CMOS Monolithic Voltage Converter
Combined Positive Supply Multiplication
and Negative Voltage Conversion
This dual function is illustrated in Figure 5. In this cir-
cuit, capacitors C1 and C3 perform the pump and
reservoir functions respectively for generation of the
negative voltage. Capacitors C2 and C4 are respec-
tively pump and reservoir for the multiplied positive
voltage. This circuit configuration, however, leads to
higher source impedances of the generated supplies.
This is due to the finite impedance of the common
charge-pump driver.
MAX660
1M
3V LITHIUM BATTERY
DURACELL DL123A
LBI
3
2
8
8 IN
OUT
2
1M
OPEN-DRAIN
LOW-BATTERY OUTPUT
5V/100mA
150µF
620k
1M
SET 6
GND SHDN
4
5
220k
MAX660
150µF
4
6
150
µF
MAX667
LBO 7
DD
1
5
+V
IN
8
NOTE:
ALL 150µF CAPACITORS ARE MAXC001, AVAILABLE FROM MAXIM.
D1
2
3
C1
4
6
D1, D2 = 1N4148
V
OUT
= -V
IN
C2
MAX660
5
Figure 6. MAX660 generates a +5V regulated output from a 3V
lithium battery and operates for 16 hours with a 40mA load.
D2
C3
C4
V
OUT
= (2V
IN
) -
(V
FD1
) - (V
FD2
)
Figure 5. Combined Positive Multiplier and Negative Converter
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9
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
