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SVFA0515S - 4.0

E-mail: vptsales@vptpower.com

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Page 6

SVFA0515S Series

6.0 TECHNICAL NOTES

Please note that many of these

functions are also demonstrated

in detail on the VPT website in the form of technical video labs.

6.1 GENERAL INFORMATION

6.1.1 Topology Description

The SVFA0515S Series is a non-isolated, fixed-frequency, radiation-hardened, synchronous buck converter. It operates from a 5 V

input and provides a stepped-down, precisely regulated, programmable output voltage at very-high efficiency. The SVFA0515S is

optimized for low voltage point of load applications.

6.1.2 External Components

The SVFA0515S Series has internal input and output capacitors. To meet the performance specifications in Section 3.2, a minimum

additional 100 µF tantalum input decoupling capacitor is required. The SVFA0515S is stable with no load capacitance. Additional output

capacitance is allowed up to the maximum listed in Section 3.2.

6.1.3 Source Impedance

The impedance of the 5 V input source can interact with the point of load converter and can affect performance. High source

impedance is often caused by a long input cable or other components added in series with the input. In some cases, additional input

capacitance will be needed to stabilize the system.

6.2 FUNCTION DESCRIPTIONS

6.2.1 On/Off Control (Inhibit)

The INH (Inhibit) pin is a control pin referenced to COM. The INH pin must be driven

using an open-collector or open-drain configuration. Pulling the INH pin low disables

the converter output. Leaving INH open enables the output, allowing the converter to

operate normally. The pin must be pulled below 1.5 V to disable the output. An

optional capacitor from INH to COM may be used to delay turn-on. The INH pin should

be left open if not used.

6.2.2 Adjusting the Output Voltage (TRIM)

The output voltage of the converter is set with an external resistor connected from the TRIM pin to the COM pin. This resistor must

have a tolerance of 1% or better to achieve an accurate output voltage. The default output voltage with the TRIM pin left open is 0.8 V.

SVFA0515S

+Vout (V)

Rtrim

(Ω)

0.8

None

0.9

205k

1.0

99.9k

1.2

47.4k

1.5

24.9k

1.8

15.9k

1.9

13.9k

2.0

12.4k

2.5

7.25k

2.8

5.4k

3.0

4.44k

3.3

3.30k

3.4

2.98k

2

COM

3

INH

1

+VIN

OPTIONAL

CAPACITOR

47K

+

-

+

-

0.7 V

210K

30K

5.1K

+VOUT

TRIM

COM

R-TRIM

+SENSE

100