icl7660aipa Intersil Corporation, icl7660aipa Datasheet - Page 7

• Manufacturer Part Number: icl7660aipa
• Description: Cmos Voltage Converters
• Manufacturer: Intersil Corporation

Typical Applications
Simple Negative Voltage Converter
The majority of applications will undoubtedly utilize the ICL7660
and ICL7660A for generation of negative supply voltages.
Figure 13 shows typical connections to provide a negative
supply negative (GND) for supply voltages below 3.5V.
The output characteristics of the circuit in Figure 13A can be
approximated by an ideal voltage source in series with a
resistance as shown in Figure 13B. The voltage source has
a value of -V+. The output impedance (R
the ON resistance of the internal MOS switches (shown in
Figure 12), the switching frequency, the value of C
and the ESR (equivalent series resistance) of C1 and C2. A
good first order approximation for R
R
O
2(R
2(R
SW1
SW2
10 F
+ R
+ R
C
+
SW3
SW4
1
-
V
-(V+)
+ ESR
+ ESR
3-32
0
FIGURE 16. CASCADING DEVICES FOR INCREASED OUTPUT VOLTAGE
C1
C1
) +
) +
O
1
2
3
4
1
2
3
4
is:
O
ICL7660A
ICL7660A
ICL7660
B
ICL7660
) is a function of
“1”
“1”
FIGURE 15. PARALLELING DEVICES
1
A
FIGURE 14. OUTPUT RIPPLE
ICL7660, ICL7660A
and C
8
7
6
5
8
7
6
5
t
2
10 F
V+
2
10 F
,
V+
+
-
C
+
-
1
RSW, the total switch resistance, is a function of supply
voltage and temperature (See the Output Source Resistance
graphs), typically 23 at 25
C
output impedance. High value capacitors will reduce the
1/(f
lower the ESR term. Increasing the oscillator frequency will
reduce the 1/(f
of a net increase in output impedance when C
there is no longer enough time to fully charge the capacitors
(f
Combining the four R
1
PUMP
t
1
1
2
3
4
PUMP
and C
1
2
3
4
R
R
O
O
ICL7660A
=
ICL7660A
ICL7660
ICL7660
2
“n”
“n”
2(R
will reduce the remaining terms, minimizing the
C
(f
1
PUMP
2 (R
SW1
) component, and low ESR capacitors will
PUMP
f
OSC
SW
1
2
+ R
) (C1)
8
7
6
5
10 F
8
7
6
5
SWX
) +
SW3
C1) term, but may have the side effect
C
+
-
terms as R
2
+
-
+ ESR
, R
(f
+ ESR
PUMP
o
C and 5V. Careful selection of
SWX
1
V
C2
C1
) (C1)
OUT
= MOSFET switch resistance)
SW
) +
, we see that:
=
R
L
-
nV+
+ 4 (ESR
1
C1
> 10 F and
) + ESR
C2