9TCS1083
MOBILE ACCESS™—CLOCK SYNTHESIZER, TEMPERATURE SENSOR, & PWM FAN CONTROLLER FOR PORTABLE DEVICES
IDT®
MOBILE ACCESS™—CLOCK SYNTHESIZER, TEMPERATURE SENSOR, & PWM FAN CONTROLLER FOR PORTABLE DEVICES 26
9TCS1083 REV 0.8 011612
Thermal Sensor
The thermal sensor in the 9TCS1083 is a low power and highly accurate temperature sensor. It is optimized to operate
between 60°C to 100°C. There are two external thermal diode connection input temperature sensors. The chip supports
diode faults and temperature alerts for the thermal sensor; Moreover, the thermal sensor has the capability to go into standby
mode for power savings.
The temperature sensor's analog to digital converter (ADC) has 11 bits of resolution. One LSB is equal to 0.125°C. The
accuracy of the temperature sensor is ±1°C between 60°C - 100°C for the two sensors.
The 9TCS1083 temperature sensor has the ability to cancel the series resistance on the remote diode inputs. Parasitic
resistances to the DXP and DXN inputs seen in series with the remote diode are caused by PCB trace resistance along with
the overall length, bulk parasitic resistance in the remote temperature transistor junctions, and series resistance in the CPU.
This resistance appears as a temperature offset in the thermal sensor measurement and is approximately +0.7°C per Ohm.
The 9TCS1083 has the ability to cancel up to 100Ω of series resistance.
The thermal sensor in 9TCS1083 outputs the measured temperature from a beta compensated temperature reading from
an external diode. The temperature sensor architecture uses an on-chip ADC as shown to convert the analog temperature
into an 11-bit digital code. Using averaging techniques along with the ADC architecture allows accurate temperature
measurements. The ability to have programmable conversion rates and adjustable averaging schemes allow the user the
flexibility to balance accuracy versus conversion speed per the system requirements.
The temperature measurement relies on the characteristics of a semiconductor junction operating at a fixed current level.
Forcing a fixed current through the temperature diodes and detecting the changes in VBE, the forward voltage of the diode,
the temperature proportionality can be determined.
External Thermal Diode Selection
The 9TCS1083 supports the following temperature diodes:
• Typical remote substrate transistor (i.e. CPU substrate PNP intrinsic diode)
• Discrete PNP transistor diode (i.e. 2N3906)
• Discrete NPN transistor diode (i.e. 2N3904)
NPN 2N3904
NPN 2N3904
Analog MUX
Channel 1
Channel 2
Local
Current Driver BGP Ref
Temp Sensor
Dector
Timing Generator
11 bit ADC
Channel 1 Temp Reg
Channel 2 Temp Reg
