MCP9808
±0.5°C Maximum Accuracy Digital Temperature Sensor
Features
General Description
• Accuracy:
- ±0.25 (typical) from –40°C to +125°C
- ±0.5°C (maximum) from –20°C to 100°C
- ±1°C (maximum) from –40°C to +125°C
- ±0.0625°C or ±1 LSb (typical) repeatability
• User-Selectable Measurement Resolution:
- +0.5°C, +0.25°C, +0.125°C, +0.0625°C
• User-Programmable Temperature Limits:
- Temperature Window Limit
- Critical Temperature Limit
• User-Programmable Temperature Alert Output
• Operating Voltage Range: 2.7V-5.5V
• Operating Current: 200 μA (typical)
• Shutdown Current: 0.1 μA (typical)
• 2-wire Interface: I2C/SMBus Compatible
• Available Packages: 2x3 DFN-8, MSOP-8
Microchip Technology Inc.’s MCP9808 digital temperature
sensor converts temperatures between –20°C and
+100°C to a digital word with ±0.25°C/±0.5°C (typical/maximum) accuracy.
The MCP9808 comes with user-programmable registers
that provide flexibility for temperature sensing
applications. The registers allow user-selectable
settings such as Shutdown or Low-Power modes and
the specification of temperature Alert window limits and
critical output limits. When the temperature changes
beyond the specified boundary limits, the MCP9808
outputs an Alert signal. The user has the option of setting
the Alert output signal polarity as an active-low or activehigh comparator output for thermostat operation, or as a
temperature Alert interrupt output for microprocessorbased systems. The Alert output can also be configured
as a critical temperature output only.
This sensor has an industry standard 400 kHz, 2-wire,
SMBus/I2C compatible serial interface, allowing up to
eight or sixteen sensors to be controlled with a single
serial bus (see Table 3-2 for available Address codes).
These features make the MCP9808 ideal for
sophisticated, multi-zone, temperature-monitoring
applications.
Typical Applications
•
•
•
•
•
•
•
•
General Purpose
Industrial Applications
Industrial Freezers and Refrigerators
Food Processing
Personal Computers and Servers
PC Peripherals
Consumer Electronics
Handheld/Portable Devices
Package Types
8-Pin 2x3 DFN*
SDA 1
SCL 2
Temperature Accuracy
40%
Alert 3
GND 4
TA = -20°C, 25°C, 85°C, 100°C
VDD = 3.3V
854 units
EP
9
8-Pin MSOP
8 VDD
SDA 1
8 VDD
7 A0
SCL 2
7 A0
6 A1
Alert 3
GND 4
6 A1
5 A2
5 A2
* Includes Exposed Thermal Pad (EP); see Table 3-1.
Occurrences
30%
20%
10%
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
-0.4
-0.5
0%
Temperature Accuracy (°C)
2011-2018 Microchip Technology Inc.
DS20005095B-page 1
MCP9808
Functional Block Diagram
Hysteresis
Shutdown
Critical Trip Lock
Alarm Window Lock
Clear Alert
Alert Status
Output Control
Critical Alert only
Band Gap
Temperature
Sensor
Alert Polarity
Alert Comp./Int.
Configuration
Temperature
ADC
TUPPER Limit
TLOWER Limit
+0.5°C
+0.25°C
+0.125°C
+0.0625°C
TCRITICAL Limit
Manufacturer ID
Device ID/Rev
Resolution
Register
Pointer
SMBus/Standard I2C
Interface
A0
DS20005095B-page 2
A1
A2
Alert
SDA
SCL
VDD
GND
2011-2018 Microchip Technology Inc.
MCP9808
1.0
ELECTRICAL
CHARACTERISTICS
Absolute Maximum Ratings †
VDD.................................................................................. 6.0V
Voltage at All Input/Output Pins .............. GND – 0.3V to 6.0V
†Notice: Stresses above those listed under “Maximum
ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of
the device at those or any other conditions above those
indicated in the operational listings of this specification
is not implied. Exposure to maximum rating conditions
for extended periods may affect device reliability.
Storage Temperature ................................... –65°C to +150°C
Ambient Temperature with Power Applied.... –40°C to +125°C
Junction Temperature (TJ)........................................... +150°C
ESD Protection on All Pins (HBM:MM) ................ (4 kV:400V)
Latch-up Current at Each Pin (+25°C) ..................... ±200 mA
TEMPERATURE SENSOR DC CHARACTERISTICS
Electrical Specifications: Unless otherwise indicated, VDD = 2.7V to 5.5V, GND = Ground and
TA = –40°C to +125 °C.
Parameters
Sym.
Min.
Typ.
Max.
Unit
Conditions
Temperature Sensor Accuracy
–20°C < TA +100 °C
TACY
–40°C < TA +125 °C
Accuracy Drift
Accuracy Repeatability
–0.5
±0.25
+0.5
°C
–1.0
±0.25
+1.0
°C
VDD = 3.3V (Note 1)
TDRIFT
—
+0.05
—
°C
VDD = 3.3V (Note 2)
TREPEAT
—
±0.0625
—
°C
48 hours at +55°C, VDD = 3.3V
—
30
—
ms
33s/sec (typical)
Temperature Conversion Time
0.5°C/bit
tCONV
0.25°C/bit
—
65
—
ms
15s/sec (typical)
0.125°C/bit
—
130
—
ms
7s/sec (typical)
0.0625°C/bit
—
250
—
ms
4s/sec (typical)
Power Supply
Operating Voltage Range
VDD
2.7
—
5.5
V
Operating Current
IDD
—
200
400
μA
Shutdown Current
ISHDN
—
0.1
2
μA
Power-on Reset (POR)
VPOR
—
2.2
—
V
Power Supply Rejection
°C/VDD
—
–0.1
—
Threshold for falling VDD
°C/V VDD = 2.7V to 5.5V, TA = +25°C
Alert Output (open-drain output, external pull-up resistor required), see Section 5.2.3, Alert Output Configuration
High-Level Current (leakage)
IOH
—
—
1
μA
VOH = VDD (Active-Low, Pull-up Resistor)
Low-Level Voltage
VOL
—
—
0.4
V
IOL= 3 mA (Active-Low, Pull-up Resistor)
Time to 63% (+89°C)
Thermal Response, from +25°C (air) to +125°C (oil bath)
8L-DFN
tRES
8L-MSOP
—
0.7
—
s
—
1.4
—
s
Note 1: Accuracy specification includes life time drift.
2: Using Accelerated Life Cycle, equivalent of 12 years of operation at +55°C.
2011-2018 Microchip Technology Inc.
