SN6507 datasheet(29/44 Pages) TI

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Assuming the same diode and LDO are used, the calculation, so VF-max = 0.5 V, VDO-max = 0.7 V, and VO-max =

15.15 V.

The input range from 18 V up to 30 V makes VIN-min = 18 V. The input range from 18 V up to 30 V with 24 V

typical makes VIN-min = 18 V. Substituting the same RDS-max = 1 Ω and ID-max = 0.5 A into the Equation above

yields to a minimum turns ratio of:

Nmin=1.03×0.5 V+0.7 V+15.1 V

18 V−1 Ω×0.5 A =0.96

(20)

• Wide-Ranging Input with Duty-Cycle Control

For converter designs with wide-input range, the duty cycle feature is useful to compensate input variaton. But

care must be taken to make sure that high turns ratios don’t lead to primary currents that exceed the specified

current limits of the device.

Nmin=1.03×VF−max+VDO−max+VO−max

VIN−typ−RDS−max×ID−max× 12Dtyp

(21)

Assuming the same diode and LDO are used, so VF-max = 0.5 V, VDO-max = 0.7 V, and VO-max = 15.15 V.

It's recommends the use to set the DC=25% at typical VIN-typ = 24 V. Substituting the same RDS-max = 1 Ω and

ID-max = 0.5 A into the Equation above yields to a minimum turns ratio of:

Nmin=1.03×0.5 V+0.7 V+15.1 V

24 V−1 Ω×0.5 A × 12×0.25=1.38

(22)

9.2.2.6 Low-Emissions Designs

For isolated power supply designs requiring low levels of radiated and conducted emissions, the following

recommendations can help minimize emissions from SN6507-Q1 and its surrounding components:

• Ensure a push-pull isolation transformer with low parasitics, like leakage inductance and parasitic

capacitances, is used to minimize common-mode currents across the isolation barrier and antenna effects in

the system.

• Use low-emissions rectifier diodes with low recovery times, like PMEG200G20ELRX or equivalent.

• Configure SN6507-Q1 for its slowest slew-rate setting to minimize high-frequency content in the switching

paths.

• Include a snubber circuit on the secondary-side of the isolation transformer to filter high-frequency content in

the switching paths.

Using these configurations may each affect system-level efficiency. The SN6507DGQEVM can be used to

evaluate these design options.

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SN6507-Q1

SLLSFM1 – SEPTEMBER 2022

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SN6507 Datasheet(PDF) 29 Page - Texas Instruments