ON NCT218MTR2G Low voltage, high accuracy temperature monitor with i2c interface Datasheet

NCT218
Low Voltage, High
Accuracy Temperature
Monitor with I2C Interface
The NCT218 is a dual−channel digital thermometer and
undertemperature/overtemperature alarm, intended for use in thermal
management systems requiring low power and size. The NCT218
operates over a supply range of 1.4 V to 2.75 V making it possible to
use it in a wide range of applications including low power devices.
The NCT218 can measure the temperature of a remote thermal diode
accurate to ±1°C and the ambient temperature accurate to ±1.75°C.
The device operates over a wide temperature range of −40°C to
+125°C.
The NCT218 includes series resistance cancellation, where up to
500 W (typical) of resistance in series with the temperature monitoring
diode can be automatically cancelled from the temperature result,
allowing noise filtering. The NCT218 has a configurable ALERT
output and overtemperature shutdown THERM pin.
Communication with the NCT218 is accomplished via the I2C
interface which is compatible with industry standard protocols.
Through this interface the NCT218s internal registers may be
accessed. These registers allow the user to read the current
temperature from both the local (ambient) and remote channels,
change the configuration settings and adjust each channels limits.
An ALERT output signals when the on−chip or remote temperatures
are out of range. The THERM output is a comparator output that can
be used to shut down the system if it exceeds the programmed limit.
The ALERT output can be reconfigured as a second THERM output, if
required.
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MARKING
DIAGRAMS
M
AY
WW
G
NCT218
AYWW
= Date Code
= Assembly year
= Work Week
= Pb−Free Device
(Note: Microdot may be in either location)
PIN ASSIGNMENTS
VDD
1
8
SCL
D+
2
7
SDA
D−
3
6
ALERT/THERM2
THERM
4
5
GND
DFN8
(Top View)
SCL
Small DFN Package
On−Chip and Remote Temperature Sensor
Low Voltage Operation: 1.4 V to 2.75 V
Low Quiescent Current:
♦ 44 mA Normal Mode (max)
♦ 20 mA Shutdown (max)
Power Saving Shutdown Mode
Operating Temperature Range of −40°C to 125°C
Series Resistance Cancellation up to 500 W
Low D− bias for Operation with Low Voltage Processors
2−wire I2C Serial Interface
Programmable Over/Undertemperature Limits
These are Pb−Free Devices
SDA
C1
GND
ALERT/
THERM2
C2
C3
B1
B3
A1
VDD
A2
D+
A3
D−
THERM2
•
•
•
•
•
•
•
T2 MG
G
WLCSP8
CASE 567DH
Features
•
•
•
•
1
DFN8
MT SUFFIX
CASE 511BU
Applications
• Smart Phones, Tablet PCs, Satellite Navigation, Smart Batteries
WLCSP8
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information on page 16 of
this data sheet.
© Semiconductor Components Industries, LLC, 2013
December, 2013 − Rev. 2
1
Publication Order Number:
NCT218/D
NCT218
ON−CHIP
TEMPERATURE
SENSOR
CONVERSION RATE
REGISTER
BUSY
RUN/STANDBY
REMOTE TEMPERATURE
VALUE REGISTERS
DIGITAL MUX
D1– 3
A−TO−D
CONVERTER
ANALOG
MUX
LOCAL TEMPERATURE
LOW−LIMIT REGISTER
LIMIT
COMPARATOR
D1+ 2
DIGITAL MUX
LOCAL TEMPERATURE
VALUE REGISTER
LOCAL TEMPERATURE
HIGH−LIMIT REGISTER
REMOTE TEMPERATURE
LOW−LIMIT REGISTER
REMOTE TEMPERATURE
HIGH−LIMIT REGISTER
ADDRESS POINTER
REGISTER
REMOTE OFFSET
REGISTERS
CONFIGURATION
REGISTERS
INTERRUPT
MASKING
EXTERNAL DIODE OPEN−CIRCUIT
STATUS REGISTER
6
4
ALERT/
THERM2
THERM
I2C INTERFACE
NCT218
1
5
VDD
GND
8
SCL
7
SDA
Figure 1. Functional Block Diagram
1.4V TO 2.75V
VDD
0.1 mF
VDD
NCT218
TYP 10 kW
SCL
Application
Processor
SDA
D+
I2C Master
ALERT/
THERM2
VDD
D–
THERM
TYP 10 kW
GND
OVERTEMPERATURE
SHUTDOWN
Figure 2. Typical Application Circuit
Table 1. PIN FUNCTION DESCRIPTION − DFN PACKAGE
Pin No.
Pin Name
Description
1
VDD
Positive Supply, 1.4 V to 2.75 V
2
D1+
Positive Connection to Remote 1 Temperature Sensor.
3
D1−
Negative Connection to Remote 1 Temperature Sensor.
4
THERM
5
GND
6
ALERT/THERM2
7
SDA
Logic Input/Output, I2C Serial Data. Requires pullup resistor to VDD.
8
SCL
Logic Input, I2C serial clock. Requires pullup resistor to VDD.
Open−Drain Output. Can be used to throttle a CPU clock in the event of an overtemperature condition. Requires pullup resistor to VDD. Active low output.
Supply Ground Connection.
Open−Drain Logic Output used as Interrupt. This can also be configured as a second THERM output. Requires pullup resistor to VDD. Active low output.
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2
NCT218
Table 2. ABSOLUTE MAXIMUM RATINGS (Note 1)
Rating
Symbol
Value
Unit
VDD
−0.3, +3
V
−0.3 to VDD + 0.25
V
D− to GND
−0.3 to +0.6
V
SCL, SDA, ALERT, THERM
−0.3 to +5.25
V
±1
mA
Supply Voltage (VDD) to GND
D+
Input current on D−
Input current on SDA, THERM
IIN
−1, +50
mA
TJ(max)
150.7
°C
Operating Temperature Range
TOP
−40 to 125
°C
Storage Temperature Range
TSTG
−65 to 160
°C
ESD Capability, Human Body Model (Note 2)
ESDHBM
2000
V
ESD Capability, Machine Model (Note 2)
ESDMM
100
V
Maximum Junction Temperature
Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality
should not be assumed, damage may occur and reliability may be affected.