DS20005095B-page 3
MCP9808
DIGITAL INPUT/OUTPUT PIN CHARACTERISTICS
Electrical Specifications: Unless otherwise indicated, VDD = 2.7V to 5.5V, GND = Ground and
TA = –40°C to +125 °C.
Parameters
Sym
Min
Typ
Max
Units
V
Conditions
Serial Input/Output (SCL, SDA, A0, A1, A2)
Input
High-Level Voltage
VIH
0.7 VDD
—
VDD
Low-Level Voltage
VIL
GND
—
0.3 VDD
V
Input Current
IIN
—
—
±5
μA
Low-Level Voltage
VOL
—
—
0.4
V
High-Level Current (leakage)
IOH
—
—
1
μA
VOH = 5.5V
Low-Level Current
IOL
6
—
—
mA
VOL = 0.6V
VHYST
—
0.05 VDD
—
V
Spike Suppression
tSP
—
—
50
ns
Capacitance
CIN
—
5
—
pF
Output (SDA)
IOL= 3 mA
SDA and SCL Inputs
Hysteresis
GRAPHICAL SYMBOL DESCRIPTION
Voltage VDD
INPUT
Voltage
V IH
OUTPUT
VDD
VOL
VIL
IOL
Current
Current
IIN
IOH
time
time
TEMPERATURE CHARACTERISTICS
Electrical Specifications: Unless otherwise indicated, VDD = 2.7V to 5.5V and GND = Ground.
Parameters
Sym
Min
Typ
Max
Units
Specified Temperature Range
TA
–40
—
+125
°C
Operating Temperature Range
TA
–40
—
+125
°C
Storage Temperature Range
TA
-65
—
+150
°C
Thermal Resistance, 8L-DFN
JA
—
68
—
°C/W
Thermal Resistance, 8L-MSOP
JA
—
211
—
°C/W
Conditions
Temperature Ranges
(Note 1)
Thermal Package Resistances
Note 1:
Operation in this range must not cause TJ to exceed Maximum Junction Temperature (+150°C).
DS20005095B-page 4
2011-2018 Microchip Technology Inc.
MCP9808
SENSOR SERIAL INTERFACE TIMING SPECIFICATIONS
Electrical Specifications: Unless otherwise indicated, VDD = 2.7V to 5.5V, TA = -40°C to +125°C, GND = Ground
and CL = 80 pF. (Note 1)
Parameters
Sym
Min
Max
Units
Conditions
2
2-Wire SMBus/I C Interface (Note 1)
fSC
0
400
kHz
Low Clock
Serial Port Clock Frequency
tLOW
1300
—
ns
(Note 2)
High Clock
tHIGH
600
—
ns
(Note 2)
Rise Time
tR
20
300
ns
tF
20
300
ns
tSU-DI
100
—
ns
Fall Time
Data in Setup Time
(Note 2, 4)
(Note 3)
Data In Hold Time
tHD-DI
0
—
ns
(Note 5)
Data Out Hold Time
tHD-DO
200
900
ns
(Note 4)
Start Condition Setup Time
tSU-START
600
—
ns
Start Condition Hold Time
tHD-START
600
—
ns
Stop Condition Setup Time
tSU-STOP
600
—
ns
Bus Free
tB-FREE
1300
—
ns
Time-out
tOUT
25
35
ms
Cb
—
400
pf
Bus Capacitive Load
Note 1:
2:
3:
4:
5:
All values referred to VIL MAX and VIH MIN levels.
If tLOW > tOUT or tHIGH > tOUT, the temperature sensor I2C interface will time-out. A Repeat Start command
is required for communication.
This device can be used in a Standard mode I2C bus system, but the requirement, tSU-DI ≥ 100 ns, must
be met. This device does not stretch the SCL Low time.
As a transmitter, the device provides internal minimum delay time, tHD-DO MIN, to bridge the undefined
region (min. 200 ns) of the falling edge of SCL, tF MAX, to avoid unintended generation of Start or Stop
conditions.
As a receiver, SDA should not be sampled at the falling edge of SCL. SDA can transition tHD-DI after SCL
toggles Low.
TIMING DIAGRAM
tHD-START
tSU-START
tHIGH
tLOW
tB-FREE
tSU-STOP
SCL
SDA
tOUT
tR, tF
tSU-DI
START Condition
2011-2018 Microchip Technology Inc.
tHD-DI/tHD-DO
Data Transmission
STOP Condition
DS20005095B-page 5
MCP9808
NOTES:
DS20005095B-page 6
2011-2018 Microchip Technology Inc.
MCP9808
2.0
TYPICAL PERFORMANCE CURVES
Note:
The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore outside the warranted range.
Note: Unless otherwise indicated, VDD = 2.7V to 5.5V, GND = Ground, SDA/SCL pulled-up to VDD and
TA = –40°C to +125 °C.
40%
VDD = 3.3V
854 units at -20°C, 25°C, 85°C, 100°C
240 units at -40°C, 125°C
30%
0.5
Occurrences
0.0
+Std. Dev.
Average
-Std. Dev.
FIGURE 2-1:
Temperature Accuracy.
FIGURE 2-4:
Histogram.
Temperature Accuracy
40%
TA = -20°C
VDD = 3.3V
827 units
TA = 85°C
VDD = 3.3V
859 units
Occurrences
30%
20%
10%
20%
10%
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
-0.5
Temperature Accuracy (°C)
-0.4
0%
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
-0.4
-0.5
0%
Temperature Accuracy (°C)
FIGURE 2-2:
Temperature Accuracy
Histogram, TA = –20°C.
FIGURE 2-5:
Temperature Accuracy
Histogram, TA = +85°C.
40%
40%
TA = 25°C
VDD = 3.3V
875 units
30%
Occurrences
20%
10%
TA = 100°C
VDD = 3.3V
856 units
20%
10%
FIGURE 2-3:
Temperature Accuracy
Histogram, TA = +25°C.
2011-2018 Microchip Technology Inc.
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
0%
-0.4
Temperature Accuracy (°C)
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
-0.4
-0.5
0%
-0.5
Occurrences
0.5
Temperature Accuracy (°C)
40%
30%
0.4
120
0.3
100
0.2
80
0.1
40
60
TA (°C)
0.0
20
-0.1
0
-0.2
-20
0%
-0.3
-40
+3 * Std. Dev.
-3 * Std. Dev.
-0.4
-1.0
Occurrences
20%
10%
-0.5
30%
TA = -20°C, 25°C, 85°C, 100°C
VDD = 3.3V
854 units
-0.5
Temperature Accuracy (°C)
1.0
Temperature Accuracy (°C)
FIGURE 2-6:
Temperature Accuracy
Histogram, TA = +100°C.
