 |
 |
|
| TC1031_05 |
|
|||||||||||||||||
 MICROCHIP
|
| |||||||||||||||||
|
5 page 
© 2005 Microchip Technology Inc. DS21342C-page 5 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 6 μA (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 50 μA. The voltage reference is disabled during shutdown, with a high-impedance output. 3.3 Shutdown Input SHDN at VIL disables both the comparator and voltage reference and reduces the supply current to less than 0.1 μA. The SHDN input cannot be allowed to float; when not used, connect it to VDD. 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 VIH. 3.4 Programmable Hysteresis Hysteresis is added to the comparators by connecting a resistor R1 between the VREF and HYST pins and another resistor R2 between the HYST pin and VSS. For no hysteresis VREF should be directly connected to HYST. The hysteresis, VHB, is equal to twice the voltage difference between the VREF and HYST pins, where: and is symmetrical around the normal (without hysterersis) threshold of the comparator. The maximum voltage allowed between the VREF and HYST pins is 80mV, giving a maximum hysteresis of 160mV. FIGURE 3-1: TC1031 PROGRAMMABLE HYSTERESIS VHB = 2 * VREF * R1/(R1 + R2) (See Figure 3-1) VREF HYST VSS TC1031 6 5 1 R1 R2 IREF R1 = VHB (2) (IREF) R2 = IREF (1.200V – ) VHB 2 Note: Size R1 and R2 such that IREF ≤ 50µA |
