TLE6368_06 Datasheet, PDF (10/59 Pages) Infineon Technologies AG – Multi-Voltage Processor Power Supply

TLE 6368 / SONIC
section 5) the output voltage level is present at the drain of the switch. As soon as the
voltage at the SW pin passes zero volts the handover to the main switch occurs and the
traditional switching behaviour of the Buck switch can be observed.
2.2 Linear Voltage Regulators
The Linear regulators offer, depending on the version, voltage rails of 5V, 3.3V and 2.6V
which can be determined by a hardware connection (see table at 2.2.2) for proper power
up procedure. Being supplied by the output of the Buck pre-regulator the power loss
within the three linear regulators is minimized.
All voltage regulators are short circuit protected which means that each regulator
provides a maximum current according to its current limit when shorted. Together with
the external charge pump the NPN pass elements of the regulators allow low dropout
voltage operation. By using this structure the linear regulators work stable even with a
minimum of 470nF ceramic capacitors at their output.
Q_LDO1 has 5V nominal output voltage, Q_LDO2 has a hardware programmable
output voltage of 3.3V or 2.6V and Q_LDO3 is also programmable to 3.3V or 2.6V (see
section 2.2.2). All three regulators are on all the time, if one regulator is not needed a
base load resistor in parallel to the output capacitance for controlled power down is
recommended.
2.2.1 Startup Sequence Linear Regulators
When acting as a 32 bit µC supply the so-called power sequencing (the dependency of
the different voltage rails to each other) is important. Within the TLE 6368 G1 / SONIC,
the following Startup-Sequence is defined (see also figure 4):
V_{Q_LDO2} ≤ V_{Q_LDO1;} V_{Q_LDO3} ≤ V_{Q_LDO1}
with V_{Q_LDO1}=5V, V_{Q_LDO2} = 2.6V or 3.3V and V_{Q_LDO3} = 2.6V or 3.3V
The power sequencing refers to the regulator itself, externally voltages applied at
Q_LDO2 and Q_LDO3 are not pulled down actively by the device if Q_LDO1 is lower
than those outputs.
That means for the power down sequencing if different output capacitors and different
loads at the three outputs of the linear regulators are used the voltages at Q_LDO2 and
Q_LDO3 might be higher than at Q_LDO1 due to slower discharging. To avoid this
behaviour three Schottky diodes have to be connected between the three outputs of the
linear regulators in that way that the cathodes of the diodes are always connected to the
higher nominal rail.
Data Sheet
10
Rev. 2.2, 2006-12-01