MAX2165ETI+ Maxim Integrated Products, MAX2165ETI+ Datasheet - Page 19

• Manufacturer Part Number: MAX2165ETI+
• Description: RF Receiver Low power, zero-IF t uner for mobile TV F
• Manufacturer: Maxim Integrated Products

Specifications of MAX2165ETI+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Unlike the tracking filter, it is not necessary to interpolate
notch filter settings for various operating frequencies.
When receiving channels below 725MHz in the presence
of cellular blockers, the TF_NTCH[3:0] bits should be pro-
grammed to the lower notch frequency that is stored in
the ROM table. When receiving channels above 725MHz
in the presence of cellular blockers the TF_NTCH[3:0]
bits can be programmed to the upper notch frequency
that is stored in the ROM table.
The MAX2165 includes programmable baseband and
tracking filters. The baseband filter bandwidth is con-
trolled through the BB_BW[3:0] bits in the Baseband
Control register (Table 12). The tracking filter’s balun fre-
quency can be programmed through the TF_BAL[3:0] in
the Tracking Filter register (Table 6).
To accommodate process variations, each part is factory
calibrated. During calibration, the best notch filter settings
for two different notch frequencies, the best balun set-
tings for 470MHz and 780MHz, and the best baseband
filter settings for 6MHz to 8MHz channels are determined.
These settings are stored in an on-chip ROM table that
must be read upon power-up and stored in the micro-
processor local memory (3 bytes total). Table 21 shows
the address and bits for each ROM table entry.
Each ROM table entry must be read using a two-step
process. First, the address of the bits to be read must be
programmed into the TFA[3:0] bits in the ROM Table
Address register (Table 15).
Once the address has been programmed, the data
stored in that address is transferred to the TRF[7:0] bits in
the ROM Table Data Readback register (Table 17). The
ROM data at the specified address can then be read
from the TRF[7:0] bits and stored in the microprocessor’s
local memory.
The TF_BAL[3:0] bits must be reprogrammed for each
channel frequency to optimize performance over the
band. The values given for 780MHz and 470MHz in the
ROM table can be used to interpolate the optimal coeffi-
cients for any other frequency using the equation:
Value BAL_L (BAL_H BAL_L) x
=
Baseband Filter and Tracking Filter
+
______________________________________________________________________________________
Interpolating Balun Coefficients
−
Reading the ROM Table
780MHz 470MHz
f 470MHz
−
Single-Conversion DVB-H Tuner
−
where:
Value = decimal value of the optimal TF_BAL[3:0] set-
ting for desired channel frequency, f
BAL_L = decimal value of the optimal TF_BAL[3:0] set-
ting for 470MHz as read from the ROM table
BAL_H = decimal value of the optimal TF_BAL[3:0] set-
ting for 780MHz as read from the ROM table
f = desired channel frequency in MHz
Example: Assume the TF_BAL[3:0] values read from
the ROM table for 780MHz and 470MHz are 14 and 2,
respectively, and we wish to program the balun for
operation at an RF frequency of 620MHz.
Using the previous equation, we can calculate:
Rounding to the nearest integer value gives us 8; there-
fore, when operating at 620MHz, the TF_BAL[3:0] bits in
the Tracking Filter register must be programmed to 1000.
The MAX2165 baseband filter is freely programmable
over a wide range of 3dB cutoff frequencies from
approximately 3.0MHz to 4.3MHz, but the exact cutoff
frequency varies from part-to-part due to manufactur-
ing process variations. To avoid requiring the user to
find the correct setting, the best setting for a 3.9MHz
cutoff frequency (i.e., 8MHz wide DVB-T/-H channels)
is determined by Maxim and stored on a ROM table on
every chip. The user needs to read this value from the
ROM table entry 0x3 (see Table 21) and write it back
into register 0xA bits BB_BW[3:0] (see Table 12) upon
powering up the MAX2165.
If a different cutoff frequency than 3.9MHz is desired, a
fixed value per Table 22 can be added or subtracted
from the number read-out of the ROM table, before
writing it back into the corresponding MAX2165 register.
This way the factory calibration is still utilized and the
resulting cutoff frequency is still reasonably accurate.
Value at 620MHz 2 (14 - 2) x
Baseband Filter Setting for RF Channels Other than
8MHz or Modulation Types Other than DVB-T
= +
Setting the Baseband Filter
620MHz 470MHz
780MHz 470MHz
−
−
= 7 8 .
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