SAA8200HL Datasheet, PDF (46/71 Pages) NXP Semiconductors – Ensation Base integrated wireless audio baseband

Philips Semiconductors
SAA8200HL
Ensation Base integrated wireless audio baseband
7.21 DC-to-DC converter
The SAA8200HL needs two supply voltages, 3.3 V for analog functions and 1.7 V for
digital functions. For normal operation one or two batteries of 1.5 V will be used as an
energy source, from which the DC-to-DC converter must generate the required voltage
levels, see Figure 14. Two inductive DC-to-DC converters will be used when the chip is
battery operated. The V_DDE pins are externally connected to pin DCDC_OUT3V3, The
V_DDI pins are connected to pin DCDC_OUT1V8. When the SAA8200HL is supplied from
USB, the outputs of the DC-to-DC converters will be overruled by two linear regulators. In
that case the supply voltages will be 3.3 V and 1.8 V. This is independent from the USB
voltage (4.0 V to 5.5 V) so a reference circuit is needed.
V_BAT(DCDC)
V_USB(DCDC)
DC
DC
switching regulator 1
vin
LDO1
vout
LINEAR REGULATOR 1
vin
LDO2
vout
LINEAR REGULATOR 2
DCDC_OUT3V3
vusb_present
V_BAT(DCDC) < 1.6 V
VDD_ALWAYS
DC
DC
switching regulator 2
DCDC_OUT1V8
LOW VOLTAGE
BANDGAP
RING OSC
DC to DC - controller
vref
ANALOG DIGITAL
DELAY POR
adjust
12 MHz
DIGITAL CORE
PLL XOSC
001aac002
Fig 14. DC-to-DC converter block schematic
During the start-up sequence the DC-to-DC controller uses the RING OSC to control the
switching regulators. After start-up the 12 MHz from the digital core is fed to the DC-to-DC
controller. In battery operation mode the output voltage DCDC_OUT1V8 and
DCDC_OUT3V3 can be controlled by three adjust bits. Care has to be taken with signal
levels (level shifters) and the start-up and shut-down from battery to USB and from USB to
battery transitions. A delay circuit uses RING OSC clocks to generate a delay of about
1 ms for the RESET_B pulse. In USB mode the delay can be generated otherwise.
The DC-to-DC converter has to operate from a single or from two batteries. This has no
consequence for the first DC-to-DC converter, this is always an up converter. In case a
single battery is used the second converter is also an up converter but it is a down
SAA8200HL_2
Preliminary data sheet
Rev. 02 — 17 October 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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