SAA8200HL Datasheet, PDF (50/71 Pages) NXP Semiconductors – Ensation Base integrated wireless audio baseband

Philips Semiconductors
SAA8200HL
Ensation Base integrated wireless audio baseband
The digital part of the controller consists of a state machine that enables the controller to
switch modes. A decision to jump to a different state is taken on the basis of the outputs of
the analog part. As a result of some of the jumps, the duration of the first phase of the
cycle is increased or decreased, see Figure 20.
sample
VTH
DISCONTINUOUS
MODE
VTH
dec. t1
sample
VTL
CONTINUOUS
MODE
VTH
VTL AND VTH
sample
inc. t1
RAMP-UP
MODE
VTL
VTL
inc. t1
001aac008
The controller will be in discontinuous mode if adjusted DCDC_OUT1V8 ≤ V_BAT(DCDC).
No forward diode from V_BAT(DCDC) to DCDC_OUT1V8 allowed.
Fig 20. Digital part of the controller
7.21.2 Linear regulators
The linear regulators will be implemented as Low Drop voltage Output (LDO) regulators
for a fixed output voltage, see Figure 21. One LDO has to handle input signals in the order
of 5.0 V so a special construction with thick gate oxide is needed. The other LDO handles
an input signal of 3.3 V thus a normal construction with thick gate oxide is sufficient. For
the loop stability the choice is made that the dominant pole lies externally. The series
resistance of Cext (ESR) gives a zero and degrades the stability and thus limited to a
maximum value. For an accurate output voltage a reference voltage is needed. This
voltage can be made with a band gap circuit. A fraction of the output voltage is fed back to
the operation amplifier. In Stop mode the LDOs should be stable to deliver only small
currents.
VIN
DCDC_OUT
EF
self-biased
operational amplifier
ON
001aac009
ESR
capacitor
V_SS
V_SS(clean)
Cext
PCB
star ground
The on terminal is connected to VUSB_PRESENT.
Fig 21. Principle of LDO
SAA8200HL_2
Preliminary data sheet
Rev. 02 — 17 October 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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