2005-2013 Microchip Technology Inc. DS21977C-page 1
MCP9805
Features
• Meets JEDEC Standard JC42.4 for Mobile
Platform Memory Module Thermal Sensor
• Temperature - to-Di gital Converter
• Accuracy with 0.25 °C/LSb Resolution:
- ±1°C (max.) from +75°C to +95°C
- ±2°C (max.) from +40°C to +125°C
- ±3°C (max.) from -20°C to +125°C
• Programmable Temperature Monitor Boundary
• Critical Tempe rature Output
• Operating Voltage Range: 3.0V to 3.6V
• 2-wire Interface: SMBus/Standard mode I2C™
Compatible
• Operating Current: 200 µA (typ.)
• Shutdown Current: 0.1 µA (typ.)
• Available Packages : 2x3 D FN-8, TSS OP-8
Typical Applications
• Dual In-line Memory Module (DIMM)
• Personal Computers (PCs) and Servers
• Hard Disk Drives and Other PC Peripherals
• General Purpose Temperature Sensor
Typical Application
Description
Microc hip Technology Inc .’s MCP98 05 digit al tem pe ra-
ture sensor converts temperatures between -40°C and
+125°C to a digital word. This sensor is designed to
meet the JEDEC standard JC42.4 for Mobile Platform
Memory Modul e Thermal Se nsor. This dev ice pr ovide s
an accuracy of ±1°C (max.) from a temperature range
of +75° C to +95°C (activ e range) an d ±2°C (max.) from
+40°C to +125°C (monitor range) as defined in the
JEDEC standard.
The MCP9805 comes with user-programmable
registers that provide flexibility for DIMM
temperature-sensing applications. The registers allow
user-selectable settings such as Shutdown or
Low-Power modes and the specification of tempera-
ture event and critical output boundaries. When the
temperature changes beyond the specified boundary
limit s , the M C P980 5 ou tpu ts an Event si gnal. The user
has th e option o f setting the Event output signal polarity
as either an active-low or active-high comparator
output for thermostat operation, or as a temperature
event interrupt output for microprocessor-based
system s. The Event output can also be configur ed as a
critical temperature output.
This sensor has a 2-wire industry-standard SMBus
and Standard mode I2C compatible (100 kHz bus
clock) serial interface protocol, allowing up to eight sen-
sors t o be contr olle d in a singl e serial bus. Th ese fea-
tures make the MCP9805 ideal for sophisticated
multi-zone temperature-monitoring applications.
Package Types
Memory
Memory Module
SPD*Temperature
Sensor
EEPROM MCP9805
3.3 VDD_SPD SDA SCLK
R
R
Event
* Serial Presence Detect
SDA
GND
Event
SCLK
8-Pin DFN (2x3)
A0 VDD
A1
A2
1
2
3
4
8
7
6
5
SDA
GND
Event
SCLK
MCP9805
1
2
3
4
8-Pin TSSOP
A0 VDD
A1
A2
8
7
6
5
Memory Module Digital Temperature Sensor
MCP9805
DS21977C-page 2 2005-2013 Microchip Technology Inc.
1.0 ELECTRICAL
CHARACTERISTICS
Absolute Maximum Ratings †
VDD....................................................................... 6.0V
Voltage at all Input/O utp ut pin s .... GND – 0.3V to 5.5V
Storage temperature ..........................-65°C to +150°C
Ambient temp. with power applied .....-40°C to +125°C
Junction Temperature (TJ)................................+150°C
ESD protection on all pins (HBM:MM)....... (4 kV:200V)
Latch-Up Current at each pin........................ ±200 mA
†Notice: Stresses above those listed under “Maximum
ratings” may c ause permanent dam age 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 m aximum rating conditions for extended periods
may affect device reliability.
DC CHARACTERISTICS
Electrical S p ecifica tions: U nless otherwis e indi cated , VDD = 3.0 V to 3.6V, GND = G round an d TA = -20°C to +12 5°C.
Parameters Sym Min Typ Max Unit Conditions
Power Supply
Operati ng Volt age Range VDD 3.0 — 3.6 V
Operati ng Curren t IDD — 200 500 µA Continuous Operation
Shutdown Current ISHDN — 0.1 2 µA Shut d ow n Mod e
Power-On Reset Threshold (POR) VPOR —2.2—VV
DD Falling Edge
Power Supply Rejection PSRDC —±0.3—°C
PSRAC —±0.5—°CV
DD = 3.3V + 150 mVpp
(0 to 1 MHz), TA = +25°C
Temperature Sensor Accuracy
Accuracy with 0.25 °C/LSb Resolution:
+75°C to +95°C TACY -1.0 ±0.5 +1.0 °C Active Temp. Range
+40°C to +125°C TACY -2.0 ±1.0 +2.0 °C Monitor Temp. Range
-20°C to +125°C TACY -3.0 ±2.0 +3.0 °C
TA = -40°C TACY —±2—°C
Internal  ADC
Conversion Time (10-bits + Sign):
0.25 °C/LSb tCONV — 65 125 ms 17 samples/sec. (typ.)
Event Output (Open-Drain)
High-Level Current (leakage) IOH ——1µAV
OH = 3.6V
Low-Level Voltage VOL ——0.4VI
OL= 3 mA
Thermal Response
Response Time (Note):
DFN tRES — 0.7 — s Time to 63% of +22°C (Air)
to +125°C (Oil Bath)
TSSOP tRES —1.5—s
Note: Thermal response with 1x1 inch dual-sided copper clad.
2005-2013 Microchip Technology Inc. DS21977C-page 3
MCP9805
Graphical Symbol Description
DIGITAL INPUT/OUTPUT PIN CHARACTERISTICS
Electrical S p ecifica tions: U nless otherwis e indi cated, VDD = 3.0V to 3.6 V, GND = Ground and TA = -20°C to +125°C.
Parameters Sym Min Typ Max Units Conditions
Serial Input/Output (SCLK, SDA, A0, A1, A2)
Input
High-L ev el Voltage VIH 2.1 — — V
Low-Level Voltage VIL ——0.8V
Input Current IIN ——±5µA
Output (SDA)
Low-Level Voltage VOL ——0.4VI
OL= 3 mA
High-Level Current (leakage) IOH ——1µAV
OH = 3.6V
Low-Level Current IOL 6——mAV
OL = 0.6V
Capacitance CIN —5—pF
SDA and SCLK Inputs
Hysteresis VHYST —0.5—V
VDD VIH
VIL
IIN
Voltage
Current
time
time
VDD
IOH
Voltage
Current
time
time
SDA & SCLK INPUTS SDA OUTPUT
VOL
IOL
MCP9805
DS21977C-page 4 2005-2013 Microchip Technology Inc.
Timing Diagram
SERIAL INTERFACE TIMING CHARACTERISTICS
Electrical Specifications: Unless otherwise indicated, VDD = 3.0V to 3.6V, GND = Ground, TA = -20°C to +125°C,
CL = 80 pF and all limits measured to 50% point.
