L6563STR View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6563STR' PDF : 43 Pages View PDF
L6563S
Application information
V(TBO)/RT, that is internally 1:1 mirrored and sunk from pin INV (#1) input of the L6563S's
error amplifier. In this way, when the mains voltage increases the voltage at TBO pin will
increase as well and so will do the current flowing through the resistor connected between
TBO and GND. Then a larger current will be sunk by INV pin and the output voltage of the
PFC pre-regulator will be forced to get higher. Obviously, the output voltage will move in the
opposite direction if the input voltage decreases.
To avoid undesired output voltage rise should the mains voltage exceed the maximum
specified value, the voltage at the TBO pin is clamped at 3V. By properly selecting the
multiplier bias it is possible to set the maximum input voltage above which input-to-output
tracking ends and the output voltage becomes constant. If this function is not used, leave
the pin open: the device will regulate a fixed output voltage.
Starting from the following data:
● Vin1 = minimum specified input RMS voltage;
● Vin2 = maximum specified input RMS voltage;
● Vo1 = regulated output voltage @ Vin = Vin1;
● Vo2 = regulated output voltage @ Vin = Vin2;
● Vox = absolute maximum limit for the regulated output voltage;
to set the output voltage at the desired values use the following design procedure:
1. Determine the input RMS voltage Vinclamp that produces Vo = Vox:
Vinclamp
=
Vox
Vo2
− Vo1
− Vo1
⋅ Vin2
−
Vox
Vo2
− Vo2
− Vo1
⋅ Vin1
and choose a value Vinx such that Vin2 ≤ Vinx < Vinclamp. This will result in a limitation
of the output voltage range below Vox (it will equal Vox if one chooses Vinx = Vinclamp)
2. Determine the divider ratio of the MULT pin (#3) bias:
k= 3
2 ⋅ Vinx
and check that at minimum mains voltage Vin1 the peak voltage on pin 3 is greater than
0.65 V.
3. Determine R1, the upper resistor of the output divider, for instance 3 MΩ.
4. Calculate the lower resistor R2 of the output divider and the adjustment resistor RT:
⎪⎪⎧R2
⎨
⎪R
⎪⎩
T
=
=
2.5
2
⋅
R1⋅
(Vo1
−
2.5)
⋅
Vin2
Vin2
⋅ k ⋅R1⋅ Vin2 − Vin1
Vo2 − Vo1
− Vin1
− (Vo2
−
2.5)⋅
Vin1
5. Check that the maximum current sourced by the TBO pin (#6) does not exceed the
maximum specified (0.2 mA):
ITBO max
=3
RT
≤ 0.2 ⋅10−3
Figure 40 shows the internal block diagram of the tracking boost function.
Doc ID 16116 Rev 4
29/43
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