GC5337 datasheet(29/49 Pages) TI

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GC5330

GC5337

www.ti.com

SLWS226 B

– DECEMBER 2010 – REVISED JANUARY 2011

Programmable Power Meters

Interval-Based Power Meter

There are three interval-based power meters which compute magnitude-squared sample values during

programmable time intervals and provide the following results:

•

Integrated magnitude-squared power

•

Peak power

•

Number of magnitude-squared values above a first threshold

•

Number of magnitude-squared values above a second threshold

An interrupt bit is set when new measurement results are available. For its input, each power meter can

independently select from the same set of internal node sources as the capture buffers.

Running-Average Power Meter for PA Protection

The running-average power meter monitors up to four signal streams on a single node, which is selectable from

the same set of internal sources as the capture buffers. For each signal stream, it measures running-average

power and counts instantaneous power values above a threshold (referred to as peaks). It can be used in

conjunction with hardware alarms for monitoring power levels for PA protection.

The running-average power meter has the following features:

•

Running average mode, with programmable forgetting factor exponent, u (0

< u < 15)

AAA y(k+1) = (1

– 2-u) × y(k) + 2-u × |x(k)|2,

AAA where x(k) is the signal sample and y(k) is the power meter output.

AAA Typically, one must set u = 11 to get 0.5-dB accuracy, u = 14 to get 0.1-dB accuracy.

•

Peak count mode: counts the number of power values, |x(k)|2, above a threshold in a specified number of

samples (window). The number of power values, threshold, and window are all programmable.

•

Flexible gating of the operation interval

Alarms

The output, y(k), from the running-average power meter can be compared on an ongoing basis to programmable

high and low thresholds (always positive). There are two alarms, alarm0 and alarm1. Each alarm is triggered (if it

is enabled) based on the programmed mode:

(0) Disabled

(1) Average power alarm. The alarm is triggered based on the following conditions:

If alarm polarity = 0 (see the alm_polarity register), y(k)

> high_threshold

If alarm polarity = 1, y(k)

< low_threshold

If alarm polarity = 2, y(k)

> high_threshold or y(k) < low_threshold

(2) Peak power alarm. The alarm is triggered based on the following conditions:

If the count of power values |x(k)|2

> peak_threshold exceeds the programmed number of

samples, peak_samples, in a programmed window, peak_window

(3) The alarm is triggered if either (1) or (2) occurs.

Alarm checks are computed on a per-antenna-stream basis. Each antenna stream y(k) result is compared to

per-stream programmable thresholds.

Once an alarm has been triggered, the output INTERRPT pin is asserted and the appropriate (alarm0 or alarm1)

alarm interrupt bit is set and, for alarm1, a programmable action takes place. The programmable action is the

same for all antenna streams, but the alarm triggering is independent for each antenna stream.

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