NE1617ADS ,Temperature monitor for microprocessor systemsGeneral descriptionThe NE1617A is an accurate two-channel temperature monitor. It measures the temp ..
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NE1617ADS
Temperature monitor for microprocessor systems
1. General descriptionThe NE1617A is an accurate two-channel temperature monitor. It measures the
temperature of itself and the temperature of a remote sensor. The remote sensor is a
diode connected transistor. This can be in the form of either a discrete NPN/PNP, such as
the 2N3904/2N3906, or a diode connected PNP built into another die, such as is done on
some Intel microprocessors.
The temperature of both the remote and local sensors is stored in a register that can be
read via a 2-wire SMBus. The temperatures are updated at a rate that is programmable
via the SMBus (the average supply current is dependent upon the update rate — the
faster the rate, the higher the current).
In addition to the normal operation, which is to update the temperature at the programmed
rate, there is a one-shot mode that will force a temperature update.
There is also an alarm that senses either an overtemperature or undertemperature
condition. The trip points for this alarm are also programmable.
The device can have one of nine addresses (determined by two address pins), so there
can be up to nine of the NE1617A on the SMBus.
It can also be put in standby mode (in order to save power). This can be done either with
software (over the SMBus) or with hardware (using the STBY pin).
2. Features and benefits Replacement for Maxim MAX1617 and Analog Devices ADM1021 Monitors local and remote temperature Local (on-chip) sensor accuracy:2 C at 60 C to 100C3 C at 40 C to 125C Remote sensor accuracy:3 C at 60 C to 100C5 C at 40 C to 125C No calibration required Programmable overtemperature/undertemperature alarm SMBus 2-wire serial interface up to 100 kHz3 V to 5.5 V supply range; 5.5 V tolerant 70 A supply current in operating mode3 A (typical) supply current in standby mode
NE1617A
Temperature monitor for microprocessor systems
Rev. 5 — 20 March 2012 Product data sheet
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systems ESD protection exceeds 2000 V HBM per JESD22-A114 and 1000 V CDM per
JESD22-C101 Latch-up testing is done to JEDEC standard JESD78, which exceeds 100 mA Small 16-lead SSOP (QSOP) package
3. Applications Desktop computers Notebook computers Smart battery packs Industrial controllersT elecommunications equipment
4. Ordering information[1] Also known as QSOP16.
Table 1. Ordering informationTamb = 40 C to +125 C.
NE1617ADS NE1617A SSOP16[1] plastic shrink small outline package; 16 leads; body width 3.9 mm;
lead pitch 0.635 mm
SOT519-1
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systems
5. Block diagramNXP Semiconductors NE1617A
Temperature monitor for microprocessor systems
6. Pinning information
6.1 Pinning
6.2 Pin description[1] These pins should either float or be tied to ground.
[2] VDD pin should be decoupled by a 0.1 F capacitor.
Table 2. Pin descriptionTEST1 1 test pin; factory use only[1]
VDD 2 positive supply[2] 3 positive side of remote sensor 4 negative side of remote sensor
TEST5 5 test pin; factory use only[1]
ADD1 6 device address 1 (3-state)
GND 7, 8 ground
TEST9 9 test pin; factory use only[1]
ADD0 10 device address 0 (3-state)
ALERT 11 open-drain output used as interrupt or SMBus alert
SDATA 12 SMBus serial data input/output; open-drain
TEST13 13 test pin; factory use only[1]
SCLK 14 SMBus clock input
STBY 15 hardware standby input
HIGH= normal operating mode
LOW= standby mode
TEST16 16 test pin; factory use only[1]
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systems
7. Functional descriptionThe 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 Figure 1 “Block diagram of NE1617A”). The
remote diode-type sensor or channel should be connected to the D+ and D pins properly. emperature 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 bit6= 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 Section 8.3.4. For each conversion, the multiplexer switches current sources
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.
7.1 Temperature measurementThe method of the temperature measurement is based on the change of the diode VBE at
two different operating current levels given by:
(1)
where:
VBE= change in base emitter voltage drop at two current levels
n = non-ideality
K = Boltzman’s constant
T = absolute temperature in Kelvin
q = charge on the electron
LN = natural logarithm
N = ratio of the two currents
The NE1617A forces two well-controlled current sources of about 10 A and 100 A and
measures the remote diode VBE. The sensed voltage between two pins D+ and D is
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 and also the non-ideality factor ‘n’ must be close
to the value of 1.008 to be compatible with the Intel Pentium III internal thermal diode that
the NE1617A was designed to work with. 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.
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systemsEven 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
than 3300 pF) connected between D+ and D is recommended. Capacitance higher than
3300 pF will introduce measurement error due to the rise time of the switched current
source.
7.2 No calibration is requiredAs mentioned in Section 7.1, the NE1617A uses two well-controlled current sources of : 1 ratio to measure the forward voltage of the diode (VBE). This technique eliminates
the diode saturation current (a heavily process and temperature dependent variable), and
results in the forward voltage being proportional to absolute temperature.
7.3 Address logicThe address pins of the NE1617A can be forced into one of three levels: LOW (GND),
HIGH (VDD), or ‘not connected’ (n.c.). Because the NE1617A samples and latches the
address pins at the starting of every conversion, it is suggested that those address pins
should be hard-wired to the logic applied, so that the logic is consistently existed at the
address pins. During the address sensing period, the device forces a current at each
address pin and compares the voltage developed across the external connection with the
predefined threshold voltage in order to define the logic level. If an external resistor is
used for the connection of the address, then its value should be less than 2 k to prevent
the error in logic detection from happening. Resistors of 1 k are recommended.
8. Temperature monitor with SMBus serial interface
8.1 Serial bus interfaceThe device can be connected to a standard 2-wire serial interface System Management
Bus (SMBus) as a slave device under the control of a master device, using two device
terminals SCLK and SDATA. The operation of the device to the bus is described with
details in the following sections.
8.2 Slave addressThe device address is defined by the logical connections applied to the device pins ADD0
and ADD1. A list of selectable addresses are shown in Table 3. The device address can
be set to any one of those nine combinations and more than one device can reside on the
same bus without address conflict. Note that the state of the device address pins is
sampled and latched not only at power-up step, but also at starting point of every
conversion.
Table 3. Device slave addressn.c. = not connected
GND GND 0011 000
GND n.c. 0011 001
GND VDD 0011 010
n.c. GND 0101 001
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systems[1] Any pull-up/pull-down resistor used to connect to GND or VDD should be 2k.
8.3 RegistersThe device contains more than 9 registers. They are used to store the data of device
set-up and operation results. Depending on the bus communication (either read or write
operations), each register may be called by different names because each register may
have different sub-addresses or commands for read and write operations. For example,
the configuration register is called as WC for write mode and as RC for read mode.
Table 4 shows the names, commands and functions of all registers as well as the register
POR states.
Remark: Attempting to write to a read-command or read from a write-command will produce an invalid result. The reserved registers are used for factory test purposes and
should not be written.
n.c. n.c. 0101 010
n.c. VDD 0101 011
VDD GND 1001 100
VDD n.c. 1001 101
VDD VDD 1001 110
Table 3. Device slave address …continuedn.c. = not connected
Table 4. Register assignmentsRIT 00h 0000 0000 read internal or local temp byte
RET 01h 0000 0000 read external or remote temp byte 02h n/a read status byte 03h 0000 0000 read configuration byte
RCR 04h 0000 0010 read conversion rate byte
RIHL 05h 0111 1111 read internal temp high limit byte
RILL 06h 1100 1001 read internal temp low limit byte
REHL 07h 0111 1111 read external temp high limit byte
RELL 08h 1100 1001 read external temp low limit byte 09h n/a write configuration byte
WCR 0Ah n/a write conversion rate byte
WIHL 0Bh n/a write internal temp high limit byte
WILL 0Ch n/a write internal temp low limit byte
WEHL 0Dh n/a write external temp high limit byte
WELL 0Eh n/a write external temp low limit byte
OSHT 0Fh n/a one-shot command 10h n/a reserved 11h n/a reserved 12h n/a reserved 13h n/a reserved
