Datasheet

TMP01
Rev. E | Page 12 of 20
Thus, the output taken from the collector of Q2 is identical
to the output of the TMP01. By picking a transistor that can
accommodate large amounts of current, many high power
devices can be switched.
The last class of high power devices discussed here are
thyristors, which includes SCRs and Triacs. Triacs are a useful
alternative to relays for switching ac line voltages. The 2N6073A
shown in Figure 21 is rated to handle 4A (rms). The opto-
isolated MOC3011 Triac features excellent electrical isolation
from the noisy ac line and complete control over the high power
Triac with only a few additional components.
TEMPERATURE
SENSOR AND
VOLTAGE
REFERENCE
VREF
VPTAT
1
2
3
4
8
7
6
5
HYSTERESIS
GENERATOR
WINDOW
COMPARATOR
Q1
TMP01
R1
R2
R3
V+
4.7kΩ
2N1711
I
C
00333-022
TEMPERATURE
SENSOR AND
VOLTAGE
REFERENCE
VREF
VPTAT
1
2
3
4
8
7
6
5
HYSTERESIS
GENERATOR
LOAD
AC
WINDOW
COMPARATOR
NC = NO CONNECT
TMP01
R1
R2
R3
NC
NC
V+ = 5V
300Ω
6
5
4
1
2
3
150Ω
2N6073A
MOC9011
00333-021
Figure 22. An External Resistor Minimizes Self-Heating
TEMPERATURE
SENSOR AND
VOLTAGE
REFERENCE
VREF
VPTAT
1
2
3
4
8
7
6
5
HYSTERESIS
GENERATOR
WINDOW
COMPARATOR
Q1
TMP01
R1
R2
R3
V+
4.7kΩ
2N1711
Q2
2N1711
I
C
4.7kΩ
00333-023
Figure 21. Controlling the 2N6073A Triac
HIGH CURRENT SWITCHING
Internal dissipation due to large loads on the TMP01 outputs
causes some temperature error due to self-heating. External
transistors remove the load from the TMP01, so that virtually
no power is dissipated in the internal transistors and no self-
heating occurs. Figure 22 through Figure 24 show a few
examples using external transistors. The simplest case, using a
single transistor on the output to invert the output signal is
shown in Figure 22. When the open collector of the TMP01
turns on and pulls the output down, the external transistor Q1
base is pulled low, turning off the transistor. Another transistor
can be added to reinvert the signal as shown in Figure 23. Now,
when the output of the TMP01 is pulled down, the first transis-
tor, Q1, turns off and its collector goes high, which turns Q2 on,
pulling its collector low.
Figure 23. Second Transistor Maintains Polarity of TMP01 Output
An example of a higher power transistor is a standard Darlington
configuration as shown in Figure 24. The part chosen, TIP-110,
can handle 2 A continuous which is more than enough to
control many high power relays. In fact, the Darlington itself
can be used as the switch, similar to MOSFETs and IGBTs.
TEMPERATURE
SENSOR AND
VOLTAGE
REFERENCE
VREF
VPTAT
1
2
3
4
8
7
6
5
HYSTERESIS
GENERATOR
WINDOW
COMPARATOR
TMP01
R1
R2
R3
V+
4.7kΩ
2N1711
RELAY
12
V
TIP-110
I
C
4.7kΩ
MOTOR
SWITCH
00333-024
Figure 24. Darlington Transistor Can Handle Large Currents