DS20005095B-page 7
MCP9808
Note: Unless otherwise indicated, VDD = 2.7V to 5.5V, GND = Ground, SDA/SCL pulled-up to VDD and
TA = -40°C to +125 °C.
40%
Temperature Accuracy (°C)
Temperature Accuracy (°C)
FIGURE 2-7:
Temperature Accuracy
Histogram, TA = –40°C.
FIGURE 2-10:
Temperature Accuracy
Histogram, TA = +125°C.
FIGURE 2-8:
Temperature.
FIGURE 2-11:
Supply Voltage.
Supply Current vs.
FIGURE 2-9:
Power-on Reset Threshold
Voltage vs. Temperature.
DS20005095B-page 8
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.5
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
0%
-0.2
0%
-0.3
10%
-0.2
20%
10%
-0.4
TA = 125°C
VDD = 3.3V
240 units
-0.3
Occurrences
30%
20%
-0.5
Occurrences
30%
TA = -40°C
VDD = 3.3V
240 units
-0.4
40%
Temperature Accuracy vs.
FIGURE 2-12:
Temperature Conversion
Time vs. Temperature.
2011-2018 Microchip Technology Inc.
MCP9808
Note: Unless otherwise indicated, VDD = 2.7V to 5.5V, GND = Ground, SDA/SCL pulled-up to VDD and
TA = -40°C to +125 °C.
FIGURE 2-13:
vs. Temperature.
SDA and Alert Output VOL
FIGURE 2-16:
Temperature.
SMBus Time-out vs.
FIGURE 2-14:
SDA IOL vs. Temperature.
FIGURE 2-17:
Temperature.
Shutdown Current vs.
FIGURE 2-15:
Response.
Package Thermal
FIGURE 2-18:
Frequency.
Power Supply Rejection vs.
2011-2018 Microchip Technology Inc.
DS20005095B-page 9
MCP9808
NOTES:
DS20005095B-page 10
2011-2018 Microchip Technology Inc.
MCP9808
3.0
PIN DESCRIPTION
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1:
3.1
PIN FUNCTION TABLE
DFN
MSOP
Symbol
Pin Function
1
1
SDA
2
2
SCL
Serial Clock Line
3
3
Alert
Temperature Alert Output
4
4
GND
5
5
A2
Slave Address
6
6
A1
Slave Address
7
7
A0
Slave Address
8
8
VDD
Power Pin
9
—
EP
Exposed Thermal Pad (EP); must be connected to GND
Serial Data Line
Ground
Serial Data Line (SDA)
SDA is a bidirectional input/output pin, used to serially
transmit data to/from the host controller. This pin
requires a pull-up resistor. (See Section 4.0 “Serial
Communication”.)
3.2
Serial Clock Line (SCL)
The SCL is a clock input pin. All communication and
timing is relative to the signal on this pin. The clock is
generated by the host or master controller on the bus.
(See Section 4.0 “Serial Communication”.)
3.3
Temperature Alert, Open-Drain
Output (Alert)
The MCP9808 temperature Alert output pin is an
open-drain output. The device outputs a signal when the
ambient temperature goes beyond the user-programmed
temperature limit. (See Section 5.2.3 “Alert Output
Configuration”).
3.4
Ground Pin (GND)
The GND pin is the system ground pin.
3.5
Address Pins (A0, A1, A2)
These pins are device address input pins.
The address pins correspond to the Least Significant
bits (LSbs) of the address bits and the Most Significant
bits (MSbs): A6, A5, A4, A3. This is illustrated in
Table 3-2.
TABLE 3-2:
Device
MCP9808
(2)
MCP9808
Note 1:
2:
3.6
MCP9808 ADDRESS BYTE
Address Code
Slave
Address
A6
A5
A4
A3
A2
A1
A0
0
0
1
1
x(1)
x
x
1
0
0
1
x
x
x
User-selectable address is shown by ‘x’.
A2, A1 and A0 must match the
corresponding device pin configuration.
Contact factory for this address code.
Power Pin (VDD)
VDD is the power pin. The operating voltage range, as
specified in the DC electrical specification table, is
applied on this pin.
3.7
Exposed Thermal Pad (EP)
There is an internal electrical connection between the
Exposed Thermal Pad (EP) and the GND pin. The EP
may be connected to the system ground on the Printed
Circuit Board (PCB).
2011-2018 Microchip Technology Inc.
DS20005095B-page 11
MCP9808
NOTES:
DS20005095B-page 12
2011-2018 Microchip Technology Inc.
MCP9808
4.0
SERIAL COMMUNICATION
4.1
2-Wire Standard Mode I2C
Protocol Compatible Interface
The MCP9808 Serial Clock (SCL) input and the
bidirectional Serial Data (SDA) line form a 2-wire
bidirectional, Standard mode, I2C compatible
communication port (refer to the Digital Input/Output
Pin Characteristics and Sensor Serial Interface
Timing Specifications tables).
The following bus protocol has been defined:
TABLE 4-1:
Term
MCP9808 SERIAL BUS
PROTOCOL DESCRIPTIONS
Description
Master
The device that controls the serial bus,
typically a microcontroller.
Slave
The device addressed by the master,
such as the MCP9808.
Transmitter Device sending data to the bus.
Receiver
Device receiving data from the bus.
START
A unique signal from the master to
initiate serial interface with a slave.
STOP
A unique signal from the master to
terminate serial interface from a slave.
Read/Write A read or write to the MCP9808
registers.
ACK
A receiver Acknowledges (ACK) the
reception of each byte by polling the bus.
NAK
A receiver Not-Acknowledges (NAK) or
releases the bus to show End-of-Data
(EOD).
Busy
Communication is not possible
because the bus is in use.
Not Busy
The bus is in the Idle state; both SDA
and SCL remain high.
Data Valid
SDA must remain stable before SCL
becomes high in order for a data bit to
be considered valid. During normal
data transfers, SDA only changes state
while SCL is low.
2011-2018 Microchip Technology Inc.
4.1.1
DATA TRANSFER
Data transfers are initiated by a Start condition
(START), followed by a 7-bit device address and a
read/write bit. An Acknowledge (ACK) from the slave
confirms the reception of each byte. Each access must
be terminated by a Stop condition (STOP).
Repeated communication is initiated after tB-FREE.
This device does not support sequential register
read/write. Each register needs to be addressed using
the Register Pointer.
This device supports the receive protocol. The register
can be specified using the pointer for the initial read.
Each repeated read or receive begins with a Start
condition and address byte. The MCP9808 retains the
previously selected register. Therefore, it outputs data
from the previously specified register (repeated pointer
specification is not necessary).
