OBSOLETE

LM3647

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SNOS517H – MARCH 2000 – REVISED APRIL 2013

LI-ION

The voltage divider network for Li-Ion must be selected with great care for maximum utilization of the batteries.

Li-Ion battery cells have a nominal voltage of 3.6V or 3.7V and the maximum voltage per cell is specified at 4.1V

or 4.2V respectively. By multiplying the number of battery cells with the maximum cell voltage, it is possible to

determined, the voltage divider network has to be dimensioned using Equation 2 and Equation 3 (SEL2 open):

Pin SEL3

GND

(2)

(3)

The LM3647 supports two different user selectable battery input voltages on the CEL pin. These are 2.675V

handle both 3.6V and 3.7V Li-Ion-cells, without changing the resistor values in the CEL pin voltage divider

network. SEL3 can also be used to obtain a better match when choosing standard series resistor values for

certain cell combinations.

Table 3. Resistor network selection Quick Guide

Li-Ion (3.6V cell)

No. of Cells

Nominal

Max

R6

R7

1

3.6V

4.1V

16k

30k

2

7.2V

8.2V

62k

30k

3

10.8V

12.3V

27k

7.5k

4

14.4V

16.4V

22k

3.9k

Li-Ion (3.7V cell)

No. of Cells

Nominal

Max

R6

R7

1

3.7V

4.2V

16k

30k

2

7.4V

8.4V

62k

30k

3

11.1V

12.6V

27k

7.5k

4

14.8V

16.8V

22k

3.9k

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