TLC770X Datasheet, PDF (13/27 Pages) Texas Instruments – BiCMOS SUPPLY VOLTAGE SUPERVISORS

The two inputs CONTROL and RESIN have a direct effect on the outputs. In this case, the RESIN input influences
both outputs, and the CONTROL input only the RESET output. The relationship can be seen in the truth table shown
in Figure 9.
Figure 9.
CONTROL
L
L
L
L
H
H
H
H
*t > t_d
Truth Table
RESIN
L
L
H
H
L
L
H
H
SENSE > V_t
false
true
false
true
false
true
false
true
RESET
H
H
H
L*
H
H
H
H
RESET
L
L
L
H*
L
L
L
H*
With a Low level at the RESIN − Input , the capacitor C_t will be discharged and the outputs switch into the active
state. After the input has again become High and the time period t_d has elapsed, the outputs switch back into the
inactive state.
The input RESIN can, for example, be used in order to activate the RESET procedure manually by means of a
switch. This input is also needed when several different supply voltages must be monitored in a single system (see
Section 5).
The CONTROL input is provided with a 1 MΩ Pull-Down resistor. If the input CONTROL is left unconnected, it will
thus be held at a Low level. The reason for this Pull-Down resistor is to ensure compatibility with the bipolar version
TL770X. With the latter device, the input REF (Pin 1) had always to be connected to a 0.1 µF capacitor; if the
TL770X is replaced in an existing circuit with the TLC770X, then no circuit changes will be necessary.
Open circuit inputs should however be avoided, with the exception of the CONTROL input, in order to ensure
reliable operation of this component.
If the CMOS inputs are not connected as in Figure 10., undefined voltage levels can arise at these inputs and cause
uncontrolled states and lateral currents, which in turn can result in a considerable increase in the current
consumption.
Figure 10. CMOS input
The reason for these undefined voltage levels at open circuit inputs is the leakage current of the circuit, and the high
insulation resistances (10¹² Ω and 10¹⁵ Ω) in the area of the inputs of these circuits. The result is that any
conceivable voltage value between V_DD and GND can result at the input IN.
The dependence of the lateral current on the voltage level at input IN is shown in Figure 11.. For all other inputs, the
lateral current at the CONTROL input was measured in the same way. If a defined High or Low level is applied to
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