SSM2211CP-REEL7 Analog Devices Inc, SSM2211CP-REEL7 Datasheet - Page 16

• Manufacturer Part Number: SSM2211CP-REEL7
• Description: IC AMP AUDIO PWR 1W MONO 8LFCSP
• Manufacturer: Analog Devices Inc
• Type: Class ABr

Specifications of SSM2211CP-REEL7

• Rohs Status: RoHS non-compliant
• Output Type: 1-Channel (Mono)
• Max Output Power X Channels @ Load: 1.5W x 1 @ 4 Ohm
• Voltage - Supply: 2.7 V ~ 5.5 V
• Features: Differential Inputs, Shutdown
• Mounting Type: Surface Mount
• Package / Case: 8-LFCSP
• Other names: SSM2211CP-REEL7; SSM2211CP-REEL7TR

SSM2211
POWER DISSIPATION
Another important advantage in using a BTL configuration is
the fact that bridged-output amplifiers are more efficient than
single-ended amplifiers in delivering power to a load. Efficiency
is defined as the ratio of the power from the power supply to the
power delivered to the load
An amplifier with a higher efficiency has less internal power
dissipation, which results in a lower die-to-case junction
temperature compared with an amplifier that is less efficient.
This is important when considering the amplifier maximum
power dissipation rating vs. ambient temperature. An internal
power dissipation vs. output power equation can be derived to
fully understand this.
The internal power dissipation of the amplifier is the internal
voltage drop multiplied by the average value of the supply
current. An easier way to find internal power dissipation is to
measure the difference between the power delivered by the
supply voltage source and the power delivered into the load.
The waveform of the supply current for a bridged-output
amplifier is shown in Figure 43.
By integrating the supply current over a period, T, and then
dividing the result by T, the I
terms of peak output voltage and load resistance
Therefore, power delivered by the supply, neglecting the bias
current for the device, is
Figure 43. Bridged Amplifier Output Voltage and Supply Current vs. Time
η
I
P
DD
SY
=
I
P
DD, PEAK
,
P
AVG
=
SY
V
L
V
PEAK
2
OUT
I
SY
V
=
DD
2
π
V
π
×
R
PEAK
R
L
V
L
PEAK
T
T
DD,AVG
can be found. Expressed in
TIME
TIME
I
DD, AVG
Rev. E | Page 16 of 24
(5)
(6)
The power dissipated internally by the amplifier is simply the
difference between Equation 6 and Equation 3. The equation
for internal power dissipated, P
delivered to the load and load resistance, is
The graph of this equation is shown in Figure 44.
Because the efficiency of a bridged-output amplifier (Equation 3
divided by Equation 6) increases with the square root of P
power dissipated internally by the device stays relatively flat and
actually decreases with higher output power. The maximum
power dissipation of the device can be found by differentiating
Equation 7 with respect to load power and setting the derivative
equal to zero. This yields
and occurs when
Using Equation 9 and the power derating curve in Figure 31,
the maximum ambient temperature can be found easily. This
ensures that the SSM2211 does not exceed its maximum
junction temperature of 150°C. The power dissipation for a
single-ended output application where the load is capacitively
coupled is given by
The graph of Equation 10 is shown in Figure 45.
P
P
P
∂
DISS
DISS
P
∂
DISS
Figure 44. Power Dissipation vs. Output Power with V
1.5
1.0
0.5
P
DISS
0
L
0
,
MAX
=
=
=
2
2
π
π
V
=
DD
π
2
2
2
V
V
R
R
2
= 5V
V
π
R
L
DD
L
V
DD
DD
2
L
DD
R
×
L
×
×
2
0.5
OUTPUT POWER (W)
R
P
1
P
P
L
L
L
L
= 16Ω
−
DISS
−
−
P
P
1
, expressed in terms of power
L
L
=
0
1.0
R
L
R
= 8Ω
L
= 4Ω
DD
= 5 V
1.5
L
, the
(10)
(7)
(8)
(9)