Rainbow Electronics MAX6632 - Manual (Page 7)

Applications Information
Thermal Considerations
The key to accurate temperature monitoring is good
thermal contact between the MAX6629–MAX6632
package and the object being monitored. In some
applications, the 6-pin SOT23 package is small enough
to fit underneath a socketed µP, allowing the device to
monitor the µP’s temperature directly. Accurate temper-
ature monitoring depends on the thermal resistance
between the object being monitored and the
MAX6629–MAX6632 die. Heat flows in and out of plas-
tic packages primarily through the leads. If the sensor
is intended to measure the temperature of a heat-gen-
erating component on the circuit board, it should be
mounted as close as possible to that component and
should share supply and ground traces (if they are not
noisy) with that component where possible. This maxi-
mizes the heat transfer from the component to the sen-
sor.
The MAX6629/MAX6630 supply current is typically
200µA, and the MAX6631/MAX6632 supply current is
typically 32µA. When used to drive high-impedance
loads, the device dissipates negligible power.
Therefore, the die temperature is essentially the same
as the package temperature.
The rise in die temperature due to self-heating is given
by the following formula:
∆T
J
= P
DISSIPATION
x θ
JA
where P DISSIPATION is the power dissipated by the
MAX6629–MAX6632, and θ
JA
is the package’s thermal
resistance.
The typical thermal resistance is +110°C/W for the
6-pin SOT23 package. To limit the effects of self-heat-
ing, minimize the output currents. For example, if the
MAX6629–MAX6632 sink 1mA, the output voltage is
guaranteed to be less than 0.4V. Therefore, an addi-
tional 0.4mW of power is dissipated within the IC. This
corresponds to a 0.044°C shift in the die temperature in
the 6-pin SOT23.
Chip Information
TRANSISTOR COUNT: 6475
PROCESS: BiCMOS
MAX6629–MAX6632
12-Bit + Sign Digital Temperature Sensors
with Serial Interface
_______________________________________________________________________________________ 7
VOLTAGE
REFERENCE
SPI-COMPATIBLE
INTERFACE
TEMPERATURE
SENSOR
12-BIT + SIGN
∑∆ ADC
MAX6629
MAX6630
MAX6631
MAX6632
SO
SCK
CS
Functional Block Diagram