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systems
8.3.1 Low power standby modesUpon POR, the device is reset to its normal free-running auto-conversion operation mode.
The device can be put into standby mode by either using hardware control (connect the
STBY pin to LOW for hardware standby mode) or using software control (set bit 6 of the
configuration register to HIGH for software standby mode). When the device is put in
either one of the standby modes, the supply current is reduced to less than 10 A if there
is no SMBus activity, all data in the device registers are retained and the SMBus interface
is still alive to bus communication. However, there is a difference in the device ADC
conversion operation between hardware standby and software standby modes. In
hardware standby mode, the device conversion is inhibited and the one-shot command
does not initiate a conversion. In software standby mode, the one-shot command will
initiate a conversion for both internal and external channels.
If a hardware standby command is received when the device is in normal mode and a
conversion is in progress, the conversion cycle will stop and data in reading temperature
registers will not be updated.
8.3.2 Configuration registerThe configuration register is used to mask the Alert interrupt and/or to put the device in
software standby mode. Only two bits of this register (bit 6 and bit 7) are used as listed in
Table 5. Bit 7 is used to mask the device ALERT output from Alert interruption when this
bit is set to logic 1, and bit 6 is used to activate the standby software mode when this bit is
set to logic1.
This register can be written or read using the commands of registers named WC and RC
accordingly. Upon Power-On Reset (POR), both bits are reset to zero.
8.3.3 External and internal temperature registersResults of temperature measurements after every ADC conversion are stored in two
registers: Internal Temp register (RIT) for internal or local diode temperature, and External emp register (RET) for external or remote diode temperature. These registers can be
only read over the SMBus. The reading temperature data is in 2's complement binary form
consisting of 7-bit data and 1-bit sign (MSB), with each data count represents 1 C, and
the MSB bit is transmitted first over the serial bus. The contents of those two registers are
updated upon completion of each ADC conversion. Table 6 shows some values of the
temperature and data.
Table 5. Configuration register bit assignments7 (MSB) MASK 0 Mask ALERT interrupt. Interrupt is enabled when this bit is LOW, and disabled when this bit is HIGH. RUN/STOP0 Standby or run mode control. When LOW, running mode
is enabled; when HIGH, standby mode is initiated.
5 to 0 - n/a reserved
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systems
8.3.4 Conversion rate registerThe conversion rate register is used to store programmable conversion data, which
defines the time interval between conversions in standard free-running auto-convert
mode. Table 7 shows all applicable data and rates for the device. Only three LSB bits of
the register are used and other bits are reserved for future use. This register can be
written to and read back over the SMBus using commands of the registers named WCR
and RCR, respectively. The POR default conversion data is 02h (0.25 Hz).
Notice that the average supply current, as well as the device power consumption, is
increased with the conversion rate.
8.3.5 Temperature limit registersThe device has four registers to be used for storing programmable temperature limits,
including the high limit and the low limit for each channel of the external and internal
diodes. Data of the temperature register (RIT and RET) for each channel are compared
with the contents of the temperature limit registers of the same channel, resulting in alarm
conditions. If measured temperature either equals or exceeds the corresponding
temperature limits, an Alert interrupt is asserted and the corresponding flag bit in the
status register is set. The temperature limit registers can be written to and read back using
Table 6. Temperature data format (2’s complement)+127 0111 1111
+126 0111 1110
+100 0110 0100
+50 0011 0010
+25 0001 1001 0000 0001 0000 0000 11111111
25 1110 0111
50 1100 1110
65 1011 1111
Table 7. Conversion rate control byte00h 0.0625 67
01h 0.125 68
02h 0.25 70
03h 0.5 75
04h 1 80
05h 2 95
06h 4 125
07h 8 180
08h to FFh (reserved) n/a
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systemscommands of registers named WIHL, WILL, WEHL, WELL, RIHL, RILL, REHL, RELL,
accordingly. The POR default values are +127 C (0111 1111) for the HIGH limit and
