SAA7806H NXP [NXP Semiconductors], SAA7806H Datasheet - Page 50

• Manufacturer Part Number: SAA7806H
• Description: One chip automotive CD audio device
• Manufacturer: NXP [NXP Semiconductors]

Philips Semiconductors
9397 750 13697
Objective data sheet
6.7.4.2 Focus position control loop
When focus is achieved and the level on the FE
enabled to switch on when the next zero crossing is detected in the FE
The focus control loop contains a digital PID controller which has 5 parameters that are
available to the user. These coefficients influence the integrating (foc_int), proportional
(foc_lead_length, part of foc_parm3) and differentiating (foc_pole_lead, part of
foc_parm1) action of the PID and a digital low-pass filter (foc_pole_noise, part of
foc_parm2) following the PID. The fifth coefficient foc_gain influences the loop gain.
Figure 30
determine the behavior.
A simplified block diagram of the focus PID system is given in
By using a zero error signal, the actuator position can be held. This action is taken if a
defect or shock is encountered. The PID is followed by a low-pass filter to reduce audible
noise in the control loop.
The desired frequencies for the loop (
Full tables are given in the Hardware Software Interface (HSI) specification . An
explanation of the parameters in these diagrams is given in
Fig 30. Bode diagram of focus PID system
Fig 31. Functional diagram of focus PID system
focus error,
FE
zero on
defect
or shock
n
Amplitude
foc_gain
(dB)
shows the transfer function of the controller, and the coefficients which
foc_int_strength
5
P
I
D
Rev. 01 — 20 June 2005
I
1/j
foc_int
1
1 j /
1
j /
P
1
3
3
to
foc_lead_length
4
2
) are used to calculate the coefficient values.
D
2
n
/
foc_pole_lead
One chip automotive CD audio device
signal is reached, the focus PID is
3
3
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
foc_pole_noise
Table
Figure
4
12.
4
31.
SAA7806
n
G
signal.
68 FO
Frequency
001aab773
G
(log Hz)
E
001aab774
actuator
50 of 73
focus