1. Refer to ELECTRICAL CHARACTERISTICS and APPLICATION INFORMATION for Safe Operating Area.
2. This device series incorporates ESD protection and is tested by the following methods:
ESD Human Body Model tested per AEC−Q100-002 (EIA/JESD22-A114)
ESD Machine Model tested per AEC-Q100-003 (EIA/JESD22-A115)
Table 3. I2C TIMING − 400 kHz
Parameter (Note 3)
Symbol
Typ
Max
Unit
400
kHz
Clock Frequency
fSCLK
10
Clock Period
tSCLK
2.5
ms
SCL High Time
tHIGH
0.6
ms
SCL Low Time
tLOW
1.3
ms
Start Setup Time
tSU;STA
0.6
ms
Start Hold Time (Note 4)
tHD;STA
0.6
ms
Data Setup Time (Note 5)
tSU;DAT
100
Data Hold Time (Note 6)
tHD;DAT
0.9
ms
SCL, SDA Rise Time
tr
300
ns
SCL, SDA Fall Time
tf
300
ns
ns
tSU;STO
0.6
ms
Bus Free Time
tBUF
1.3
ms
Glitch Immunity
tSW
Stop Setup Time
3.
4.
5.
6.
Min
50
ns
Guaranteed by design, but not production tested.
Time from 10% of SDA to 90% of SCL.
Time for 10% or 90% of SDA to 10% of SCL.
A device must internally provide a hold time of at least 300 ns for the SDA signal to bridge the undefined region of the falling edge of SCL.
tR
tLOW
tF
tHD;STA
SCLK
tHIGH
tHD;STA
tHD;DAT
tSU;STA
tSU;STO
tSU;DAT
SDATA
tBUF
STOP START
START
Figure 3.
I2 C
Timing Diagram
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3
STOP
NCT218
Table 4. ELECTRICAL CHARACTERISTICS
(TA = TMIN to TMAX, VDD = 1.6 V to 2.75 V. All specifications for −40°C to +125°C, unless otherwise noted.)
Test Conditions
Max
Unit
+125
°C
TD = −40°C to +125°C
±1
°C
VDD = 1.6 V to 2.75 V
TA = 25°C to 85°C
TA = −40°C to +125°C
±1.75
±3
°C
Remote Sensor Source Current
High Level
Middle Level
Low Level
Parameter
Min
Typ
TEMPERATURE SENSOR
−40
Measurement Range
REMOTE SENSOR ACCURACY
VDD = 1.6 V to 2.75 V
TA = 25°C to 85°C
LOCAL SENSOR ACCURACY
200
75
12.5
mA
D− Voltage
0.2
V
ADC Resolution
10
Bits
Conversion time
60
ms
0.25
°C
500
W
Undervoltage Lockout Threshold
1.32
V
Power−On Reset Threshold
0.9
V
Temperature Resolution
Series Resistance Cancelled
Per thermal input pin – 300 W total at 25°C
POWER REQUIREMENTS
1.4
Supply Voltage
Quiescent Current (IDD)
I2C
inactive – 0.0625
Conversions/Sec Rate, 1.8 V VDD
I2C active, 400 kHz
15
Standby Current (ISTBY)
I2C
1
10
2.75
V
44
mA
20
mA
30
inactive
I2C active, 400 kHz
DIGITAL INPUT/OUTPUT
Input Logic Levels
VIH
0.7 x VDD
2.75
V
VIL
−0.5
0.3 x VDD
V
1
mA
Input Current
0 < VIN < 2.75 V
Output Logic Levels
VOL SDA, ALERT, THERM
VDD > 2 V, IOL = 3 mA
0
0.4
V
VDD < 2 V, IOL = 3 mA
0
0.2 x VDD
V
Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product
performance may not be indicated by the Electrical Characteristics if operated under different conditions.
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4
NCT218
Theory of Operation
Temperature Measurement Method
The NCT218 is a local and remote temperature sensor and
over/under temperature alarm, with the added ability to
automatically cancel the effect of 500 W (typical) of
resistance in series with the temperature monitoring diode.
When the NCT218 is operating normally, the on−board
ADC operates in a free running mode. The analog input
multiplexer alternately selects either the on−chip
temperature sensor to measure its local temperature or the
remote temperature sensor. The ADC digitizes these signals
and the results are stored in the local and remote temperature
value registers.
The local and remote measurement results are compared
with the corresponding high, low, and THERM temperature
limits, stored in eight on−chip registers. Out−of−limit
comparisons generate flags that are stored in the status
register. A result that exceeds the high temperature limit or
the low temperature limit causes the ALERT output to
assert. The ALERT output also asserts if an external diode
fault is detected. Exceeding the THERM temperature limits
causes the THERM output to assert low. The ALERT output
can be reprogrammed as a second THERM output.
The limit registers are programmed and the device
controlled and configured via the serial I2C. The contents of
any register are also read back via the I2C. Control and
configuration functions consist of switching the device
between normal operation and standby mode, selecting the
temperature measurement range, masking or enabling the
ALERT output, switching Pin 6 between ALERT and
THERM2, and selecting the conversion rate.
A simple method of measuring temperature is to exploit
the negative temperature coefficient of a diode, measuring
the base emitter voltage (VBE) of a transistor operated at
constant current. However, this technique requires
calibration to null the effect of the absolute value of VBE,
which varies from device to device.
The technique used in the NCT218 measures the change
in VBE when the device operates at three different currents.
Previous devices used only two operating currents, but it is
the use of a third current that allows automatic cancellation
of resistances in series with the external temperature sensor.
Figure 4 shows the input signal conditioning used to
measure the output of an external temperature sensor. This
figure shows the external sensor as a substrate transistor, but
it can equally be a discrete transistor. If a discrete transistor
is used, the collector is not grounded but is linked to the base.
To prevent ground noise interfering with the measurement,
the more negative terminal of the sensor is not referenced to
ground, but is biased above ground by an internal resistor at
the D− input. C1 may be added as a noise filter (a
recommended maximum value of 1000 pF). However, a
better option in noisy environments is to add a filter, as
described in the Noise Filtering section. See the Layout
Considerations section for more information on C1.
To measure DVBE, the operating current through the
sensor is switched among three related currents. As shown
in Figure 4, N1 x I and N2 x I are different multiples of the
current, I. The currents through the temperature diode are
switched between I and N1 x I, giving DVBE1; and then
between I and N2 x I, giving DVBE2. The temperature is then
calculated using the two DVBE measurements. This method
also cancels the effect of any series resistance on the
temperature measurement.
The resulting DVBE waveforms are passed through a
65 kHz low−pass filter to remove noise and then to a
chopper−stabilized amplifier. This amplifies and rectifies
the waveform to produce a dc voltage proportional to DVBE.
The ADC digitizes this voltage producing a temperature
measurement. To reduce the effects of noise, digital filtering
is performed by averaging the results of 16 measurement
cycles for low conversion rates. At rates of 16−, 32− and
64−conversions/second, no digital averaging occurs. Signal
conditioning and measurement of the internal temperature
sensor are performed in the same manner.
