MCP9805-BE/ST Microchip Technology, MCP9805-BE/ST Datasheet - Page 25

• Manufacturer Part Number: MCP9805-BE/ST
• Description: IC,TEMPERATURE SENSOR,TSSOP,8PIN,PLASTIC
• Manufacturer: Microchip Technology

Specifications of MCP9805-BE/ST

• Rohs Compliant: YES
• Function: Temp Monitoring System (Sensor)
• Topology: ADC (Sigma Delta), Register Bank
• Sensor Type: Internal
• Sensing Temperature: -40°C ~ 125°C
• Output Type: I²C™/SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP
• Temperature Threshold: Programmable
• Full Temp Accuracy: 3 C
• Digital Output - Bus Interface: I2C, SMBus
• Digital Output - Number Of Bits: 10 bit
• Supply Voltage (max): 3.6 V
• Supply Voltage (min): 3 V
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 20 C
• Supply Current: 500 uA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

6.0
6.1
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:
Interface.
The number of devices connected to the bus is limited
only by the maximum rise and fall times of the SDA and
SCLK lines. Unlike I
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 (V
3.3 V system ranges 9 k
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
requirements.
A possible configuration using multiple devices on the
SMBus is shown in Figure 6-2.
FIGURE 6-2:
SMBus.
© 2005 Microchip Technology Inc.
Temperature
must
MCP9805
Master
Sensor
APPLICATIONS INFORMATION
Connecting to the Serial Bus
meet
DD
). The pull-up resistor values for a
2
R
C specifications, SMBus does not
the
Pull-up Resistors On Serial
Multiple Devices on DIMM
V
SDA SCLK
DD
R
same
to 33 k . Minimizing bus
R
pull-down
Event
MCP9805
SDA
SCLK
EEPROM
24LCS52
Slave
current
6.2
The MCP9805 does not require any additional compo-
nents besides the master controller in order to measure
temperature. However, it is recommended that a
decoupling capacitor of 0.1 µF to 1 µF be used
between the V
ceramic capacitor is recommended. It is necessary for
the capacitor to be located as close as possible to the
power and ground pins of the device in order to provide
effective noise protection.
6.3
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-heating error is negligible because of the relatively
small current consumption of the MCP9805. A
temperature accuracy error of approximately 0.5°C
could result from self-heating if the communication pins
sink/source the maximum current specified.
For example, if the Event output is loaded to maximum
I
of self-heating.
EQUATION 6-1:
At room temperature (T
I
power dissipation T is 0.2°C for the DFN-8 package
and 0.5°C for the TSSOP-8 package.
OL
T
DD
Where:
V
I
, Equation 6-1 can be used to determine the effect
=
OL_Event, SDA
OL_Event, SDA
= 500 µA and V
JA V DD I DD
Layout Considerations
Thermal Considerations
T
T
T
JA
A
J
DD
+
= T
= Junction Temperature
= Ambient Temperature
= Package Thermal Resistance
= Event and SDA Output V
= Event and SDA Output I
V OL_Event I OL_Event
and GND pins. A high-frequency
DD
(0.4 V
(3 mA
J -
EFFECT OF
SELF-HEATING
= 3.6V, the self-heating due to
T
A
A
max
max
= +25°C) with maximum
MCP9805
)
)
+
DS21977B-page 25
V OL_SDA I OL_SDA
OL
OL