Datasheet

and the serial interface. Enter shutdown by programming
the shutdown bit of the configuration register high. While
in shutdown, the temperature register retains the last
conversion result and can be read at any time. The ADC
is turned off, reducing the device current draw to 30µA
(max). The outputs of ALERT and OVERT are latched
upon entering shutdown, and the fault queue is held in
reset. After coming out of shutdown, the temperature
register continues to read the last converted temperature,
until the next conversion result is available.
Thermal Considerations
The MAX6633/MAX6634/MAX6635 supply current is typ-
ically 200µA when the serial interface is inactive. When
used to drive high-impedance loads, the devices dissipate
negligible power; therefore, the die temperature is essen-
tially the same as the package temperature. The key to
accurate temperature monitoring is good thermal contact
between the MAX6633/MAX6634/MAX6635 package and
the monitored device or circuit. Heat flows in and out of
plastic packages primarily through the leads. Short, wide
copper traces leading to the temperature monitor ensure
that heat transfers quickly and reliably. 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
MAX6633/MAX6634/MAX6635, and θ
JA
is the package's
thermal resistance.
The typical thermal resistance is 170°C/W for the 8-pin
SO package. To limit the effects of self-heating, mini-
mize the output currents. For example, if the MAX6634/
MAX6635 sink 4mA with the maximum ALERT V
L
specifi-
cation of 0.8V, an additional 3.2mW of power is dissipated
within the IC. This corresponds to a 0.54°C rise in the die
temperature.
Applications Information
Figure 10 shows the MAX6634 used as a simple ther-
mostat to control a heating element. Figure 11 shows the
MAX6635 used as a temperature-triggered fan controller.
Table 1. Address Selection
MAX6633
A3 A2 A1 A0 ADDRESS
GND GND GND GND 1000 000
GND GND GND V
CC
1000 001
GND GND V
CC
GND 1000 010
GND GND V
CC
V
CC
1000 011
GND V
CC
GND GND 1000 100
GND V
CC
GND V
CC
1000 101
GND V
CC
V
CC
GND 1000 110
GND V
CC
V
CC
V
CC
1000 111
V
CC
GND GND GND 1001 000
V
CC
GND GND V
CC
1001 001
V
CC
GND V
CC
GND 1001 010
V
CC
GND V
CC
V
CC
1001 011
V
CC
V
CC
GND GND 1001 100
V
CC
V
CC
GND V
CC
1001 101
V
CC
V
CC
V
CC
GND 1001 110
V
CC
V
CC
V
CC
V
CC
1001 111
MAX6634
A2 A1 A0 ADDRESS
GND GND GND 1001 000
GND GND V
CC
1001 001
GND V
CC
GND 1001 010
GND V
CC
V
CC
1001 011
V
CC
GND GND 1001 100
V
CC
GND V
CC
1001 101
V
CC
V
CC
GND 1001 110
V
CC
V
CC
V
CC
1001 111
MAX6635
A1 A0 ADDRESS
GND GND 1001 000
GND V
CC
1001 001
V
CC
GND 1001 010
V
CC
V
CC
1001 011
MAX6633/MAX6634/
MAX6635
12-Bit Plus Sign Temperature Sensors
with SMBus/I
2
C-Compatible Serial Interface
www.maximintegrated.com
Maxim Integrated │ 12