Philips TDA1301T Datasheet

Philips Semiconductors Product speciﬁcation

Digital servo processor (DSIC2) TDA1301T

FEATURES

The DSIC2 realizes the following servo functions:

• Diode signal preprocessing

• Focus servo loop

• Radial servo loop

• Sledge motor servo loop

• Three-line serial interface via the microcontroller

The other features include:

• Full digital signal processing

• Low power consumption, down to 30 mW

• Low voltage supply 3 to 5.5 V

• Integrated analog-to-digital converters and digital servo

loop filters

• Double speed possible

• Easy application

– Single supply voltage – Small number of external components; only

6 decoupling capacitors – Flexible system oscillator circuitry – Usable for single/double Foucault and astigmatic

focus – Full automatic radial error signal initialization offset

control and level initialization for track position

indicator – No external adjustments required; no component

ageing – Wide range of adjustable servo characteristics – Simple 3-line serial command interface

– 28-pin SO package – Great flexibility towards different CD mechanisms – Full and transparent application information

• High robustness/shock insensitivity – Sophisticated track-loss (TL) detection mechanism – Fast focus restart procedure – Extended radial error signal – Adjustable radial shock detector – Defect drop-out detector

• Fully automatic jump procedure for radial servo

• Automatic focus start-up procedure and built-in FOK

(Focus OK)

• Fast radial jump or access procedure

• Self-operational servo-control without continuous

communication via the microcontroller

• Direct communication to photodiode optics; no external preprocessing.

GENERAL DESCRIPTION

The TDA1301T is a fully digital servo processor which has been designed to provide all servo functions, except the spindle motor control, in two-stage three-spot compact disc systems. The device offers a high degree of integration, combined with the low additional cost of external components. The servo characteristics have a wide range of adjustment via a three-line serial interface. This offers an enormous flexibility with respect to applications for different CD mechanisms. The circuit is optimized for low-power low-voltage applications.

QUICK REFERENCE DATA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

DDD

DDA

DDD

DDA

DDD(q)

i(cd)

i(sd)

tot

amb

digital supply voltage 3.0 − 5.5 V analog supply voltage 3.0 − 5.5 V digital supply current − 5 − mA analog supply current − 5 − mA digital quiescent supply current − − 10 µA central diode input currents (D1 to D4) note 1 − − 15.8 µA satellite diode input currents (R1 and R2) note 1 − − 7.9 µA total power dissipation − 50 − mW operating ambient temperature −40 − +85 °C

Note

1. f

= 4.2336 MHz; VRL = 0 V; VRH = 2.5 V (externally applied).

sys

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Philips Semiconductors Product speciﬁcation

Fig.1 Block diagram.

Digital servo processor (DSIC2) TDA1301T

ORDERING INFORMATION

EXTENDED TYPE

NUMBER

TDA1301T 28 SO28L plastic SOT136A

BLOCK DIAGRAM

PINS PIN POSITION MATERIAL CODE

PACKAGE

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Philips Semiconductors Product speciﬁcation

Fig.2 Pin configuration.

Digital servo processor (DSIC2) TDA1301T

PINNING

SYMBOL PIN DESCRIPTION

RST 1 reset input (active LOW) LDON 2 laser drive on output V

SSA

D1 5 unipolar current input

D2 6 unipolar current input

D3 7 unipolar current input

D4 9 unipolar current input

R1 10 unipolar current input

R2 11 unipolar current input

DDA

XTAL TEST1 14 test input 1 TEST2 15 test input 2 OTD 16 off-track detector output CLKO 17 clock output XTALO 18 oscillator output XTALI 19 oscillator input V

DDD1

SSD

RA 22 radial actuator output FO 23 focus actuator output SL 24 sledge output SILD 25 serial interface load input SICL 26 serial interface clock input SIDA 27 serial interface data input/output V

DDD2

3 analog ground 4 reference input for reference voltage

generator

(central diode signal input)

8 reference input for ADC

(central diode signal input)

(satellite diode signal input)

(satellite diode signal input) 12 analog supply voltage 13 oscillator reference input

ref

20 digital power supply 1 21 digital ground

28 digital power supply 2

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Philips Semiconductors Product speciﬁcation

–

]

4–

D3 D4+

----------------------

–=

Fig.3 Diode configuration.

Digital servo processor (DSIC2) TDA1301T

FUNCTIONAL DESCRIPTION Three spots front-end

The photo detector in a two-stage three-spots compact disc system normally contains six discrete elements. Four of these elements (in the event of single Foucault: three elements) carry the central aperture (CA) signal while the other two elements (satellite signals) carry the radial tracking information. Besides the HF signal, which is finally applied to both of the audio channels, the central aperture also contains information for the focus servo loop. To enable the HF signal to be processed, the frequency contents of the central aperture signal must be divided into an HF data part and an LF servo part. The HF signal is processed outside the DSIC2 by the TDA1302 or a discrete amplifier-equalizer. The necessary crossover point, to extract the LF servo part, is compensated for in the amplifier.

