NE1617ADS,112 NXP Semiconductors, NE1617ADS,112 Datasheet - Page 5

• Manufacturer Part Number: NE1617ADS,112
• Description: IC TEMP MONITOR 16SSOP
• Manufacturer: NXP Semiconductors

Specifications of NE1617ADS,112

• Function: Temp Monitoring System (Sensor)
• Topology: ADC, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -55°C ~ 125°C, External Sensor
• Output Type: SMBus™
• Output Alarm: Yes
• Output Fan: No
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Temperature Sensor Function: Temp Sensor
• Interface Type: Serial (2-Wire)
• Operating Temperature (min): 0C
• Operating Temperature (max): 125C
• Operating Temperature Classification: Military
• Operating Supply Voltage (min): 3V
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 935268119112; NE1617ADS; NE1617ADS

NXP Semiconductors
7. Functional description
NE1617A_4
Product data sheet
7.1 Remote diode selection
The NE1617A contains an integrating A-to-D converter, an analog multiplexer, a status
register, digital data registers, SMBus interface, associated control logic and a local
temperature sensor or channel (refer to
remote diode-type sensor or channel should be connected to the D+ and D pins properly.
Temperature measurements or conversions are either automatically and periodically
activated when the device is in free-running mode (both STBY pin = HIGH, and the
configuration register bit 6 = LOW) or generated by one-shot command. The free-running
period is selected by changing the programmable data of the conversion rate register, as
described in
through the remote and local temperature sensors over a period of time, about 60 ms, and
the voltages across the diode-type sensors are sensed and converted into the
temperature data by the A-to-D converter. The resulting temperature data is then stored in
the temperature registers, in 8-bit two's complement word format and automatically
compared with the limits which have been programmed in the temperature limit registers.
Results of the comparison are reflected accordingly by the flags stored in the status
register, an out-of-limit condition will set the ALERT output pin to its LOW state. Because
both channels are automatically measured for each conversion, the results are updated
for both channels at the end of every successful conversion.
The method of the temperature measurement is based on the change of the diode V
two different operating current levels given by:
where:
The NE1617A forces two well-controlled current sources of about 10 A and 100 A and
measures the remote diode V
limited between 0.25 V and 0.95 V. The external diode must be selected to meet this
voltage range at these two current levels. The diode-connected PNP transistor provided
on the microprocessor is typically used, or the discrete diode-connected transistor
2N3904 or 2N3906 is recommended as an alternative.
Even though the NE1617A integrating A-to-D converter has a good noise performance,
using the average of 10 measurement cycles, high frequency noise filtering between D+
and D should be considered. An external capacitor of 2200 pF typical (but not higher
V
K = Boltzman’s constant
T = absolute temperature in Kelvin
q = charge on the electron
LN = natural logarithm
N = ratio of the two currents
BE
V
BE
=
= change in base emitter voltage drop at two current levels
KT
------- -
q
Section
LN N
8.3.4. For each conversion, the multiplexer switches current sources
Rev. 04 — 30 July 2009
BE
. The sensed voltage between two pins D+ and D is
Temperature monitor for microprocessor systems
Figure 1 “Block diagram of
NE1617A”). The
NE1617A
© NXP B.V. 2009. All rights reserved.
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(1)
at