l6599atn STMicroelectronics, l6599atn Datasheet - Page 13

• Manufacturer Part Number: l6599atn
• Description: Improved High-voltage Resonant Controller
• Manufacturer: STMicroelectronics

L6599AT
6.1
Figure 4.
Oscillator
The oscillator is programmed externally by means of a capacitor (CF) connected from pin 3
(CF) to ground, which is alternately charged and discharged by the current defined with the
network connected to pin 4 (RF
2 mA source capability and the higher the current sourced by the pin, the higher the
oscillator frequency. The block diagram in
explains the operation.
The network that loads the RF
1.
2.
3.
A resistor RF
minimum operating frequency.
A resistor RF
phototransistor that transfers the feedback signal from the secondary side back to the
primary side. While in operation, the phototransistor modulates the current through this
branch - thus modulating the oscillator frequency - to perform output voltage regulation.
The value of RF
operated when the phototransistor is fully saturated.
An R-C series circuit (CSS+RSS) connected between the pin and ground that enables
the setup of a frequency shift at startup (see
contribution of this branch is zero during steady-state operation.
Typical system block diagram
max
min
max
connected between the pin and ground, which determines the
connected between the pin and the collector of the (emitter-grounded)
determines the maximum frequency at which the half-bridge is
Doc ID 15534 Rev 1
min
min
pin is generally made up of three branches:
). The pin provides an accurate 2 V reference with about
Figure 5
Section 6.3:
shows a simplified internal circuit that
Soft-start). Note that the
Application information
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