Datasheet

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
CMOS Monolithic Voltage Converter
_______________________________________________________________________________________ 9
1M
1M
2
3
4
8
8
6
2
7
1
6
54
5
620k
220k
150µF
150
µF
150µF
3V LITHIUM BATTERY
DURACELL DL123A
OPEN-DRAIN
LOW-BATTERY OUTPUT
5V/100mA
MAX660
MAX667
IN OUT
LBO
DD
SET
GND SHDN
NOTE: ALL 150µF CAPACITORS ARE MAXC001, AVAILABLE FROM MAXIM.
LBI
1M
Figure 5. Combined Positive Multiplier and Negative Converter
5
3
4
8
6
2
C1
C3
C4
C2
D2
D1
+V
IN
D1, D2 = 1N4148
V
OUT
= -V
IN
V
OUT
= (2V
IN
) -
(V
FD1
) - (V
FD2
)
MAX660
Figure 6. MAX660 generates a +5V regulated output from a 3V
lithium battery and operates for 16 hours with a 40mA load.