TMP01GBC AD [Analog Devices], TMP01GBC Datasheet - Page 11

• Manufacturer Part Number: TMP01GBC
• Description: Low Power, Programmable Temperature Controller
• Manufacturer: AD [Analog Devices]

REV. C
The last class of high power devices discussed here are Thyris-
tors, which includes SCRs and Triacs. Triacs are a useful alter-
native to relays for switching ac line voltages. The 2N6073A
shown in Figure 15e is rated to handle 4A (rms). The
optoisolated MOC3011. Triac shown features excellent electri-
cal isolation from the noisy ac line and complete control over
the high power Triac with only a few additional components.
High Current Switching
As mentioned above, internal dissipation due to large loads on
the TMP01 outputs will cause 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 16 shows a few ex-
amples using external transistors. The simplest case, using a
single transistor on the output to invert the output signal is
shown in Figure 16a. When the open-collector of the TMP01
turns “ON” and pulls the output down, the external transistor
Q1’s base will be pulled low, turning off the transistor. Another
transistor can be added to reinvert the signal as shown in Figure
16b. Now, when the output of the TMP01 is pulled down, the
first transistor, Q1, turns off and its collector goes high, which
turns Q2 on, pulling its collector low. 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.
R1
R2
R3
1
2
3
4
NC = NO CONNECT
VREF
Figure 15e. Controlling the 2N6073A Triac
HYSTERESIS
GENERATOR
TEMPERATURE
COMPARATOR
REFERENCE
SENSOR &
VOLTAGE
WINDOW
TMP01
R1
R2
R3
VPTAT
1
2
3
4
8
7
6
5
VREF
Figure 16c. Darlington Transistor Can Handle Large Currents
V+ = 5V
NC
NC
HYSTERESIS
GENERATOR
1
2
3
TEMPERATURE
COMPARATOR
300
REFERENCE
SENSOR &
MOC3011
VOLTAGE
WINDOW
5
4
6
TMP01
150
VPTAT
2N6073A
LOAD
8
7
6
5
AC
4.7k
–11–
V+
An example of a higher power transistor is a standard Darling-
ton configuration as shown in Figure 16c. The part chosen,
TIP-110, can handle 2A 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.
Figure 16a. An External Resistor Minimizes Self-Heating
R2
R1
R3
2N1711
Figure 16b. Second Transistor Maintains Polarity of
TMP01 Output
4.7k
R1
R2
R3
1
2
3
4
+12V
VREF
TIP-110
GENERATOR
HYSTERESIS
1
2
3
4
VREF
TEMPERATURE
COMPARATOR
REFERENCE
SENSOR &
VOLTAGE
WINDOW
HYSTERESIS
GENERATOR
I
C
TEMPERATURE
COMPARATOR
REFERENCE
SENSOR &
VOLTAGE
WINDOW
RELAY
TMP01
VPTAT
TMP01
MOTOR
SWITCH
VPTAT
8
7
6
5
8
7
6
5
4.7k
V+
V+
4.7k
Q1
2N1711
4.7k
TMP01
Q1
2N1711
I
C
Q2
2N1711
I
C