TLE 6365
Buck Converter
A stabilized logic supply voltage (typ. 5 V) for general purpose is realized in the system
by a buck converter. An external buck-inductance LBU is PWM switched by a high side
DMOS power transistor with the programmed frequency (pin R).
The buck converter uses the temperature compensated bandgap reference voltage (typ.
2.8 V) for its regulation loop.
This reference voltage is connected to the non-inverting input of the error amplifier and
an internal voltage divider supplies the inverting input. Therefore the output voltage VCC
is fixed due to the internal resistor ratio to typ. 5.0 V.
The output of the error amplifier goes to the inverting input of the PWM comparator as
well as to the buck compensation output BUC.
When the error amplifier output voltage exceeds the sawtooth voltage the output power
MOS-transistor is switched on. So the duration of the output transistor conduction phase
depends on the VCC level. A logic signal PWM with variable pulse width is generated.
External loop compensation is required for converter stability, and is formed by
connecting a compensation resistor-capacitor series-network (RBUC, CBUC) between pin
BUC and GND.
In the case of overload or short-circuit at VCC (the output current exceeds the buck
overcurrent threshold IBUOC) the DMOS output transistor is switched off by the
overcurrent comparator immediately.
In order to protect the VCC input as well as the external load against catastrophic failures,
an overvoltage protection is provided which switches off the output transistor as soon as
the voltage at pin VCC exceeds the internal fixed overvoltage threshold VCCOVOFF = typ.
6.0 V.
Also a battery undervoltage protection is implemented in the TLE 6365 to avoid wrong
operation of the following supplied devices, the typical threshold when decreasing the
battery voltage is at VSUVOFF = typ. 4.0 V.
Data Sheet
10
Rev. 1.9, 2007-07-30
INFINEON [ Infineon ]