Parameters Sym Min Typ Max Units Conditions
2-Wire SMBus/Standard Mode I2C™ Compat ible Interfa ce (Note)
Serial Port Clock Frequency fSC 10 — 100 kHz
Low Clock tLOW 4.7 — — µs
High Clock tHIGH 4.0 — — µs
Rise Time tR— — 1000 ns (VIL MAX - 0.15V) to (VIH MIN + 0.15V)
Fall Time tF— — 300 ns (VIH MIN + 0.15V) to (VIL MAX - 0.15V)
Data Setup Before SCLK High tSU-DATA 250 — — ns
Data Hold After SCLK Low tHD-DATA 300 — — ns
Start Condition Setup Time tSU-START 4.7 — — µs
Start Condition Hold Time tHD-START 4.0 — — µs
Stop Condition Setup Time tSU-STOP 4.0 — — µs
Bus Free tB-FREE 4.7 — — µs
Time Out tOUT 25 40 50 ms
Note: The serial interface specification min./max. limits are specified by characterization (not production tested).
tSU-START
tH-START
tSU-DATA
tSU-STOP
tB-FREE
SCLK
SDA
tH-DATA
tHIGH tLOW
tOUT tR, tF
START Condition Data Transmission STOP Condition
TEMPERATURE CHARACTERISTICS
Electrical Specifications: Unless otherwise indicated, VDD = 3.0V to 3.6V, GND = Ground.
Parameters Sym Min Typ Max Units Conditions
Temperature Ranges
Specifie d Temperature R ange TA-20 — +125 °C
Operati ng Temperature Range TA-40 — +125 °C Note 1
Storage Temperature Range TA-65 — +150 °C
Thermal Package Resistances
Thermal Resistance, 8L-DFN JA —41—°C/W
Thermal Resistance, 8L-TSSOP JA — 123.7 — °C/W
Note 1: Operation in this range must not cause TJ to exceed Maximum Junction Temperature (+150°C).
2005-2013 Microchip Technology Inc. DS21977C-page 5
MCP9805
2.0 TYP ICAL PERFORMANCE CURVES
Note: Unless oth erwise noted: VDD = 3.0V to 3.6V, GND = Ground, Cde_cap = 0.1 µF
FIGURE 2-1: Average Temperatu re
Accuracy.
FIGURE 2-2: Temperature Accuracy
Histogram, TA = +95°C.
FIGURE 2-3: Temperature Accuracy
Histogram, TA = +75°C.
FIGURE 2-4: Supply Current vs. Ambient
Temperature.
FIGURE 2-5: Shutdown Current vs.
Ambient Temperatu re .
FIGURE 2-6: Power-on Reset Threshold
Voltage vs. Ambient Temperature.
Note: The g r ap hs and t ables prov id ed followi ng thi s n ote are a st a tis tic al s umm ar y b as ed on a lim ite d 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.
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
-40-200 20406080100120
TA (°C)
Temperature Accuracy (°C)
VDD= 3.3V to 3.6V
Spec. Limits
0%
10%
20%
30%
40%
50%
60%
70%
-1.00
-0.75
-0.50
-0.25
0.00
0.25
0.50
0.75
1.00
Temperature Accuracy (°C)
Occurrences
TA = +95°C
VDD = 3.3V
120 samples
0%
10%
20%
30%
40%
50%
60%
70%
-1.00
-0.75
-0.50
-0.25
0.00
0.25
0.50
0.75
1.00
Temperature Accuracy (°C)
Occurrences
TA = +75°C
VDD = 3.3V
120 samples
100
150
200
250
300
350
400
450
500
-40-200 20406080100120
TA (°C)
IDD (µA)
VDD = 3.3V to 3.6V
0.00
0.50
1.00
1.50
2.00
-40-200 20406080100120
TA (°C )
ISHDN (µA)
VDD = 3.3V to 3.6V
0
0.5
1
1.5
2
2.5
3
-40-200 20406080100120
TA (°C)
VPOR (V)
MCP9805
DS21977C-page 6 2005-2013 Microchip Technology Inc.
Note: Unless oth erwise noted: VDD = 3.0V to 3.6V, GND = Ground, Cde_cap = 0.1 µF.
FIGURE 2-7: Event and SDA VOL vs.
Ambient Temperature.
FIGURE 2-8: Conversion Rate vs.
Ambient Temperature.
FIGURE 2-9: Power Supply Rejection vs.
Frequency.
FIGURE 2-10: SDA IOL vs. Ambient
Temperature.
FIGURE 2-11: Temperature Accuracy vs.
VDD.
FIGURE 2-12: Package Thermal
Response.
0
0.1
0.2
0.3
0.4
-40-200 20406080100120
TA (°C)
Event & SDA V OL (V)
Event, VDD = 3.0V to 3.6V
SDA, VDD = 3.0V
VDD = 3.3V
VDD = 3.6V
IOL
= 3mA
35
50
65
80
95
110
125
-40 -20 0 20 40 60 80 100 120
TA (°C)
tCONV (ms)
VDD = 3.0V to 3.6V
-1.0
-0.5
0.0
0.5
1.0
100 1,000 10,000 100,000 1,000,000
Frequency (Hz)
Normalized Temp. Error (°C)
PSRAC, VDD = 3.3V + 150mVPP (AC) TA = 25°C
100 1k 10k 100k 1M100k 1M10k 100k 1M1k 10k 100k 1M
1k 10k 100k 1M
TA = +25°C
No decoupling capacitor
6
12
18
24
30
36
42
48
-40-200 20406080100120
TA (°C)
SDA IOL (mA)
VDD
= 3.6V
VDD = 3.0V
VDD = 3.3V
VOL
= 0.6V
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
-40-200 20406080100120
TA (°C)
Temperature Accuracy (°C)
VDD = 3.0V
VDD = 3.6V PSRDC = 0.3°C/V
0%
20%
40%
60%
80%
100%
120%
-2 0 2 4 6 8 10121416
Time (s)
Thermal Response (%)
22°C (Air) to +125°C (Oil bath)
TSSOP-8
DFN-8
2005-2013 Microchip Technology Inc. DS21977C-page 7
MCP9805
3.0 PIN DESCRIPTION
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1: PIN FUNCTION TABLES
3.1 Slave Add ress Pins (A0, A1, A2 )
A0, A1 and A2 are device slave address input pins.
The address pins correspond to the Least Significant
bits (LSbs) of the address byte (see Section 5.1.4
“Address Byte”). The Most Significant bits A6, A5, A4,
A3 are factory set. This is shown in Table 3-2.
3.2 Ground Pin (GND)
The GND pin is the system ground pin.
3.3 Open-Drai n 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 5.0 “Serial
Communication”).
3.4 Open-Drain Serial Clock Line
(SCLK)
The SCLK 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 5.0 “Serial Communication”).
3.5 Open-Drain Temperature Event
Output pin (Even t)
The MCP9805 Event pin is an open-drain output. The
devi ce outputs a sig nal when t he ambien t te mperature
goes beyond the user-programmed temperature limit.
(see Section 4.2.3 “Event Output Configuration”).
3.6 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.
DFN/TSSOP Symbol Pin Function
1 A0 Slave Address
2 A1 Slave Address
3 A2 Slave Address
4 GND Ground
5 SDA Serial Data Line
6 SCLK Serial Clock Line
7 Event Temperature Event Outp ut
8V
DD Power
TABLE 3-2: MCP9805 ADDRESS BYTE
Device Address Code Slave Address
A6 A5 A4 A3 A2 A1 A0
MCP9805 0 0 1 1 X X X
Note: User-selectable address is shown by X.
MCP9805
DS21977C-page 8 2005-2013 Microchip Technology Inc.
4.0 FUNCTIONAL DESCRIPTION
The MCP9805 temperature sensors consist of a band
gap temperature sensor, a Delta-Sigma
Analog-to-Digital Converter ( ADC) and
user-programmable registers using a 2-wire
SMBus/Standard mode I2C compatible serial interface
protocol. Figure 4-1 shows a block diagram of the
register structure.
