RT5508WSC datasheet(23/57 Pages) RICHTEK

23 / 57 page

RT5508

is a registered trademark of Richtek Technology Corporation

DS5508-01

March

2017

www.richtek.com



RNML : Nominal resistance of coil (

)



RApp

The

application

resistance

between

amplifier and the loudspeaker, normalized to

RNML. The application resistance is assumed to

be constant through all time.

PI Control Loop :



The parameters for PI-control loop:



RMaxExcess : The maximum tolerable resistance

growth ratio. 8-bit unsigned number representing

the value 1/256 to 255/256



PdictWeight : The weighting of prediction



Kp: proportional gain of PI-controller



KiKpRatio : ratio of Ki/Kp

This value of rMaxExcess should be set correctly

considering the material dependent scale factor and

the

ambient

temperature

when

the

resistance

calibration procedure is activated.

Excursion Control Loop

Speaker (Impedance) Identification

IIR with 2nd to 5th order can be chosen in this

implementation. 3rd order is generally sufficient for the

mobile devices, and 5th order is reserved for the case

when vented-box is implemented. The impedance

coefficients update is disabled at PWDN/SUSPD/Off

/Fault/Mute mode or when the input signal power is

below the threshold of the signal detector (Silence

mode).

The parameters for impedance identification



SglEn : enable the adaptation in single-tone case



SIBlocks : block size to average coefficient update

vector



SIOrd : order of IIR filter



InitImpIDMu : step size to update coefficient in

initial stage



ImpIDMU : step size in normal stage

Excursion Prediction

The excursion is predicted by integrating the back emf,

which is induced by the coil movement and direct

proportional to its velocity scaled by the Bl factor.

Resistance Calibration :

A measurement of resistance is activated by register

control, after this procedure, the initial value of DCR is

saved to One-Time-Program (OTP) memory.

The command/status for DC Resistance Calibration :



DCRCalEn : Trigger the automatic DCR calibration

procedure once



InitDCR : Calibrated DC resistance value

Bl Calibration

Bl factor

)

(



can be calibrated to check if the preset

coefficient is adequate.

The command/status for Bl Calibration :



BlCalEn : Trigger the automatic Bl calibration

procedure once



InitBlFactor : Calibrated Bl factor

Speaker Damage Detection

In two cases the loudspeaker is considered as

damaged :

1. The DCR deviates for a scale above predefined

value.

2. The Resonant deviates for a scale above or below

predefined value.

The parameters for Damage detection :



rMaxDamage : Threshold of resistor growth,

specified by 0 to 1, represents the ratio with

respect to the value of initial calibrated resistor.

“0”

is a special setting that disables this function.



fScaleDamage : The boundary for resonant

frequency drift vs. the preset resonant frequency.

0~1,



fRes x fScaleDamage > fRes0 or fRes < fRes0 x

fScaleDamage will trigger the damage event.



DamgeRecoveryTime : The time (seconds) to

recovery from damaged situations. “0” is a special

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