55 C (1100 1001) for the LOW limit.
8.3.6 One-shot commandThe one-shot command is not actually a data register as such and a write operation to it
will initiate an ADC conversion. The send byte format of the SMBus, as described later,
with the use of OSHT command (0Fh), is used for this writing operation. In normal
free-running-conversion operation mode of the device, a one-shot command immediately
forces a new conversion cycle to begin. However, if a conversion is in progress when a
one-shot command is received, the command is ignored. In software standby mode the
one-shot command generates a single conversion and comparison cycle and then puts
the device back in its standby mode after the conversion. In hardware standby mode, the
one shot is inhibited.
8.3.7 Status registerThe content of the status register reflects condition status resulting from all of these
activities: comparisons between temperature measurements and temperature limits, the
status of ADC conversion, and the hardware condition of the connection of external diode
to the device. Bit assignments and bit functions of this register are listed in Table 8. This
register can only be read using the command of register named RS. Upon POR, the
status of all flag bits are reset to zero. The status byte is cleared by any successful read of
the status register unless the fault condition persists.
Notice that any one of the fault conditions, except the conversion busy, also introduces an
Alert interrupt to the SMBus that will be described in Section 8.3.8. Also, whenever a
one-shot command is executed, the status byte should be read after the conversion is
completed, which is about 170 ms after the one-shot command is sent.
[1] These flags stay HIGH until the status register is read or POR is activated.
[2] This flag stays HIGH until POR is activated.
8.3.8 Alert interruptThe ALERT output is used to signal Alert interruption from the device to the SMBus and is
active LOW. Because this output is an open-drain output, a pull-up resistor (10 k typical)
to VDD is required, and slave devices can share a common interrupt line on the same
SMBus. An Alert interrupt is asserted by the device whenever any one of the fault
conditions, as described in Section 8.3.7 “Status register”, occurs: measured temperature
equals or exceeds corresponding temp limits, the remote diode is physically disconnected
from the device pins. Alert interrupt signal is latched and can only be cleared by reading
Table 8. Status register bit assignment7 (MSB) BUSY n/a HIGH when the ADC is busy converting
6IHLF[1] 0 HIGH when the internal temperature high limit has tripped ILLF[1] 0 HIGH when the internal temperature low limit has tripped
4EHLF[1] 0 HIGH when the external temperature high limit has tripped
3ELLF[1] 0 HIGH when the external temperature low limit has tripped
2OPEN[2] 0 HIGH when the external diode is opened
1 to 0 - 0 reserved
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systemsthe Alert Response byte from the Alert Response Address, which is a special slave
address to the SMBus. The ALERT output cannot be reset by reading the device status
register.
The device was designed to accommodate the Alert interrupt detection capability of the
SMBus.1 Basically, the SMBus provides Alert response interrupt pointers in order to
identify the slave device which has caused the Alert interrupt. The 7-bit Alert response
slave address is 0001 100 and the Alert response byte reflects the slave address of the
device which has caused Alert interrupt. Bit assignments of the Alert response byte are
listed in Table 9. The ALERT output will be reset to HIGH state upon reading the Alert
response slave address unless the fault condition persists.
8.4 Power-up default conditionUpon power-up reset (power is switched off-on), the NE1617A goes into this default
condition:
Interrupt latch is cleared, the ALERT output is pulled HIGH by the external pull-up
resistor.
The auto-conversion rate is at 0.25 Hz; conversion rate data is 02h.
