L6714 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
L6714
STMicroelectronics
'L6714' PDF : 70 Pages View PDF
Thermal monitor
22 Thermal monitor
L6714
L6714 continuously senses the system temperature through TM pin: depending on the
voltage sensed by this pin, the device sets free the VR_FAN pin as a warning and, after
further temperature increase, also the VR_HOT pin as an alarm condition.
These signals can be used to give a boost to the system fan (VR_FAN) and improve the VR
cooling, or to initiate the CPU low power state (VR_HOT) in order to reduce the current
demand from the processor so reducing also the VR temperature. In a different manner,
VR_FAN can be used to initiate the CPU low power state so reducing the processor current
requirements and VR_HOT to reset the system in case of further dangerous temperature
increase.
Thermal sensors is external to the PWM control IC since the controller is normally not
located near the heat generating components: it is basically composed by a NTC resistor
and a proper biasing resistor RTM. NTC must be connected as close as possible at the
system hot-spot in order to be sure to control the hottest point of the VR.
Typical connection is reported in Figure 25 that also shows how the trip point can be easily
programmed by modifying the divider values in order to cross the VR_FAN and VR_HOT
thresholds at the desired temperatures.
Both VR_HOT and VR_FAN are active high and open drain outputs. Thermal Monitoring
Output are enabled if Vcc > UVLOVCC.
Figure 25. System thermal monitor typical connections.
+5V
Sense Element
(Place remotely, near Hot Spot)
TM
RTM
4.00
3.80
3.60
3.40
3.20
3.00
2.80
2.60
2.40
2.20
2.00
80
TM Voltage - NTC=3300/4250K
Rtm = 330
Rtm = 390
Rtm = 470
85
90
95
100
105
110
115
120
Temperature [degC]
60/70
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