L6699D STMicroelectronics, L6699D Datasheet - Page 33

• 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

L6699
This concern applies to converters designed with a high resonance frequency (indicatively,
> 150 kHz), so that they run at high frequency also at full load. Otherwise, the converter runs
at high frequency at light load, where the current flowing in the MOSFETs of the half bridge
leg is low, so that, generally, a slight R
this point anyway and the following equation is useful to estimate the drop on the bootstrap
driver:
Equation 14
where Qg is the gate charge of the external Power MOSFET, R
the bootstrap DMOS (150
equals about half the switching period minus the deadtime T
MOSFET with a total gate charge of 30 nC, the drop on the bootstrap driver is about 3 V at a
switching frequency of 200 kHz and with a deadtime of 300 ns:
Equation 15
If a significant drop on the bootstrap driver is an issue, an external ultra-fast diode can be
used, therefore saving the drop on the R
recommended to add a small resistor (in the ten Ω) in series to the diode to prevent the
bootstrap capacitor from being charged to a voltage exceeding the absolute maximum rating
(18 V), in case of significant negative spikes on the half bridge midpoint when the high-side
MOSFET turns off.
Figure 23. Bootstrap supply: standard
circuit
V
V
Drop
Drop
=
Ω
I =
, typ.) and T
. 2
ch
Doc ID 022835 Rev 2
· 5
arg
e
10
R
30
(
-
DS
6
DS(on)
·
-
10
)
charge
on
. 0
DS(on)
-
+
· 3
9
rise is not an issue. However, it is wise to check
V
10
is the ON-time of the bootstrap driver, which
Figure 24. Bootstrap supply: internal
F
of the internal DMOS. In this case it is also
=
-
6
T
150
ch
Q
arg
g
+
e
0
R
bootstrap synchronous diode
6 .
(
D
DS
. For example, using a
DS(on)
=
)
on
2
+
6 .
V
is the ON-resistance of
V
F
Bootstrap section
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