2005-2013 Microchip Technology Inc. DS21977C-page 1
MCP9805
Features
• Meets JEDEC Standard JC42.4 for Mobile
Platform Memory Module Thermal Sensor
• Temperature-to-Digital 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 Temperature Output
• Operating Voltage Range: 3.0V to 3.6V
• 2-wire Interface: SMBus/Standard mode I
2
C™
Compatible
• Operating Current: 200 µA (typ.)
• Shutdown Current: 0.1 µA (typ.)
• Available Packages: 2x3 DFN-8, TSSOP-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
Microchip Technology Inc.’s MCP9805 digital tempera-
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 Module Thermal Sensor. This device provides
an accuracy of ±1°C (max.) from a temperature range
of +75°C to +95°C (active range) and ±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
limits, the MCP9805 outputs an Event signal. The user
has the option of 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
systems. The Event output can also be configured as a
critical temperature output.
This sensor has a 2-wire industry-standard SMBus
and Standard mode I
2
C compatible (100 kHz bus
clock) serial interface protocol, allowing up to eight sen-
sors to be controlled in a single serial bus. These 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 V
DD_SPD SDA SCLK
R
R
Event
* Serial Presence Detect
SDA
GND
Event
SCLK
8-Pin DFN (2x3)
A0
V
DD
A1
A2
1
2
3
4
8
7
6
5
SDA
GND
Event
SCLK
MCP9805
1
2
3
4
8-Pin TSSOP
A0
V
DD
A1
A2
8
7
6
5
Memory Module Digital Temperature Sensor
