Rainbow Electronics MAX6635 - Manual (Page 12)

MAX6633/MAX6634/MAX6635
and the serial interface. Enter shutdown by program-
ming 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 shut-
down, 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
typically 200µA when the serial interface is inactive.
When used to drive high-impedance loads, the devices
dissipate negligible power; therefore, the die tempera-
ture is essentially the same as the package tempera-
ture. 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 pack-
age’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 specification 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 thermo-
stat to control a heating element. Figure 11 shows the
MAX6635 used as a temperature-triggered fan controller.
Chip Information
TRANSISTOR COUNT: 12,085
PROCESS: BiCMOS
12-Bit Plus Sign Temperature Sensors with
SMBus/I
2 C-Compatible Serial Interface
12 ______________________________________________________________________________________
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
Table 1. Address Selection