SAA8200HL Datasheet, PDF (47/71 Pages) NXP Semiconductors – Ensation Base integrated wireless audio baseband

Philips Semiconductors
SAA8200HL
Ensation Base integrated wireless audio baseband
converter when two batteries are used. Pin DOWNSEL selects the type of converter and
thus how many batteries are connected. If pin DOWNSEL is HIGH the SAA8200HL
operates from two batteries and the second DC-to-DC converter is a down converter. If
pin DOWNSEL is LOW the SAA8200HL operates from one battery and the second
DC-to-DC converter is an up converter, see Figure 15
upconverter
Fig 15. Up and down converter topology
downconverter
001aac003
7.21.1 Controller
The controller consists of an analog and a digital part. The analog part compares the
output voltage VOUT[1,2] with a programmable voltage window in eight possible adjust
settings. The digital part computes the switching time such that the output voltage stays
within this window. In the analog part is one restive divider with a programmable output,
see Figure 16.
Together with reference voltage V_ref the voltage window is defined. The output of the
resistive divider is compared to the reference voltage with comparators with added offset.
The outputs VTH (voltage too high) and VTL (voltage too low) are based on the
comparison.
When VTH is asserted means that VIN is higher than the upper limit of the window,
indicating to the digital part of the controller that the output voltage must be lowered.
When VTL is asserted it indicates that VIN is lower than the lower limit of the window,
indicating to the digital part of the controller that the output voltage must be higher. When
neither is asserted, VIN is between the lower and upper limit of the window, indicating to
the digital part of the controller that the output voltage is in the limits of the window and it
does not have to change the output voltage. This is the normal mode of operating and is
called continuous mode because the coil continuously carries current.
In continuous mode the digital part of the controller generates switching cycles at a fixed
frequency. During the first part of such a cycle (t1) switch 1 will be closed and switch 2 will
be opened, during the last part of the cycle (t2) switch 2 will be closed and switch 1 will be
opened. The length of t1 as a fraction of the cycle time is set such that the required output
voltage is generated. When the output voltage runs outside the window this length is
updated such that the output voltage falls within the window again.
SAA8200HL_2
Preliminary data sheet
Rev. 02 — 17 October 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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