4.1.2
MASTER/SLAVE
The bus is controlled by a master device (typically a
microcontroller) that controls the bus access and
generates the Start and Stop conditions. The MCP9808
is a slave device and does not control other devices in
the bus. Both master and slave devices can operate as
either transmitter or receiver. However, the master
device determines which mode is activated.
4.1.3
START/STOP CONDITION
A high-to-low transition of the SDA line (while SCL is
high) is the Start condition. All data transfers must be
preceded by a Start condition from the master. A
low-to-high transition of the SDA line (while SCL is
high) signifies a Stop condition.
If a Start or Stop condition is introduced during data
transmission, the MCP9808 releases the bus. All data
transfers are ended by a Stop condition from the
master.
DS20005095B-page 13
MCP9808
4.1.4
ADDRESS BYTE
4.1.5
Following the Start condition, the host must transmit an
8-bit address byte to the MCP9808. The address for the
MCP9808 temperature sensor is ‘0011,A2,A1,A0’ in
binary, where the A2, A1 and A0 bits are set externally
by connecting the corresponding pins to VDD ‘1’ or GND
‘0’. The 7-bit address, transmitted in the serial bit stream,
must match the selected address for the MCP9808 to
respond with an ACK. Bit 8 in the address byte is a
read/write bit. Setting this bit to ‘1’ commands a read
operation, while ‘0’ commands a write operation (see
Figure 4-1).
Address Byte
SCL
1 2
SDA
0
0
3
4
5
6
7
1 1 A2 A1 A0
Start
Address
Code
8
9
A
C
K
Slave
Address R/W
MCP9808 Response
See Table 3-2.
FIGURE 4-1:
DS20005095B-page 14
Device Addressing.
DATA VALID
After the Start condition, each bit of data in the
transmission needs to be settled for a time specified by
tSU-DATA before SCL toggles from low-to-high (see the
Sensor Serial Interface Timing Specifications section).
4.1.6
ACKNOWLEDGE (ACK/NAK)
Each receiving device, when addressed, must
generate an ACK bit after the reception of each byte.
The master device must generate an extra clock pulse
for ACK to be recognized.
The Acknowledging device pulls down the SDA line for
tSU-DATA before the low-to-high transition of SCL from
the master. SDA also needs to remain pulled down for
tH-DATA after a high-to-low transition of SCL.
During read, the master must signal an End-of-Data
(EOD) to the slave, by not generating an ACK bit
(NAK), once the last bit has been clocked out of the
slave. In this case, the slave will leave the data line
released to enable the master to generate the Stop
condition.
4.1.7
TIME-OUT
If the SCL stays low or high for the time specified by
tOUT, the MCP9808 temperature sensor resets the
serial interface. This dictates the minimum clock speed
as outlined in the specification.
2011-2018 Microchip Technology Inc.
MCP9808
5.0
FUNCTIONAL DESCRIPTION
The MCP9808 temperature sensors consist of a bandgap-type temperature sensor, a Delta-Sigma Analog-toDigital Converter ( ADC), user-programmable
registers and a 2-wire SMBus/I2C protocol compatible
serial interface. Figure 5-1 shows a block diagram of
the register structure.
Hysteresis
Shutdown
Critical Trip Lock
Alarm Win. Lock
Clear Alert
Alert Status
Output Control
Critical Alert Only
Band Gap
Temperature
Sensor
Alert Polarity
Alert Comp/Int
Configuration
Temperature
ADC
TUPPER Limit
TLOWER Limit
+0.5°C
+0.25°C
+0.125°C
+0.0625°C
TCRITICAL Limit
Manufacturer ID
Device ID/Rev
Resolution
Register
Pointer
SMBus/Standard I2C
Interface
A0
FIGURE 5-1:
A1
A2
Alert
SDA
SCL
VDD
GND
Functional Block Diagram.
2011-2018 Microchip Technology Inc.
DS20005095B-page 15
MCP9808
5.1
Registers
Section 5.2.3 “Alert Output Configuration”). In
addition, the Critical Temperature Limit register is used
to provide an additional critical temperature limit.
The MCP9808 has several registers that are
user-accessible. These registers include the Temperature register, Configuration register, Temperature Alert
Upper Boundary and Lower Boundary Limit registers,
Critical Temperature Limit register, Manufacturer
Identification register and Device Identification register.
The Configuration register provides access to
configure the MCP9808 device’s various features.
These registers are described in further detail in the
following sections.
The Temperature register is read-only, used to access
the ambient temperature data. This register is doublebuffered and it is updated every tCONV. The Temperature
Alert Upper Boundary and Lower Boundary Limit
registers are read/write registers. If the ambient
temperature drifts beyond the user-specified limits, the
MCP9808 outputs a signal using the Alert pin (refer to
The registers are accessed by sending a Register
Pointer to the MCP9808, using the serial interface. This
is an 8-bit write-only pointer. However, the four Least
Significant bits are used as pointers and all unused bits
(Register Pointer) need to be cleared or set to ‘0’.
Register 5-1 describes the pointer or the address of
each register.
REGISTER 5-1:
REGISTER POINTER (WRITE-ONLY)
W-0
W-0
W-0
W-0
—
—
—
—
W-0
W-0
W-0
W-0
Pointer bits
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 7-4
W: Writable bits
Write ‘0’.
Bits 7-4 must always be cleared or written to ‘0’. This device has additional registers that are reserved
for test and calibration. If these registers are accessed, the device may not perform according to the
specification.
bit 3-0
Pointer bits
0000 =RFU, Reserved for Future Use (Read-Only register)
0001 =Configuration register (CONFIG)
0010 =Alert Temperature Upper Boundary Trip register (TUPPER)
0011 =Alert Temperature Lower Boundary Trip register (TLOWER)
0100 =Critical Temperature Trip register (TCRIT)
0101 =Temperature register (TA)
0110 =Manufacturer ID register
0111 =Device ID/Revision register
1000 =Resolution register
1xxx =Reserved(1)
Note 1:
Some registers contain calibration codes and should not be accessed.
DS20005095B-page 16
2011-2018 Microchip Technology Inc.
