Rainbow-electronics MAX1681 Manual de usuario descargar pdf (Pagina 9)

Combined Doubler and Inverter

Figure 3 shows a single MAX1680/MAX1681 as an

inverter and a doubler. The maximum output current is

the sum of the loads on the two outputs and is still limit-

ed to 125mA. As the device is loaded, the output volt-

ages move toward ground. In this particular

configuration, connect LV to GND (inverter). The diodes

used in the circuit cause a drop of approximately 0.7V

in the doubler’s output voltage, impacting efficiency.

Compatibility with the MAX660 and

MAX860/MAX861

The MAX1680/MAX1681 can be used in place of the

MAX860/MAX861, except for the SHDN and FSEL pins.

The MAX1680/MAX1681 shut down with a high input

voltage, compared with the MAX860/MAX861. The

MAX1680/MAX1681 have only two frequency choices.

Replacing the MAX660 with the MAX1680/MAX1681

involves a wiring change, as the external oscillator pin

is replaced by the shutdown feature. Table 5 compares

the devices.

MAX1680/MAX1681

125mA, Frequency-Selectable,

Switched-Capacitor Voltage Converters

_______________________________________________________________________________________ 9

MAX1681

FSEL IN

INPUT

CAP+ SHDN

GND

1µF

CAP- OUT

GND

MAX1681

"n"

FSEL IN

CAP+ SHDN

1µF

OUT

NOTE: USE 4.7µF CAPACITORS FOR MAX1680. V

OUT

= -V

INPUT

CAP- OUT

OUT

OF SINGLE DEVICE

NUMBER OF DEVICES (n)

Figure 2. Paralleling MAX1680/MAX1681s to Increase Output Current

MAX1681

FSEL IN

INPUT

CAP+ SHDN

GND1µF

1µF

CAP- OUT

OUT

= -V

INPUT

IN4148

OUT

= 2V

INPUT

-V

FD1

-V

FD2

NOTE: USE 4.7µF CAPACITORS FOR MAX1680.

Figure 3. Combined Doubler and Inverter

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

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Rainbow-electronics MAX1681 Manual de usuario Pagina 9

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