Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

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9

Hysteresis

Hysteresis increases the comparator’s noise margin by

increasing the upper threshold or decreasing the lower

threshold (see Figure 8). The hysteresis prevents the

is near the low-battery threshold. This is especially

important for applications where the load on the battery

creates significant fluctuations in battery voltages.

Fixed Hysteresis (MAX6427–MAX6432)

The MAX6427/MAX6428/MAX6429 total hysteresis is the

For the MAX6430/MAX6431/MAX6432, the total hysteresis

Adjustable Hysteresis (MAX6433–MAX6438)

Figure 7 shows the correct connections for the external

resistor-dividers. To adjust the low-battery threshold

LTHIN, resistor R2 between LTHIN and HTHIN, and R3

between HTHIN and GND. The hysteresis for the

MAX6433–MAX6438 is determined by an external resis-

tor-divider network (see Resistor-Value Selection sec-

tion of Applications Information). The hysteresis for the

MAX6436/MAX6437/MAX6438 is the differences

R

Q

S

Q

LBO TIMEOUT

PERIOD

LTHIN

HTHIN

( ) ARE FOR THE MAX6435

EXTERNAL

RESISTOR-

DIVIDER

615

mV

LBO

(LBO)

+

-

Figure 3. MAX6433/MAX6434/MAX6435 Functional Diagram