MAX1680 Maxim, MAX1680 Datasheet - Page 9

• Manufacturer Part Number: MAX1680
• Description: 125mA / Frequency-Selectable / Switched-Capacitor Voltage Converters
• Manufacturer: Maxim

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.
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.
Figure 2. Paralleling MAX1680/MAX1681s to Increase Output Current
Compatibility with the MAX660 and
1 F
Combined Doubler and Inverter
NOTE: USE 4.7 F CAPACITORS FOR MAX1680.
_______________________________________________________________________________________
Switched-Capacitor Voltage Converters
FSEL
CAP+
GND
CAP-
MAX1681
SHDN
OUT
LV
IN
MAX860/MAX861
125mA, Frequency-Selectable,
+V
INPUT
1 F
R
V
OUT
OUT
= -V
=
NUMBER OF DEVICES (n)
R
INPUT
OUT
OF SINGLE DEVICE
Figure 3. Combined Doubler and Inverter
NOTE: USE 4.7 F CAPACITORS FOR MAX1680.
1 F
1 F
FSEL
CAP+
GND
CAP-
MAX1681
1 F
FSEL
CAP+
GND
CAP-
SHDN
OUT
MAX1681
LV
IN
"n"
1 F
SHDN
OUT
LV
IN
+V
INPUT
IN4148
D2
D1
IN4148
1 F
1 F
V
OUT
1 F
1 F
V
V
OUT
OUT
= 2V
= -V
-V
-V
FD1
FD2
INPUT
INPUT
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