Series Resistance Cancellation
Parasitic resistance to the D+ and D− inputs to the
NCT218, seen in series with the remote diode, is caused by
a variety of factors, including PCB track resistance and track
length. This series resistance appears as a temperature ofset
in the remote sensor’s temperature measurement. This error
typically causes a 0.5°C offset per ohm of parasitic
resistance in series with the remote diode.
The NCT218 automatically cancels the effect of this
series resistance on the temperature reading, giving a more
accurate result, without the need for user characterization of
this resistance. The NCT218 is designed to automatically
cancel typically up to 150 W of resistance. By using an
advanced temperature measurement method, this process is
transparent to the user. This feature permits resistances to be
added to the sensor path to produce a filter, allowing the part
to be used in noisy environments. See the section on Noise
Filtering for more details.
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5
NCT218
VDD
I
N1 x I
N2 x I
IBIAS
VOUT+
D+
C1*
REMOTE
SENSING
TRANSISTOR
TO ADC
LPF
fC = 65 kHz
D–
VOUT−
BIASING
RESISTOR
* Capacitor C1 is optional. It is only necessary in noisy environments. C1 = 1000 pF max.
Figure 4. Input Signal Conditioning
Temperature Measurement Results
The extended temperature range is selected by setting
Bit 2 of the configuration register to 1. The temperature
range is 0°C to 127°C when Bit 2 equals 0. A valid result is
available in the next measurement cycle after changing the
temperature range.
In extended temperature mode, the upper and lower
temperature that can be measured by the NCT218 is limited
by the remote diode selection. The temperature registers can
have values from −64°C to +191°C. However, most
temperature sensing diodes have a maximum temperature
range of −55°C to +150°C. Above +150°C, they may lose
their semiconductor characteristics and approximate
conductors instead. This results in a diode short. In this case,
a read of the temperature result register gives the last good
temperature measurement. Therefore, the temperature
measurement on the external channel may not be accurate
for temperatures that are outside the operating range of the
remote sensor.
It should be noted that although both local and remote
temperature measurements can be made while the part is in
extended temperature mode, the NCT218 itself should not
be exposed to temperatures greater than those specified in
the absolute maximum ratings section. Further, the device is
only guaranteed to operate as specified at ambient
temperatures from −40°C to +125°C.
The results of the local and remote temperature
measurements are stored in the local and remote temperature
value registers and compared with limits programmed into
the local and remote high and low limit registers.
The local temperature value is in Register 0x00 and has a
resolution of 1°C. The external temperature value is stored
in two registers, with the upper byte in Register 0x01 and the
lower byte in Register 0x10. Only the two MSBs in the
external temperature low byte are used giving the external
temperature measurement a resolution of 0.25°C. Table 5
lists the data format for the external temperature low byte.
Table 5. EXTENDED TEMPERATURE RESOLUTION
(Remote Temperature Low Byte)
Extended Resolution
Remote Temperature
Low Byte
0.00°C
0 000 0000
0.25°C
0 100 0000
0.50°C
1 000 0000
0.75°C
1 100 0000
When reading the full external temperature value, read the
LSB first. This causes the MSB to be locked (that is, the
ADC does not write to it) until it is read. This feature ensures
that the results read back from the two registers come from
the same measurement.
Temperature Data Format
The NCT218 has two temperature data formats. When the
temperature measurement range is from 0°C to 127°C
(default), the temperature data format for both internal and
external temperature results is binary. When the
measurement range is in extended mode, an offset binary
data format is used for both internal and external results.
Temperature values are offset by 64°C in the offset binary
data format. Examples of temperatures in both data formats
are shown in Table 6.
Temperature Measurement Range
The temperature measurement range for both internal and
external measurements is, by default, 0°C to +127°C.
However, the NCT218 can be operated using an extended
temperature range. The extended measurement range is
−64°C to +191°C. Therefore, the NCT218 can be used to
measure the full temperature range of an external diode,
from −55°C to +150°C.
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6
NCT218
Temperature Value Registers
Table 6. TEMPERATURE DATA FORMAT
(Temperature High Byte)
Temperature
Binary
Offset Binary
(Note 1)
-55°C
0 000 0000 (Note 2)
0 000 1001
0°C
0 000 0000
0 100 0000
+1°C
0 000 0001
0 100 0001
+10°C
0 000 1010
0 100 1010
+25°C
0 001 1001
0 101 1001
+50°C
0 011 0010
0 111 0010
+75°C
0 100 1011
1 000 1011
+100°C
0 110 0100
1 010 0100
+125°C
0 111 1101
1 011 1101
+127°C
0 111 1111
1 011 1111
+150°C
0 111 1111 (Note 3)
1 101 0110
The NCT218 has three registers to store the results of local
and remote temperature measurements. These registers can
only be written to by the ADC and can be read by the user
over the I2C. The local temperature value register is at
Address 0x00.
The external temperature value high byte register is at
Address 0x01, with the low byte register at Address 0x10.
The power−on default for all three registers is 0x00.
Configuration Register
The configuration register is Address 0x03 at read and
Address 0x09 at write. Its power−on default is 0x00. Only four
bits of the configuration register are used. Bit 0, Bit 1, Bit 3,
and Bit 4 are reserved; only zeros should be written to these.
Bit 7 of the configuration register masks the ALERT
output. If Bit 7 is 0, the ALERT output is enabled. This is the
power−on default. It Bit 7 is set to 1, the ALERT output is
disabled. This applies only if Pin 6 is configured as ALERT.
If Pin 6 is configured as THERM2, then the value of Bit 7
has no effect.
If Bit 6 is set to 0, which is power−on default, the device
is in operating mode with ADC converting. If Bit 6 is set to
1, the device is in standby mode and the ADC does not
convert. The I2C does, however, remain active in standby
mode; therefore, values can be read from or written to the
NCT218 via the I2C. The ALERT and THERM output are
also active in standby mode. Changes made to the register in
standby mode that affect the THERM or ALERT outputs
cause these signals to be updated.
Bit 5 determines the configuration of Pin 6 on the
NCT218. If Bit 5 is 0 (default), then Pin 6 is configured as
a ALERT output. If Bit 5 is 1, then Pin 6 is configured as a
THERM2 output. Bit 7, the ALERT mask bit, is only active
when Pin 6 is configured as an ALERT output. If Pin 6 is set
up as a THERM2 output, then Bit 7 has no effect.
Bit 2 sets the temperature measurement range. If Bit 2 is
0 (default value), the temperature measurement range is set
between 0°C to +127°C. Setting Bit 2 to 1 sets the
measurement range to the extended temperature range
(−64°C to +191°C).
1. Offset binary scale temperature values are offset by
64°C.
2. Binary scale temperature measurement returns 0°C for all
temperatures < 0°C.
3. Binary scale temperature measurement returns 127°C for
all temperatures > 127°C.
The user can switch between measurement ranges at any
time. Switching the range likewise switches the data format.
The next temperature result following the switching is
reported back to the register in the new format. However, the
contents of the limit registers do not change. It is up to the
user to ensure that when the data format changes, the limit
registers are reprogrammed as necessary. More information
on this is found in the Limit Registers section.
NCT218 Registers
The NCT218 contains 22, 8−bit registers in total. These
registers store the results of remote and local temperature
measurements, high and low temperature limits, and
configure and control the device. See the Address Pointer
Register section through the Consecutive ALERT Register
section of this data sheet for more information on the NCT218
registers. Additional details are shown in Table 7 through
Table 11. The entire register map is available in Table 12.
Table 7. CONFIGURATION REGISTER BIT
ASSIGNMENTS
Address Pointer Register
The address pointer register itself does not have, nor does
it require, an address because the first byte of every write
operation is automatically written to this register. The data
in this first byte always contains the address of another
register on the NCT218 that is stored in the address pointer
register. It is to this register address that the second byte of
a write operation is written, or to which a subsequent read
operation is performed.
The power−on default value of the address pointer register
is 0x00. Therefore, if a read operation is performed
immediately after power−on, without first writing to the
address pointer, the value of the local temperature is returned
because its register address is 0x00.
Name
Function
7
MASK1
0 = ALERT Enabled
1 = ALERT Masked
0
6
RUN/STOP
0 = Run
1 = Standby
0
5
ALERT/
THERM2
0 = ALERT
1 = THERM2
0
4, 3
Reserved
2
Temperature
Range Select
1, 0
Reserved
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7
Power−On
Default
Bit
0
0 = 0°C to 127°C
1 = Extended Range
0
0
NCT218
Conversion Rate Register
provided which applies to both THERM channels. This
hysteresis value can be reprogrammed to any value after
powerup (Register Address 0x21).
It is important to remember that the temperature limits
data format is the same as the temperature measurement data
format. Therefore, if the temperature measurement uses
default binary, then the temperature limits also use the
binary scale. If the temperature measurement scale is
switched, however, the temperature limits do not
automatically switch. The user must reprogram the limit
registers to the desired value in the correct data format. For
example, if the remote low limit is set at 10°C with the
default binary scale, the limit register value is 0000 1010b.
If the scale is switched to offset binary, the value in the low
temperature limit register needs to be reprogrammed to
0100 1010b.
The conversion rate register is Address 0x04 at read and
Address 0x0A at write. The lowest four bits of this register
are used to program the conversion rate by dividing the
internal oscillator clock by 1, 2, 4, 8, 16, 32, 64, 128, 256,
512, 1024 to give conversion times from 15.5 ms (Code
0x0A) to 16 seconds (Code 0x00). For example, a
conversion rate of eight conversions per second means that
beginning at 125 ms intervals, the device performs a
conversion on the internal and the external temperature
channels.
The conversion rate register can be written to and read
back over the I2C. The higher four bits of this register are
unused and must be set to 0. The default value of this register
is 0x08, giving a rate of 16 conversions per second. Use of
slower conversion times greatly reduces the device power
consumption.
Status Register
Table 8. CONVERSION RATES
Code
Conversion/Second
Time (Seconds)
0x00
0.0625
16
0x01
0.125
8
0x02
0.25
4
0x03
0.5
2
0x04
1
1
0x05
2
500 m
0x06
4
250 m
0x07
8
125 m
0x08
16
62.5 m
0x09
32
31.25 m
0x0A
64
15.5 m
0x0B to 0xFF
Reserved
The status register is a read−only register at Address 0x02.
It contains status information for the NCT218. When Bit 7
of the status register is high, it indicates that the ADC is bisy
converting. The other bits in this register flag the
out−of−limit temperature measurements (Bit 6 to Bit 3, and
Bit 1 to Bit 0) and the remote sensor open circuit (Bit 2).
If Pin 6 is configured as an ALERT output, the following
applies: If the local temperature measurement exceeds its
limits, Bit 6 (high limit) or Bit 5 (low limit) of the status
register asserts to flag this condition. If the remote
temperature measurement exceeds its limits, then Bit 4 (high
limit) or Bit 3 (low limit) asserts. Bit 2 asserts to flag an open
circuit condition on the remote sensor. These five flags are
NOR’ed together, so if any of them is high, the ALERT
interrupt latch is set and the ALERT output goes low.
Reading the status register clears the five flags, Bit 6 to
Bit 2, provided the error conditions causing the flags to be
set have gone away. A flag bit can be reset only if the
corresponding value register contains an in−limit
measurement or if the sensor is good.
The ALERT interrupt latch (output) is reset by either
reading the status register or by issuing the device with an
ARA. In order for either of the above to work the error
condition must have gone away.
When Flag 1 and/or Flag 0 are set, the THERM output
goes low to indicate that the temperature measurements are
outside the programmed limits. The THERM output does
not need to be reset, unlike the ALERT output. Once the
measurements are within the limits, the corresponding status
register bits are automatically reset and the THERM output
goes high. The user may add hysteresis by programming
Register 0x21. The THERM output is reset only when the
temperature falls to limit value minus the hysteresis value.
When Pin 6 is configured as THERM2, only the high
temperature limits are relevant. If Flag 6 and/or Flag 4 are
set, the THERM2 output goes low to indicate that the
temperature measurements are outside the programmed
limits. Flag 5 and Flag 3 have no effect on THERM2. The
behavior of THERM2 is otherwise the same as THERM.
Limit Registers
The NCT218 has eight limit registers: high, low, and
THERM temperature limits for both local and remote
temperature measurements. The remote temperature high
and low limits span two registers each, to contain an upper
and lower byte for each limit. There is also a THERM
hysteresis register. All limit registers can be written to, and
read byck over I2C. See Table 12 for details of the limit
register addresses and their power−on default values.
When Pin 6 is configured as an ALERT output, the high
limit registers perform a > comparison, while the low limit
registers perform a ≤ comparison. For example, if the high
limit register is programmed with 80°C, then measuring
81°C results in an out−of−limit condition, setting a flag in
the status register. If the low limit register is programmed
with 0°C, measuring 0°C or lower resutls in an out−of−limit
condition.
