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

6.2 Comparison of the Bipolar and BiCMOS Versions
The BiCMOS version TLC770X was developed specially for applications in battery operated circuits. The more
demanding requirements of this version, with respect to low power drain and high precision of the analog parts of the
circuit, made necessary the use of combined bipolar and CMOS technology. The processes used in manufacture,
having structural dimensions of 2 µm, only allow the use of supply voltages of up to 6 V. For higher supply voltages,
it will be more appropriate to use the well-known bipolar version TL770X.
A significant improvement of the BICMOS version is the very low current consumption. Whereas the TL770X has a
typical current consumption 1.8 mA, the corresponding value for the BiCMOS version is only 10 µA. The power
consumption of a system can thus be significantly reduced by using the TLC770X.
An improvement with respect to the bipolar version is the need for fewer external components. The input REF of the
TL770X must be made with a capacitor, in order to avoid oscillation of the reference voltage. This capacitor is not
needed with the TLC770X. The REF input has been replaced by the CONTROL input, which provides the additional
option of making access directly to the RESET output. Pull-Up and Pull-Down resistors at the outputs are not
necessary with the BiCMOS version, since it incorporates a Totem-Pole output circuit.
If the intention is to replace a TL770X with a TLC770X in an existing system, no circuit changes will in most cases be
necessary. The capacitor of 0.1 µF at the REF pin which is needed with the bipolar version can remain in circuit. It
will be held in a discharged state (Low level) by the integrated resistor at the input which is now known as
CONTROL. With the same value of the capacitor C_t at the input, the TLC770X gives a delay time which is about
50 % longer than the TL770X. If necessary, the value of the capacitor can be appropriately reduced. The Pull-Up or
Pull-Down resistors which are necessary at the outputs of the TL770X do not need to be removed when a TLC770X,
with Totem-Pole output and not needing a Pull-Up resistor, is used. It is, however, necessary to make sure that the
output current of the circuit resulting from the resistor does not exceed the maximum value specified in the Data
Sheet. If however the Pull-Up resistor with the bipolar version was connected to a higher potential than the supply
voltage of the integrated circuit, then this resistor must be removed. When the TLC7701 is used instead of the
TL7702 (both circuits do not have any integrated voltage divider at the SENSE input), then the external voltage
divider must be changed appropriately (see Section 3).
Providing as it does a very precise threshold voltage, the Supply Voltage Supervisor series TLC770X is most
suitable for designing simple and reliable Reset circuits.
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