Application examples
Figure 11. Typical Variation of the Reference Voltage Vref versus
supply Voltage Variations
As has already been mentioned the supply voltage supervisors of the series TL77xxA incorporate
extremely stable reference voltage source which can be accessed at the V terminal. This voltage source
ref
can also be used when in other applications a constant voltage source is required. As shown in picture 11,
the reference voltage V varies less than 10 mV, when the supply voltage is changed from 3.5¼ 18 V.
ref
The same stability of the reference voltage is maintained, when the ambient temperature is changed.
Figure 12 shows the typical characteristic. The references voltage varies only 16mV, when the ambient
temperature is changed from -40 ¼ 85 °C.
Vref
2,522 V
2,52 V
2,518 V
2,516 V
2,514 V
2,512 V
2,51 V
2,508 V
2,506 V
-40
-20
0
20
40
60
80
100 T
a
/ C
°
Figure 12. Typical Variation of the Reference Voltage Vref versus
Ambient Temperature Variations
When using the integrated reference voltage to supply other circuits, the designer has to consider that
maximum current available from this voltage source is in the order of 100mA only. With higher loads, the
stability of the reference voltage suffers. For higher currents a buffer in the form of an operational amplifier
connected as an emitter follower is recommended (figure 13). If the voltage monitor section of the circuit is
not used in this application, the capacitor C is not required. This terminal may then be left open. The inputs
t
SENSE and RESIN are connected to ground.
10
Literature Number: SLVAE04
TI [ TEXAS INSTRUMENTS ]