Exceeding either the local or remote THERM limit asserts
THERM low. When Pin 6 is configured as THERM2,
exceeding either the local or remote high limit asserts
THERM2 low. A default hysteresis value of 10°C is
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NCT218
Table 9. STATUS REGISTER BIT ASSIGNMENTS
Bit
Name
7
BUSY
6
LHIGH
(Note 4)
1 when local high temperature limit is
tripped
5
LLOW
(Note 4)
1 when local low temperature limit is
tripped
4
Table 10. SAMPLE OFFSET REGISTER CODES
Function
Offset Value
0x11
0x12
-128°C
1000 0000
00 00 0000
-4°C
1111 1100
00 00 0000
-1°C
1111 1111
00 00 0000
-0.25°C
1111 1111
10 00 0000
0°C
0000 0000
00 00 0000
+0.25°C
0000 0000
01 00 0000
+1°C
0000 0001
00 00 0000
+4°C
0000 0100
00 00 0000
+127.75°C
0111 1111
11 00 0000
1 when ADC is converting
RHIGH
(Note 4)
1 when remote high temperature limit
is tripped
3
RLOW
(Note 4)
1 when remote low temperature limit is
tripped
2
OPEN
(Note 4)
1 when remote sensor is an open circuit
1
RTHRM
1 when remote THERM limit is tripped
0
LTHRM
1 when local THERM limit is tripped
One−Shot Register
The one−shot register is used to initiate a conversion and
comparison cycle when the NCT218 is in standby mode,
after which the device returns to standby. Writing to the
one−shot register address (0x0F) causes the NCT218 to
perform a conversion and comparison on both the internal
and the external temperature channels. This is not a data
register as such, and it is the write operation to Address 0x0F
that causes the one−shot conversion. The data written to this
address is irrelevant and is not stored.
4. These flags stay high until the status register is read or
they are reset by POR unless Pin 6 is configured as
THERM2. Then, only Bit 2 remains high until the status
register is read or is reset by POR.
Offset Register
Offset errors can be introduced into the remote temperature
measurement by clock noise or when the thermal diode is
located away from the hot spot. To achieve the specified
accuracy on this channel, these offsets must be removed.
The offset register can also be used to nullify the effect of
varying nf, the non−ideality factor of the remote sensing
diode. By default the NCT218 is trimmed to operate with an
nf value of 1.008 but the offset register allows other diodes
to be used without affecting the temperature result.
The offset value is stored as a 10−bit, twos complement
value in Register 0x11 (high byte) and Register 0x12 (low
byte, left justified). Only the upper two bits of Register 0x12
are used. The MSB of Register 0x11 is the sign bit. The
minimum, programmable offset is −128°C, and the
maximum is +127.75°C. The value in the offset register is
added to, or subtracted from, the measured value of the
remote temperature.
The offset register powers up with a default value of 0°C
and has no effect unless the user writes a different value to it.
Consecutive ALERT Register
The value written to this register determines how many
out−of−limit measurements must occur before an ALERT is
generated. The default value is that one out−of−limit
measurement generates an ALERT. The maximum value
that can be chosen is 4. The purpose of this register is to
allow the user to perform some filtering of the output. This
is particularly useful at the fastest three conversion rates,
where no averaging takes place. This register is at Address
0x22.
Table 11. CONSECUTIVE ALERT REGISTER CODES
Register Value
Number of Out-of-Limit
Measurements Required
yxxx 000x
1
yxxx 001x
2
yxxx 011x
3
yxxx 111x
4
Note: x = don’t care bits, and y = Bus timeout bit.
Default = 0. See interface section for more information.
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NCT218
Table 12. LIST OF REGISTERS
Read Address (Hex)
Write Address (Hex)
Name
Power−On Default
Not Applicable
Not Applicable
Address Pointer
00
Not Applicable
Local Temperature Value
0000 0000 (0x00)
01
Not Applicable
External Temperature Value High Byte
0000 0000 (0x00)
02
Not Applicable
Status
03
09
Configuration
0000 0000 (0x00)
04
0A
Conversion Rate
0000 1000 (0x08)
05
0B
Local Temperature High Limit
0101 0101 (0x55) (85°C)
06
0C
Local Temperature Low Limit
0000 0000 (0x00) (0°C)
07
0D
External Temperature High Limit High Byte
0101 0101 (0x55) (85°C)
External Temperature Low Limit High Byte
0000 0000 (0x00) (0°C)
Undefined
Undefined
08
0E
Not Applicable
0F (Note 1)
10
Not Applicable
External Temperature Value Low Byte
0000 0000 (0x00)
11
11
External Temperature Offset High Byte
0000 0000 (0x00)
12
12
External Temperature Offset Low Byte
0000 0000 (0x00)
13
13
External Temperature High Limit Low Byte
0000 0000 (0x00)
14
14
External Temperature Low Limit Low Byte
19
19
External THERM Limit
0110 1100 (0x6C) (108°C)
20
20
Local THERM Limit
0101 0101 (0x55) (85°C)
21
21
THERM Hysteresis
0000 1010 (0x0A) (0x10°C)
22
22
Consecutive ALERT
0000 0001 (0x01)
FE
Not Applicable
Manufacturer ID
0001 1010 (0x1A)
FF
Not Applicable
Die Revision Code
One−Shot
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0000 0000 (0x00)
0xXX
NCT218
SERIAL INTERFACE
Control of the NCT218 is carried out via the I2C
compatible serial interface. The NCT218 is connected to this
bus as a slave device, under the control of a master device.
The NCT218 has a bus timeout feature. When this is
enabled, the bus times out after typically 25 ms of no
activity. After this time, the NCT218 resets the SDA line
back to its idle state (high impedance) and waits for the next
start condition. However, this feature is not enabled by
default. Bit 7 of the consecutive alert register (Address =
0x22) should be set to enable it.
pulling the data line high during the low period
before the ninth clock pulse. This is known as no
acknowledge. The master takes the data line low
during the low period before the tenth clock pulse,
then high during the tenth clock pulse to assert a
stop condition.
To write data to one of the device data registers, or to read
data from it, the address pointer register must be set so that
the correct data register is addressed. The first byte of a write
operation always contains a valid address that is stored in the
address pointer register. If data is to be written to the device,
the write operation contains a second data byte that is written
to the register selected by the address pointer register.
This procedure is illustrated in Figure 5. The device
address is sent over the bus followed by R/W set to 0. This
is followed by two data bytes. The first data byte is the
address of the internal data register to be written to, which
is stored in the address pointer register. The second data byte
is the data to be written to the internal data register.
When reading data from a register there are two
possibilities.
• If the address pointer register value of the NCT218 is
unknown or not the desired value, it is first necessary to
set it to the correct value before data can be read from
the desired data register. This is done by writing to the
NCT218 as before, but only the data byte containing
the register read address is sent, because data is not to
be written to the register see Figure 5.
A read operation is then performed consisting of the
serial bus address, R/W bit set to 1, followed by the
data byte read from the data register see Figure 7.
• If the address pointer register is known to be at the
desired address, data can be read from the
corresponding data register without first writing to the
address pointer register and the bus transaction shown
in Figure 6 can be omitted.
Addressing the Device
In general, every I2C device has a 7−bit device address,
except for some devices that have extended 10−bit
addresses. When the master device sends a device address
over the bus, the slave device with that address responds.
The NCT218 is available with one device address, 0x4C. An
NCT218 with address 0x4D is also available for systems
requiring more than one NCT218 devices.
The serial bus protocol operates as follows:
1. The master initiates data transfer by establishing a
start condition, defined as a high to low transition
on the serial data line SDA, while the serial clock
line SCL remains high. This indicates that an
address/data stream is going to follow. All slave
peripherals connected to the serial bus respond to
the start condition and shift in the next eight bits,
consisting of a 7−bit address (MSB first) plus a
read/write (R/W) bit, which deternimes the
direction of the data transfer i.e. whether data is
written to, or read from, the slave device. The
peripheral with the address corresponding to the
transmitted address responds by pulling the data
line low during the low period before the ninth
clock pulse, known as the acknowledge bit. All
other devices on the bus now remain idle while the
selected device waits for data to be read from or
written to it. If the R/W bit is a zero then the
master writes to the slave device. If the R/W bit is
a one then the master reads from the slave device.
2. Data is sent over the serial bus in sequences of
nine clock pulses, eight bits of data followed by an
acknowledge bit from the receiver of data.
Transitions on the data line must occur during the
low period of the clock signal and remain stable
during the high period, since a low−to−high
transition when the clock is high can be interpreted
as a stop signal.
3. When all data bytes have been read or written,
stop conditions are established. In write mode, the
master pulls the data line high during the tenth
clock pulse to assert a stop condition. In read
mode, the master overrides the acknowledge bit by
Notes:
• It is possible to read a data byte from a data register
•
without first writing to the address pointer register.
However, if the address pointer register is already at the
correct value, it is not possible to write data to a register
without writing to the address pointer register because
the first data byte of a write is always written to the
address pointer register.
Some of the registers have different addresses for read
and write operations. The write address of a register
must be written to the address pointer if data is to be
written to that register, but it may not be possible to
read data from that address. The read address of a
register must be written to the address pointer before
data can be read from that register.
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NCT218
1
9
1
9
SCL
SDA
A6
A5
A4
A3
A2
A1
A0
D7
R/W
START BY
MASTER
D6
D5
D4
D3
D2
D1
D0
STOP BY
MASTER
ACK. BY
NCT218
ACK. BY
NCT218
FRAME 2
ADDRESS POINTER REGISTER BYTE
FRAME 1
SERIAL BUS ADDRESS BYTE
Figure 5. Writing to the Address Pointer Register
1
9
1
9
SCL
SDA
A6
A5
A4
A3
A2
A1
A0
D7
R/W
D6
D5
D4
D3
D2
D1
D0
ACK. BY
NCT218
START BY
MASTER
ACK. BY
NCT218
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
1
9
SCL (CONTINUED)
D7
SDA (CONTINUED)
D6
D5
D4
D3
D2
D1
D0
ACK. BY
NCT218
STOP BY
MASTER
FRAME 3
DATA BYTE
Figure 6. Writing a Register Address to the Address Pointer Register,
then Writing a Single Byte of Data to a Register
1
9
1
9
SCL
SDA
A6
A5
A4
A3
A2
A1
A0
D7
R/W
D6
D5
D4
D3
D2
D1
ACK. BY
NCT218
START BY
MASTER
D0
NO ACK. BY
MASTER
STOP BY
MASTER
DEVICE
ADDRESS
NO
STOP
ACK
FRAME 2
DATA BYTE FROM REGISTER
FRAME 1
SERIAL BUS ADDRESS BYTE
Figure 7. Reading a Byte of Data from a Register
ALERT Output
MASTER RECEIVES SMBALERT
This is applicable when Pin 6 is configured as an ALERT
output. The ALERT output goes low whenever an
out−of−limit measurement is detected, or if the remote
temperature sensor is open circuit. It is an open−drain output
and requires a pullup resistor to VDD. Several ALERT
outputs can be wire−OR’ed together, so that the common
line goes low if one or more of the ALERT outputs goes low.
The ALERT output can be used as an interrupt signal to a
processor, or as an SMBALERT. Slave devices on the bus
cannot normally signal to the bus master that they want to
talk, but the SMBALERT function allows them to do so.
One or more ALERT outputs can be connected to a
common SMBALERT line that is connected to the master.
When the SMBALERT line is pulled low by one of the
devices, the following procedure occurs (see Figure 8):
START
ALERT RESPONSE
ADDRESS
MASTER SENDS
ARA AND READ
COMMAND
RD ACK
DEVICE SENDS
ITS ADDRESS
Figure 8. Use of SMBALERT
1. SMBALERT is pulled low.
2. Master initiates a read operation and sends the
alert response address (ARA = 0001 100). This is
a general call address that must not be used as a
specific device address.
3. The device whose ALERT output is low responds
to the alert response address and the master reads
its device address. As the device address is seven
bits, an LSB of 1 is added. The address of the
device is now known and it can be interrogated in
the usual way.
4. If more than one device’s ALERT output is low,
the one with the lowest device address takes
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NCT218
The THERM output asserts low if the external or local
temperature exceeds the programmed THERM limits.
THERM temperature limits should normally be equal to or
greater than the high temperature limits. THERM is reset
automatically when the temperature falls back within the
THERM limit. A hysteresis value can be programmed; in
which case, THERM resets when the temperature falls to the
limit value minus the hysteresis value. This applies to both
local and remote measurement channels. The power−on
hysteresis default value is 10°C, but this can be
reprogrammed to any value after powerup.
The hysteresis loop on the THERM outputs is useful when
THERM is used, for example, as an on/off controller for a
fan. The user’s system can be set up so that when THERM
asserts, a fan is switched on to cool the system. When
THERM goes high again, the fan can be switched off.
Programming a hysteresis value protects from fan jitter,
where the temperature hovers around the THERM limit, and
the fan is constantly switched.
priority, in accordance with normal bus arbitration.
Once the NCT218 has responded to the alert
response address, it resets its ALERT output,
provided that the error condition that caused the
ALERT no longer exists. If the SMBALERT line
remains low, the master sends the ARA again, and
so on until all devices whose ALERT outputs were
low have responded.
Low Power Standby Mode
The NCT218 can be put into low power standby mode by
setting Bit 6 of the configuration register. When Bit 6 is low,
the NCT218 operates normally. When Bit 6 is high, the ADC
is inhibited, and any conversion in progress is terminated
without writing the result to the corresponding value
register. However, the I2C is still enabled. Power
consumption in the standby mode is reduced to 12 mA if
there is no bus activity.
