SP6660DS/11 SP6660 200mA Charge Pump Inverter or Doubler © Copyright 2000 Sipex Corporation
17
OSC
OUT
SP6660
C1
5
1
2
7
4
FC
C2
CAP+
CAP-
GND
6
8
3
LV
C4
C3
V+
D1
D2
+V
IN
V
OUT1
= (2 x V
IN
) - V
FD1
- V
FD2
V
OUT2
= -V
IN
V
OUT1
V
OUT2
where V
OUT1
= positive doubled output voltage,
V
IN
= input voltage,
V
FD1
= forward bias voltage across D1,
V
FD2
= forward bias voltage across D2, and
V
OUT2
= inverted output voltage.
Figure 27. The SP6660 Connected for Negative Voltage Conversion with Positive Supply Multiplication
Circuit for Negative Voltage Conversion
with Positive Supply Multiplication
A designer can use the circuit in Figure 27 to
provide both an inverted output voltage at V
OUT1
and a positive multiple of V
IN
at V
OUT2
(subtracting the forward biased voltages of D1
and D2). Capacitor C1 is for the charge pump
and capacitor C2 is for the reservoir function to
generate the inverted output voltage at V
OUT2
.
Capacitor C3 is for the charge pump and capacitor
C4 is for the reservoir function to generate the
multiplied positive output voltage at V
OUT1
.
Designers should pay special attention to the
possibility of higher source impedances at the
generated supplies due to the finite impedance
of the common charge pump driver.