Diode signal processing

The analog signals from the photo detectors are converted into a digital representation using analog-to-digital converters. The ADCs are designed to convert unipolar currents into a digital code. The dynamic range of the input currents is adjustable within a given range and is dependent on the ADC input reference voltages V

and

VRH. The maximum current for the central diodes signals is given in equation (1).

i max( )fsysVRHVRL

( ) 1.5 106–×××= µA[

(1)

The maximum current for the satellite signals is given in equation (2).

i max( )fsysVRHVRL

is generated internally. There are four different levels

–( ) 0.75 106–×××= µA[

(2)

(1.0, 1.5, 2.0 and 2.5 V) which can be selected under software control. In the application VRL is connected to V

. It is also possible to drive VRH with an external

SSA

voltage source but in this situation the internal voltage source has to be switched off (software controlled).

Signal conditioning

The digital codes retrieved from the ADCs are applied to logic circuitry to obtain the various control signals. The signals from the central aperture detectors are processed so that the normalized focus error signal (FE) given in equation (3) is realized:

D1 D2–

---------------------D1 D2+

D3 D

(3)

Where the detector set-up is assumed to be as illustrated in Fig.3.

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Philips Semiconductors Product speciﬁcation

( )

R1 R2+( ) Sum_gain×–

[]sin=

Digital servo processor (DSIC2) TDA1301T

In the event of single Foucault focusing method, the DSIC2 signal conditioning can be switched under software control so that the signal processing conforms to that given in equation (4).

FEn2

×=

---------------------D1 D2+

(4)

D1 D2–

The FEn thus obtained is further processed by a proportional integral and differential filter section (PID). A focus OK flag (FOK) is generated by means of the central aperture signal and an adjustable reference level. This signal is used to provide extra protection for the Track-Loss (TL) generation, the focus start-up procedure and the drop-out detection. The radial or tracking error signal is generated by the satellite detector signals R1 and R2. The radial error signal (RE) can be formulated as per equation (5).

R1 R2–( ) RE_gain×

R1 R2+( ) RE_offset×

(5)

Where the index ‘s’ indicates the automatic scaling operation which is performed on the radial error signal.

This scaling is necessary to avoid non-optimum dynamic range usage in the digital representation and, also, to reduce radial bandwidth spread. The radial error signal will also be released from offset during disc start-up. The four signals from the central aperture detectors, together with the satellite detector signals, generate a track position signal (TPI) which can be formulated as per equation (6).

TPI D1 D2 D3 D4+ + +

(6)

Where the weighting factor Sum_gain is generated internally in the DSIC2 during initialization.

Focus control

The following focus servo functions are incorporated in the DSIC2 digital controller.

OCUS START-UP

F Five initially loaded coefficients influence the start-up

behaviour of the focus controller. The automatically generated triangular voltage can be influenced by 3 parameters, for the height (ramp_heigth) and DC-offset (ramp_offset) of the triangle and its steepness (ramp_inc). To protect against false focus point detections two parameters are available. One is an absolute level on the CA signal (CA_start) and the other is an absolute level on the FEn signal (FE_start). When the CA_start level is

reached, the FOK signal becomes true. If the FOK signal is true when the level on the FEn signal is reached the focus PID is enabled and switches on when the next zero crossing is detected in the FEn signal.

FOCUS POSITION CONTROL LOOP The focus control loop contains a digital PID controller

which has 5 parameters available to the user. These coefficients influence the integrating (foc_int), proportional (foc_prop) and differentiating (foc_pole_lead) action of this PID and the digital low-pass filter (foc_pole_noise) which follows the PID. The fifth coefficient (foc_gain) influences the loop gain.

ROP-OUT DETECTION

This detector can be influenced by one parameter (CA_drop). The FOK signal will become false and the integrator of the PID will hold if the CA signal drops below the programmed absolute CA level. When the FOK signal becomes false it is assumed, initially, to be caused by a black dot.

FOCUS LOSS DETECTION AND FAST RESTART Whenever FOK is false for longer than approximately

3 ms, it is assumed that the focus point is lost. A fast restart procedure is initiated which is capable of restarting the focus loop within 200 to 300 ms depending on the programmed coefficients set by the microcontroller.

FOCUS LOOP GAIN SWITCHING The gain of the focus control loop (foc_gain) can be

multiplied by a factor of 2 or divided by a factor of 2 during normal operation. The integrator value of the PID is corrected accordingly. The differentiating (foc_pole_lead) action of the PID can be switched at the same time as the gain switching is performed.

Radial control

The following radial servo functions are incorporated in the DSIC2 digital controller.

LEVEL INITIALIZATION During start-up an automatic adjustment procedure is

activated to set the values of the radial error gain (RE_gain), offset (RE_offset) and satellite sum signal gain (Sum_gain) for TPI level generation. The initialization procedure runs in a radial open-loop situation and is ≤300 ms. This start-up time period may coincide with the last part of the turn table motor start-up time period.

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