When the device is in standby mode, it is possible to
initiate a one−shot conversion of both channels by writing to
the one−shot register (Address 0x0F), after which the device
returns to standby. It does not matter what is written to the
one−shot register, all data written to it is ignored. It is also
possible to write new values to the limit register while in
standby mode. If the values stored in the temperature value
registers are outside the new limits, an ALERT is generated,
even though the NCT218 is still in standby.
Table 13. THERM HYSTERESIS
THERM Hysteresis
Binary Representation
0°C
0 000 0000
1°C
0 000 0001
10°C
0 000 1010
Figure 9 shows how the THERM and ALERT outputs
operate. The ALERT output can be used as a SMBALERT
to signal to the host via the I2C that the temperature has risen.
The user can use the THERM output to turn on a fan to cool
the system, if the temperature continues to increase. This
method ensures that there is a fail−safe mechanism to cool
the system, without the need for host intervention.
Sensor Fault Detection
At its D+ input, the NCT218 contains internal sensor fault
detection circuitry. This circuit can detect situations where
an external remote diode is either not connected or
incorrectly connected to the NCT218. A simple voltage
comparator trips if the voltage at D+ exceeds VDD −
300 mV (typical), signifying an open circuit between D+
and D−. The output of this comparator is checked when a
conversion is initiated. Bit 2 of the status register (open flag)
is set if a fault is detected. If the ALERT pin is enabled,
setting this flag causes ALERT to assert low.
If the user does not wish to use an external sensor with the
NCT218, tie the D+ and D− inputs together to prevent
continuous setting of the open flag.
TEMPERATURE
1005C
905C
THERM LIMIT
805C
THERM LIMIT − HYSTERESIS
705C
HIGH TEMP LIMIT
605C
505C
405C
The NCT218 Interrupt System
RESET BY MASTER
The NCT218 has two interrupt outputs, ALERT and
THERM. Both have different functions and behavior.
ALERT is maskable and responds to violations of software
programmed temperature limits or an open−circuit fault on
the external diode. THERM is intended as a fail−safe
interrupt output that cannot be masked.
If the external or local temperature exceeds the
programmed high temperature limits, or equals or exceeds
the low temperature limits, the ALERT output is asserted
low. An open−circuit fault on the external diode also causes
ALERT to assert. ALERT is reset when serviced by a master
reading its device address, provided the error condition has
gone away and the status register has been reset.
ALERT
1
4
THERM
2
3
Figure 9. Operation of the ALERT and THERM
Interrupts
• If the measured temperature exceeds the high
temperature limit, the ALERT output asserts low.
• If the temperature continues to increase and exceeds the
THERM limit, the THERM output asserts low. This can
be used to throttle the CPU clock or switch on a fan.
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NCT218
• The THERM output deasserts (goes high) when the
Application Information
temperature falls to THERM limit minus hysteresis.
The default hysteresis value is 10°C.
• The ALERT output deasserts only when the
temperature has fallen below the high temperature
limit, and the master has read the device address and
cleared the status register.
• Pin 6 on the NCT218 can be configured as either an
ALERT output or as an additional THERM output.
• THERM2 asserts low when the temperature exceeds the
programmed local and/or remote high temperature
limits. It is reset in the same manner as THERM and is
not maskable.
• The programmed hysteresis value also applies to
THERM2.
Figure 10 shows how THERM and THERM2 operate
together to implement two methods of cooling the system.
In this example, the THERM2 limits are set lower than the
THERM limits. The THERM2 output is used to turn on a
fan. If the temperature continues to rise and exceeds the
THERM limits, the THERM output provides additional
cooling by throttling the CPU.
Noise Filtering
For temperature sensors operating in noisy environments,
the industry standard practice was to place a capacitor across
the D+ and D− pins to help combat the effects of noise.
However, large capacitances affect the accuracy of the
temperature measurement, leading to a recommended
maximum capacitor value of 1,000 pF. Although this
capacitor reduces the noise, it does not eliminate it, making
it difficult to use the sensor in a very noisy environment.
The NCT218 has a major advantage over other devices
when it comes to eliminating the effects of noise on the
external sensor. The series resistance cancellation feature
allows a filter to be constructed between the external
temperature sensor and the part. The effect of any filter
resistance seen in series with the remote sensor is
automatically cancelled from the temperature result.
The construction of a filter allows the NCT218 and the
remote temperature sensor to operate in noisy environments.
Figure 11 shows a low−pass R−C−R filter, where R = 100 W
and C = 1 nF. This filtering reduces both common−mode and
differential noise.
100 W
TEMPERATURE
905C
REMOTE
TEMPERATURE
SENSOR
THERM LIMIT
805C
705C
605C
100 W
1 nF
D−
Figure 11. Filter Between Remote Sensor and
NCT218 Factors Affecting Diode Accuracy
THERM2 LIMIT
505C
D+
405C
Remote Sensing Diode
305C
THERM2
THERM
1
The NCT218 is designed to work with substrate
transistors built into processors or with discrete transistors.
Substrate transistors are generally PNP types with the
collector connected to the substrate. Discrete types are either
PNP or NPN transistors connected as diodes (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+.
To reduce the error due to variations in both substrate and
discrete transistors, consider several factors:
• The ideality factor, nF, of the transistor is a measure of
the deviation of the thermal diode from ideal behavior.
The NCT218 is trimmed for an nF value of 1.008. The
following equation may be used to calculate the error
introduced at a temperature, T (°C), when using a
transistor whose nF does not equal 1.008. Consult the
processor data sheet for the nF values.
4
2
3
Figure 10. Operation of the THERM and THERM2
Interrupts
• When the THERM2 limit is exceeded, the THERM2
signal asserts low.
• If the temperature continues to increase and exceeds the
THERM limit, the THERM output asserts low.
• The THERM output deasserts (goes high) when the
•
temperature falls to THERM limit minus hysteresis. In
Figure 10, there is no hysteresis value shown.
As the system cools further, and the temperature falls
below the THERM2 limit, the THERM2 signal resets.
Again, no hysteresis value is shown for THERM2.
DT + (nF * 1.008)ń1.008
Both the external and internal temperature measurements
cause THERM and THERM2 to operate as described.
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(273.15 Kelvin ) T)
NCT218
To factor this in, the user writes the DT value to the ofset
register. It is then automatically added to, or subtracted from,
the temperature measurement.
