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.

CMOS Monolithic Voltage Converter

_______________________________________________________________________________________

9

1M

1M

2

3

4

8

8

6

2

7

1

6

54

5

620k

220k

150

µF

150

µF

150

µF

3V LITHIUM BATTERY

DURACELL DL123A

OPEN-DRAIN

LOW-BATTERY OUTPUT

5V/100mA

MAX660

MAX667

IN

OUT

LBO

DD

SET

GND SHDN

NOTE: ALL 150

µF 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

D1, D2 = 1N4148

MAX660

Figure 6. MAX660 generates a +5V regulated output from a 3V

lithium battery and operates for 16 hours with a 40mA load.