L6699D STMicroelectronics, L6699D Datasheet - Page 32

• Manufacturer Part Number: L6699D
• Description: AC/DC Switching Converters Enhanced High Volt Res CTRL 600V
• Manufacturer: STMicroelectronics
• Type: High Voltage Controllersr

Specifications of L6699D

• Product Category: AC/DC Switching Converters
• Output Voltage: 13.3 V
• Input / Supply Voltage (max): 8.85 V
• Input / Supply Voltage (min): 16 V
• Switching Frequency: 235 kHz
• Supply Current: 3 mA
• Operating Temperature Range: - 25 C to + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SO-16
• Number Of Outputs: 1
• Output Current: 800 mA

Latched shutdown
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Latched shutdown
The L6699 is equipped with a comparator having the non-inverting input externally available
on pin 8 (DIS) and with the inverting input internally referenced to 1.85 V. As the voltage on
the pin exceeds the internal threshold, the IC is immediately shut down, the PFC_STOP pin
is asserted low and the quiescent consumption reduced to a low value. The information is
latched and it is necessary to let the voltage on the V
reset the latch, de-assert the pin PFC_STOP, and restart the IC.
This function is useful to implement a latched overtemperature protection very easily by
biasing the pin with a divider from an external reference voltage (e.g. pin 4,
the upper resistor is an NTC physically located close to a heating element like the MOSFET,
or a secondary diode or the transformer.
An OVP can be implemented as well, e.g. by sensing the output voltage and transferring an
overvoltage condition via an optocoupler. A latch-mode OCP protection can be implemented
by connecting this pin to DELAY (pin 2).
Bootstrap section
The supply of the floating high-side section is obtained by means of a bootstrap circuitry.
This solution normally requires a high voltage fast-recovery diode (D
charge the bootstrap capacitor C
replaces this external diode. It is realized by means of a high voltage DMOS, working in the
third quadrant and driven synchronously with the low-side driver (LVG), with a diode in
series to the source, as shown in
The diode prevents that any current can flow from the
quickly turned off when the internal capacitor of the pump is not fully discharged. To drive
the synchronous DMOS, a voltage higher than the supply voltage V
voltage is obtained by means of an internal charge pump (
The bootstrap structure introduces a voltage drop while recharging C
side driver is on), which increases with the operating frequency and with the size of the
external Power MOSFET. It is the sum of the drop across the R
across the series diode. At low frequency this drop is very small and can be neglected but,
as the operating frequency increases, it must be taken into account. In fact, the drop
reduces the amplitude of the driving signal and can significantly increase the R
external high-side MOSFET and then its conductive loss.
Doc ID 022835 Rev 2
BOOT
Figure 24
. In the L6699 a patented integrated structure,
.
CC
V
BOOT
pin go below the UVLO threshold to
Figure 24
pin back to V
DS(on)
CC
).
BOOT
BOOT
and the forward drop
is necessary. This
,
CC
(i.e. when the low
Figure 23
RF
if the supply is
min
DS(on)
), where
) to
L6699
of the