• Some CPU manufacturers specify the high and low
current levels of the substrate transistors. The high
current level of the NCT218, IHIGH, is 200 mA, IMID is
75 mA and the low level current, ILOW, is 12.5 mA. If
the NCT218 current levels do not match the current
levels specified by the CPU manufacturer, it may
become necessary to remove an offset. The CPU data
sheet should advise whether this offset needs to be
removed and how to calculate it. This offset is
programmed to the ofset register. It is important to note
that if more than one offset must be considered, the
algebraic sum of these offsets must be programmed to
the offset register.
and spacing is recommended. Provide a ground plane
under the tracks, if possible.
GND
5 MIL
5 MIL
D+
5 MIL
5 MIL
D−
5 MIL
5 MIL
GND
5 MIL
Figure 12. Typical Assignment of Signal Tracks
• Try to minimize the number of copper/solder joints that
Thermal Inertia and Self−Heating
•
Accuracy depends on the temperature of the remote
sensing diode and/or the internal temperature sensor being
at the same temperature as that being measured. Many
factors can affect this. Ideally, place the sensor in good
thermal contact with the part of the system being measured.
If it is not, the thermal inertia caused by the sensor’s mass
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 SOT−23,
placed in close proximity to it. The on−chip sensor, however,
is often remote from the processor and only monitors the
general ambient temperature around the package. How
accurately the temperature of the board and/or the forced
airflow reflects the temperature to be measured dictates the
accuracy of the measurement. Self−heating due to the power
dissipated in the NCT218 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.
•
•
Layout Considerations
Digital boards can be electrically noisy environments, and
the NCT218 is measuring very small voltages from the
remote sensor, so care must be taken to minimize noise
induced at the sensor inputs. Take the following precautions:
• Place the NCT218 as close as possible to the remote
sensing diode. Provided that the worst noise sources,
that is, clock generators, data/address buses, and CRTs
are avoided, this distance can be 4 inches to 8 inches.
• Route the D+ and D– tracks close together, in parallel,
with grounded guard tracks on each side. To minimize
inductance and reduce noise pickup, a 5 mil track width
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 as
1°C corresponds to about 200 mV, and thermocouple
voltages are about 3 mV/°C of temperature difference.
Unless there are two thermocouples with a big
temperature differential between them, thermocouple
voltages should be much less than 200 mV.
Place a 0.1 mF bypass capacitor close to the VDD pin.
In extremely noisy environments, place an input filter
capacitor across D+ and D− close to the NCT218. This
capacitance can effect the temperature measurement, so
ensure that any capacitance seen at D+ and D− is, at
maximum, 1,000 pF. This maximum value includes the
filter capacitance, plus any cable or stray capacitance
between the pins and the sensor diode.
If the distance to the remote sensor is more than 8
inches, the use of twisted pair cable is recommended. A
total of 6 feet to 12 feet is needed. For really long
distances (up to 100 feet), use a shielded twisted pair,
such as the Belden No. 8451 microphone cable.
Connect the twisted pair to D+ and D− and the shield to
GND close to the NCT218. Leave the remote end of the
shield unconnected to avoid ground loops. Because the
measurement technique uses switched current sources,
excessive cable or filter capacitance can affect the
measurement. When using long cables, the filter
capacitance can be reduced or removed.
Power Supply Rise Time
When powering up the NCT218 you must ensure that the
power supply voltage rises above 1.32 in less than 5 ms. If
a rise time of longer than this occurs then power-on-reset
will be caused and yield unpredictable results.
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NCT218
Table 14. ORDERING INFORMATION
Package Type
Shipping†
NCT218MTR2G
WDFN8
(Pb−Free)
3000 / Tape & Reel
NCT218FCT2G
WLCSP8
(Pb−Free)
3000 / Tape & Reel
Device Number
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
http://onsemi.com
16
NCT218
PACKAGE DIMENSIONS
WDFN8 2x1.8, 0.5P
CASE 511BU
ISSUE O
D
L
A
B
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ASME Y14.5M, 1994.
2. CONTROLLING DIMENSION: MILLIMETERS.
3. DIMENSION b APPLIES TO PLATED
TERMINAL AND IS MEASURED BETWEEN
0.15 AND 0.20 MM FROM TERMINAL TIP.
4. COPLANARITY APPLIES TO THE EXPOSED
PAD AS WELL AS THE TERMINALS.
L
L1
PIN ONE
REFERENCE
0.10 C
2X
ÍÍ
ÍÍ
0.10 C
2X
DETAIL A
E
ALTERNATE TERMINAL
CONSTRUCTIONS
ÉÉÉ
ÉÉÉ
TOP VIEW
EXPOSED Cu
DETAIL B
0.10 C
A
0.08 C
NOTE 4
MOLD CMPD
DETAIL B
ALTERNATE
CONSTRUCTIONS
A1
A3
SIDE VIEW
e/2
C
SEATING
PLANE
e
7X
MILLIMETERS
MIN
MAX
0.70
0.80
0.00
0.05
0.20 REF
0.20
0.30
2.00 BSC
1.80 BSC
0.50 BSC
0.45
0.55
--0.15
0.55
0.65
RECOMMENDED
SOLDERING FOOTPRINT*
7X
DETAIL A
1
DIM
A
A1
A3
b
D
E
e
L
L1
L2
PACKAGE
OUTLINE
0.73
L
4
L2
2.10
8
0.83
5
8X
BOTTOM VIEW
b
0.10
M
C A
0.05
M
C
1
B
8X
0.32
NOTE 3
0.50
PITCH
DIMENSIONS: MILLIMETERS
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
http://onsemi.com
17
NCT218
PACKAGE DIMENSIONS
WLCSP8, 1.155x1.655
CASE 567DH
ISSUE O
PIN A1
REFERENCE
0.05 C
2X
0.05 C
2X
D
A B
ÈÈ
ÈÈ
E
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ASME Y14.5M, 1994.
2. CONTROLLING DIMENSION: MILLIMETERS.
3. COPLANARITY APPLIES TO SPHERICAL
CROWNS OF SOLDER BALLS.
DIM
A
A1
A2
b
D
E
eD
eE
TOP VIEW
A2
MILLIMETERS
MIN
MAX
0.60
0.50
0.17
0.24
0.36 REF
0.24
0.29
1.155 BSC
1.655 BSC
0.40 BSC
0.40 BSC
0.05 C
RECOMMENDED
SOLDERING FOOTPRINT*
A
0.05 C
NOTE 3
8X
A1
C
SIDE VIEW
PACKAGE
OUTLINE
eD
b
0.40
PITCH
eE
0.05 C A B
0.03 C
0.40
PITCH
SEATING
PLANE
1
8X
2
A1
3
0.23
DIMENSIONS: MILLIMETERS
A
B
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
C
BOTTOM VIEW
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