LTE Module Series
EM05 Hardware Design
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Do not route signal traces under crystals, oscillators, magnetic devices and RF signal traces. It is
important to route the USB differential traces in inner-layer with ground shielding on not only upper
and lower layers but also right and left sides.
If USB connector is used, please keep the ESD protection components to the USB connector as
close as possible. Pay attention to the influence of junction capacitance of ESD protection
components on USB data lines. Typically, the capacitance value should be less than 1pF.
Keep traces of USB data test points short to avoid noise coupled on USB data lines. If possible,
reserve a 0
Ω
resistor on these two lines.
3.10. PCM and I2C Interfaces
EM05 provides one Pulse Code Modulation (PCM) digital interface for audio design, which supports the
following modes:
Primary mode (short frame synchronization, works as both master and slave)
Auxiliary mode* (long frame synchronization, works as master only)
In primary mode, the data is sampled on the falling edge of the PCM_CLK and transmitted on the rising
edge. The PCM_SYNC falling edge represents the MSB. In this mode, PCM_CLK supports 128kHz,
256kHz, 512kHz, 1024kHz and 2048kHz for different speech codecs.
In auxiliary mode*, the data is sampled on the falling edge of the PCM_CLK and transmitted on the rising
edge. The PCM_SYNC rising edge represents the MSB. In this mode, PCM interface operates with a
128kHz PCM_CLK and an 8kHz, 50% duty cycle PCM_SYNC only.
EM05 supports 8-bit A-law* and
μ-law*, and also 16-bit linear data formats. The following figures show the
primary mode’s timing relationship with 8kHz PCM_SYNC and 2048kHz PCM_CLK, as well as the
auxiliary mode’s timing relationship with 8kHz PCM_SYNC and 128kHz PCM_CLK.
PCM_CLK
PCM_SYNC
PCM_OUT
MSB
LSB
MSB
125us
1
2
256
255
PCM_IN
MSB
LSB
MSB
Figure 20: Primary Mode Timing
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