National Semiconductor LM48511, Руководство пользователя

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Connections
TABLE 1. LME49600 Demonstration Board Connections
Designator Function or Use
Supply Voltage (VDD) The supply voltage operating range is from 3.0V to 5.5V, but the absolute maximum rating is 9V.
Audio Input
The two center pins of the 4 pin connector on the left above are used as differential inputs into the
LM48511, or two single-ended inputs when one center pin and an outer ground pin are paired.
Speaker (Audio Output)
The differential output for an 8
Ω
or 4
Ω
speaker.
SD_Amp
If SD_Amp is set LOW, the independent internal audio amplifier is disabled, and when set HIGH
the amplifier is enabled.
SS_EN Enable
If SS_EN Enable is set LOW, the spread spectrum function is disabled, and when set HIGH the
spread spectrum is enabled.
SD_Boost
If SD_Boost is set low, the independent regulator is disabled, and when set HIGH, the regulator is
enabled.
FB_SEL
When LOW (FB_SEL0), the regulator output voltage PV1 is as follows:
PV1 = VFB {1 + [25.5k
Ω
/ 4.87k
Ω]}
where V
FB
= 1.23V
When LOW (FB_SEL1), the regulator output voltage PV1 is as follows:
PV1 = VFB {1 + [25.5k
Ω
/9.31k
Ω] }
where V
FB
= 1.23V
PCB Layout Guidelines
This section provides general practical guidelines for PCB
layouts that use various power and ground traces. Designers
should note that these are only “rule-of-thumb” recommen-
dations and the actual results are predicated on the final
layout.
POWER AND GROUND CIRCUITS
Star trace routing techniques can have a major positive im-
pact on low-level signal performance. Star trace routing refers
to using individual traces that radiate from a signal point to
feed power and ground to each circuit or even device.
LAYOUT HELPFUL HINTS:
1. Avoid routing traces under the inductor.
2. Use three separate grounds that eventually connect to one
point:
a. Signal or quiet ground (GND2)
b. Ground for the LM48511 device (GND1)
c. SW (GND3)(switch ground)
i. This trace for the switch ground carries the heaviest cur-
rent (3A) and therefore is the nosiest. Make this trace as wide
and short as possible and keep at a distance from the quiet
ground and device ground. Give distance priority to the quiet
ground.
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