Texas Instruments LM48310SDBD Evaluation Module LM48310SDBD/NOPB LM48310SDBD/NOPB Datenbogen
Produktcode
LM48310SDBD/NOPB
-120
-100
-80
-60
-40
-20
0
10
100
1000
10000
100000
FREQUENCY (Hz)
C
R
O
SST
AL
K
(d
B
)
SNAS430D – NOVEMBER 2007 – REVISED MAY 2013
Figure 30. Crosstalk vs Frequency
DIFFERENTIAL AMPLIFIER EXPLANATION
As logic supplies continue to shrink, system designers are increasingly turning to differential analog signal
handling to preserve signal to noise ratios with restricted voltage signs. The LM48310 features a fully differential
speaker amplifier. A differential amplifier amplifies the difference between the two input signals. Traditional audio
power amplifiers have typically offered only single-ended inputs resulting in a 6dB reduction of SNR relative to
differential inputs. The LM48310 also offers the possibility of DC input coupling which eliminates the input
coupling capacitors. A major benefit of the fully differential amplifier is the improved common mode rejection ratio
(CMRR) over single ended input amplifiers. The increased CMRR of the differential amplifier reduces sensitivity
to ground offset related noise injection, especially important in noisy systems.
handling to preserve signal to noise ratios with restricted voltage signs. The LM48310 features a fully differential
speaker amplifier. A differential amplifier amplifies the difference between the two input signals. Traditional audio
power amplifiers have typically offered only single-ended inputs resulting in a 6dB reduction of SNR relative to
differential inputs. The LM48310 also offers the possibility of DC input coupling which eliminates the input
coupling capacitors. A major benefit of the fully differential amplifier is the improved common mode rejection ratio
(CMRR) over single ended input amplifiers. The increased CMRR of the differential amplifier reduces sensitivity
to ground offset related noise injection, especially important in noisy systems.
POWER DISSIPATION AND EFFICIENCY
The major benefit of a Class D amplifier is increased efficiency versus a Class AB. The efficiency of the
LM48310 is attributed to the region of operation of the transistors in the output stage. The Class D output stage
acts as current steering switches, consuming negligible amounts of power compared to their Class AB
counterparts. Most of the power loss associated with the output stage is due to the IR loss of the MOSFET on-
resistance, along with switching losses due to gate charge.
LM48310 is attributed to the region of operation of the transistors in the output stage. The Class D output stage
acts as current steering switches, consuming negligible amounts of power compared to their Class AB
counterparts. Most of the power loss associated with the output stage is due to the IR loss of the MOSFET on-
resistance, along with switching losses due to gate charge.
SHUTDOWN FUNCTION
The LM48310 features a low current shutdown mode. Set SD = GND to disable the amplifier and reduce supply
current to 0.01µA.
current to 0.01µA.
Switch SD between GND and V
DD
for minimum current consumption is shutdown. The LM48310 may be disabled
with shutdown voltages in between GND and V
DD
, the idle current will be greater than the typical 0.1µA value.
The LM48310 shutdown input has and internal pulldown resistor. The purpose of this resistor is to eliminate any
unwanted state changes when SD is floating. To minimize shutdown current, SD should be driven to GND or left
floating. If SD is not driven to GND or floating, an increase in shutdown supply current will be noticed.
unwanted state changes when SD is floating. To minimize shutdown current, SD should be driven to GND or left
floating. If SD is not driven to GND or floating, an increase in shutdown supply current will be noticed.
AUDIO AMPLIFIER POWER SUPPLY BYPASSING/FILTERING
Proper power supply bypassing is critical for low noise performance and high PSRR. Place the supply bypass
capacitors as close to the device as possible. Typical applications employ a voltage regulator with 10µF and
0.1µF bypass capacitors that increase supply stability. These capacitors do not eliminate the need for bypassing
of the LM48310 supply pins. A 1µF capacitor is recommended.
capacitors as close to the device as possible. Typical applications employ a voltage regulator with 10µF and
0.1µF bypass capacitors that increase supply stability. These capacitors do not eliminate the need for bypassing
of the LM48310 supply pins. A 1µF capacitor is recommended.
12
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: