L6699D STMicroelectronics, L6699D Datasheet - Page 20

• 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

Application information
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the operating frequency is essentially determined by the current sunk by the optocoupler's
phototransistor.
During this frequency sweep phase the operating frequency decays following the
exponential charge of C
gets slower and slower. This counteracts the non-linear frequency dependence of the tank
circuit that makes the converter's input impedance change little as frequency is away from
resonance and change very quickly as frequency approaches resonance frequency (see
Figure 13
As a result, the DC input current smoothly increases, without the peaking that occurs with
linear frequency sweep, and the output voltage reaches the regulated value with almost no
overshoot.
Typically, R
Equation 5
where f
Figure 20
Figure 12. Soft-start circuit
start
).
to see some significant signals during the soft-start phase.
SS
is recommended to not be over 300 kHz. Please refer to the timing diagram of
and C
SS
is selected based on the following relationships:
SS
: then, it initially changes relatively quickly but the rate of change
R
SS
Doc ID 022835 Rev 2
=
f
f
RF
start
min
min
-
1
;
Figure 13. Input impedance vs.
C
SS
=
· 3
R
10
frequency curve in an LLC
resonant half bridge
SS
-
3
L6699