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TC77-3.3MOA

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P22
TC77
DS20092B-page 10 2002-2012 Microchip Technology Inc.
FIGURE 3-2: Temperature Read Timing Diagram - (Reading only the first 13 Bits of the
Temperature Register).
FIGURE 3-3: Temperature Read Followed By A Write To The Configuration Register Timing.
Diagram.
It is recommended that the user write all ‘0’s or all ‘1’s
to the Configuration register. While the following codes
can be transmitted to the TC77, any other code may
put the TC77 into a test mode reserved by Microchip for
calibration and production verification tests.
• 00 hex
• 01 hex
• 03 hex
• 07 hex
•0F hex
•1F hex
•3F hex
•7F hex
•FF hex
The following communication steps can be used to
obtain the Manufacturer's ID and put the device into the
Continuous Conversion mode. The Manufacturer’s ID
register is only accessible for a read operation, if the
TC77 is in Shutdown mode.
1. CS
goes low to initiate the communication cycle.
2. Read 16 bits of temperature data from the
Temperature register.
3. Write 16 bits of data (i.e. XXFF hex) to the Con-
figuration register to enter Shutdown mode.
4. Read the 16 bits from the Manufacturer's ID reg-
ister (C15:C8 = 54 hex) to verify that the sensor
is a Microchip device.
5. Write 8 to 16 bits of data (00 or 0000 hex) to
enter Continuous Conversion Mode.
6. Return CS
high to terminate the communication
cycle.
The time between a complete temperature conversion
and data transmission is approximately 300 msec.
CS
CLK
SI/O
t
CS-SCK
HI-Z
HI-Z
T
T
T
12
11
10
T
9
T
7
T
6
T
5
T
4
T
3
T
2
T
1
T
0
1813
T
8
CS
CLK
SI/O
t
CS-SCK
HI-Z
18 8 8 81
HI-Z
11
HI-Z
TEMPERATURE REGISTER
Notes:
1. Bit 2 = 0 during power-up for the first
temperature conversion.
2. Bit 2 =1 after the completion of the first tem-
perature conversion following power-up or a
reset event.
3. Bits 1 and 0 are “DON”T CARES”.
CONFIGURATION REGISTER
Notes:
1. XX00 = Continuous Conversion Mode
2. XXFF = Shutdown Mode
T
12
T
11
T
10
T
9
T
8
T
7
T
6
T
5
T
4
T
3
T
2
T
1
T
0
BIT
2
C
15
C
14
C
13
C
12
C
11
C
10
C
9
C
8
C
7
C
6
C
5
C
4
C
3
C
2
C
1
C
0
2002-2012 Microchip Technology Inc. DS20092B-page 11
TC77
4.0 INTERNAL REGISTER
STRUCTURE
The TC77 Internal register structure consists of three
registers. The Temperature and Manufacturer’s Identi-
fication registers are read only, while the Configuration
register is write only.
TABLE 4-1: REGISTERS FOR TC77
4.1 Configuration Register (CONFIG)
The Configuration register is write only. This register
selects either Shutdown, Continuous Conversion or
Test modes:
• C15:C0 = XXXX/XXXX 1111/1111 (Shutdown
mode)
• C15:C0 = XXXX/XXXX 0000/0000 (Continuous
Conversion mode)
• The TC77 is in Shutdown mode when bits C0 to
C7 are all equal to ‘1’s. The TC77 will be in the
Continuous Conversion mode if a ‘0’ in any bit
location from C0 to C7 is written to the Configura-
tion register. The TC77 is in the Continuous
Conversion mode at power-up.
It is recommended that the user write all ‘0’s or all ‘1’s
to the Configuration register because other bit codes
may put the TC77 in a test mode used for calibration
and production verification tests. Section 3.3 lists the
Configuration register bit codes that can be written to
the TC77 without having the device enter a production
test mode.
During Shutdown mode, the serial bus is still active.
The current consumption of the TC77 will be less than
1 µA during the time between serial communication.
4.2 Temperature Register (TEMP)
The Temperature register is read only and holds the
temperature conversion data. Bits 0 and 1 are unde-
fined and will be tri-state outputs during a read
sequence. Bit 2 is set to a logic ‘1’ after completion of
the first temperature conversion following a power-up
or reset event. Bit 2 is set to a logic ‘0’ during the time
needed to complete the first temperature conversion.
Therefore, the status of bit 2 can be monitored to indi-
cate that the TC77 has completed the first temperature
conversion. Bits 15:3 contain the 13 bit two’s comple-
ment data from the temperature conversion.
4.3 Manufacturer’s ID Register (M_ID)
The Manufacturer’s Identification code is contained in
this read only register. The Manufacturer ID register is
only available for a read operation when the TC77 is in
Shutdown mode. The Manufacturer’s ID code is con-
tained in bits 15:8 and is equal to 54 hex to indicate a
Microchip device. Bits 1:0 are undefined and will be tri-
state outputs during a read sequence, while bits 7:2 are
set to ‘0’.
Name
Bit
15
Bit
14
Bit
13
Bit
12
Bit
11
Bit
10
Bit
9
Bit
8
Bit
7
Bit
6
Bit
5
Bit
4
Bit
3
Bit
2
Bit
1
Bit
0
Value at Powerup/Reset
CONFIG C15 C14 C13 C12 C11 C10 C9 C8 C7 C6 C5 C4 C3 C2 C1 C0 XXXX/XXXX 0000/0000
TEMP T12T11T10T9 T8 T7T6T5T4T3T2T1T0 * x x1111/1111 0000/0*XX
M_ID 01010100000000xx0101/0100 0000/00XX
* Bit 2 = 0 during power-up; otherwise, bit 2 =1
TC77
DS20092B-page 12 2002-2012 Microchip Technology Inc.
5.0 APPLICATION INFORMATION
The TC77 does not require any additional components
in order to measure temperature. However, it is recom-
mended that a decoupling capacitor of 0.1 µF to 1 µF
be provided between the V
DD
and V
SS
(Ground) pins (a
high frequency ceramic capacitor should be used). It is
necessary for the capacitor to be located as close as
possible to the integrated circuit (IC) power pins in
order to provide effective noise protection to the TC77.
The TC77 measures temperature by monitoring the
voltage of a diode located on the IC die. A low-imped-
ance thermal path between the die and the printed cir-
cuit board (PCB) is provided by the IC pins of the TC77.
Therefore, the TC77 effectively monitors the tempera-
ture of the PCB board. The thermal path between the
ambient air is not as efficient because the plastic IC
housing package functions as a thermal insulator.
Thus, the ambient air temperature (assuming that a
large temperature gradient exists between the air and
PCB) has only a small effect on the temperature
measured by the TC77.
A potential for self-heating errors can exist if the TC77
SPI communication lines are heavily loaded. Typically,
the self-heating error is negligible because of the rela-
tively small current consumption of the TC77. A tem-
perature accuracy error of approximately 0.5°C will
result from self-heating if the SPI communication pins
sink/source the maximum current specified for the
TC77. Therefore, to maximize the temperature accu-
racy, the output loading of the SPI signals should be
minimized.
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TC77-3.3MOA

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Board Mount Temperature Sensors High-Accuracy 13-bit
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