TC1031_05 Datasheet, PDF (5/14 Pages) Microchip Technology – Linear Building Block - Low Power Voltage Reference with Programmable Hysteresis Comparator and Shutdown

TC1031
3.0 DETAILED DESCRIPTION
The TC1031 is one of a series of very low-power, linear
building block products targeted at low-voltage, single-
supply applications. Minimum operating voltage for the
device is 1.8V, and typical supply current is only 6μA
(fully enabled). It combines one comparator and a
voltage reference in a single package. The comparator
and reference outputs are in a high-impedance state
during shutdown.
3.1 Comparator
The TC1031 contains one comparator with program-
mable hysteresis. The range of the inputs extends
beyond both supply voltages by 200mV. The compara-
tor outputs will swing to within several millivolts of the
supplies depending on the load current being driven.
The comparator exhibits a propagation delay and
supply current which is largely independent of supply
voltage. The low input bias current and offset voltage
make it suitable for high impedance precision
applications.
The comparator is disabled during shutdown and has
high-impedance output.
3.2 Voltage Reference
A 2.0% tolerance, internally biased, 1.20V bandgap
voltage reference is included in the TC1031. It has a
push-pull output capable of sourcing and sinking at
least 50μA. The voltage reference is disabled during
shutdown, with a high-impedance output.
3.3 Shutdown Input
SHDN at V_IL disables both the comparator and voltage
reference and reduces the supply current to less than
0.1μA. The SHDN input cannot be allowed to float;
when not used, connect it to V_DD. The outputs are in a
high impedance state when the TC1031 is disabled.
The comparator’s inputs and output can be driven from
rail-to-rail by an external voltage when the TC1031 is
disabled. No latchup will occur when the device is
driven to its enabled state when SHDN is set to V_IH.
3.4 Programmable Hysteresis
Hysteresis is added to the comparators by connecting
a resistor R1 between the V_REF and HYST pins and
another resistor R2 between the HYST pin and V_SS.
For no hysteresis V_REF should be directly connected to
HYST. The hysteresis, V_HB, is equal to twice the
voltage difference between the V_REF and HYST pins,
where:
V_HB = 2 * V_REF * R1/(R1 + R2) (See Figure 3-1)
and is symmetrical around the normal (without
hysterersis) threshold of the comparator. The
maximum voltage allowed between the V_REF and H_YST
pins is 80mV, giving a maximum hysteresis of 160mV.
FIGURE 3-1:
TC1031 PROGRAMMABLE HYSTERESIS
R1
I_REF
6 _VREF
5
HYST
R1 = ^VHB
(2) (I_REF)
( ) ^{1.200V – VHB}
R2 =
2
I_REF
R2
1
V_SS
TC1031
Note: Size R1 and R2 such that I_REF ≤ 50µA
© 2005 Microchip Technology Inc.
DS21342C-page 5