T emperature limits for both channels are +127 C for high limit, and 55 C for low
limit.
Command pointer register is set to ‘00’ for quickly reading the RIT.
8.5 Fault detectionThe NE1617A has a fault detector to the diode connection. The connection is checked
when a conversion is initiated and the proper flags are set if the fault condition has
occurred. The NE1617A implements the collision arbitration function per System Management Bus Specification Revision 1.1, dated
December 11, 1998, which conforms to standard I2C-bus arbitration as described in NXP document UM10204, “I2C-bus
specification and user manual”.
Table 9. Alert response (Alert response address 0001 100) bit description7 (MSB) ADD7 indicate address B6 of alerted device ADD6 indicate address B5 of alerted device ADD5 indicate address B4 of alerted device ADD4 indicate address B3 of alerted device ADD3 indicate address B2 of alerted device ADD2 indicate address B1 of alerted device ADD1 indicate address B0 of alerted device
0 (LSB) 1 logic1
Table 10. Fault detectionopened LOW 127C B2 and B4
shorted LOW 127 CB4
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systems
8.6 SMBus interfaceThe device can communicate over a standard 2-wire serial interface System Management
Bus (SMBus) using the device pins SCLK and SDATA. The device employs four standard
SMBus protocols: write byte, read byte, send byte and receive byte. Data formats of those
protocols are shown in Figure 3 with following notifications:
The SMBus master initiates data transfer by establishing a START condition (S) and
terminates data transfer by generating a STOP condition (P).
Data is sent over the serial bus in sequence of 9 clock pulses according to each 8-bit
data byte followed by 1-bit status of the device acknowledgement.
The 7-bit slave address is equivalent to the selected address of the device.
The command byte is equivalent to the selected command of the device register.
The ‘send byte’ format is often used for the one-shot conversion command.
The ‘receive byte’ format is used for quicker transfer data from a device reading
register that was previously selected by a read byte format.
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systems
9. Application design-in information
9.1 Factors affecting accuracy
9.1.1 Remote sensing diodeThe NE1617A is designed to work with substrate transistors built into processors’ CPUs
or with discrete transistors. Substrate transistors are generally PNP types with the
collector connected to the substrate. Discrete types can be either a PNP or an NPN
transistor connected as a diode (base shorted to collector). If an NPN transistor is used,
the collector and base are connected to D+ and the emitter to D. If a PNP transistor is
used, the collector and base are connected to D and the emitter to D+. Substrate
transistors are found in a number of CPUs. To reduce the error due to variations in these
substrate and discrete transistors, a number of factors should be taken into consideration:
The ideality factor, nf, of the transistor. The ideality factor is a measure of the deviation
of the thermal diode from the ideal behavior. The NE1617A is trimmed for an nf value
of 1.008. Equation 2 can be used to calculate the error introduced at a temperature C when using a transistor whose nf does not equal 1.008. Consult the processor
data sheet for nf values.
This value can be written to the offset register and is automatically added to or
subtracted from the temperature measurement.
(2)
Some CPU manufacturers specify the high and low current levels of the substrate
transistors. The Isource high current level of the NE1617A is 100 A and the low level
current is 10 A.
If a discrete transistor is being used with the NE1617A, the best accuracy is obtained by
choosing devices according to the following criteria:
Base-emitter voltage greater than 0.25 V at 6 mA, at the highest operating
temperature.
Base-emitter voltage less than 0.95 V at 100 mA, at the lowest operating temperature.
Base resistance less than 100.
Small variation in hFE (say 50 to 150) that indicates tight control of VBE characteristics.
Transistors such as 2N3904, 2N3906, or equivalents in SOT23 packages are suitable
devices to use. See Table 11 for representative devices.
