LM97593VH National Semiconductor, LM97593VH Datasheet - Page 31

• Manufacturer Part Number: LM97593VH
• Description: 12BIT ADC, 2CH, DDC/AGC, 128PQFP
• Manufacturer: National Semiconductor

Specifications of LM97593VH

• Resolution (bits): 12bit
• Input Channel Type: Differential
• Data Interface: Serial
• Supply Voltage Range - Analogue: 3V To 3.6V
• Supply Voltage Range - Digital: 1.6V To 2V, 3V To 3.6V
• Supply: RoHS Compliant
• Sampling Rate: 65MSPS
• Rohs Compliant: Yes
• Lead Free Status / Rohs Status: Not Compliant

response through to the second filter. The latter can then be
programmed as a Nyquist (typically a root-raised-cosine) filter
for matched filtering of digital data.
The complete channel filter response for standard coefficients
is shown in Figure 29. Passband flatness is shown in Figure
30. The complete filter response for GSM coefficients is
shown in Figure 31. GSM Passband flatness is shown in Fig-
ure 32.
The mask shown in Figure 31 is derived from the ETSI GSM
5.05 specifications for a normal Basestation Transceiver
(BTS). For interferers, 9dB was added to the carrier to inter-
ference (C/I) ratios. For blockers, 9dB was added to the
difference between the blocker level and 3dB above the ref-
erence sensitivity level.
4.6 Channel Bandwidth vs. Sample Rate
When the LM97593 is used for GSM systems, a bandwidth of
about 200kHz is desired. With a sample rate of 52MHz, the
total decimation of 192 provides the desired 270.833kHz out-
put sample rate. This output sample rate in combination with
the FIR filter coefficients create the desired channel band-
width. If the sample rate is increased to 65MHz, the decima-
tion must also be increased to 65MHz/270.833kHz or 240.
This new decimation rate will maintain the same output
FIGURE 28. F2 GSM frequency response
FIGURE 27. F2 STD frequency response
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bandwidth. The output bandwidth may only be changed in re-
lation to the output sample rate by creating a new set of FIR
filter coefficients. As the filter bandwidth
FIGURE 31. CIC, F1, & F2 GSM frequency response
FIGURE 29. CIC, F1, & F2 STD frequency response
FIGURE 30. CIC, F1, & F2 STD Passband Flatness
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