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TDA1301T Folha de dados(PDF) 6 Page - NXP Semiconductors |
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TDA1301T Folha de dados(HTML) 6 Page - NXP Semiconductors |
6 / 14 page March 1994 7 Philips Semiconductors Product specification Digital servo processor (DSIC2) TDA1301T Automatic gain adjustment: as a result of this initialization the amplitude of the RE signal is adjusted within 10% around the nominal RE amplitude. Offset adjustment: the additional offset in RE due to the limited accuracy of the start-up procedure is less than 50 nm. TPI level generation: the accuracy of the initialization procedure is such that the duty cycle range of TPI becomes 0.4 < δ < 0.6 {δ = TPI(HIGH)/TPI(period)}. SLEDGE HOME Sledge moves to reference position (end_stop_switch) at the inner side of the disc with user defined voltage. TRACKING CONTROL The actuator is controlled using a PID loop-filter with user defined coefficients and gain. For stable operation between the tracks, the S-curve is extended over 3 ⁄ 4 track. Upon request from the microcontroller S-curve extension over 2 tracks is used, automatically changing to access control when these two tracks are exceeded. Both modes of S-curve extension make use of a track-count mechanism as described in Section “Off-track counting” . In this mode track counting results in automatic ‘return-to-zero track’, to avoid major music rhythm disturbances in the audio output to provide improved shock resistance. The sledge is continuously controlled using the filtered value of the integrator contents of the actuator, or upon request by the microcontroller. The microcontroller can read out this integrator value and provides the sledge with step pulses to reduce power consumption. Filter coefficients of the continuous sledge control can be preset by the user. ACCESS The access procedure is divided into 2 different modes, depending on the requested jump size. The access procedure makes use of a track counting mechanism (see Section “Off-track counting” ), a velocity signal based upon the number of tracks passed within a fixed time interval, a velocity setpoint calculated from the number of tracks to go and a user programmable parameter indicating the maximum sledge performance. If the number of tracks to go is greater than break_dist the sledge jump mode will be activated (otherwise the actuator jump will be performed). The requested jump size together with the required sledge braking distance at maximum access speed defines the value break_dist. During the actuator jump mode, velocity control with a PI controller is used for the actuator. The sledge is then continuously controlled using the filtered value of the integrator contents of the actuator. All filter parameters (for actuator and sledge) are user programmable. In the sledge jump mode, maximum power (user programmable) is applied to the sledge in the correct direction, while the actuator becomes Idle (the contents of the actuator integrator leaks to zero just after the sledge jump mode is initiated). Table 1 Access procedure. Note 1. Can be preset by the microcontroller. Defect detector A built-in defect detector prevents the light spot from going out-of-focus and going off-track due to disc drop-out excitations. The defect detector can be switched ON or OFF under software control and can be applied to the focus control only, or to both the focus and radial control. The detected defect signal holds the focus and radial loop filter outputs. The hold signal is generated whenever the reflected light intensity drops rapidly (<1.5 ms) down to 75% of the actual intensity level. Shock detector The shock detector can be switched ON during normal track following. The shock detector detects, within an adjustable frequency band, whether the disturbances in the radial spot position relative to the track exceeds an adjustable level. Every time the radial tracking error (RE) exceeds this level the radial control bandwidth is switched directly to twice the original bandwidth. The shock detection level is adjustable in 64 steps from 0 to 100% of the nominal radial amplitude. The bandpass filter (BPF) lower frequency ( −3 dB) can be fixed at 0 or 20 Hz. Independently, the BPF upper frequency ( −3 dB) can be fixed at 750 or 1850 Hz. Off-track counting TPI is a flag which is used to indicate whether the spot is positioned on the track (with a margin of 1 ⁄ 4 of the track-pitch). ACCESS TYPE JUMP SIZE ACCESS SPEED Actuator jump 1 − break distance (1) decreasing velocity Sledge jump break (1) − 32768 minimum power to sledge (1) |
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Descrição semelhante - TDA1301T |
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