Datasheet

The transistor must be a small-signal type with a base
resistance less than 100Ω. Tight specifications for forward
current gain (+50 to +150, for example) indicate that the
manufacturer has good process controls and that the
devices have consistent Vbe characteristics. (See Table
6 for recommended devices.)
For heatsink mounting, the 500-32BT02-000 thermal sen-
sor from Fenwal Electronics is a good choice. This device
consists of a diode-connected transistor, an aluminum
plate with screw hole, and twisted-pair cable (Fenwal Inc.,
Milford MA, 508-478-6000).
Twisted-Pair and Shielded Cables
For remote-sensor distances greater than 8 inches, or in
particularly noisy environments, use a twisted-pair cable.
A practical length is 6 feet to 12 feet. For longer distances,
the best solution is a shielded twisted-pair cable such
as that used for audio microphones. For example, the
Table 6. Remote-Sensor Transistor
Manufacturers
Table 5. Output Data Format
Table 4. Input Selection
*Temperature-measurement mode
SEL3 SEL2 SEL1 SEL0 POSITIVE INPUT (IN+) NEGATIVE INPUT (IN-)
0 0 0 0 AIN0 AIN5
0 0 0 1 AIN1 AIN5
0 0 1 0 AIN2 AIN5
0 0 1 1 AIN3 AIN5
0 1 0 0 AIN4 AIN5
0 1 0 1 — —
0 1 1 0 AIN5 AIN5
0 1 1 1 Internal diode anode* Internal diode cathode
1 0 0 0 AIN0 AIN1
1 0 0 1 AIN2 AIN3
1 0 1 0 — —
1 0 1 1 V
DD
/4 GND
1 1 0 0 External diode 1 anode* (AIN0) External diode 1 cathode (AIN1)
1 1 0 1 External diode 2 anode* (AIN2) External diode 2 cathode (AIN3)
1 1 1 0 — —
1 1 1 1 — —
D9 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 S0 S1 S2 0 0
MANUFACTURER MODEL NUMBER
Central Semiconductor
(USA)
CMPT3904
Fairchild Semiconductor
(USA)
MMBT3904
Motorola (USA) MMBT3904
Rohm Semiconductor
(Japan)
SST3904
Siemens (Germany) SMB3904
Zetex (England) FMMT3904CT-ND
MAX1098/MAX1099 10-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
www.maximintegrated.com
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