FIGURE 4-1: Register Structure Block Diagram.
Clear Event Output Interrupt
Temperature Register (TA)
Temperat ure Uppe r-Boun dar y (TUPPER)
Temperature Lower-Boundary (TLOWER)
Configuration Register
 ADC
Band Gap
Temperature
Sensor
Event Output Status
Enable/Disable Event Output
Critic al Even t Outp ut onl y
Event Output Polarity, Active-High/Low
Critical Temperature Limit (TCRIT)
Device Capa bilit y Register
Measurement Resolution
Measur eme nt Acc urac y
Temperature Event Output
Register Pointer SMBus/Standard I2C™
Interface
Critical Boundary Trip Lock
Event Boundary Window Lock bit
Continuous Conversion or Shutdown
Event Output Hysteresis
Manufacturer Identification Register
Device Identification and Revision Register
Event Output Comparator/Interrupt
Measurement Range
VDD GND SDA SCLKA2 EventA0 A1
2005-2013 Microchip Technology Inc. DS21977C-page 9
MCP9805
4.1 Registers
The MCP9805 has several registers that are
user-ac cess ible. Th ese regis ters in clude the C ap abilit y
register, Configuration register, Event Temperature
Upper-Boundary and Lower-Boundary Trip registers,
Critical Temperature Trip register, Temperature regis-
ter, Manufacturer Identification register and Device
Identification register.
The Temperature register is read-only, used to access
the ambient temperature data. The data is loaded in
parallel to this register after tCONV. The Event
Temperature Upper-Boundary and Lower-Boundary
Trip registers are read/writes. If the ambient tempera-
ture drifts beyond the user-specified limits, the
MCP9805 o utput s a signa l usin g the Ev ent pi n (refer to
Section 4.2.3 “Event Output Configuration”). In
addition, the Critical Temperature Trip register is used
to provide an additional critical temperature limit.
The Capability register is used to provide bits
describing the MCP9805’s capability in measurement
resolution, measurement range and device accuracy.
The device Configuration register provides access to
configure the MCP9805’s various features. These
registers are described in further detail in the following
sections.
The registers are accessed by sending a Register
Pointer to the MC P9805 u sing the s erial interfac e. Thi s
is an 8-bit write-only pointer. However, the three Least
Significant bits (3-LSbs) are used as pointers and all
unused bits (bits 7-3) need to be cleared or set to ‘0’.
Register 4-1 describes the pointer or the address of
each register.
REGISTER 4-1: REGISTER ADDRESS POINTER (WRITE-ONLY)
W-0 W-0 W-0 W-0 W-0 W-0 W-0 W-0
0000 0P2 P1 P0
bit 7 bit 0
bit 7-3 Writable Bits: Write ‘0’
Bits 7-3 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 2-0 Pointer Bits:
000 = Capability register
001 = Configuration register (CONFIG)
010 = Event Temperature Upper-Boundary Trip register (TUPPER)
011 = Event Temperature Lower-Boundary Trip register (TLOWER)
100 = Critical Temperature Trip register (TCRIT)
101 = Temperature register (TA)
110 = Manufacturer ID register
111 = Device ID/Revision register
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
MCP9805
DS21977C-page 10 2005-2013 Microchip Technology Inc.
4.1.1 CAPABILITY REGISTER
This is a re ad-o nly re gis te r u sed to identify the te mp er-
ature sensor capability. In this case, the MCP9805 is
capable of providing temperature at 0.25°C resolution,
measuring temperature below and above 0°C,
providing ±1°C and ±2°C accuracy over the active and
monitor temperature ranges (respectively) and provid-
ing user-programmable temperature event boundary
trip limits. Register 4-2 describes the Capability
register. These functions are des cri be d in furth er de tail
in the following sections.
REGISTER 4-2: CAPABILITY REGISTER (READ-ONLY) ADDRESS ‘0000 0000’b
bit 15-5 Unimplemented: Re ad as ‘0’
bit 4-3 RES OLUTION bits:
00 = 0.5 °C/LSb
01 = 0.25 °C/LSb (default resolution)
10 = 0.125 °C/LSb
11 = 0.0625 °C/LSb
bit 2 TEMPERAT URE MEASUREMENT RANGE (Meas. Range) bit:
0 =T
A 0x0000 (Hexadecimal) for temperature below 0°C
1 = The part can measure temperature below 0°C
bit 1 ACCURACY bit:
0 =Accuracy ±2°C from +75°C to +95°C (Active Range) and ±3°C from +40°C to +125°C
(Monitor Range)
1 =Accuracy ±1°C from +75°C to +95°C (Active Range) and ±2°C from +40°C to +125°C
(Monitor Range)
bit 0 B ASIC CAPABILITY (Temp. Event) bit:
0 = No defined function (This bit will never be cleared or set to ‘0’).
1 = The part has temperature boundary trip limits (TUPPER/TLOWER/TCRIT registers) and a temperautre
event output (JC 42.4 required feature).
Upper-Half:
U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0
————————
bit 15 bit 8
Lower-Half:
U-0 U-0 U-0 R-0 R-1 R-1 R-1 R-1
— Resolution Meas.
Range Accuracy Temp.
Event
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
2005-2013 Microchip Technology Inc. DS21977C-page 11
MCP9805
4.1.2 SENSOR CONFIGURATION
REGISTER (CONFIG)
The MCP9805 has a 16-bit Configuration register
(CONFIG) that allows the user to set various functions
for a robust temperature monitoring system. Bits 10
thru 0 are used to select Ev ent outpu t boundary hyster-
esis , device S hutdown or Low-Pow er mode , te mpera-
ture boundary and critical temperature lock,
temperature Event output enable/disable. In addition,
the user can select the Event output condition (output
set for TUPPER and TLOWER temperature boundary or
TCRIT only), read Event output status and set Event
outp ut p ol ar i ty a nd mo de (C om para t or Ou tpu t or I n te r-
rupt Output mode).
The temperature hysteresis bits 10 and 9 can be used
to prevent output chatter when the ambient tempera-
ture gradually changes beyond the user-specified
temperature boundary (see Section 4.2.2 “Tempera-
ture Hysteresis (THYST)”. The Continuous Conversion
or Shut down mode is selected us ing bit 8. In Shut down
mode, the band gap temperature sensor circuit stops
converting temperature and the Ambient Temperature
register (TA) holds the previous su cc es sfully conv erte d
temperature data (see Section 4.2.1 “Shutdown
Mode”). Bits 7 and 6 are used to lock the
user-specified boundaries TUPPER, TLOWER and TCRIT
to prevent an accidental rewrite. Bits 5 thru 0 are used
to configure the temperature Event output pin. All
functions are described in Register 4-3 (see
Section 4.2.3 “Event Output Configuration”).
REGISTER 4-3: CONFIGURATION REGISTER (CONFIG) ADDRESS ‘0000 0001’b
bit 15-11 Unimplemented: Read as ‘0’
bit 10-9 Limit Hysteresis (THYST) bits:
00 = 0°C (power-up default)
01 = 1.5°C
10 = 3.0°C
11 = 6.0°C
(Refer to Section 4.2.3 “Event Output Configuration”)
bit 8 Shutdown Mode (SHDN) 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 cann ot b e se t ‘1’ when either of the lock bits is set (bit 6 and bit 7). However, it can be cleared ‘0’
for Continuo us Conv ers io n while loc ke d. (Refer to Section 4.2.1 “Shutdown Mod e”)
bit 7 TCRIT Lock Bit (Crit. Lock) bit:
0 = Unlocked. TCRIT register can be written. (power-up default)
1 = Locked. TCRIT register cannot be written to.
