ICL828 Datasheet, PDF (6/7 Pages) Intersil Corporation – Switched-Capacitor Voltage Inverter

ICL828
Voltage Splitting
The bidirectional characteristics of the switches of the
ICL828 can be used to split a higher supply in half as shown
below.
+V_IN
+
- ^C2
C1 = C2 = C3 = 47µF
GND
+
C3
-
OUT C+
INPUT
C1- _GND
-+
C1
V_OUT
(V_OUT = 1/2V_IN)
FIGURE 16. SPLIT SUPPLY APPLICATION
The combined load will be evenly shared between the two
external capacitors because the switches share the load in
parallel, the output resistance is approximately half of the
standard voltage inverter.
Equivalent Circuit
R_OUT
1/2
V_IN
FIGURE 17.
Typical value for R_OUT in the above equivalent circuit would
be 6Ω to 7Ω for an input voltage of 5V. The power efficiency
for the circuit would be:
P_EFF = (I_OUT*V_OUT)/(1/2(V_IN*I_OUT))+(V_IN*I_Q)
Typical values for ICL828 in this application,
I_Q = 22µA, R_OUT = 6Ω to 7Ω
and V_OUT = 1/2V_IN*R_LOAD/(R_OUT + R_LOAD).
The ICL828 used as a voltage splitting circuit is an efficient
means to providing a split supply application as shown in
Figures 16 through 19.
100
90
80
70
60
0 10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
FIGURE 18. EFFICIENCY vs OUTPUT CURRENT FOR SPLIT
SUPPLY APPLICATION
2.5
V_IN = 5V
2.3
2.1
1.9
1.7
1.5
0
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
FIGURE 19. OUTPUT CURRENT vs OUTPUT VOLTAGE FOR
SPLIT SUPPLY APPLICATIONS
6