TLE6711_07 Datasheet, PDF (13/25 Pages) Infineon Technologies AG – Multifunctional Voltage Regulator and Watchdog

TLE 6711
Circuit Description
4.3.1 Boost Status Output OVL
For supervision of the Boost output voltage an open drain DMOS output is used. The output is high impedance in
normal operation and low during the warning.
The OVL goes LOW if the PWM comparator output (see Figure 8) remains HIGH for clock time period. This occurs
when the Error-Signal falls below the minimum value of the Error-Ramp, this mean that Boost voltage falls below
a certain threshold voltage.
The OVL output used as a warning for insufficient Boost voltage.
4.4
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 L_BU is PWM switched by a high side DMOS power transistor with the programmed
frequency (pin R).
The buck regulator supply is given by the boost converter output V_BOOST, in case of a battery power-down the
stored energy of the boost converter capacitor is used.
Like the boost converter, 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 V_CC 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 V_CC level. A logic signal PWM with
variable pulse width is generated.
BUC
Pin 6
V_CC
Pin 7
R_Prot1
200 Ω
V_CC
R_VCC1
22kΩ
Error
AMP
R_VCC2
28kΩ
= V_REF
2.8 V
GND GND
V_CC
R_VCC3
39.7k Ω
R _VCC4
10.3kΩ
OV
COMP _{H when}
+
OV at V_CC
-
= V_thOV
1.2 V
GND GND
UV
H when ^COMP
UV at V_Boost
=
V_thUV
4V
L when
OC
COMP
GND Overcurrent
V_thOC
18 mV
L when
Overcurrent
Error-
Signal
PWM
COMP
H when
Error-Signal
<
Error-Ramp
Error-
Ramp
L when
T_j > 175 ˚C
Output Stage
OFF when H
NOR 1
1
Error-FF
R& _Q
OFF when H
PWM-FF
R& _Q
H = ^INV
OFF 1
NAND 2
&
&
Q
S
Boost
Driver
Supply
H=
ON
Gate
Driver
V_Boost
Pin 9
R_Sense
18 mΩ
BDS
Pin 10
Power
D-MOS
BUO
Pin 8
R
Pin 1
Oscillator
V_max
V_min
t_r t_f t_{r t}
Schmitt-trigger 1
&
V_high
Q
S
Ramp ^Vlow _{tr tf tr t} Clock
AEB02947
Figure 10 Buck Converter Block Diagram
Data Sheet
13
Rev. 3.4, 2007-08-16