When enabled, this bit remains set ‘1’ or locked until cleared by internal reset (Section 4.3 “Summary of
Power-up Default”). This bit does not require a double-write.
.
Upper-Half:
U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0
————— T
HYST SHDN
bit 15 bit 8
Lower-Half:
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 Event Stat. Event Cnt. Event
Sel. Event
Pol. Event
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 x = Bit is unknown
MCP9805
DS21977C-page 12 2005-2013 Microchip Technology Inc.
bit 6 TUPPER and TLOWER Boundary Window Lock (Win. Lock) bit:
0 = Unlocked. TUPPER and TLOWER registers can be written. (power-up default)
1 = Locked. TUPPER and TLOWER registers cannot be written.
When enabled, this bit remains set ‘1’ or locked until cleared by internal reset (Section 4.3 “Summary of
Power-up Default”). This bit does not require a double-write.
bit 5 Interrupt Clear (Int. Clear) bit:
0 = No effect. (power-up default)
1 = Clear interrupt output. When read this bit returns ‘0’.
bit 4 Event Output Status (Event Stat.) bit:
0 = Event output is not asserted by the device. (power-up def ault)
1 = Event output is assert ed as a comparator/interrupt or critical temperature output.
bit 3 Event Output Control (Event Cnt.) bit:
0 = Disabled. (pow e r-up defa ul t)
1 = Enabled.
This bit can not be altered when either of the lock bits is set (bit 6 and bit 7).
bit 2 Event Output Select (Event Sel.) bit:
0 = Event output for TUPPER, TLOWER and TCRIT. (power-up default)
1 =T
A TCRIT only. (TUPPER and TLOWER temperature boundaries are disabled.)
When the Alarm Window Lock bit is set ‘1’ (bit 6), this bit cannot be altered until unlocked.
bit 1 Event Output Polarity (Event Pol.) bit:
0 = Active-low. (power-up default)
1 = Active-high.
This bit cannot be altered when either of the lock bits is set (bit 6 and bit 7).
bit 0 Event Output Mode (Event Mod.) bit:
0 = Comparator o utp ut. (powe r-up defa ul t)
1 = Interrupt output.
This bit cannot be altered when either of the lock bits is set (bit 6 and bit 7).
REGISTER 4-3: CONFIGURATION REGISTER (CONFIG) ADDRESS ‘0000 0001’b
(CONTINUED)
.
Upper-Half:
U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0
————— T
HYST SHDN
bit 15 bit 8
Lower-Half:
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 Event Stat. Event Cnt. Event
Sel. Event
Pol. Event
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 x = Bit is unknown
2005-2013 Microchip Technology Inc. DS21977C-page 13
MCP9805
4.1.3 TEMPERATURE EVENT
UPPER/LOWER/CRITICAL
BOUNDARY TRIP REGISTERS
(TUPPER/TLOWER/TCRIT)
The MCP9805 has a 16-bit read/write Event output
Temperature Upper-Bou ndary T rip re gister (TUPPER), a
16-bit Lower-Boundary Trip register (TLOWER) and a
16-bit Critical Boundary Trip register (TCRIT) that
contains 11-bit data in two’s compliment format
(0.2 5 °C/ L Sb) . T his da ta r e pr es en ts t h e m ax im um a nd
minimum temperature boundary or temperature
window that can be used to monitor ambient tempera-
ture. If this feature is enabled (Section 4.1.2 “Sensor
Configuration Register (CONFIG)”) and the ambient
temperature exceeds the specified boundary or
window, the MCP9805 asserts an Event output. (Refer
to Section 4.2.3 “Event Output Configuration”).
REGISTER 4-4: UPPER/LOWER/CRITICAL TEMPERATURE BOUNDARY TRIP REGISTERS
(TUPPER/TLOWER/TCRIT) ADDRESS ‘0000 0010’b/‘0000 0011’b/‘0000 0100’b
bit 15-1 3 Unimplemented: Read as ‘0’
bit 12 SIGN bit:
0 =T
A 0°C
1 =T
A 0°C
bit 11-2 TUPPER/TLOWER/TCRIT bits:
Temperature boundary trip data in two’s compliment format.
bit 1-0 Unimplemented: Read as ‘0’
Note: This table reflects the three 16-bit registers TUPPER, TLOWER and TCRIT located at address ‘0000 0010’b,
‘0000 0011’b and ‘0000 0100’b, respectively (see Register 4-1).
Upper-Half:
U-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
———SIGN2
7 °C/LSb 26 °C/LSb 25 °C/LSb 24 °C/LSb
bit 15 bit 8
Lower-Half:
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 U-0 U-0
23 °C/LSb 22 °C/LSb 21 °C/LSb 20 °C/LSb 2-1 °C/LSb 2-2 °C/LSb — —
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
MCP9805
DS21977C-page 14 2005-2013 Microchip Technology Inc.
4.1.4 AMBIENT TEMPERATURE
REGISTER (TA)
The MCP9805 uses a band gap temperature sensor
circuit to output anal og volt age proporti onal to abs olute
tempera ture. An intern al  ADC is u sed to conv ert the
analog voltage to a digital word. The converter resolu-
tion is set to 0.25 °C/LSb + sign (1 1-bit data). The digital
word is loaded to a 16-bit read-only Ambient Tempera-
ture regis ter (TA) that cont ai ns 11-bit tempe rature dat a
in tw o’s compl ement format.
The TA register b its (bit s 12 thru 0) are doub le-buf fered.
Therefore , the user can access the register whil e, in the
background, the MCP9805 performs an analog-to-dig-
ital conversion of the band gap temperature sensor.
The temperature data from the  ADC is loaded in
parallel to TA at tCONV refresh rate.
The TA magnitude in decimal to ambient temperature
conversion is shown in Equation 4-1:
EQUATION 4-1: DECIMAL CODE TO
TEMPERATURE
CONVERSION
In addition, the TA register uses three bits (bits 15, 14
and 13) to reflect the Event pin state. This allows the
user to identify the cause of the Event output trigger
(see Section 4.2.3 “Event Output Configuration”);
bit 15 i s s et to ‘ 1’ i f TA is greater than or equal to T CRIT,
bit 14 is set to ‘1’ i f T A is greater t han TUPPER and bit 13
is set to ‘1’ if TA is less than TLOWER.
The TA register bit assignment and boundary
conditions are described in Register 4-5.
TACode 2 2–
=
Where:
TA= Ambient Temperature (°C)
Code = MCP9805 output magnitude in
decimal
REGISTER 4-5: AMBIENT TEMPERATURE REGISTER (TA) ADDRESS ‘0000 0101’b
bit 15 TA vs. TCRIT(1) bit:
0 =T
A TCRIT
1 =T
A TCRIT
bit 14 TA vs. TUPPER(1) bit:
0 =T
A TUPPER
1 =T
A TUPPER
bit 13 TA vs. TLOWER(1) bit:
0 =T
A TLOWER
1 =T
A TLOWER
bit 12 SIGN bit:
0 =T
A 0°C
1 =T
A 0°C
Note 1: Not affected by the status of the Event output configuration (bits 5 to 0 of CONFIG) and THYST = 0°C,
Register 4-3.
2: Bit 1 may remain set ‘1’ for some devices indicating 2-3 °C/LSb or 0.125°C temperature resolution,
depending on the state of the device calibration code.
