TLE6368_06 datasheet(10/59 Pages) INFINEON

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TLE 6368 / SONIC

Data Sheet

Rev. 2.2, 2006-12-01

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):

VQ_LDO2 ≤ VQ_LDO1; VQ_LDO3 ≤ VQ_LDO1

with VQ_LDO1=5V, VQ_LDO2 = 2.6V or 3.3V and VQ_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.

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