ssm2517 Analog Devices, Inc., ssm2517 Datasheet - Page 14

• Manufacturer Part Number: ssm2517
• Description: Pdm Digital Input, Mono 2.4 W Class-d Audio Amplifier Ssm2517
• Manufacturer: Analog Devices, Inc.

SSM2517
PDM PATTERN CONTROL
The SSM2517 has a simple control mechanism that can set the
part for low power states and control functionality. This is
accomplished by sending a repeating 8-bit pattern to the device.
Different patterns set different functionality (see Table 8).
Any pattern must be repeated a minimum of 128 times. The
part is automatically muted when a pattern is detected so that
a pattern can be set while the part is operational without a
pop/click due to pattern transition.
All functionality set via patterns returns to its default value after
a clock-loss power-down.
Table 8. PDM Watermarking Pattern Control Descriptions
Pattern
0xAC
0xD8
0xD4
0xD2
0xD1
0xE1
0xE2
0xE4
EMI NOISE
The SSM2517 uses a proprietary modulation and spread-
spectrum technology to minimize EMI emissions from the
device. For applications that have difficulty passing FCC
Class-B emission tests, the SSM2517 includes a modulation
select mode (ultralow EMI emissions mode) that significantly
reduces the radiated emissions at the Class-D outputs, particu-
larly above 100 MHz. This mode is enabled by activating PDM
Watermarking Pattern 0xE1 (see Table 8).
Control Description
Power-down. All blocks off except for PDM interface.
Normal start-up time.
Gain optimized for PVDD = 5 V operation.
Overrides GAIN_FS pin setting.
Gain optimized for PVDD = 3.6 V operation.
Overrides GAIN_FS pin setting.
Gain optimized for PVDD = 2.5 V operation.
Overrides GAIN_FS pin setting.
f
Ultralow EMI mode.
Half clock cycle pulse mode for power savings.
Special 32 kHz/128 × f
S
set to opposite value determined by GAIN_FS pin.
S
operation mode.
Rev. A | Page 14 of 16
OUTPUT MODULATION DESCRIPTION
The SSM2517 uses three-level, Σ-Δ output modulation. Each
output can swing from PGND to PVDD and vice versa. Ideally,
when no input signal is present, the output differential voltage is
0 V because there is no need to generate a pulse. In a real-world
situation, noise sources are always present.
Due to this constant presence of noise, a differential pulse is
generated, when required, in response to this stimulus. A small
amount of current flows into the inductive load when the differ-
ential pulse is generated.
Most of the time, however, the output differential voltage is 0 V,
due to the Analog Devices, Inc., three-level, Σ-Δ output modula-
tion. This feature ensures that the current flowing through the
inductive load is small.
When the user wants to send an input signal, an output pulse
(OUT+ and OUT−) is generated to follow the input voltage.
The differential pulse density (VOUT) is increased by raising
the input signal level. Figure 30 depicts three-level, Σ-Δ output
modulation with and without input stimulus.
Figure 30. Three-Level, Σ-Δ Output Modulation With and Without Input Stimulus
VOUT
VOUT
VOUT
OUT+
OUT+
OUT+
OUT–
OUT–
OUT–
OUTPUT = 0V
OUTPUT > 0V
OUTPUT < 0V
+5V
0V
+5V
0V
+5V
0V
–5V
+5V
0V
+5V
0V
+5V
0V
+5V
0V
+5V
0V
0V
–5V