Upper-Half:
R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0
TA Vs. TCRIT TA Vs. TUPPER TA Vs. TLOWER SIGN 27 °C/LSb 26 °C/LSb 25 °C/LSb 24 °C/LSb
bit 15 bit 8
Lower-Half:
R-0 R-0 R-0 R-0 R-0 R-0 U-0 U-0
23 °C/LSb 22 °C/LSb 21 °C/LSb 20 °C/LSb 2-1 °C/LSb 2-2 °C/LSb —(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 x = bit is unknown
2005-2013 Microchip Technology Inc. DS21977C-page 15
MCP9805
bit 11-2 Ambient Temperature (TA) bits:
10-bit Ambient Temperature data in two’s compliment format.
bit 1, 0 Unimplemented: Read as ‘0’ (Note 2)
REGISTER 4-5: AMBIENT TEMPERATURE REGISTER (TA) ADDRESS ‘0000 0101’b
(CONTINUED)
Note 1: Not affected by the status of the Event output configuration (bits 5 to 0 of CONFIG) and THYST = 0°C,
Register 4-3.
2: Bit 1 may remain set ‘1’ for some devices indicating 2-3 °C/LSb or 0.125°C temperature resolution,
depending on the state of the device calibration code.
Upper-Half:
R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0
TA Vs. TCRIT TA Vs. TUPPER TA Vs. TLOWER SIGN 27 °C/LSb 26 °C/LSb 25 °C/LSb 24 °C/LSb
bit 15 bit 8
Lower-Half:
R-0 R-0 R-0 R-0 R-0 R-0 U-0 U-0
23 °C/LSb 22 °C/LSb 21 °C/LSb 20 °C/LSb 2-1 °C/LSb 2-2 °C/LSb —(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 x = bit is unknown
MCP9805
DS21977C-page 16 2005-2013 Microchip Technology Inc.
4.1.5 MANUFACTURER ID REGISTER
This re gister is used to i dentify the device m anufacturer
in order to perform manufacturer-specific operations.
The manufacturer ID for the MCP9805 is 0x0054
(hexadecimal).
4.1.6 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 device revision. The device ID for the MCP9805
is 0x00 (hex).
The revision begins with 0x00 (hex) for the first release,
with the number being incremented as revised versions
are released.
REGISTER 4-1: MANUFACTURER ID REGISTER (READ-ONLY) ADDRESS ‘0000 0110’b
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
REGISTER 4-2: DEVICE ID AND DEVICE REVISION (READ-ONLY) ADDRESS ‘0000 0111’b
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
2005-2013 Microchip Technology Inc. DS21977C-page 17
MCP9805
4.2 Sensor Feature Description
4.2.1 SHUTDOWN MODE
Shutdown mode disables all power-consuming
activities (including temperature sampling operations)
while leaving the serial interface active. This mode is
select ed 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 ‘0’ to enable Continuous
Conversion mode, or until power is recycled.
The Shutdown bit (bit 8) cannot be set to ‘1’ while bits
6 and 7 of CONFIG (Lock bits) are set to ‘1’. However,
it can be cleared ‘0’ or returned to Continuous
Conve r si on while locked .
In Shut down m ode, all registe rs can be read or written.
However , the serial bus activity increases the shutdown
current. In addition, if the device is shutdown while the
Event pin is asserted as active-low or deasserted
active-low (see Section 4.2.3.1 “Comparator Mode”
and Section 4.2.3.2 “Int errupt Mode”), the dev ice will
retain the active-low state. This increases the
shutdown current due to the additional Event output
pull -do wn current .
4.2.2 TEMPERATURE HYSTERESIS
(THYST)
A hysteres is of 0°C , 1.5°C, 3°C or 6°C can be s electe d
for the TUPPER, TLOWER and TCRIT temperate bo undar-
ies using bits 10 and 9 of CONFIG. The hysteresis
applies for decreasing temperature on ly (hot to cold), or
as temperature drifts below the specified limit.
The TUPPER, TLOWER and TCRIT boundary conditions
are described graphically in Figure 4-2.
4.2.3 EVENT OUTPUT CONFIGURATION
The Event output can be enabled using bit 3 of
CONFIG (Event output control bit) and can be
configured as either a comparator output or as Interrupt
Output m ode using bit 0 of CON FIG (Event mode). The
polarity can also be specified as an active-high or
active-low using bit 1 of CONFIG (Event polarity).
When the ambient temperature increases above the
critica l tempera ture limit , the Event output is forced to a
comparator output (regardless of bit 0 of CONFIG).
When t he te mperat ure dri fts below t he crit ical t emper-
ature lim it, the Event output auto matically retur ns to the
state specified by bit 0 of CONFIG.
The status of the Event output can be read using bit 4
of CONFIG (Event status).
Bit 7 and 6 of the CONFIG register can be used to lock
the TUPPER, TLOWER and TCRIT registers. The bits
prevent false triggers at the Event output due to an
accidental rewrite to these registers.
The Even t output c an also be used as a critic al temp er-
ature output using bit 2 of CONFIG (critical output
only). When this feature is selected, the Event output
becomes a comparator output. In this mode, the
interrupt output configuration (bit 0 of CONFIG) is
ignored.
4.2.3.1 Comparator Mode
Comparator mode is selected using bit 0 of CONFIG. In
this mode, the Event output is asserted as active-high
or active-low using bit 1 of CONFIG. Figure 4-2 shows
the conditions that toggle the Event output.
If the device enters Shutdown mode with asserted
Event output, the output remains asserted during
Shutdown. The device must be operating in Continu-
ous Conversion mode for tCONV; the TA vs. TUPPER,
TLOWER and TCRIT boundary conditions need to be
satisfied in order for the Event output to deassert.
Comparator mode is useful for thermostat-type applica-
tions, such as turning on a cooling fan or triggering a
system shutdown when the temperature exceeds a
safe operating range.
4.2.3.2 Interrupt Mode
Interrupt mode is selected using bit 0 of CONFIG. In
this mode, the Event output is asserted as active-high
or active-low using bit 1 of CONFIG. The output is
deasserted by setting ‘1’ to bit 5 of CONFIG (interrupt
clear). Shutting down the device will not reset or deas-
sert the Event output. However, clearing the interrupt
using bit 5 of CONFIG while in Shutdown mode will
deassert the Event output.
This mode is ignored when the Event output is used as
critical temperature output only (bit 2 of CONFIG).
Interrupt mode applies to interrupt-driven, microcon-
troller-based systems. The microcontroller receiving
the interrupt will have to acknowledge the interrupt by
setting ‘1’ to bit 5 of CONFIG.
MCP9805
DS21977C-page 18 2005-2013 Microchip Technology Inc.
FIGURE 4-2: Event Output Boundary Conditions.
TUPPER
TLOWER
Event Output
TCRIT
TA
TUPPER - THYST
(Active-Low)
Comparator
Interrupt
S/W Int. Clear
Critical
TCRIT - THYST
123456
Note Event O utput Bounda ry
Conditions Event Ou tput TA bits
Comparator Interrupt Critical 15 14 13
1TA  TLOWER HLH000
2TA TLOWER - THYST LLH001
3TA  TUPPER LLH010
4 TA TUPPER - THYST HLH000
5 TA TCRIT LLL100
6TA TCRIT - THYST LHH010
*When TA  TCRIT and TA TCRIT - THYST, the Event output is in Comparator mode and bit 0 of
CONFIG (Interrupt mode) is ignored.
TLOWER -THYST
TLOWER -THYST
TUPPER - THYST
1342
Note: *
2005-2013 Microchip Technology Inc. DS21977C-page 19
MCP9805
4.3 Summary of Power-up Default
The MCP9805 has an internal Power-on Reset (POR)
circuit . If th e po we r su ppl y v ol t age VDD drifts below the
VPOR threshold, the device resets the registers to the
power-up def ault sett ings.
Table 4-6 shows the power-up default summary.
TABLE 4-6: POWER-UP DEFAULTS
Registers Default Register
Data (Hex) Power-up Default
Register Description
Address (Hex) Register Label
0x00 Capability 0x000F 0.25 °C/LSb
Measures Temperature Below 0°C
±1°C Accu racy Ove r Active Ran ge
Basic Capability (Event ou tput)
0x01 CONFIG 0x0000
Compar ator Mode
Active-Low Output
Event and Critical output
Output Enabled
Event Not Asserted
Interrupt Cleared
Event Limits Unlocked
Critical Limit Unlocked
Continuous Conversion
0°C Hysteresis
0x02 TUPPER 0x0000 0°C
0x03 TLOWER 0x0000 0°C
0x04 TCRIT 0x0000 0°C
0x05 TA0x0000 0°C
0x06 Manufacturer ID 0x0054 0x0054 (hex)
0x07 Device ID/Device Revision 0x0000 0x0000 (hex)
MCP9805
DS21977C-page 20 2005-2013 Microchip Technology Inc.
5.0 SERIAL COMMUNICATION
5.1 2-Wire SMBus/Standard Mode
I2C™ Protocol-Compatible
Interface
The MCP9805 serial clock input (SCLK) and the
bidirectional serial data line (SDA) form a 2-Wire
bidirectional SMBus/Standard mode I2C compatible
communication port (refer to the Digital Input/Output
Pin Characteristics Table and Serial Interface Timing
Characteristics Table).
The following bus protocol has been defined:
TABLE 5-1: MCP9805 SERIAL BUS
PROTOCOL DESCRIPTIONS
5.1.1 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
confirm s the re ceptio n of eac h byte . Each acc ess mus t
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
(see Figure 5-4). Each repeated read or receive can
then be followed with a Start condition, followed by an
address byte. The MCP9805 retains the previously
selected register. Therefore, it expects a read from the
previously-specified register (repeated pointer
specification is not necessary).
5.1.2 MASTER/SLAVE
The bus is controlled by a master device (typically a
microcontroller) that controls the bus access and gener-
ates the Start and Stop conditions. Th e MCP9805 is a
slave device and does not control ot her 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.
5.1.3 START/STOP CONDITION
A hig h- to - lo w t ran si t i on of t h e SD A l in e (w hi l e SC LK is
high) is the Start condition. All data transfers must be
preceded by a St art condition from the master . If a St art
condition is generated during data transfer, the
MCP9805 resets and accepts the new Start condition.
A low-t o-high tra nsition of th e SDA line (w hile SCLK is
high) signifies a Stop condition. If a Stop condition is
introduced during data transmission, the MCP9805
releases the bus. All data transfers are ended by a Stop
condition from the master . However, for continuous data
reception from the previously-specified pointer
(Register 4-1), a Start condition can be introduced at the
end of da ta re cepti on. Th e MCP 9805 r etains the previ-
ously-s e t p ointer. Ther efo re, t her e i s no need to repeat
the pointer specification (see Register 5-4).
5.1.4 ADDRESS BYTE
Following the Start condition, the host must transmit an
8-bit address byte to the MCP9805. The address for the
MCP9805 i s ‘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 ad dr ess for the M C P98 0 5 to resp ond with
an ACK. Bit 8 in the address byte is a read/write bit.
Setting this bit to ‘1’ commands a re ad operatio n, while
‘0’ commands a write operation (see Figure 5-1).
Term Description
Master The device that controls the serial bus,
typically a microcontroller.
Slave The device addressed by the master,
such as the MCP9805.
Transmitter Device sending data to the bus.
Receiver Device receiving data from the bus.
START A unique signal from 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 MCP9805
registers.
ACK A rece iver Ackn owle dges (ACK) the
reception of each byte by polling the
bus.
NAK A receiver N ot-A ck nowl edg es (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 SCLK remain high.
Data Valid SDA must remain stable before SCLK
becomes high in order for a data bit to
be considered valid. During normal
dat a transfe rs, SDA only cha nges st ate
while SCLK is low.
2005-2013 Microchip Technology Inc. DS21977C-page 21
MCP9805
FIGURE 5-1: Device Addressing.
5.1.5 DATA VALID
After the Start condition, each bit of data in transmis-
sion nee ds to be settled for a tim e specified by tSU-DATA
before SCLK toggles from low-to-high (see Serial
Interface Timing Characteristics).
5.1.6 ACKNOWLEDGE (ACK)
Each receiving device, when addressed, is obliged to
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 ackno w led gin g dev ic e pul ls down the SDA lin e for
tSU-DATA bef ore the low- to-high transi tion o f SCLK from
the master. SDA also needs to remain pulled down for
tH-DATA after a high-to-low transition of SCLK.
During read, the master must signal an End-of-Data
(EOD) to the slave by no t genera ting an ACK bit (NAK)
onc e the l ast b it ha s been cloc ked ou t of the sl ave. I n
this case, the slave will leave the data line released to
enable the master to generate the Stop condition.
5.1.7 TIME OUT
If the SCLK stays high or low for a time specified by
tOUT, the MCP9805 releases the bus and resets the
serial interface. The master will have to restart the
communication cycle with a Start condition. This
dictates the minimum clock speed.
123456789
SCLK
SDA 0 0 1 1 A2 A1 A0
Start
Address Byte
Slave
Address R/W
MCP9805 Response
Code Address
A
C
K
MCP9805
DS21977C-page 22 2005-2013 Microchip Technology Inc.
5.2 Timing Diagram
FIGURE 5-2: Read 1-byte and 2-byte data from a Register.
S = START Condition
P = STOP Condition
SDA A
C
K
0011A
Pointer
0000 PA
C
K
S2A
1A
01P
0
12345678 12345678
SCLK
0
Address Byte
A
C
K
0011AN
A
K
S P
2A
1A
0D
7D
6D
5D
4D
3D
2D
1D
0
12345678 12345678
Address Byte Data
R
MCP9805 MCP9805
MCP9805 Master
W
SDA A
C
K
0011A
Pointer
0000 PA
C
K
S2A
1A
01P
0
12345678 12345678
SCLK
0
Address Byte
A
C
K
0011A
MSb Data
A
C
KN
A
K
S P
2A
1A
0D
7D
6D
5D
4D
3D
2D
1D
0
12345678 12345678 12345678
Address Byte LSb Data
RD
15 D
14 D
13 D
12 D
11 D
10 D
9D
8
MCP9805 MCP9805
MCP9805 Master Master
W
SDA
SCLK
SDA
SCLK
Read 1-byte Data
Read 2-byte Data
P
2
P
2
2005-2013 Microchip Technology Inc. DS21977C-page 23
MCP9805
FIGURE 5-3: Write 1-byte and 2-byte data from a Register.
