NCT203
Low Voltage, High
Accuracy Temperature
Monitor with I
2
C Interface
The NCT203 is a digital thermometer and undertemperature/
overtemperature alarm, intended for use in thermal management
systems requiring low power and size. The NCT203 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 NCT203 can measure the ambient temperature accurate to
±1.75°C.
The device operates over a wide temperature range of
−40
to
+125°C.
The NCT203 has a configurable ALERT output and over−
temperature shutdown THERM pin.
Communication with the NCT203 is accomplished via the I
2
C
interface which is compatible with industry standard protocols.
Through this interface the NCT203s internal registers may be
accessed. These registers allow the user to read the current
temperature, change the configuration settings and adjust limits.
An ALERT output signals when the on−chip temperature is 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.
Features
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DFN8
MT SUFFIX
CASE 511BU
PIN ASSIGNMENTS
V
DD
NC
NC
THERM
1
2
3
4
8
7
6
5
SCL
SDA
ALERT/THERM2
GND
DFN
(Top View)
•
•
•
•
•
•
•
•
•
Small DFN Package
On−Chip 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
2−wire I
2
C Serial Interface
Programmable Over/Undertemperature Limits
This is a Pb−Free Device
MARKING DIAGRAM
1
J2 MG
G
J2
M
G
= Specific Device Code
= Date Code
= Pb−Free Device
(*Note: Microdot may be in either location)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 13 of this data sheet.
Applications
•
Smart Phones, Tablet PCs, Satellite Navigation, Smart Batteries
©
Semiconductor Components Industries, LLC, 2013
June, 2013
−
Rev. 2
1
Publication Order Number:
NCT203/D
NCT203
Table 2. ABSOLUTE MAXIMUM RATINGS
(Note 1)
Rating
Supply Voltage (V
DD
) to GND
SCL, SDA, ALERT, THERM
Input current on SDA, THERM
Maximum Junction Temperature
Operating Temperature Range
Storage Temperature Range
ESD Capability, Human Body Model (Note 2)
ESD Capability, Machine Model (Note 2)
I
IN
T
J(max)
TOP
T
STG
ESD
HBM
ESD
MM
Symbol
V
DD
Value
−0.3,
+3
−0.3
to +5.25
−1,
+50
150.7
−40
to 125
−65
to 160
2000
100
Unit
V
V
mA
°C
°C
°C
V
V
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
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. I
2
C TIMING
−
400 kHz
Parameter
(Note 3)
Clock Frequency
Clock Period
SCL High Time
SCL Low Time
Start Setup Time
Start Hold Time (Note 4)
Data Setup Time (Note 5)
Data Hold Time (Note 6)
SCL, SDA Rise Time
SCL, SDA Fall Time
Stop Setup Time
Bus Free Time
Glitch Immunity
3.
4.
5.
6.
Symbol
f
SCLK
t
SCLK
t
HIGH
t
LOW
t
SU;STA
t
HD;STA
t
SU;DAT
t
HD;DAT
t
r
t
f
t
SU;STO
t
BUF
t
SW
0.6
1.3
50
Min
10
2.5
0.6
1.3
0.6
0.6
100
0.9
300
300
Typ
Max
400
Unit
kHz
ms
ms
ms
ms
ms
ns
ms
ns
ns
ms
ms
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.
t
LOW
SCLK
t
HD;STA
t
HD;DAT
SDATA
t
BUF
STOP START
START
STOP
t
HIGH
t
SU;DAT
t
SU;STA
t
SU;STO
t
R
t
F
t
HD;STA
Figure 3. I
2
C Timing Diagram
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NCT203
Theory of Operation
The NCT203 is an on−chip temperature sensor and
over/under temperature alarm. When the NCT203 is
operating normally, the on−board ADC operates in a free
running mode. The ADC digitizes the signals from the
temperature sensor and the results are stored in the
temperature value register.
The measurement results are compared with the
corresponding high, low, and THERM temperature limits,
stored in the 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.
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 I
2
C. The contents of
any register are also read back via the I
2
C. 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.
Temperature Measurement Method
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.
Temperature Measurement Results
The results of the temperature measurement are stored in
the temperature value register and compared with limits
programmed into the high and low limit registers.
The temperature value is in Register 0x00 and has a
resolution of 1°C.
Temperature Measurement Range
A simple method of measuring temperature is to exploit
the negative temperature coefficient of a diode, measuring
the base emitter voltage (V
BE
) 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 NCT203 measures the change
in VBE when the device operates at different currents.
To measure
DV
BE
, the operating current through the
sensor is switched among related currents. 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
DV
BE1
; and then between I and N2 x I, giving
DV
BE2
.
The temperature is then calculated using the two
DV
BE
measurements.
The resulting
DV
BE
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
DV
BE
.
The ADC digitizes this voltage producing a temperature
The temperature measurement range is, by default, 0°C to
+127°C. However, the NCT203 can be operated using an
extended temperature range. The extended measurement
range is
−64°C
to +191°C. Therefore, the NCT203 can be
used to measure the full temperature range of the NCT203,
from
−40°C
to +125°C.
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 NCT203 is limited
by the device temperature range of
−40°C
to +125°C. The
temperature register can have values from
−64°C
to +191°C.
It should be noted that although temperature
measurements can be made while the part is in extended
temperature mode, the NCT203 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.
Temperature Data Format
The NCT203 has two temperature data formats. When the
temperature measurement range is from 0°C to 127°C
(default), the temperature data format for temperature
results is binary. When the measurement range is in
extended mode, an offset binary data format is used.
Temperature values are offset by 64°C in the offset binary
data format. Examples of temperatures in both data formats
are shown in Table 5.
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