Electronic Components Datasheet Search |
|
ISL5416KIZ Datasheet(PDF) 9 Page - Intersil Corporation |
|
ISL5416KIZ Datasheet(HTML) 9 Page - Intersil Corporation |
9 / 71 page 9 ISL5416 VGA/RF Attenuator (A/D Range Control) The range control section monitors the output of the A/D and adjusts the RF/IF gain to maintain a desired A/D output range. The gain adjustments are in 6 dB steps. The levels, adjustment rates, and gain to bit mapping are programmable. The range control section uses three programmable thresholds. Two thresholds, an upper and a lower threshold, are compared against the average magnitude of the A/D output. The range control adjusts the gain to keep the average A/D output between the upper and lower thresholds. If the average is above the upper threshold, an internal attenuator control register is increased by a programmable amount. If the average is below the lower threshold, the gain attenuator control register is decreased by a separate programmed amount. The number of samples averaged for each decision is programmable. The adjustments to the attenuator control register can be less than 6 dB to further filter the inputs. Only the three MSBs of the attenuator control register are used to control the RF/IF gain, and these are weighted as 6, 12, 24 dB steps. The third threshold, an immediate threshold, is compared against the magnitude of each A/D sample. If the magnitude of any A/D sample exceeds the threshold, the attenuator control register is immediately increased by the amount programmed for the immediate threshold. Because there will be some time delay from a register change until the effect of the change is seen at the A/D, the immediate threshold is disabled for a programmable number of clock cycles after it has been triggered. To maximize the input sensitivity the range control also includes a programmable bias. If the average signal is between the upper and lower threshold, the bias value is added from the attenuator control register. This bias removes attenuation when it is no longer needed to avoid missing small signals due to high input noise figure. Four counters control the amount of time that the input is averaged and align the adjustments to time slot boundaries. One counts out the time slot period. If desired, this counter can be reset by a SYNCInX signal to align its count to the system timing. A second counter provides a programmable delay from the start of the first counter's period to the start of the integration period. This compensates for system delays or allows the adjustments to be made over a certain portion of the time slot. The third counter sets the integration period for averaging the input samples for the upper and lower threshold decisions. The fourth counter controls the number of integration periods per time slot. See Figure 2 for a block diagram. Note that the counters are ignored for the immediate threshold decisions. The user can program a separate code for output on the EOUT bus for each of the eight possible states of the three MSBs of the attenuator control register. These codes can be up to 8 bits, but if four gain control sections are used, only four bits are available for each gain control section. The mapping of the gain control bits to EOUT bits is done in GWA = 0001h and the codes are programmed in IWA = 0*17h and 0*18h. The three MSBs of the attenuator control register can be routed internally to the channels to be used as the floating- point exponents. This adds gain in 6 dB steps to compensate for the 6 dB steps of RF attenuator. The MSBs can be added to the input exponent bits if desired. There is a programmable delay from the attenuator control register to the channel input to compensate for RF/IF filter group delay and A/D and ISL5416 pipeline delays. |
Similar Part No. - ISL5416KIZ |
|
Similar Description - ISL5416KIZ |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |