LT3575IFE#PBF Linear Technology, LT3575IFE#PBF Datasheet - Page 17

• Manufacturer Part Number: LT3575IFE#PBF
• Description: IC FLYBACK CONVERTER 16TSSOP
• Manufacturer: Linear Technology
• Type: Flyback, Isolatedr

Specifications of LT3575IFE#PBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: Adj to 60V
• Current - Output: 2.5A
• Frequency - Switching: 1MHz
• Voltage - Input: 3 ~ 40 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: *
• Package / Case: 16-TSSOP Exposed Pad, 16-eTSSOP, 16-HTSSOP
• Voltage - Supply: 3 V ~ 40 V
• Frequency-max: 1MHz
• Pwm Type: Regulator
• Buck: No
• Boost: No
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Duty Cycle: -

APPLICATIONS INFORMATION
Zener clamps. Among them, RCD is widely used. Figure 9
shows the RCD snubber in a fl yback converter.
A typical switch node waveform is shown in Figure 10.
During switch turn-off, the energy stored in the leakage
inductance is transferred to the snubber capacitor, and
eventually dissipated in the snubber resistor.
The snubber resistor affects the spike amplitude V
duration t
t
to the output voltage sensing.
The previous steps fi nish the fl yback power stage design.
5. Select the feedback resistor for proper output voltage.
Using the resistor Tables 1-4, select the feedback resistor
R
SP
FB
2
1
, and program the output voltage to 5V. Adjust the
is about 150ns. Prolonged t
L I
S PK SW
Figure 9. RCD Snubber in a Flyback Converter
2
SP
, the snubber resistor is adjusted such that
f
C
V V
C
R
D
(
L
C
S
R
3575 F09
N V
•
SP
OUT
may cause distortion
)
C
and
R
voltage. R
A small capacitor in parallel with R
noise during the voltage spike, however, the capacitor
should limit to 10pF. A large capacitor causes distortion
on voltage sensing.
6. Optimize the compensation network to improve the
The transient performance is optimized by adjusting the
compensation network. For best ripple performance, select
a compensation capacitor not less than 1.5nF, and select
a compensation resistor not greater than 50k.
7. Current limit resistor, soft-start capacitor and UVLO
Use the current limit resistor R
limit if a compact transformer design is required. Soft-start
capacitor helps during the start-up of the fl yback converter .
Select the UVLO resistor divider for intended input opera-
tion range. These equations are aforementioned.
TC
transient performance.
resistor divider
resistor for temperature compensation of the output
V
IN
REF
Figure 10. Typical Switch Node Waveform
V
C
is selected as 6.04k.
t
SP
NV
OUT
LIM
to lower the current
REF
fi lters out the
LT3575
3575 F10
17
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