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systems
9.1.2 Thermal inertia and self-heatingAccuracy depends on the temperature of the remote-sensing diode and/or the internal
temperature sensor being at the same temperature as that being measured, and a
number of factors can affect this. Ideally, the sensor should be in good thermal contact
with the part of the system being measured, for example, the processor. If it is not, the
thermal inertia caused by the mass of the sensor causes a lag in the response of the
sensor to a temperature change. In the case of the remote sensor, this should not be a
problem, since it is either a substrate transistor in the processor or a small package
device, such as the SOT23, placed in close proximity to it.
The on-chip sensor, however, is often remote from the processor and is only monitoring
the general ambient temperature around the package. The thermal time constant of the
SSOP16 package in still air is about 140 seconds, and if the ambient air temperature
quickly changed by 100 C, it would take about 12 minutes (five time constants) for the
junction temperature of the NE1617A to settle within 1 C of this. In practice, the
NE1617A package is in electrical and therefore thermal contact with a printed-circuit
board and can also be in a forced airflow. How accurately the temperature of the board
and/or the forced airflow reflect the temperature to be measured also affects the accuracy.
Self-heating due to the power dissipated in the NE1617A or the remote sensor causes the
chip temperature of the device or remote sensor to rise above ambient. However, the
current forced through the remote sensor is so small that self-heating is negligible. In the
case of the NE1617A, the worst-case condition occurs when the device is converting at conversions per second while sinking the maximum current of 1 mA at the ALERT
output. In this case, the total power dissipation in the device is about 11 mW. The thermal
resistance, Rth(j-a), of the SSOP16 package is about 121 C/W.
In practice, the package has electrical and therefore thermal connection to the printed
circuit board, so the temperature rise due to self-heating is negligible.
Table 11. Representative diodes for temperature sensingRohm UMT3904
Diodes Inc. MMBT3904-7
Philips MMBT3904
ST Micro MMBT3904
ON Semiconductor MMBT3904LT1
Chenmko MMBT3904
Infineon Technologies SMBT3904E6327
Fairchild Semiconductor MMBT3904FSCT
National Semiconductor MMBT3904N623
NXP Semiconductors NE1617A
Temperature monitor for microprocessor systems
9.1.3 Layout considerationsDigital boards can be electrically noisy environments, and the NE1617A is measuring very
small voltages from the remote sensor, so care must be taken to minimize noise induced
at the sensor inputs. The following precautions should be taken. Place the NE1617A as close as possible to the remote sensing diode. Provided that
the worst noise sources, that is, clock generators, data/address buses, and CRT s, are
avoided, this distance can be four to eight inches. Route the D+ and D tracks close together, in parallel, with grounded guard tracks on
each side. Provide a ground plane under the tracks if possible. Use wide tracks to minimize inductance and reduce noise pickup. 10 mil track
minimum width and spacing is recommended (see Figure4). Try to minimize the number of copper/solder joints, which can cause thermocouple
effects. Where copper/solder joints are used, make sure that they are in both the D+
and D path and at the same temperature.
Thermocouple effects should not be a major problem since 1 C corresponds to about
200 V and thermocouple voltages are about 3 V/C of temperature difference.
Unless there are two thermocouples with a big temperature differential between them,
thermocouple voltages should be much less than 200 V. Place a 0.1 F bypass capacitor close to the VDD pin. In very noisy environments,
place a 1000 pF input filter capacitor across D+ and D close to the NE1617A. If the distance to the remote sensor is more than eight inches, the use of twisted pair
cable is recommended. This works up to about six feet to 12 feet. For really long distances (up to 100 feet), use shielded twisted pair, such as
Belden #8451 microphone cable. Connect the twisted pair to D+ and D and the
shield to GND close to the NE1617A. Leave the remote end of the shield
unconnected to avoid ground loops.
Because the measurement technique uses switched current sources, excessive cable
and/or filter capacitance can affect the measurement. When using long cables, the filter
capacitor can be reduced or removed.
Cable resistance can also introduce errors. 1 resistance introduces about 1 C error.
