4

LBI

Vdown

t1

Vup

LBO

Figure 3 Timing waveform

Applications Information

R1 and R2 Selection

LBI pin senses the battery voltage via the resistor divider formed by R1 and R2 in Figure 1 and Figure 2.

Choosing the proper R1 and R2 values is a balance between accuracy and power consumption. The leakage

current into LBI pin travels through the resistor divider and introduce an error, If extremely high resistor

values are used, the leakage current introduces a significant error; While with extremely low resistor values,

the error becomes negligible, but the resistive divider draws more power from the battery than necessary

and shortens battery life.

The battery voltage at which LBO should activate is calculated by the following equation:

Where,

Vrth is the rising threshold

So the maximum R1 value should be decided by the acceptable error, and the minimum value should be

decided by the battery power consumption due to R1 and R2’s presence.

Adding External Capacitance to Enhance Noise Immunity

If monitoring voltages in a noisy environment, add a bypass capacitor of 0.1μF from battery terminal to

GND as close as possible to the device. For systems with large transients, additional capacitance may be

required. A small capacitor (<1nF) from LBI pin to GND may provide additional noise immunity.

Negative-Going LBI Transients

In addition to issuing a low output at LBO pin during power-up, power-down, and brownout conditions of

the monitored voltage, the

HM6100 is relatively immune to short-duration negative-going LBI transients

(glitches). As the magnitude of the transient increases (goes farther below the down trip point), the

maximum allowable pulse width decreases. Typically, a LBI transient that goes 35mV below the down trip

point and lasts 10µs or less will not cause a low LBO output. A bypass capacitor from LBI pin to GND

provides additional transient immunity.

Therefore, high-impedance CMOS logic inputs connected to LBO can drift to undetermined voltages. This

HM6100

Shenzhen H&M Semiconductor Co.Ltd

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