HWD2190 Datasheet, PDF (18/32 Pages) List of Unclassifed Manufacturers – 1 Watt Audio Power Amplifier

Application Information
BRIDGED CONFIGURATION EXPLANATION
As shown in Figure 1, the HWD2190 has two operational
amplifiers internally, allowing for a few different amplifier
configurations. The first amplifier’s gain is externally config-
urable, while the second amplifier is internally fixed in a
unity-gain, inverting configuration. The closed-loop gain of
the first amplifier is set by selecting the ratio of R_f to R_IN
while the second amplifier’s gain is fixed by the two internal
20kΩ resistors. Figure 1 shows that the output of amplifier
one serves as the input to amplifier two which results in both
amplifiers producing signals identical in magnitude, but out
of phase by 180˚. Consequently, the differential gain for the
IC is
A_VD= 2 *(R_f/R_IN)
By driving the load differentially through outputs Vo1 and
Vo2, an amplifier configuration commonly referred to as
“bridged mode” is established. Bridged mode operation is
different from the classical single-ended amplifier configura-
tion where one side of the load is connected to ground.
A bridge amplifier design has a few distinct advantages over
the single-ended configuration, as it provides differential
drive to the load, thus doubling output swing for a specified
supply voltage. Four times the output power is possible as
compared to a single-ended amplifier under the same con-
ditions. This increase in attainable output power assumes
that the amplifier is not current limited or clipped. In order to
choose an amplifier’s closed-loop gain without causing ex-
cessive clipping, please refer to the Audio Power Amplifier
Design section.
A bridge configuration, such as the one used in the HWD2190,
also creates a second advantage over single-ended amplifi-
ers. Since the differential outputs, Vo1 and Vo2, are biased
at half-supply, no net DC voltage exists across the load. This
eliminates the need for an output coupling capacitor which is
required in a single supply, single-ended amplifier configura-
tion. Without an output coupling capacitor, the half-supply
bias across the load would result in both increased internal
IC power dissipation and also possible loudspeaker damage.
EXPOSED-DAP PACKAGE PCB MOUNTING
CONSIDERATIONS FOR THE HWD2190LD
The HWD2190LD’s exposed-DAP (die attach paddle) package
(LD) provides a low thermal resistance between the die and
the PCB to which the part is mounted and soldered. The
HWD2190LD package should have its DAP soldered to the
grounded copper pad (heatsink) under the HWD2190LD (the
NC pins, no connect, and ground pins should also be directly
connected to this copper pad-heatsink area). The area of the
copper pad (heatsink) can be determined from the LD Power
Derating graph. If the multiple layer copper heatsink areas
are used, then these inner layer or backside copper heatsink
areas should be connected to each other with 4 (2 x 2) vias.
The diameter for these vias should be between 0.013 inches
and 0.02 inches with a 0.050inch pitch-spacing. Ensure
efficient thermal conductivity by plating through and solder-
filling the vias.
POWER DISSIPATION
Power dissipation is a major concern when designing a
successful amplifier, whether the amplifier is bridged or
single-ended. A direct consequence of the increased power
delivered to the load by a bridge amplifier is an increase in
internal power dissipation. Since the HWD2190 has two opera-
tional amplifiers in one package, the maximum internal
power dissipation is 4 times that of a single-ended amplifier.
The maximum power dissipation for a given application can
be derived from the power dissipation graphs or from Equa-
tion 1.
P_DMAX = 4*(V_DD)²/(2π²R_L) (1)
It is critical that the maximum junction temperature T_JMAX of
150˚C is not exceeded. T_JMAX can be determined from the
power derating curves by using P_DMAX and the PC board foil
area. By adding additional copper foil, the thermal resistance
of the application can be reduced, resulting in higher P_DMAX.
Additional copper foil can be added to any of the leads
connected to the HWD2190. Refer to the APPLICATION IN-
FORMATION on the HWD2190 reference design board for an
example of good heat sinking. If T_JMAX still exceeds 150˚C,
then additional changes must be made. These changes can
include reduced supply voltage, higher load impedance, or
reduced ambient temperature. Internal power dissipation is a
function of output power. Refer to the Typical Performance
Characteristics curves for power dissipation information for
different output powers and output loading.
POWER SUPPLY BYPASSING
As with any amplifier, proper supply bypassing is critical for
low noise performance and high power supply rejection. The
capacitor location on both the bypass and power supply pins
should be as close to the device as possible. Typical appli-
cations employ a 5V regulator with 10 µF tantalum or elec-
trolytic capacitor and a ceramic bypass capacitor which aid
in supply stability. This does not eliminate the need for
bypassing the supply nodes of the HWD2190. The selection of
a bypass capacitor, especially C_BYPASS, is dependent upon
PSRR requirements, click and pop performance (as ex-
plained in the section, Proper Selection of External Com-
ponents), system cost, and size constraints.
SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the
HWD2190 contains a shutdown pin to externally turn off the
amplifier’s bias circuitry. This shutdown feature turns the
amplifier off when a logic low is placed on the shutdown pin.
By switching the shutdown pin to ground, the HWD2190 supply
current draw will be minimized in idle mode. While the device
will be disabled with shutdown pin voltages less than
0.5V_DC, the idle current may be greater than the typical
value of 0.1µA. (Idle current is measured with the shutdown
pin grounded).
In many applications, a microcontroller or microprocessor
output is used to control the shutdown circuitry to provide a
quick, smooth transition into shutdown. Another solution is to
use a single-pole, single-throw switch in conjunction with an
external pull-up resistor. When the switch is closed, the
shutdown pin is connected to ground and disables the am-
plifier. If the switch is open, then the external pull-up resistor
will enable the HWD2190. This scheme guarantees that the
shutdown pin will not float thus preventing unwanted state
changes.