SDA A
C
K
0011A0000 A
C
K
S2A
1A
0
12345678 12345678
SCLK
0
Address Byte
W
MCP9805 MCP9805
P
1P
0
MSb Data
A
C
KA
C
KP
D
7D
6D
5D
4D
3D
2D
1D
0
12345678 12345678
LSb Data
D
15 D
14 D
13 D
12 D
11 D
10 D
9D
8
Pointer
S = START Condition
P = STOP Condition
MCP9805
SDA A
C
K
0011A0000 A
C
K
S2A
1A
0
12345678 12345678
SCLK
0
Address Byte
W
MCP9805 MCP9805
P
1P
0A
C
KP
D
7D
6D
5D
4D
3D
2D
1D
0
12345678
Data
Pointer
Write 1-byte Data
Write 2-byt e Data
MCP9805
MCP9805
P
2
P
2
MCP9805
DS21977C-page 24 2005-2013 Microchip Technology Inc.
FIGURE 5-4: Receive 1-byte Data from Previously Set Pointer.
S = START Condition
P = STOP Condition
SDA A
C
K
0011A
Pointer
0000 PA
C
K
S2A
1A
01P
0
12345678 12345678
SCLK
0
Address Byte
A
C
K
0011AN
A
K
S2A
1A
0D
7D
6D
5D
4D
3D
2D
1D
0
12345678 12345678
Address Byte Data
R
MCP9805 MCP9805
MCP9805 Master
W
A
C
K
0011AN
A
K
S2A
1A
0D
7D
6D
5D
4D
3D
2D
1D
0
12345678 12345678
Address Byte Data
R
MCP9805 Master
Note: User can continue to receive 1-byte or 2-byte data (depending on the specific register)
indefinitely from a previously-set Register Pointer.
This device does not support sequential read/write.
SDA
SCLK
SDA
SCLK
Register Pointer Setting for Continuous Reception(Note)
Receiv e 1-byte Data
Receive Another 1-byte Data
P
2
2005-2013 Microchip Technology Inc. DS21977C-page 25
MCP9805
6.0 APPLICATIONS INFORMATION
6.1 Connecting to the Serial Bus
The SDA and SCLK serial interface pins are
open-drain pins that require pull-up resistors. This
configuration is shown in Figure 6-1.
FIGURE 6-1: Pull-up Resistors On Serial
Interface.
The number of devices connected to the bus is limited
only by the max imum rise and fall times o f the SDA and
SCLK lines. Unlike I2C specific ations, SMBu s do es not
specify a maximum bus capacitance value. Rather, the
SMBus specification requires that the maximum
current through the pull-up resistor be 350 µA and
minimum 100 µA. Because of this, the value of the
pull-up resistors will vary depending on the system’s
bias voltage (VDD). The pull-up resistor values for a
3.3 V system ranges 9 k to 33 k. Minimizing bus
capacitance is still very important as it directly affects
the rise and fall times of the SDA and SCLK lines.
Although SMBus specifications only require the SDA
and SCLK lines to pull-down 350 µA, with a maximum
voltage drop of 0.4 V, the MCP9805 is designed to
meet a maximum voltage drop of 0.4 V, with 3 mA of
current. This allows lower pull-up resistor values to be
used, allowing the MCP9805 to handle higher bus
capacitance. In such applications, all devices on the
bus must meet the same pull-down current
requirements.
A possible configuration using multiple devices on the
SMBus is shown in Figure 6-2.
FIGURE 6-2: Multipl e Device s on DIMM
SMBus.
6.2 Layout Considerations
The MCP9805 does not require any additional compo-
nents besides the master controller in order to mea sure
temperature. However, it is recommended that a
decoupling capacitor of 0.1 µF to 1 µF be used
between the VDD and GND pins. A high-frequency
cera mic c a paci tor is re co mmen d ed . I t is ne c es sa ry fo r
the c apaci tor to be loc ate d as clo se a s po ssibl e to the
power and ground pins of the device in or der to provid e
effective noise protection.
6.3 Thermal Con siderations
A potential for self-heating errors can exist if the
MCP9805 SDA, SCLK and Event lines are heavily
loaded with pull-ups (high current). Typically, the
self-hea ting error is ne gl igi ble be ca use of the relatively
small current consumption of the MCP9805. A
temperature accuracy error of approximately 0.5°C
could re sult from sel f-heating if th e communicati on pins
sink/s ourc e the ma xi mum curre nt speci fied.
For exampl e, if the Event out put is load ed to maxim um
IOL, Equation 6-1 can be used to determine the effect
of self-heating.
EQUATION 6-1: EFFECT OF
SELF-HEATING
At room temperature (TA = +25°C) with maximum
IDD = 500 µA and VDD = 3.6V, the self-heating due to
power dissipation T is 0.2°C for the DFN-8 package
and 0.5°C for the TSSOP-8 package.
SDA
SCLK
VDD
R
R
Microcontroller
MCP9805
Event
R
Master Slave
SDA SCLK
MCP9805
Temperature
Sensor 24LCS52
EEPROM
TJA VDD IDD VOL_Event IOL_Event VOL_SDA IOL_SDA
++=
Where:
T=T
J - TA
TJ= Junction Temperature
TA= Ambient Temper ature
JA = Package Thermal Resistance
VOL_ Event, SDA = Event and SDA Output VOL
(0.4 Vmax)
IOL_ Event, SDA = Event and SDA Output IOL
(3 mAmax)
MCP9805
DS21977C-page 26 2005-2013 Microchip Technology Inc.
7.0 PACKAGING INFORMATION
7.1 Package Marking Information
8-Lead DFN (MC) Example:
XXX
YWW
NN
ABA
536
56
8-Lead TSSOP (ST) Example:
XXXX
YYWW
NNN
805B
0536
256
Legend: XX...X Customer-specific information
Y Year code (last digit of calendar year)
YY Year code (last 2 digits of calendar year)
WW Week code (week of January 1 is week ‘01’)
NNN Alphanu me ric trac ea bil ity code
Pb-free JEDEC designator for Matte Tin (Sn)
*This package is Pb-free. The Pb-free JEDEC designator ( )
can be found on the outer packaging for this package.
Note: In the even t the full M icroc hip p art numb er cann ot be mark ed on one line, it w ill
be carried over to the next line, thus limiting the number of available
characters for customer-specific information.
3
e
3
e
2005-2013 Microchip Technology Inc. DS21977C-page 27
MCP9805
8-Lead Plastic Dual Flat No-Lead Package (MC) 2x3x0.9 mm Body (DFN) – Saw Singulated
L
E2
A3
A1 A
TOP VIEW
D
E
EXPOSED
PAD
METAL
D2
BOTTOM VIEW
2 1
bp
n
(
NOTE 3
)
EXPOSED
TIE BAR
PIN 1
(
NOTE 1
)
ID INDEX
AREA
(
NOTE 2
)
CONFIGURATION
CONTACT
ALTERNATE
DETAIL
K
3.
Package may have one or more exposed tie bars at ends.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
REF: Reference Dimension, usually without tolerance, for information purposes only.
JEDEC Equivalent MO-229 VCED-2
See ASME Y14.5M
See ASME Y14.5M
MILLIMETERS
*
0.50 BSC
2.00 BSC
0.20 REF.
3.00 BSC
1.
Pin 1 visual index feature may vary, but must be located within the hatched area.
.039.035
.031 0.80AOverall Height
2.
Exposed pad may vary according to die attach paddle size.
*
Controlling Parameter
Contact Length §
Notes:
Contact Width
Standoff
Overall Width
Overall Length
Contact Thickness
Exposed Pad Width
Exposed Pad Length
.010.008
L
b .012 0.20
.001
.008 REF.
.079 BSC
–
–
.118 BSC
D
.051
.059
D2
E2
E
.000
A3
A1
.069
.075 1.30
**
1.50
**
.002 0.00
Dimension Limits
Pitch
Number of Pins
INCHES
.020 BSC
MIN
n
e
NOM
Units
8MAX MIN
1.00
0.90
0.25 0.30
–
–1.75
1.90
0.02 0.05
8
NOM MAX
Contact-to-Exposed Pad
§
.012
K.016 0.40.020 0.30 0.50
**
Not within JEDEC parameters
§
Significant Charac t eris t i c
.008 – – 0.20 ––
DWG No. C04-123
Revised 09-12-05
Note: For th e mo s t c urr e nt pac kag e d r awi n gs , plea se se e th e M ic roc hi p Pa c ka gi n g Spe ci f ic ati on lo c at e d
at http://www.microchip.com/packaging
MCP9805
DS21977C-page 28 2005-2013 Microchip Technology Inc.
8-Lead Plastic Thin Shrink Small Outline (ST) – 4.4 mm Body (TSSOP)
A2
A
A1
L
c
1
2D
n
p
B
E
E1
10°5°0°10°5°0°
Mold Draft Angle Bottom 10°5°0°10°5°0°
Mold Draft Angle Top 0.300.250.19.012.010.007BLead Width 0.200.150.09.008.006.004
c
Lead Thickness
0.700.600.50.028.024.020LFoot Length 3.103.002.90.122.118.114DMolded Package Length 4.504.404.30.177.173.169E1Molded Package Width 6.506.386.25.256.251.246EOverall Width 0.150.100.05.006.004.002A1Standoff 0.950.900.85.037.035.033A2Molded Package Thickness 1.101.051.00.043.041.039AOverall Height 0.65.026
p
Pitch 88
n
Number of Pins MAXNOMMINMAXNOMMINDimension Limits MILLIMETERS
*
INCHESUnits
Foot Angle
0° 4° 8° 0° 4° 8°
Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed .005" (0.127mm) per side.
Notes:
JEDEC Equivalent: MO-153 Revised 07-21-05
*
Controlling Parameter
Drawing No. C04-086
Note: For the most current package drawings, please see the Microchip Packaging Specification located
at http://www.microchip.com/packaging
2005-2013 Microchip Technology Inc. DS21977C-page 29
MCP9805
APPENDIX A: REVISION HISTORY
Revision C (January 2013)
Added a note to each package outline drawing.
Revision B (September 2005)
• Added the text “for Mobile Platform Memory
Module Thermal Sensor” to first bullet under
Features section.
Revision A (September 2005)
• Original Rel ease of this Document.
MCP9805
DS21977C-page 30 2005-2013 Microchip Technology Inc.
NOTES:
2005-2013 Microchip Technology Inc. DS21977C-page 31
MCP9805
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
Device: MCP9805: Digital Temperature Sensor
MCP9805T: Digital Temperature Sensor
(Tape and Ree l)
Grade: B = ±1°C (max.) from +75° C to +95°C,
B±2°C (max.) from +40° C to +125°C, and
B±3°C (max.) from -20°C to +125°C
Temperature Range: E = -40°C to +125°C
Package: MC = Dual Flat No Lead (2x3 mm Body), 8-lead
ST = Plastic Thin Shrink Small Outline (4x4 mm Body),
8-lead
PART NO. X/XX
PackageTemperature
Range
Device
Examples:
a) MCP9805T-BE/MC: Tape and Reel,
Extend ed Temp.,
8LD DFN pkg.
b) MCP9805-BE/ST: Extended Temp.,
8LD TSSOP pkg.
c) MCP9805T-BE/ST: Tape and Reel,
Extend ed Temp.,
8LD TSSOP pkg.
–X
Grade
MCP9805
DS21977C-page 32 2005-2013 Microchip Technology Inc.
NOTES:
2005-2013 Microchip Technology Inc. DS21977C-page 33
Information contained in this publication regarding device
applications a nd the lik e is provided only f or yo ur convenience
and may be supers ed ed by u pda t es . It is y our responsibil it y to
ensure that your application meets with your specifications.
MICROCHIP MAKES NO REPRESENTATIONS OR
WARRANTIES OF ANY KIND WHETHER EXPRESS OR
IMPLIED, WRITTEN OR ORAL, STATUTORY OR
OTHERWISE, RELATED TO THE INFORMATION,
INCLUDING BUT NOT LIMITED TO ITS CONDITION,
QUALITY, PERFORMANCE, MERCHANTABILITY OR
FITNESS FOR PURPOSE. Microchip disclaims all liability
arising from this information and its use. Use of Microchip
devices in life support and/or safety applications is entirely at
the buyer’s risk, and the buyer agrees to defend, indemnify and
hold harmless Microchip from any and all damages, claims,
suits, or expenses resulting from such use. No licenses are
conveyed, implicitly or otherwise, under any Microchip
intellectual property rights.
Trademarks
The Microchip name and logo, the Microchip logo, dsPIC,
FlashFlex, KEELOQ, KEELOQ logo, MPLAB, PIC, PICmicro,
PICSTART, PIC32 logo, rfPIC, SST, SST Logo, SuperFlash
and UNI/O are registered trademarks of Microchip T echnology
Incorporated in the U.S.A. and other countries.
FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor,
MTP, SEEVAL and The Embedded Control Solutions
Company are registered trademarks of Microchip Technology
Incorporated in the U.S.A.
Silicon Storage Technology is a registered trademark of
Microchip Technology Inc. in other countries.
Analog-for-the-Digital Age, Application Maestro, BodyCom,
chipKIT, chipKI T logo, CodeGuard, dsPICDEM ,
dsPICDEM.net, dsPICworks, dsSPEAK, ECAN,
ECONOMONIT OR, FanSense, HI-TIDE , In-Circuit Seria l
Programm ing, ICSP, Mindi, MiWi, MPASM, MPF, MPLAB
Certified logo, MPLIB, MPLINK, mTouch, Omniscient Code
Generation, PICC, PICC-18, PICDEM, PICDEM.net, PICkit,
PICtail, REAL ICE, rfLAB, Select Mode, SQI, Serial Quad I/O,
Total Endurance, TSHARC, UniWinDriver, WiperLock, ZENA
and Z-Scale are trademarks of Microchip Technology
Incorporated in the U.S.A. and other countries.
SQTP is a service mark of Microchip T echnology Incorporated
in the U.S.A.
GestIC and ULPP are registered trademarks of Microchip
Tec hnolog y Germany II Gm bH & Co. & KG, a subsidiary of
Microchip Technology Inc., in other countries.
All other trademarks mentioned herein are property of their
respective companies.
© 2005-2013, Microchip Technology Incorporated, Printed in
the U.S.A., All Rights Reserved.
Printed on recycled paper.
ISBN: 9781620769225
Note the following details of the code protection feature on Microchip devices:
• Microchip products meet the specification contained in their particular Microchip Data Sheet.
• Microchip believes that its f amily of products is one of t he most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
• Microchip is willing to work with the customer who is concerned about the integrity of their code.
• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is c onstantly evolving. We a t Microc hip are co m mitted to continuously improving the code prot ect ion featur es of our
products. Attempts to break Microchip’ s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Microchip received ISO/TS-16949:2009 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hoppin g
devices, Serial EEPROMs, microperiph erals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
QUALITY MANAGEMENT S
YSTEM
CERTIFIED BY DNV
== ISO/TS 16949 ==
DS21977C-page 34 2005-2013 Microchip Technology Inc.
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