9TCS1082
MOBILE ACCESS™—CLOCK SYNTHESIZER & TEMPERATURE SENSOR FOR PORTABLE DEVICES SYNTHESIZERS
IDT®
MOBILE ACCESS™—CLOCK SYNTHESIZER & TEMPERATURE SENSOR FOR PORTABLE DEVICES 21
9TCS1082 REV 0.7 012312
Thermal Sensor
The thermal sensor in the 9TCS1082 is a low power and highly accurate temperature sensor. It is optimized to operate
between 60°C to 100°C. There is one external thermal diode connection input and one internal diode temperature sensor.
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.
The 9TCS1082 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 9TCS1082 has the ability to cancel up to 100Ω of series resistance.
The thermal sensor in 9TCS1082 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 9TCS1082 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
Analog MUX
Channel 1
Current Driver BGP Ref
Temp Sensor
Dector
Timing Generator
11 bit ADC
Temperature Reg
