ISL5416_14 Datasheet, PDF (44/71 Pages) Intersil Corporation – Four-Channel Wideband Programmable

ISL5416
TABLE 39. LOWER THRESHOLD, ATTENUATOR CHANGE (IWA = 0*13h) RESET STATE = 0x00000000h
CONTROL IS SHARED FOR AIN/BIN AND FOR CIN/DIN
THIS
P(31:0)
FUNCTION
31:30 RESERVED. Set to 0.
29:16
ATTENUATION STEP 3.
Amount to decrease the attenuation control register if the average input magnitude is below the lower threshold. 14-bit value loads
the LSBs of a 17-bit accumulator. The 3 MSBs of the 17-bit load are hard-wired to “111” , so the load value should be masked from
a negative number. The MSB of the 14-bit value is weighted at 6 dB so the value at all zeros would be ~12 dB (decrease in
attenuation).
15:0 THRESHOLD 3.
Lower threshold value. If the accumulated and normalized input magnitude is below this value, the attenuation control accumulator is
adjusted by the amount programmed in bits 29:16.
TABLE 40. UPPER THRESHOLD, ATTENUATOR CHANGE (IWA = 0*14h) RESET STATE = 0x00000000h
CONTROL IS SHARED FOR AIN/BIN AND FOR CIN/DIN
THIS
P(31:0)
FUNCTION
31:30 RESERVED. Set to 0.
29:16
ATTENUATION STEP 2.
Amount to increase the attenuation control register if the average input magnitude is above the upper threshold. 14-bit value loads
the LSBs of a 17-bit accumulator. The 3 MSBs of the 17-bit load are hard-wired to “000” . The MSB of the 14-bit value is weighted at
6 dB so the value at all ones would be ~12 dB (increase in attenuation).
15:0 THRESHOLD 2.
Upper threshold value. If the accumulated and normalized input magnitude is above this value, the attenuation control accumulator
is adjusted by the amount programmed in bits 29:16.
TABLE 41. IMMEDIATE THRESHOLD, ATTENUATOR GAIN (IWA = 0*15h) RESET STATE = 0x00000000h
CONTROL IS SHARED FOR AIN/BIN AND FOR CIN/DIN
THIS
P(31:0)
FUNCTION
31:30 RESERVED. Set to 0.
29:16
ATTENUATION STEP 1.
Amount to increase the attenuation control register if the sample-by-sample input magnitude is above the immediate threshold. 14-
bit value loads the LSBs of a 17-bit accumulator. The 3 MSBs of the 17-bit load are hard-wired to “000” . The MSB of the 14-bit value
is weighted at 6 dB so the value at all ones would be ~12 dB (increase in attenuation). This change happens immediately. Subsequent
changes due to crossing this threshold are held off by the delay in location IWA = 0*10, bits 31:24.
15:0 THRESHOLD 1.
Immediate threshold value. If the input magnitude is above this value, the attenuation control accumulator is adjusted by the amount
programmed in bits 29:16.
NOTES ON THRESHOLDS:
The input range is -32768 to 32767 (0x8000 to 0x7FFF)
The magnitude range is 0 to 32768 ( 0x0000 to 0x8000)
The immediate threshold is 0 to 65536 (0x0000 to 0xFFFF)
The magnitude must be greater than the immediate threshold to trigger.
The integration period is 2 to 2¹⁶.
The integrated magnitude range is 0x00000000 to 0x80000000
The normalization divider range is 2¹ to 2¹⁶, so with the maximum dividers:
The averaged output is 0x0000 to 0x8000
The upper and lower thresholds are 0 to 65536 (0x0000 to 0xFFFF)
To trigger the upper and lower comparisons:
The magnitude must be greater than the upper threshold.
The magnitude must be less than lower threshold.
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