TCM1617 Datasheet, PDF (6/14 Pages) Microchip Technology – SMBus Thermal Sensor with External Diode Input

SMBus Thermal Sensor with External Diode Input
TCM1617
remains active, and all registers may be read from and
written to normally. The INT_TEMP and EXT_TEMP regis-
ters will contain whatever data was valid at the time of
Standby. (Transitions on SDA or SCL due to external bus
activity may increase the Standby power consumption.)
D+
Bi-directional. this pin connects to the anode of the
external diode and is the positive A/D input. Current is
injected into the external diode from the TCM1617, and the
temperature proportional V_BE is measured and converted to
digital temperature data.
D–
Bi-directional. This pin connects to the cathode of the
external diode. Current is sunk from the external diode into
the TCM1617 through this pin. It also is the negative input
terminal to the TCM1617’s A/D converter. This node is kept
at approximately 0.7V above GROUND.
V_DD
Input. Power supply input. See electrical specifications.
GND
Input. Ground return for all TCM1617 functions.
FUNCTIONAL DESCRIPTION
The TCM1617 acquires and converts temperature infor-
mation from two separate sources, both silicon junction
diodes, with a basic accuracy of ±1°C. One is located on the
TCM1617 die; the other is connected externally. The exter-
nal diode may be located on another IC die. The analog-to-
digital converter on the TCM1617 alternately converts tem-
perature data from the two sensors and stores them sepa-
rately in internal registers.
The system interface is a slave SMBus port with an
ALERT# (SMBALERT#) interrupt output. The interrupt is
triggered when one or more of four preset temperature
thresholds are tripped (see Figure 1). These four thresholds
are user-programmable via the SMBus port. Additionally,
the temperature data can be read at any time through the
SMBus port. Nine SMBus addresses are programmable for
the TCM1617, which allows for a multi-sensor configuration.
Also, there is low-power Standby mode where temperature
acquisition is suspended.
STANDBY MODE
The TC1617 allows the host to put it into a low power
mode (I_DD = 10 µA, max) Standby mode. In this mode, the
A/D converter is halted, and the temperature data registers
are frozen. The SMBus port operates normally. Standby
mode can be enabled with either the STBY# input pin or the
CHIP STOP bit in the CONFIG register. The following table
summarizes this operation.
ASSERT
ALERT#
ASSERT
ALERT#
EXT_TEMP
INT_TEMP
EXT_HLIM
ASSERT
ALERT#
ASSERT
ALERT#
INT_HLIM
EXT_LLIM
INT_LLIM
ALERT#
Time
Note: This diagram inplies that the appropriate setpoint is moved, temporarily, after each ALERT#
event to suppress re-assertion of ALERT# immediately after the ARA/de-assertion.
Figure 1. Temperature-vs-Setpoint Event Generation
SMBUS SLAVE ADDRESS
The two pins ADD1 and ADD0 are tri-state input pins
which determine the 7-Bit SMBus slave address of the
TCM1617. The address is latched during POR.
SERIAL PORT OPERATION
Standby Mode Operation
STBY#
0
1
1
1
Chip Stop Bit
Don’t Care
0
1
1
One Shot?
Don’t Care
Don’t Care
No
Yes
Operating Mode
Standby
Normal
Standby
Normal
(1 Conversion Only,
then Standby)
TCM1617-1 2/5/99
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 2001 Microchip Technology Inc. DS21485A