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MB3817_03 Datasheet, PDF (20/28 Pages) Fujitsu Component Limited. – Switching Regulator Controller | |||
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MB3817
s METHOD OF SETTING THE DEAD TIME
When the device is set for step-up inverted output based on the flyback method, the output transistor is fixed to
a full-on state (ON-duty = 100%) at power switch-on. To prevent this problem, you may determine the voltages
on the DTC terminals (pin 6) from the VREF voltage so you can easily set the output transistorâs dead time
(maximum ON-duty) independently for each channel as shown below.
When the voltage on the DTC terminals (pin 6) is lower than the triangular-wave output voltage from the oscillator,
the output transistor turns off. The dead time calculation formula assuming that triangular-wave amplitude â
0.4 V and triangular-wave minimum voltage â
1.4 V is given below.
Duty
(ON)
MAX
=:
Vdt
â 1.0
0.4
V
Ã
100
[%]
When you do not use these DTC terminals, connect them to VREF terminal.
⢠When using DTC to set dead time
16 VREF
Ra
6 DTC
Vdt
Rb
⢠When not using DTC to set dead time
16 VREF
6 DTC
20
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