trip point is avoided by the processor
by requiring that the temperature be above/below the trip
point for a predetermined period of time. A counter inside the
processor is used to track this time and it has to be incre-
mented to a max count for an above temperature trip and
decremented to zero when below the trip temperature setting,
to remove the trip.
The minimum time for PROCHOT assertion is time depen-
dant on the FSB frequency. The minimum time that the pro-
cessor asserts PROCHOT is estimated to be 187 µs.
12.12 PROCHOT MONITORING
PROCHOT monitoring is meant to achieve two goals. One
goal is to measure the percentage of time that PROCHOT is
asserted over a programmable time period. The result of this
measurement can be read from an 8-bit register where one
LSB equals 1/256th of the PROCHOT Time Interval (0.39%).
The second goal is to have a status register that indicates, as
a coarse percentage, the amount of time a processor has
been throttled. This second goal is required in order to com-
municate information over the NIC using ASF, i.e. status can
be sent, not values.
To achieve the first goal, the PROCHOT input is monitored
over a period of time as defined by the PROCHOT Time In-
terval Register. At the end of each time period, the 8-bit
measurement is transferred to the Current PROCHOT regis-
ter. Also at the end of each measurement period, the Current
PROCHOT register value is moved to the Average PRO-
CHOT register by adding the new value to the old value and
dividing the result by 2. Note that the value that is averaged
into the Average PROCHOT register is not the new measure-
ment but rather the previous measurement. If the SMBus
writes to the Current PROCHOT register, the capture cycle
restarts. Also note, that a strict average of two 8-bit values
may result in Average PROCHOT reflecting a value that is
one LSB lower than the Current PROCHOT in steady state.
It should be noted that the 8-bit result has a positive bias of
one half of an LSB. This is necessary because a value of 00h
represents that PROCHOT was not asserted at all during the
sampling window. Any amount of throttling results in a reading
of 01h.
The following table demonstrates the mapping for the 8-bit
result:
8–Bit Result
0
1
2
Exactly 0%
Between 0% and 0.39%
Between 0.39% and 0.78%
Percentage Thottled
16
To achieve the second goal, the LM96194 has several com-
parators that compare the measured percentage reading
against several fixed and 1 variable value. The variable value
is user programmable.
The result of these comparisons generates several error sta-
tus bits described in the following table:
These status bits are reflected in the PROCHOT Error Status
Register.
In S3 and S4/5 sleep states, the PROCHOT Monitoring func-
tion does not run. VRD_Hot is disabled from activating PRO-
CHOT pin in S3 and S4/5. The Current PROCHOT registers
are reset to 00h and the Average PROCHOT registers hold
their current state. Once the sleep state changes back to S0,
the monitoring function is restarted. After the first PRO-
CHOT measurement has been made, the measurement is
written directly into the Current and Average PROCHOT reg-
isters without performing any averaging. Averaging returns to
normal on the second measurement.
12.13 PROCHOT OUTPUT CONTROL
In some cases, it is necessary for the LM96194 to drive the
PROCHOT output low. There are several conditions that
cause this to happen.
Whenever one of the VRD_HOT input is asserted, the PRO-
CHOT pin is asserted by the LM96194. The response time is
less than 10 µs. When the VRD_HOT input is de-asserted,
the PROCHOT pin is no longer asserted by the LM96194.
This response is disabled in sleep states 3 and 4/5 and can
be disabled through the PROCHOT Control register.
Software can manually program the LM96194 to drive a PWM
type signal onto PROCHOT. This is done via the PRO-
CHOT Override register. See the description of this register
for more details.
100% Throttle
Greater than or equal to 75%
and less than 100%
Greater than or equal to 50%
and less than 75%
Greater than or equal to 25%
and less than 50%
Greater than or equal to
12.5% and less than 25%
Greater than 0% and less
than 12.5%
Greater than 0%
Greater than user limit
8–Bit Result
Status Description
253
254
255
…
…
n
…
Between (n-1)/256 and n/256
…
Between 98.4% and 98.8%
Between 98.8% and 99.2%
Greater than 99.2%
Percentage Thottled
PROCHOT was never de-
asserted during monitoring
interval.
193
not 100%
129
65
33
0 < measured value < 33
0 < measured value
user limit < measured value
Comparison Formula
≤
≤
≤
≤
measured value < 129
measured value < 65
measured value and
measured value < 193