SSM2135_03 Datasheet, PDF (10/16 Pages) Analog Devices – Dual Single-Supply Audio Operational Amplifier

SSM2135
5V SUPPLY
AD1868
VL
18-BIT
DAC
VBL
DL
18-BIT
LL ^SERIAL
REG.
CK
DR
18-BIT
LR SERIAL
REG.
DGND
VBR
18-BIT
DAC
VREF
VREF
VOL
AGND
VOR
VS
7.68k⍀
330pF
7.68k⍀
330pF
9.76k⍀
1/2
SSM2135
7.68k⍀
100pF
220␮F
LEFT
CHANNEL
OUTPUT
47k⍀
9.76k⍀
7.68k⍀
100pF
1/2
SSM2135
220␮F
RIGHT
CHANNEL
OUTPUT
47k⍀
Figure 5. 5 V Stereo 18-Bit DAC
18-Bit Stereo CD-DAC Output Amplifier
The SSM2135 makes an ideal single-supply stereo output
amplifier for audio D/A converters because of its low noise and
distortion. Figure 5 shows the implementation of an 18-bit
stereo DAC channel. The output amplifier also provides low-pass
filtering for smoothing the oversampled audio signal. The filter’s
cutoff frequency is set at 22.5 kHz and has a maximally flat
response from dc to 20 kHz.
As mentioned above, the amplifier’s outputs can drive directly
into a stereo headphone that has impedance as low as 25 W with
no additional buffering required.
Single Supply Differential Line Driver
Signal distribution and routing is often required in audio systems,
particularly portable digital audio equipment for professional
applications. Figure 6 shows a single supply line driver circuit
that has differential output. The bottom amplifier provides a 2 V
dc bias for the differential amplifier in order to maximize the
output swing range. The amplifier can output a maximum of
0.8 V rms signal with a 5 V supply. It is capable of driving into
600 W line termination at a reduced output amplitude.
1k⍀
+5V _{10␮F+0.1␮F}
100␮F
AUDIO IN
1k⍀
10k⍀
2.0V
1␮F
1/2
SSM2135
DIFFERENTIAL
AUDIO OUT
1k⍀
1/2
SSM2135
2.5k⍀
0.1␮F
100⍀
+5V
1/2
SSM2135
+5V
7.5k⍀
5k⍀
Figure 6. Single-Supply Differential Line Driver
Single-Supply Differential Line Receiver
Receiving a differential signal with minimum distortion is achieved
using the circuit in Figure 7. Unlike a difference amplifier (a
subtractor), the circuit has a true balanced input impedance
regardless of input drive levels. That is, each input always pre-
sents a 20 kW impedance to the source. For best common-mode
rejection performance, all resistors around the differential amplifier
must be very well matched. Best results can be achieved using a
10 kW precision resistor network.
DIFFERENTIAL
AUDIO IN
20k⍀
10k⍀
+5V _{10␮F+0.1␮F}
1/2
SSM2135
20k⍀
20k⍀
1␮F
2.0V
1/2
SSM2135
+5V
10⍀ ^10␮F
AUDIO
OUT
100⍀
1/2
SSM2135
7.5k⍀
+5V
5k⍀
0.1␮F
2.5k⍀
Figure 7. Single-Supply Balanced Differential
Line Receiver
Pseudo-Reference Voltage Generator
For single-supply circuits, a reference voltage source is often
required for biasing purposes or signal offsetting purposes. The
circuit in Figure 8 provides a supply splitter function with low
output impedance. The 1 mF output capacitor serves as a charge
reservoir to handle a sudden surge in demand by the load as
well as providing a low ac impedance to it. The 0.1 mF feedback
capacitor compensates the amplifier in the presence of a heavy
capacitive load, maintaining stability.
The output can source or sink up to 12 mA of current with a
5 V supply, limited only by the 100 W output resistor. Reducing
the resistance will increase the output current capability.
Alternatively, increasing the supply voltage to 12 V also
improves the output drive to more than 25 mA.
–10–
REV. E