MAX871 MAXIM [Maxim Integrated Products], MAX871 Datasheet - Page 7

• Manufacturer Part Number: MAX871
• Description: Switched-Capacitor Voltage Inverters
• Manufacturer: MAXIM [Maxim Integrated Products]

capacitors. Because both the inverter and doubler use
part of the charge-pump circuit, loading either output
causes both outputs to decline toward GND. Make sure
the sum of the currents drawn from the two outputs
does not exceed 40mA.
Under heavy loads, where higher supply is sourcing cur-
rent into OUT, the OUT supply must not be pulled above
ground. Applications that sink heavy current into OUT
require a Schottky diode (1N5817) between GND and
OUT, with the anode connected to OUT (Figure 7).
Good layout is important, primarily for good noise per-
formance. To ensure good layout, mount all compo-
nents as close together as possible, keep traces short
to minimize parasitic inductance and capacitance, and
use a ground plane.
Figure 4. Cascading MAX870s or MAX871s to Increase
Output Voltage
C1
5
3
4
MAX870
MAX871
“1”
_______________________________________________________________________________________
Heavy Output Current Loads
Switched-Capacitor Voltage Inverters
2
1
C1
+V
Layout and Grounding
IN
…
…
C2
3
4
5
V
MAX870
MAX871
OUT
“n”
= -nV
IN
2
1
V
C2
OUT
Figure 5. Paralleling MAX870s or MAX871s to Reduce Output
Resistance
Figure 6. Combined Doubler and Inverter
Figure 7. High V- Load Current
C1
C1
R
OUT
=
R
NUMBER OF DEVICES
OUT
3
4
5
3
4
5
OF SINGLE DEVICE
MAX870
MAX871
MAX870
MAX871
“1”
C3
MAX870
MAX871
2
1
C1
2
1
+V
+V
GND
OUT
IN
IN
4
1
…
…
D2
D1
5
3
4
V
MAX870
MAX871
OUT
D1, D2 = 1N4148
C2
C4
“n”
= -V
V
(V
V
IN
OUT
OUT
FD1
) - (V
= -V
= (2V
2
1
IN
FD2
IN
) -
)
V
C2
OUT
7