ACT8865
Rev 2, 11-Feb-14
can be read by the system microprocessor via the
I2C interface. If an output voltage is lower than the
power-OK threshold, typically 7% below the
programmed regulation voltage, that regulator's
OK[ ] bit will be 0.
close as possible to the IC, and avoiding the use of
via if possible. The inductor, input filter capacitor,
and output filter capacitor should be connected as
close together as possible, with short, direct, and
wide traces. The ground nodes for each regulator's
power loop should be connected at a single point in
a star-ground configuration, and this point should
be connected to the backside ground plane with
multiple via. The output node for each regulator
should be connected to its corresponding OUTx pin
through the shortest possible route, while keeping
sufficient distance from switching nodes to prevent
noise injection. Finally, the exposed pad should be
directly connected to the backside ground plane
using multiple via to achieve low electrical and
thermal resistance.
If a DC/DC's nFLTMSK[-] bit is set to 1, the
ACT8865 will interrupt the processor if that DC/DC's
output voltage falls below the power-OK threshold.
In this case, nIRQ will assert low and remain
asserted until the OK[ ] bit has been read via I2C.
PCB Layout Considerations
High switching frequencies and large peak currents
make PC board layout an important part of step-
down DC/DC converter design.
Step-down DC/DCs exhibit discontinuous input
current, so the input capacitors should be placed as
Table 4:
REGx/VSET[ ] Output Voltage Setting
REGx/VSET[5:3]
REGx/VSET[2:0]
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
0.600
0.625
0.650
0.675
0.700
0.725
0.750
0.775
0.800
0.825
0.850
0.875
0.900
0.925
0.950
0.975
1.000
1.025
1.050
1.075
1.100
1.125
1.150
1.175
1.200
1.250
1.300
1.350
1.400
1.450
1.500
1.550
1.600
1.650
1.700
1.750
1.800
1.850
1.900
1.950
2.000
2.050
2.100
2.150
2.200
2.250
2.300
2.350
2.400
2.500
2.600
2.700
2.800
2.900
3.000
3.100
3.200
3.300
3.400
3.500
3.600
3.700
3.800
3.900
Innovative PowerTM
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