HMC900LP5E Datasheet, PDF (17/26 Pages) Hittite Microwave Corporation – 50 MHz DUAL PROGRAMMABLE LOW PASS FILTER with DRIVER

v04.0811
HMC900LP5E
50 MHz DUAL PROGRAMMABLE
LOW PASS FILTER with DRIVER
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Table 10. Calibration Code Look up Table
fine_bandwidth_code [3:0]
min
(MHz/MHz)
fine_tune_ratio
typ
(MHz/MHz)
0000
0.790
0.803
0001
0.818
0.832
0010
0.846
0.862
0011
0.878
0.893
0100
0.909
0.926
0101
0.943
0.959
0110
0.976
0.994
0111
1.012
1.030
1000
10.48
1.068
1001
1.087
1.107
1010
1.128
1.148
1011
1.169
1.189
max
(MHz/MHz)
0.818
0.846
0.878
0.909
0.943
0.976
1.012
1.048
1.087
1.128
1.169
1.210
3. Program the SPI for the given device with the coarse and fine bandwidth code, and instruct the device to use
the provided instructions.
a. Write coarse_bandwidth_code[3:0] to Reg 02h bits [9:6]
b. Write fine_bandwidth_code[3:0] to Reg 03h bits [3:0]
c. Instruct HMC900LP5E to use provided codes by setting Reg 01h bit 4.
Filter Bandwidth Setting After Calibration
After the initial filter calibration is completed as above the filter bandwidth can be changed to an arbitrary bandwidth
by recalculating coarse_bandwidth_code[3:0] and fine_bandwidth_code[3:0] from the previously determined ctune.
This results in the same coarse_bandwidth_code[3:0] and fine_bandwidth_code[3:0] as if the HMC900LP5E was
recalibrated as described above.
If ctune is unknown but the current desired frequency is known then the value of ctune needs to be estimated based on
the values of coarse_bandwidth_code[3:0] and fine_bandwidth_code[3:0] and the corresponding nominal frequencies
in Table 9 and Table 10.
For example, if the 3 dB bandwidth for the HMC900LP5E was factory pre-programmed to a customer defined
requirement of 34 MHz and coarse_bandwidth_code[3:0] and fine_bandwidth_code[3:0] are “0111” and “1001”
respectively (as determined from Reg 0Ah for a pre-programmed part or from Reg 02h for a non programmed part)
then ctune can be estimated as follows:
1. Lookup the nominal coarse bandwidth and fine bandwidth frequencies.
a. From Table 9 the nominal coarse frequency is 35.0 MHz
b. From Table 10 the nominal fine normalized frequency is 1.107 MHz/ MHz or simply 1.107
2. Estimate ctune as:

ctune=(35 MHz * 1.107 )/ 34 MHz = 1.13956
This value of ctune can now be used to calculate any arbritary filter frequency as described above.
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