MCP9808
TABLE 5-1:
BIT ASSIGNMENT SUMMARY FOR ALL REGISTERS
(See Section 5.3, Summary of Power-on Default for Power-on Defaults)
Register
Pointer
(Hex)
MSB/
LSB
7
6
5
4
3
2
1
0
0x00
MSB
0
0
0
0
0
0
0
0
LSB
0
0
0
1
1
1
1
1
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
Bit Assignment
MSB
0
0
0
0
0
LSB
Crt Loc
Win Loc
Int Clr
Alt Stat
Alt Cnt
Alt Sel
Alt Pol
Alt Mod
MSB
0
0
0
SIGN
27°C
26°C
25°C
24°C
LSB
23°C
22°C
21°C
20°C
2-1°C
2-2°C
7
Hysteresis
6
SHDN
0
0
5
4
MSB
0
0
0
SIGN
2 °C
2 °C
2 °C
LSB
23°C
22°C
21°C
20°C
2-1°C
2-2°C
0
0
MSB
0
0
0
SIGN
27°C
26°C
25°C
24°C
LSB
23°C
22°C
21°C
20°C
2-1°C
2-2°C
7
6
2 °C
0
0
5
4
MSB
TA TCRIT
TA TUPPER
TA TLOWER
SIGN
2 °C
2 °C
2 °C
2 °C
LSB
23°C
22°C
21°C
20°C
2-1°C
2-2°C
2-3°C
2-4°C
MSB
0
0
0
0
0
0
0
0
LSB
0
1
0
1
0
1
0
0
MSB
0
0
0
0
0
1
0
0
LSB
0
0
0
0
0
0
0
0
LSB
0
0
0
0
0
0
1
1
2011-2018 Microchip Technology Inc.
DS20005095B-page 17
MCP9808
5.1.1
SENSOR CONFIGURATION
REGISTER (CONFIG)
user-specified
temperature
boundary
(see
Section 5.2.2 “Temperature Hysteresis (THYST)”.
The Continuous Conversion or Shutdown mode is
selected using bit 8. In Shutdown mode, the band gap
temperature sensor circuit stops converting
temperature and the Ambient Temperature register
(TA) holds the previous temperature data (see
Section 5.2.1 “Shutdown Mode”). Bits 7 and 6 are
used to lock the user-specified boundaries TUPPER,
TLOWER and TCRIT to prevent an accidental rewrite.
The Lock bits are cleared by resetting the power. Bits 5
through 0 are used to configure the temperature Alert
output pin. All functions are described in Register 5-2
(see Section 5.2.3 “Alert Output Configuration”).
The MCP9808 has a 16-bit Configuration register
(CONFIG) that allows the user to set various functions for
a robust temperature monitoring system. Bits 10 through
0 are used to select the temperature alert output
hysteresis, device shutdown or Low-Power mode,
temperature boundary and critical temperature lock, and
temperature Alert output enable/disable. In addition, Alert
output condition (output set for TUPPER and TLOWER
temperature boundary or TCRIT only), Alert output status
and Alert output polarity and mode (Comparator Output
or Interrupt Output mode) are user-configurable.
The temperature hysteresis bits 10 and 9 can be used
to prevent output chatter when the ambient
temperature
gradually
changes
beyond
the
REGISTER 5-2:
CONFIG: CONFIGURATION REGISTER ( ADDRESS ‘0000 0001’b)
U-0
U-0
U-0
U-0
U-0
—
—
—
—
—
R/W-0
R/W-0
THYST
R/W-0
SHDN
bit 15
bit 8
R/W-0
R/W-0
R/W-0
R-0
R/W-0
R/W-0
R/W-0
R/W-0
Crit. Lock
Win. Lock
Int. Clear
Alert Stat.
Alert Cnt.
Alert Sel.
Alert Pol.
Alert Mod.
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
bit 15-11
Unimplemented: Read as ‘0’
bit 10-9
THYST: TUPPER and TLOWER Limit Hysteresis bits
00 =0°C (power-up default)
01 =+1.5°C
10 =+3.0°C
11 =+6.0°C
x = Bit is unknown
(Refer to Section 5.2.3 “Alert Output Configuration”.)
This bit can not be altered when either of the Lock bits are set (bit 6 and bit 7).
This bit can be programmed in Shutdown mode.
bit 8
SHDN: Shutdown Mode bit
0 = Continuous conversion (power-up default)
1 = Shutdown (Low-Power mode)
In shutdown, all power-consuming activities are disabled, though all registers can be written to or read.
This bit cannot be set to ‘1’ when either of the Lock bits is set (bit 6 and bit 7). However, it can be
cleared to ‘0’ for continuous conversion while locked (refer to Section 5.2.1 “Shutdown Mode”).
DS20005095B-page 18
2011-2018 Microchip Technology Inc.
MCP9808
REGISTER 5-2:
bit 7
CONFIG: CONFIGURATION REGISTER ( ADDRESS ‘0000 0001’b)
Crit. Lock: TCRIT Lock bit
0 = Unlocked. TCRIT register can be written (power-up default)
1 = Locked. TCRIT register can not be written
When enabled, this bit remains set to ‘1’ or locked until cleared by an internal Reset (Section 5.3
“Summary of Power-on Default”).
This bit can be programmed in Shutdown mode.
bit 6
Win. Lock: TUPPER and TLOWER Window Lock bit
0 = Unlocked; TUPPER and TLOWER registers can be written (power-up default)
1 = Locked; TUPPER and TLOWER registers can not be written
When enabled, this bit remains set to ‘1’ or locked until cleared by a Power-on Reset (Section 5.3
“Summary of Power-on Default”).
This bit can be programmed in Shutdown mode.
bit 5
Int. Clear: Interrupt Clear bit
0 = No effect (power-up default)
1 = Clear interrupt output; when read, this bit returns to ‘0’
This bit can not be set to ‘1’ in Shutdown mode, but it can be cleared after the device enters Shutdown
mode.
bit 4
Alert Stat.: Alert Output Status bit
0 = Alert output is not asserted by the device (power-up default)
1 = Alert output is asserted as a comparator/Interrupt or critical temperature output
This bit can not be set to ‘1’ or cleared to ‘0’ in Shutdown mode. However, if the Alert output is configured as Interrupt mode, and if the host controller clears to ‘0’, the interrupt, using bit 5 while the device
is in Shutdown mode, then this bit will also be cleared ‘0’.
bit 3
Alert Cnt.: Alert Output Control bit
0 = Disabled (power-up default)
1 = Enabled
This bit can not be altered when either of the Lock bits are set (bit 6 and bit 7).
This bit can be programmed in Shutdown mode, but the Alert output will not assert or deassert.
bit 2
Alert Sel.: Alert Output Select bit
0 = Alert output for TUPPER, TLOWER and TCRIT (power-up default)
1 = TA > TCRIT only (TUPPER and TLOWER temperature boundaries are disabled)
When the Alarm Window Lock bit is set, this bit cannot be altered until unlocked (bit 6).
This bit can be programmed in Shutdown mode, but the Alert output will not assert or deassert.
bit 1
Alert Pol.: Alert Output Polarity bit
0 = Active-low (power-up default; pull-up resistor required)
1 = Active-high
This bit cannot be altered when either of the Lock bits are set (bit 6 and bit 7).
