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10. GND wiring pattern

When both a small-signal GND and high current GND are present, single-point grounding (at the set standard point) is

recommended, in order to separate the small-signal and high current patterns, and to be sure the voltage change stemming

from the wiring resistance and high current does not cause any voltage change in the small-signal GND. In the same way,

care must be taken to avoid wiring pattern fluctuations in any connected external component GND.

11. Output capacitor (C3)

Do not fail to connect a output capacitor to VTT output terminal for stabilization of output voltage. The capacitor connected to

VTT output terminal works as a loop gain phase compensator. Insufficient capacitance may cause an oscillation. It is

recommended to connect a 10 μF ceramic capacitor (X5R or X7R) near to VTT and GND, though it depends on ambient

temperature and other conditions. A low ESR ceramic capacitor may reduce a loop gain phase margin and may cause an

oscillation, which may be improved by connecting a resistor in series with the OS-capacitor (several-hundred μF). It is

therefore requested to carefully check under the actual temperature and load conditions to be applied.

12. Input capacitors (C1 and C2)

These input capacitors are used to reduce the output impedance of power supply to be connected to the input terminals (VCC

and VTT_IN). Increase in the power supply output impedance may result in oscillation or degradation in ripple rejecting

characteristics. It is recommended to use a low temperature coefficient 1μF (for VCC) and 10μF (for VTT_IN) capacitor, but it

depends on the characteristics of the power supply input, and the capacitance and impedance of the pc board wiring pattern.

It is therefore requested to carefully check under the actual temperature and load conditions to be applied.

13. Input terminals (VCC, VTT_IN and REF)

VCC, VTT_IN and REF terminals of this IC are made up independent one another. To VCC terminal, the UVLO function is

provided for malfunction protection. REF pin includes the Enable circuit. Irrespective of the input order of the inputs

terminals, VTT output is activated to provide the output voltage when UVLO voltages reach the threshold voltage while REF

voltage reaches the threshold of EN pin.

14.REF pin (R1 , R2 , C4)

REF pin controls this IC’s status ON or OFF. When REF voltage reaches EN-ON voltage, the output voltage operates. Then

BD3537F does not include “soft start function” so set the start up time by the value of extra components R1, R2 and C4.

15. Operating range

Within the operating range, the operation and function of the circuits are generally guaranteed at an ambient temperature

within the range specified. The values specified for electrical characteristics may not be guaranteed, but drastic change may

not occur to such characteristics within the operating range.

16. Allowable loss Pd

For the allowable loss, the thermal derating characteristics are shown in the Exhibit, which should be used as a guide. Any

uses that exceed the allowable loss may result in degradation in the functions inherent to IC including a decrease in current

capability due to chip temperature increase. Use within the allowable loss.

17. Built-in thermal shutdown protection circuit

Thermal shutdown protection circuit is built-in to prevent thermal breakdown. Turns VTT output to OFF when the thermal

shutdown protection circuit activates. This thermal shutdown protection circuit is originally intended to protect the IC itself.

It is therefore requested to conduct a thermal design not to exceed the temperature under which the thermal shutdown

protection circuit can work.

18. The use in the strong electromagnetic field may sometimes cause malfunction, to which care must be taken.

In the event that load containing a large inductance component is connected to the output terminal, and generation of

back-EMF at the start-up and when output is turned OFF is assumed, it is requested to insert a protection diode.

19. In the event that load containing a large inductance component is

connected to the output terminal, and generation of back-EMF at the

start-up and when output is turned OFF is assumed, it is requested

to insert a protection diode.

20. We are certain that examples of applied circuit diagrams are recommendable,

but you are requested to thoroughly confirm the characteristics before using the IC.

In addition, when the IC is used with the external circuit changed, decide the IC with sufficient margin provided

while consideration is being given not only to static characteristics but also variations of external parts and our IC including

transient characteristics.

OUTPUT PIN

(Example)