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AD6636 Datasheet(PDF) 24 Page - Analog Devices |
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AD6636 Datasheet(HTML) 24 Page - Analog Devices |
24 / 80 page AD6636 Rev. A | Page 24 of 80 Figure 26 is a block diagram of the peak detector logic. The MSR contains the absolute magnitude of the peak detected by the peak detector logic. POWER MONITOR HOLDING REGISTER MAGNITUDE STORAGE REGISTER COMPARE A>B TO MEMORY MAP FROM MEMORY MAP FROM INPUT PORTS LOAD CLEAR LOAD LOAD IS COUNT = 1? DOWN COUNTER TO INTERRUPT CONTROLLER POWER MONITOR PERIOD REGISTER Figure 26. ADC Input Peak Detector Block Diagram Mean Power Mode (Control Bits 01) In this mode, the mean power of the input port signal is integrated (by adding an accumulator) over a programmable time period (given by AMPR) to give the mean power of the input signal. This mode is set by programming Logic 1 in the power monitor function select bits of the power monitor control register for each individual input port. The 24-bit AMPR, representing the period over which integration is performed, must be programmed before activating this mode. After enabling this mode, the value in the AMPR is loaded into a monitor period timer, and the countdown is started immediately. The 15-bit mean power of input signal is right- shifted by nine bits to give 6-bit data. This 6-bit data is added to the contents of a 24-bit holding register, thus performing an accumulation. The integration continues until the monitor period timer reaches a count of 1. When the monitor period timer reaches a count of 1, the value in the MSR is transferred to the power-monitor holding register (after some formatting), which can be read through the microport or the serial port. The monitor period timer is reloaded with the value in the AMPR, and the countdown is started. Also, the first input sample signal power is updated in the MSR, and the accumulation continues with the subsequent input samples. If the interrupt is enabled, an interrupt is generated, and the interrupt status register is updated when the AMPR reaches a count of 1. Figure 27 illustrates the mean power-monitoring logic. The value in the MSR is a floating-point number with 4 MSBs and 20 LSBs. If the 4 MSBs are EXP and the 20 LSBs are MAG, the value in dBFS can be decoded by Mean Power = 10 log ⎥⎦ ⎤ ⎢⎣ ⎡ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − − ) ( 1 20 2 2 EXP MAG POWER MONITOR HOLDING REGISTER ACCUMULATOR TO MEMORY MAP FROM MEMORY MAP FROM INPUT PORTS LOAD CLEAR LOAD IS COUNT = 1? DOWN COUNTER TO INTERRUPT CONTROLLER POWER MONITOR PERIOD REGISTER Figure 27. ADC Input Mean Power-Monitoring Block Diagram Threshold Crossing Mode (Control Bits 10) In this mode of operation, the magnitude of the input port signal is monitored over a programmable time period (given by AMPR) to count the number of times it crosses a certain programmable threshold value. This mode is set by program- ming Logic 1x (where x is a don’t care bit) in the power-monitor function select bits of the power monitor control register for each individual input port. Before activating this mode, the user needs to program the 24-bit AMPR and the 10-bit upper threshold register for each individual input port. The same upper threshold register is used for both power monitoring and gain control (see the ADC Gain Control section). After entering this mode, the value in the AMPR is loaded into a monitor period timer, and the countdown is started. The magnitude of the input signal is compared to the upper threshold register (programmed previously) on each input clock cycle. If the input signal has magnitude greater than the upper threshold register, then the MSR register is incremented by 1. The initial value of the MSR is set to 0. This comparison and increment of the MSR register continues until the monitor period timer reaches a count of 1. When the monitor period timer reaches a count of 1, the value in the MSR is transferred to the power monitor holding register, which can be read through the microport or the serial port. The monitor period timer is reloaded with the value in the AMPR, and the countdown is started. The MSR register is also cleared to a value of 0. If interrupts are enabled, an interrupt is generated, and the interrupt status register is updated when the AMPR reaches a count of 1. Figure 28 illustrates the threshold crossing logic. The value in the MSR is the number of samples that have an amplitude greater than the threshold register. POWER MONITOR HOLDING REGISTER COMPARE A > B UPPER THRESHOLD REGISTER COMPARE A > B TO MEMORY MAP FROM MEMORY MAP FROM MEMORY MAP FROM INPUT PORTS LOAD CLEAR LOAD IS COUNT = 1? DOWN COUNTER TO INTERRUPT CONTROLLER POWER MONITOR PERIOD REGISTER B A Figure 28. ADC Input Threshold Crossing Block Diagram |
Número de pieza similar - AD6636_15 |
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Descripción similar - AD6636_15 |
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