This bit can be programmed in Shutdown mode, but the Alert output will not assert or deassert.
bit 0
Alert Mod.: Alert Output Mode bit
0 = Comparator output (power-up default)
1 = Interrupt output
This bit cannot be altered when either of the Lock bits are set (bit 6 and bit 7).
This bit can be programmed in Shutdown mode, but the Alert output will not assert or deassert.
2011-2018 Microchip Technology Inc.
DS20005095B-page 19
MCP9808
Writing to the CONFIG Register to Enable the Event Output Pin b:
1
2
3
4
5
6
7
8
0
0
1
1
A
2
A
1
A
0
W C
1
2
3
4
5
6
7
8
0
0
0
0
0
0
0
1
SCL
SDA
S
A
K
Address Byte
A
C
K
Configuration Pointer
MCP9808
MCP9808
1
2
3
4
5
6
7
8
0
0
0
0
0
0
0
0
A
C
K
1
2
3
4
5
6
7
8
0
0
0
0
1
0
0
0
MSB Data
A
C
K
P
LSB Data
MCP9808
MCP9808
Note: This is an example routine (see Appendix A: “Source Code”).
i2c_start();
// send START command
i2c_write(AddressByte & 0xFE);
//WRITE Command (see Section 4.1.4 “Address Byte”)
//also, make sure bit 0 is cleared ‘0’
i2c_write(0x01);
// Write CONFIG Register
i2c_write(0x00);
// Write data
i2c_write(0x08);
// Write data
i2c_stop();
// send STOP command
FIGURE 5-2:
Timing Diagram for Writing to the Configuration Register (see Section 4.0 “Serial
Communication”).
DS20005095B-page 20
2011-2018 Microchip Technology Inc.
MCP9808
Reading the CONFIG Register:
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
Note:
SCL
SDA
0
S
0
1
A
1
A
2
1
A
A
0
W C
K
0
Address Byte
0
0
0
0
0
0
It is not necessary to
select the Register
Pointer if it was set
from the previous
read/write.
A
C
K
1
Configuration Pointer
MCP9808
1
2
3
4
5
6
7
8
0
0
1
1
A
2
A
1
A
0
R C
MCP9808
1
2
3
4
5
6
7
8
0
0
0
0
0
0
0
0
1
2
3
4
5
6
7
8
0
0
0
0
1
0
0
0
SCL
SDA
S
A
K
Address Byte
A
C
K
MSB Data
MCP9808
N
A
K
P
LSB Data
Master
Master
Note: This is an example routine (see Appendix A: “Source Code”).
i2c_start();
// send START command
i2c_write(AddressByte & 0xFE);
//WRITE Command (see Section 4.1.4 “Address Byte”)
//also, make sure bit 0 is cleared ‘0’
i2c_write(0x01);
// Write CONFIG Register
i2c_start();
// send Repeat START command
i2c_write(AddressByte | 0x01);
//READ Command
//also, make sure bit 0 is set ‘1’
UpperByte = i2c_read(ACK);
// READ 8 bits
//and Send ACK bit
LowerByte = i2c_read(NAK);
// READ 8 bits
//and Send NAK bit
i2c_stop();
// send STOP command
FIGURE 5-3:
Timing Diagram for Reading from the Configuration Register (see Section 4.0 “Serial
Communication”).
2011-2018 Microchip Technology Inc.
DS20005095B-page 21
MCP9808
5.1.2
UPPER/LOWER/CRITICAL
TEMPERATURE LIMIT REGISTERS
(TUPPER/TLOWER/TCRIT)
The MCP9808 has a 16-bit read/write Alert Output
Temperature Upper Boundary register (TUPPER), a 16-bit
Lower Boundary register (TLOWER) and a 16-bit Critical
Boundary register (TCRIT) that contain 11-bit data in
two’s complement format (0.25°C). This data represents
REGISTER 5-3:
the maximum and minimum temperature boundary or
temperature window that can be used to monitor
ambient temperature. If this feature is enabled
(Section 5.1.1 “Sensor Configuration Register
(CONFIG)”) and the ambient temperature exceeds the
specified boundary or window, the MCP9808 asserts an
Alert output. (Refer to Section 5.2.3 “Alert Output
Configuration”).
TUPPER/TLOWER/TCRIT UPPER/LOWER/CRITICAL TEMPERATURE LIMIT REGISTER
( ADDRESS ‘0000 0010’b/‘0000 0011’b/‘0000 0100’b)(1)
U-0
U-0
U-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
—
—
—
Sign
27°C
26°C
25°C
24°C
bit 15
bit 8
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
U-0
U-0
23°C
22°C
21°C
20°C
2-1°C
2-2°C
—
—
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
bit 15-13
Unimplemented: Read as ‘0’
bit 12
Sign: Sign bit
0 = TA 0°C
1 = TA 0°C
bit 11-2
TUPPER/TLOWER/TCRIT: Temperature Boundary bits
Temperature boundary trip data in two’s complement format.
bit 1-0
Unimplemented: Read as ‘0’
Note 1:
x = Bit is unknown
This table shows two 16-bit registers for TUPPER, TLOWER and TCRIT, located at ‘0000 0010b’,
‘0000 0011b’ and ‘0000 0100b’, respectively.
DS20005095B-page 22
2011-2018 Microchip Technology Inc.
MCP9808
Writing +90°C to the TUPPER Register b:
1
2
3
4
5
6
7
8
0
0
1
1
A
2
A
1
A
0
W C
1
2
3
4
5
6
7
8
0
0
0
0
0
0
1
0
SCL
SDA
S
A
K
Address Byte
A
C
K
TUPPER Pointer
MCP9808
MCP9808
1
2
3
4
5
6
7
8
0
0
0
0
0
1
0
1
A
C
K
1
2
3
4
5
6
7
8
1
0
1
0
0
0
0
0
MSB Data
A
C
K
P
LSB Data
MCP9808
MCP9808
Reading from the TUPPER Register:
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
Note:
SCL
SDA
S
0
0
1
1
A
2
A
1
A
0
A
W C
K
0
Address Byte
0
0
0
0
0
1
0
It is not necessary to
select the Register
Pointer if it was set
from the previous
read/write.
A
C
K
TUPPER Pointer
MCP9808
MCP9808
1
2
3
4
5
6
7
8
0
0
1
1
A
2
A
1
A
0
R C
1
2
3
4
5
6
7
8
0
0
0
0
0
1
0
1
1
2
3
4
5
6
7
8
1
0
1
0
0
0
0
0
SCL
SDA
S
A
K
Address Byte
A
C
K
MSB Data
MCP9808
N
A
K
P
LSB Data
Master
Master
FIGURE 5-4:
Timing Diagram for Writing and Reading from the TUPPER Register (see Section 4.0
“Serial Communication”).
2011-2018 Microchip Technology Inc.
DS20005095B-page 23
MCP9808
5.1.3
AMBIENT TEMPERATURE
REGISTER (TA)
In addition, the TA register uses three bits (TA)
to reflect the Alert pin state. This allows the user to
identify the cause of the Alert output trigger (see
Section 5.2.3 “Alert Output Configuration”); bit 15 is
set to ‘1’ if TA is greater than or equal to TCRIT, bit 14 is
set to ‘1’ if TA is greater than TUPPER and bit 13 is set to
‘1’ if TA is less than TLOWER.
The MCP9808 uses a band gap temperature sensor
circuit to output analog voltage proportional to absolute
temperature. An internal ADC is used to convert the
analog voltage to a digital word. The digital word is
loaded to a 16-bit read-only Ambient Temperature
register (TA) that contains 13-bit temperature data in
two’s complement format.
The TA register bit assignment and boundary
conditions are described in Register 5-4.
The TA register bits (TA) are double-buffered.
Therefore, the user can access the register, while in the
background, the MCP9808 performs an Analog-toDigital conversion. The temperature data from the
ADC is loaded in parallel to the TA register at tCONV
refresh rate.
REGISTER 5-4:
TA: AMBIENT TEMPERATURE REGISTER ( ADDRESS ‘0000 0101’b)(1)
R-0
R-0
R-0
TA vs. TCRIT(1)
TA vs. TUPPER(1)
TA vs. TLOWER(1)
R-0
R-0
R-0
R-0
R-0
SIGN
27 °C
26 °C
25 °C
24 °C
bit 15
bit 8
R-0
3 °C
2
R-0
R-0
R-0
R-0
R-0
R-0
R-0
22 °C
21 °C
20 °C
2-1 °C
2-2 °C(2)
2-3 °C(2)
2-4 °C(2)
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
bit 15
TA vs. TCRIT bit(1)
0 = TA TCRIT
1 = TA TCRIT
bit 14
TA vs. TUPPER bit(1)
0 = TA TUPPER
1 = TA TUPPER
bit 13
TA vs. TLOWER bit(1)
0 = TA TLOWER
1 = TA TLOWER
bit 12
SIGN bit
0 = TA 0°C
1 = TA 0°C
bit 11-0
TA: Ambient Temperature bits(2)
12-bit ambient temperature data in two’s complement format.
Note 1:
2:
x = Bit is unknown
Bits 15, 14 and 13 are not affected by the status of the Alert Output Configuration (CONFIG bits,
Register 5-2).
Bits 2, 1 and 0 may remain clear at ‘0’ depending on the status of the Resolution register (Register 5-7).
The power-up default is 0.25°C/bit; bits 1 and 0 remain clear ‘0’.
DS20005095B-page 24
2011-2018 Microchip Technology Inc.
MCP9808
5.1.3.1
TA Bits to Temperature Conversion
To convert the TA bits to decimal temperature, the
upper three boundary bits (TA) must be
masked out. Then, determine the SIGN bit (bit 12) to
check positive or negative temperature, shift the bits
accordingly, and combine the upper and lower bytes of
the 16-bit register. The upper byte contains data for
temperatures greater than +32°C while the lower byte
contains data for temperature less than +32°C, including fractional data. When combining the upper and
lower bytes, the upper byte must be right-shifted by
4 bits (or multiply by 24) and the lower byte must be leftshifted by 4 bits (or multiply by 2-4). Adding the results
of the shifted values provides the temperature data in
decimal format (see Equation 5-1).
instruction code, outlined in Example 5-1, shows the
communication flow; also see Figure 5-5 for the timing
diagram.
EQUATION 5-1:
Temperature TA 0°C
4
–4
T A = UpperByte 2 + LowerByte 2
Temperature 0°C
4
–4
T A = 256 – UpperByte 2 + LowerByte 2
Where:
TA = Ambient Temperature (°C)
UpperByte = TA bit 15 to bit 8
The temperature bits are in two’s compliment format,
therefore, positive temperature data and negative temperature data are computed differently. Equation 5-1
shows the temperature computation. The example
EXAMPLE 5-1:
BYTES TO
TEMPERATURE
CONVERSION
LowerByte = TA bit 7 to bit 0
SAMPLE INSTRUCTION CODE
This example routine assumes the variables and I2C communication subroutines are predefined
(see Appendix A: “Source Code”):
i2c_start();
// send START command
i2c_write (AddressByte & 0xFE);
//WRITE Command (see Section 4.1.4 “Address Byte”)
//also, make sure bit 0 is cleared ‘0’
i2c_write(0x05);
// Write TA Register Address
i2c_start();
//Repeat START
i2c_write(AddressByte | 0x01);
// READ Command (see Section 4.1.4 “Address Byte”)
//also, make sure bit 0 is Set ‘1’
UpperByte = i2c_read(ACK);
// READ 8 bits
//and Send ACK bit
LowerByte = i2c_read(NAK);
// READ 8 bits
//and Send NAK bit
i2c_stop();
// send STOP command
//Convert the temperature data
//First Check flag bits
if ((UpperByte & 0x80) == 0x80){
//TA ≥ TCRIT
}
if ((UpperByte & 0x40) == 0x40){
//TA > TUPPER
}
if ((UpperByte & 0x20) == 0x20){
//TA < TLOWER
}
UpperByte = UpperByte & 0x1F;
//Clear flag bits
if ((UpperByte & 0x10) == 0x10){
//TA < 0°C
UpperByte = UpperByte & 0x0F;//Clear SIGN
Temperature = 256 - (UpperByte x 16 + LowerByte / 16);
}else
//TA
≥ 0°C
Temperature = (UpperByte x 16 + LowerByte / 16);
//Temperature = Ambient Temperature (°C)
2011-2018 Microchip Technology Inc.
DS20005095B-page 25
MCP9808
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
Note:
SCL
SDA
S
0
0
1
1
A
2
A
1
A
0
A
W C
K
0
0
Address Byte
0
0
0
1
0
1
It is not necessary to
select the Register
Pointer if it was set from
the previous read/write.
A
C
K
TA Pointer
MCP9808
1
2
3
4
5
6
7
8
0
0
1
1
A
2
A
1
A
0
R C
MCP9808
1
2
3
4
5
6
7
8
0
0
0
0
0
0
0
1
1
2
3
4
5
6
7
8
1
0
0
1
0
1
0
0
SCL
SDA
S
A
K
Address Byte
A
C
K
MSB Data
MCP9808
N
A
K
P
LSB Data
Master
Master
FIGURE 5-5:
Timing Diagram for Reading +25.25°C Temperature from the TA Register
(see Section 4.0 “Serial Communication”).
DS20005095B-page 26
2011-2018 Microchip Technology Inc.
MCP9808
5.1.4
MANUFACTURER ID REGISTER
This register is used to identify the manufacturer of the
device in order to perform manufacturer-specific
operation. The Manufacturer ID for the MCP9808 is
0x0054 (hexadecimal).
REGISTER 5-5:
MANUFACTURER ID REGISTER – READ-ONLY ( ADDRESS ‘0000 0110’b)
R-0
R-0
R-0
R-0
R-0
R-0
R-0
R-0
Manufacturer ID
bit 15
bit 8
R-0
R-1
R-0
R-1
R-0
R-1
R-0
R-0
Manufacturer ID
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
bit 15-0
x = Bit is unknown
Device Manufacturer Identification bits
1
2
3
4
5
6
7
8
0
0
1
1
A
2
A
1
A
0
W C
K
1
2
3
4
5
6
7
8
0
0
0
0
0
1
1
0
Note:
SCL
SDA
S
A
Address Byte
It is not necessary to
select the Register
Pointer if it was set
from the previous
read/write.
A
C
K
Manufacturer ID Pointer
MCP9808
1
2
3
4
5
6
7
8
0
0
1
1
A
2
A
1
A
0
R C
MCP9808
1
2
3
4
5
6
7
8
0
0
0
0
0
0
0
0
1
2
3
4
5
6
7
8
0
1
0
1
0
1
0
0
SCL
SDA
S
A
K
Address Byte
A
C
K
MSB Data
MCP9808
N
A
K
P
LSB Data
Master
Master
FIGURE 5-6:
Timing Diagram for Reading the Manufacturer ID Register (see Section 4.0 “Serial
Communication”).
2011-2018 Microchip Technology Inc.
DS20005095B-page 27
MCP9808
5.1.5
DEVICE ID AND REVISION
REGISTER
The upper byte of this register is used to specify the
device identification and the lower byte is used to
specify the device revision. The Device ID for the
MCP9808 is 0x04 (hex).
The revision begins with 0x00 (hex) for the first release,
with the number being incremented as revised versions
are released.
REGISTER 5-6:
DEVICE ID AND DEVICE REVISION – READ-ONLY ( ADDRESS ‘0000 0111’b)
R-0
R-0
R-0
R-0
R-0
R-1
R-0
R-0
Device ID
bit 15
bit 8
R-0
R-0
R-0
R-0
R-0
R-0
R-0
R-0
Device Revision
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
bit 15-8
Device ID: Bit 15 to bit 8 are used for device ID
bit 7-0
Device Revision: Bit 7 to bit 0 are used for device revision
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
x = Bit is unknown
8
Note:
SCL
SDA
S
0
0
1
1
A
2
A
1
A
0
A
W C
K
0
Address Byte
0
0
0
0
1
1
1
It is not necessary to
select the Register
Pointer if it was set
from the previous
read/write.
A
C
K
Device ID Pointer
MCP9808
1
2
3
4
5
6
7
8
0
0
1
1
A
2
A
1
A
0
R C
MCP9808
1
2
3
4
5
6
7
8
0
0
0
0
0
1
0
0
1
2
3
4
5
6
7
8
0
0
0
0
0
0
0
0
SCL
SDA
S
A
K
Address Byte
A
C
K
MSB Data
MCP9808
N
A
K
P
LSB Data
Master
Master
FIGURE 5-7:
Timing Diagram for Reading Device ID and Device Revision Register (see
Section 4.0 “Serial Communication”).
DS20005095B-page 28
2011-2018 Microchip Technology Inc.
MCP9808
5.1.6
RESOLUTION REGISTER
This register allows the user to change the sensor
resolution
(see
Section 5.2.4
“Temperature
Resolution”). The POR default resolution is
+0.0625°C. The selected resolution is also reflected in
the Capability register (see Register 5-2).
REGISTER 5-7:
RESOLUTION REGISTER ( ADDRESS ‘0000 1000’b)
U-0
U-0
U-0
U-0
U-0
U-0
—
—
—
—
—
—
R/W-1
R/W-1
Resolution
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
bit 7-2
Unimplemented: Read as ‘0’
bit 1-0
Resolution bits
00 = +0.5°C (tCONV = 30 ms typical)
01 = +0.25°C (tCONV = 65 ms typical)
10 = +0.125°C (tCONV = 130 ms typical)
11 = +0.0625°C (power-up default, tCONV = 250 ms typical)
1
2
3
4
5
6
7
8
0
0
1
1
A
2
A
1
A
0
W C
1
2
3
4
5
6
7
8
0
0
0
0
1
0
0
0
x = Bit is unknown
1
2
3
4
5
6
7
8
0
0
0
0
0
0
1
1
SCL
SDA
S
A
K
Address Byte
A
C
K
Resolution Pointer
MCP9808
A
C
K
P
Data
MCP9808
MCP9808
FIGURE 5-8:
Timing Diagram for Changing TA Resolution to +0.0625°C b (see
Section 4.0 “Serial Communication”).
2011-2018 Microchip Technology Inc.
DS20005095B-page 29
MCP9808
5.2
5.2.1
SENSOR FEATURE DESCRIPTION
Shutdown mode disables all power consuming
activities (including temperature sampling operations)
while leaving the serial interface active. This mode is
selected by setting bit 8 of CONFIG to ‘1’. In this mode,
the device consumes ISHDN. It remains in this mode
until bit 8 is cleared to ‘0’ to enable Continuous
Conversion mode or until power is recycled.
The Shutdown bit (bit 8) cannot be set to ‘1’ while the
CONFIG bits (Lock bits) are set to ‘1’. However, it
can be cleared to ‘0’ or returned to Continuous
Conversion mode while locked.
In Shutdown mode, all registers can be read or written.
However, the serial bus activity increases the shutdown
current. In addition, if the device is in shutdown while
the Alert pin is asserted, the device will retain the active
state during shutdown. This increases the shutdown
current due to the additional Alert output current.
5.2.2
TEMPERATURE HYSTERESIS
(THYST)
A hysteresis of 0°C, +1.5°C, +3°C or +6°C can be
selected for the TUPPER, TLOWER and TCRIT temperate
boundaries, using bits 10 and 9 of CONFIG. The
hysteresis applies for decreasing temperature only (hot
to cold) or as temperature drifts below the specified
limit.
The Hysteresis bits can not be changed if either of the
Lock bits (CONFIG
