Rainbow Electronics MAX864 - Manual (Page 8)

MAX864
Dual-Output Charge Pump with Shutdown
8 _______________________________________________________________________________________
__________Applications Information
Positive and Negative Converter
The most common application of the MAX864 is as a
dual charge-pump voltage converter that provides pos-
itive and negative outputs of two times a positive input
voltage for biasing analog circuitry (Figure 3). Select a
charge-pump frequency high enough so it does not
interfere with other circuitry, but low enough to maintain
low supply current. See Table 1 for the correct device
configuration.
Paralleling Devices
Paralleling multiple MAX864s reduces the output resis-
tance of both the positive and negative converters
(Figure 4). The effective output resistance is the output
resistance of one device divided by the total number of
devices. Separate C1 and C2 charge-pump capacitors
are required for each MAX864, but the reservoir capac-
itors C3 and C4 can be shared.
MAX864
C1+
1
2
3
4
5
6
7
8
C1-
16
15
14
13
12
11
10
9
C2
IN
SEE TABLE 1
C1
C3
C4
V
IN
(+1.75V TO +6.0V)
C2+
C2-
GND
V-
SHDN
FC0
FC1
+2 x V IN
-2 x V IN
V+
N.C.
N.C.
IN
GND
N.C.
N.C.
Figure 3. Positive and Negative Converter