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參數(shù)資料
| 型號： | AD1991ASV |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | Class D/1-Bit Audio Power Output Stage |
| 中文描述： | 20 W, 4 CHANNEL, AUDIO AMPLIFIER, PQFP52 |
| 封裝： | MS-026ACC, TQFP-52 |
| 文件頁數(shù)： | 8/11頁 |
| 文件大?。?/td> | 194K |
| 代理商： | AD1991ASV |
REV. 0
–8–
AD1991
APPLICATION CONSIDERATIONS
Good board layout and decoupling are vital for correct operation
of the AD1991. Due to the fact that the part switches high currents,
there is the potential for large PV
DD
bounce each time a transis-
tor transitions. This can cause unpredictable operation of the part.
To avoid this potential problem, close chip decoupling is essen-
tial. It is also recommended that the decoupling capacitors be
placed on the same side of the board as the AD1991 and connected
directly to the PV
DD
and PGND pins. By placing the decoupling
capacitors on the other side of the board and decoupling through
vias, the effectiveness of the decoupling is reduced. This is
because vias have inductive properties and, therefore, prevent
very fast discharge of the decoupling capacitors. Best operation
is achieved with at least one decoupling capacitor on each side of
the AD1991 or optionally two capacitors per side can be used to
further reduce the series resistance of the capacitor. If these
decoupling recommendations cannot be followed and decoupling
through vias is the only option, the vias should be made as large
as possible to increase surface area, thereby reducing inductance
and resistance.
Figures 5 and 6 show two possible layouts to provide close chip
decoupling. In both cases, the PV
DD
to PGND decoupling is as
close as possible to the pins of the AD1991. One solution uses
surface-mount capacitors that offer low inductance; however, each
output (OUTA, OUTB, OUTC, and OUTD) must be brought
through vias to another layer of the board to be brought to the
LC filter. The other solution uses through-hole capacitors that
have higher inductance but allow the outputs to connect directly
to the LC filter. In this solution, the inductor for OUTA and
OUTC would span the PV
DD
trace. These diagrams show four
decoupling capacitors from PV
DD
to PGND; however, this may
not be necessary if capacitors with low series resistance are
used. Another close chip capacitor is used for AV
DD
to AGND
decoupling, with the actual power connections to the capacitors
being done through vias. This is quite acceptable since AV
DD
is
a low current stable supply. Finally, a close chip capacitor is used
to decouple DV
DD
to DGND. This is quite important since DV
DD
is a digital supply whose current will change dynamically and,
therefore, requires good decoupling. For both PV
DD
and DV
DD
,
additional reservoir capacitors should be used to augment the
close chip decoupling, especially for PV
DD
, which usually has very
large transients.
THERMAL CONSIDERATIONS
Careful consideration must be given to heat sinking the AD1991,
particularly in applications where the ambient temperature can
be much higher than normal room temperature. The three
thermal resistances of
JC
,
CA
, and
JA
should be known in
order to correctly heat sink the part. These values specify the
temperature difference between two points, per unit power
dissipation.
JC
specifies the temperature difference between the
junction (die) and the case (package) for each watt of power
dissipated in the die. The AD1991 is specified with a
JC
of
1
°
C/W, which means that for each watt of power dissipated in
the part, the junction (or die) temperature will be 1oC higher
than the case (or package) temperature.
The value of
CA
, the difference between the case and ambient
temperatures, is entirely dependent on the size of heat sink
attached to the case, the material used, the method of attach-
ment, and the airflow over the heat sink. The value of
CA
is
specified as 26
°
C/W for no heat sink and no airflow over the device.
Finally,
JA
is the sum of the
JC
and
CA
values, and will be
between 1
°
C/W and 27
°
C/W depending on the heat sink used.
This is the temperature difference between the junction (die) and
ambient temperature around the case (package) for each watt
dissipated in the part.
The AD1991 is specified to have a thermal shutdown of typically
150
°
C die temperature. Good design procedures allow for a
margin, so the system should be designed such that the AD1991
die never goes above 140
°
C. Knowing the maximum desirable
die temperature, the efficiency of the AD1991, the maximum
ambient temperature, and the maximum power that will be
delivered to the load, the necessary
CA
can be calculated. For an
8
load, the AD1991 has a typical efficiency of 87%, which
can be reduced slightly to be conservative. For this example,
assume an 85% efficiency. If the power delivered to the loads is
to be 2
20 W rms continuous power, the power dissipated in
the AD1991 can be calculated as follows:
Power Supplied to Loads = 40 W rms
Total Power Supplied to the AD1991 = (40/85
Power Dissipated in the AD1991 = 7 W rms
If the ambient temperature can reach 85
°
C maximum, the allowable
difference between the die temperature and ambient temperature
is (140 – 85) = 55
°
C. This gives a
JA
requirement of (55/7) =
7.9
°
C/W. This requires a heat sink that gives a
CA
of 6.9
°
C/W.
The size and type of heat sink required can now be calculated.
If adequate heat sinking is not applied to the AD1991, the system
will suffer from the AD1991 going into thermal shutdown. It is
advisable to also use the thermal warning output on the AD1991
to attenuate the power being delivered to help prevent thermal
shutdown.
100) = 47 W rms
POWER-UP CONSIDERATIONS
Careful power-up is necessary when using the AD1991 to
ensure correct operation and to avoid possible latch-up issues.
The AD1991 should be held in RESET with MUTEB asserted
until all three power supplies have stabilized. Once the supplies
have stabilized, the part can be brought out of RESET, and
following this, MUTEB can be negated.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AD1991 | Class D/1-Bit Audio Power Output Stage |
| AD1991ASVRL | Class D/1-Bit Audio Power Output Stage |
| AD1994ACPZRL | Audio Switching Amplifier |
| AD1994ACPZRL7 | Audio Switching Amplifier |
| AD203SN | Circular Connector; No. of Contacts:8; Series:LJTPQ00R; Body Material:Aluminum; Connecting Termination:Crimp; Connector Shell Size:17; Circular Contact Gender:Socket; Circular Shell Style:Wall Mount Receptacle |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD1991ASVRL | 制造商:Analog Devices 功能描述:Audio Amp Speaker 1-CH Mono/2-CH Stereo/4-CH Stereo 40W Class-D 52-Pin TQFP T/R |
| AD1991ASVZ | 制造商:Analog Devices 功能描述:Audio Amp Speaker 1-CH Mono/2-CH Stereo/4-CH Stereo 40W Class-D 52-Pin TQFP 制造商:Analog Devices 功能描述:AUDIO POWER O/P STAGE CLASS D 1991 |
| AD1991ASVZRL | 制造商:Analog Devices 功能描述:Audio Amp Speaker 1-CH Mono/2-CH Stereo/4-CH Stereo 40W Class-D 52-Pin TQFP T/R |
| AD1992 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Audio Switching Amplifier |
| AD1992_06 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Audio Switching Amplifier |
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