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PDF NCT1008 Data sheet ( Hoja de datos )
| Número de pieza | NCT1008 | |
| Descripción | +-1 C Temperature Monitor | |
| Fabricantes | ON Semiconductor | |
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NCT1008
+15C Temperature Monitor
with Series Resistance
Cancellation
The NCT1008 is a dual−channel digital thermometer and
undertemperature/overtemperature alarm, intended for use in PCs and
thermal management systems. It is register−compatible with the
ADM1032 and ADT7461. A feature of the NCT1008 is series
resistance cancellation, where up to 1.5 kW (typical) of resistance in
series with the temperature monitoring diode can be automatically
cancelled from the temperature result, allowing noise filtering. The
NCT1008 has a configurable ALERT output and an extended,
switchable temperature measurement range.
The NCT1008 can measure the temperature of a remote thermal
diode accurate to ±1°C and the ambient temperature accurate to ±3°C.
The temperature measurement range defaults to 0°C to +127°C,
compatible with the ADM1032, but it can be switched to a wider
measurement range of −64°C to +191°C.
The NCT1008 communicates over a 2−wire serial interface,
compatible with system management bus (SMBus/I2C) standards. The
default SMBus/I2C address of the NCT1008 is 0x4C. An NCT1008D is
available with an SMBus/I2C address of 0x4D. This is useful if more
than one NCT1008 is used on the same SMBus/I2C.
An ALERT output signals when the on−chip or remote temperature is
out of range. The THERM output is a comparator output that allows
on/off control of a cooling fan. The ALERT output can be reconfigured
as a second THERM output, if required.
Features
• On−Chip and Remote Temperature Sensor
• 0.25°C Resolution/1°C Accuracy on Remote Channel
• 1°C Resolution/1°C Accuracy on Local Channel
• Series Resistance Cancellation Up to 1.5 kW
• Extended, Switchable Temperature Measurement Range
0°C to +127°C (Default) or –64°C to +191°C
• Register−Compatible with ADM1032 and ADT7461
• Remote THERM Limit of 108°C
• 2−Wire SMBus/I2C Serial Interface with SMBus Alert Support
• Programmable Over/Undertemperature Limits
• Offset Registers for System Calibration
• Up to Two Overtemperature Fail−Safe THERM Outputs
• Small 8−Lead DFN
• 240 mA Operating Current, 5 mA Standby Current
• Compatible with 1.8 V Logic
• Pb−Free Packages are Available
Applications
• Smart Phones
• Desktop and Notebook Computers
• Smart Batteries
• Automotive
• Embedded Systems
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http://onsemi.com
WDFN8
CASE 511AT
1
DFN8
CASE 506BJ
1
MARKING DIAGRAMS
1
8xMG
G
1 NCT 8
1008x
ALYWG
G
8x = Device Code (Where x = C or D)
M = Date Code
G = Pb−Free Package
x = C or D
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = Pb−Free Package
(Note: Microdot may be in either location)
PIN ASSIGNMENT
VCC 1
8 SCLK
D+ 2
7 SDATA
D− 3
6 ALERT/THERM2
THERM 4
5 GND
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 18 of this data sheet.
© Semiconductor Components Industries, LLC, 2010
August, 2010 − Rev. 3
1
Publication Order Number:
NCT1008/D
1 page  
NCT1008
TYPICAL CHARACTERISTICS
3.5
DEV 1 DEV 8
DEV 15
3.0
DEV 2 DEV 9
DEV 16
DEV 3 DEV 10 MEAN
2.5 DEV 4 DEV 11 HIGH 4R
DEV 5 DEV 12 LOW 4R
2.0
DEV 6
DEV 7
DEV 13
DEV 14
1.5
1.0
0.5
0
–0.5
–1.0
–50
0 50 100
TEMPERATURE (5C)
150
Figure 3. Local Temperature Error vs. Temperature
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–0.5
–1.0
–50
DEV 1
DEV 2
DEV 3
DEV 4
DEV 5
DEV 6
DEV 7
DEV 8
DEV 9
DEV 10
DEV 11
DEV 12
DEV 13
DEV 14
DEV 15
DEV 16
HIGH 4R
LOW 4R
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0 50 100
TEMPERATURE (5C)
150
Figure 4. Remote Temperature Error vs. Actual
Temperature
10
5
D+ TO GND
0
–5
D+ TO VCC
–10
–15
–20
–25
1
10
LEAKAGE RESISTANCE (MΩ)
100
Figure 5. Temperature Error vs. D+/D− Leakage
Resistance
0
–2
–4
–6
–8
–10
DEV 3
–12 DEV 2
–14
DEV 4
–16
–18
0
5 10 15 20
CAPACITANCE (nF)
25
Figure 6. Temperature Error vs. D+/D− Capacitance
1000
900
DEV 2BC
800
700
600
500
DEV 4BC
400
300 DEV 3BC
200
100
0
0.01
0.1 1 10
CONVERSION RATE (Hz)
Figure 7. Operating Supply Current vs.
Conversion Rate
100
422
420
DEV 2BC
418
416
414 DEV 3BC
DEV 4BC
412
410
408
3.0 3.1 3.2 3.3 3.4 3.5 3.6
VDD (V)
Figure 8. Operating Supply Current vs. Voltage
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5
5 Page 
NCT1008
Table 5. Status Register Bit Assignments
Bit Name
Function
7
BUSY
1 when ADC is converting
6 LHIGH 1 when local high temperature limit is
(Note 1) tripped
5
LLOW
1 when local low temperature limit is
(Note 1) tripped
4 RHIGH 1 when remote high temperature limit is
(Note 1) tripped
3 RLOW 1 when remote low temperature limit is
(Note 1) tripped
2
OPEN
1 when remote sensor is an open circuit
(Note 1)
1 RTHRM 1 when remote THERM limit is tripped
0 LTHRM 1 when local THERM limit is tripped
1. 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 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.
Table 6. Sample Offset Register Codes
Offset Value
−128°C
−4°C
−1°C
−0.25°C
0°C
+0.25°C
+1°C
+4°C
+127.75°C
0x11
1000 0000
1111 1100
1111 1111
1111 1111
0000 0000
0000 0000
0000 0001
0000 0100
0111 1111
0x12
w0w0w00.D0a0t0a0Sheet4U.com
00 00 0000
00 000000
10 00 0000
00 00 0000
01 00 0000
00 00 0000
00 00 0000
11 00 0000
One−Shot Register
The one−shot register is used to initiate a conversion and
comparison cycle when the NCT1008 is in standby mode,
after which the device returns to standby. Writing to the
one−shot register address (0x0F) causes the NCT1008 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.
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 7. 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 = SMBus timeout bit.
Default = 0. See SMBus section for more information.
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