MAX828/MAX829
Switched-Capacitor Voltage Inverters
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Heavy Output Current Loads
When under heavy loads, where higher supply is sourcing
current 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).
Layout and Grounding
Good layout is important, primarily for good noise perfor-
mance. To ensure good layout, mount all components as
close together as possible, keep traces short to mini-
mize parasitic inductance and capacitance, and use a
ground plane.
Shutting Down the MAX828/MAX829
For a similar device with logic-controlled shutdown,
please refer to the MAX1719/MAX1720/MAX1721. To
add manual shutdown control to the MAX828/MAX829,
use the circuit in Figure 8. The output resistance of the
MAX828/MAX829 will typically be 20Ω plus two times
the output resistance of the buffer driving IN. The 0.1µF
capacitor at the IN pin absorbs the transient input cur-
rents of the MAX828/MAX829.
The output resistance of the buffer driving the IN pin can
be reduced by connecting multiple buffers in parallel.
The polarity of the SHUTDOWN signal can also be
changed by using a noninverting buffer to drive IN.
