The maximum voltage at the comparator input for normal operation is up to (Vs) – 1.5 V. There are special considerations when overdriving the reference inputs (pins 3 and 6). Driving either or both inputs high enough to drive 1 mA back into the reference introduces errors into the reference. Figure 7-6 shows the basic input structure. A general guideline is to limit the voltage on both inputs to a total of 20 V. The exact limit depends on the available voltage and whether either or both inputs are subject to the large voltage. When making this determination, consider the 20 kΩ from each input back to the comparator. Figure 7-7 shows the maximum input voltage that avoids creating a reference error when driving both inputs (an equivalent resistance back into the reference of 10 kΩ).

Figure 7-6 Limit Current Into Reference ≤ 1 mA

Figure 7-7 Overdriving Comparator Inputs Without Generating a Reference Error

Figure 7-8 Polyswitch Warning and Fault Detection Circuit

Figure 7-9 Lead-Acid Battery Protection Circuit