Rainbow-electronics MAX6781 Manual de usuario descargar pdf (Pagina 8)

MAX6775–MAX6781

Low-Power, 1%-Accurate Battery

Monitor in µDFN and SC70 Packages

8 _______________________________________________________________________________________

Selector Guide

PART LBO OUTPUT OUTPUT TYPE HYSTERESIS PIN-PACKAGE

MAX6775XK_+T Single Push-Pull Fixed 5 SC70-5

MAX6775LT_+T Single Push-Pull Fixed 6 µDFN-6

MAX6776XK_+T Single Open-Drain Fixed 5 SC70-5

MAX6776LT_+T Single Open-Drain Fixed 6 µDFN-6

MAX6777XK+T Single Push-Pull Adjustable 5 SC70-5

MAX6777LT+T Single Push-Pull Adjustable 6 µDFN-6

MAX6778XK+T Single Open-Drain Adjustable 5 SC70-5

MAX6778LT+T Single Open-Drain Adjustable 6 µDFN-6

MAX6779LT_+T Dual Push-Pull Fixed 6 µDFN-6

MAX6780LT_+T Dual Open-Drain Fixed 6 µDFN-6

MAX6781LT_+T Dual Mixed Fixed 6 µDFN-6

Calculating an External

Hysteresis Resistive Divider

Setting the hysteresis externally requires calculating

three resistor values, as indicated in Figure 3. First cal-

culate R

using:

and R

using:

(as in the above example). Where R

equals R

HYST

, determine the total resistor-divider current,

TOTAL

, at the trip voltage using:

Then, determine R

HYST

using:

where V

HYST

is the required hysteresis voltage.

Finally, determine R

using:

= R

- R

HYST

Monitoring a Battery Voltage Higher

Than the Allowable V

BATT

For monitoring higher voltages, supply power to BATT

that is within the specified supply range, and power the

input resistive divider from the high voltage to be moni-

tored. Do not exceed the Absolute Maximum Ratings.

Adding External Capacitance to

Reduce Noise and Transients

If monitoring voltages in a noisy environment, add a

bypass capacitor of 0.1µF from BATT to GND as close

as possible to the device. For systems with large tran-

sients, additional capacitance may be required. A small

capacitor (<1nF) from LBI_ to GND may provide addi-

tional noise immunity.

HYST

TOTAL

BATT

VxR

LBIR H

LBIR BATT

−

exV

A BATT

1 2 3 4 5 6 7 8 9 10 11 12

MAX6775–MAX6781 1

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Rainbow-electronics MAX6781 Manual de usuario Pagina 8

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