NCP785B

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7

APPLICATION INFORMATION

The typical application circuit for the NCP785B device is shown below.

Figure 3. Typical Application Schematic

NCP785B

GND

2.2μF

22μF

15V – 450V

3.3V, 5V, 12V, 15V

EN

OFF

ON

Input Decoupling (C1)

A 1

mF capacitor either ceramic or electrolytic is

recommended and should be connected close to the input pin

of NCP785B. Higher value 2.2

mF is necessary to keep the

input voltage above the required minimum input voltage at

full load for AC voltage as low as 85 V with half wave

rectifier.

Output Decoupling (C2)

The NCP785B Regulator does not require any specific

Equivalent Series Resistance (ESR). Thus capacitors

exhibiting ESRs ranging from a few m

W up to 0.5 W can be

used safely. The minimum decoupling value is 22

mF. The

regulator accepts ceramic chip capacitors as well as

tantalum devices or low ESR electrolytic capacitors. Larger

values improve noise rejection and load transient response.

Layout Recommendations

wide. When the impedance of these lines is high, there is a

chance to pick up noise or to cause the malfunction of

regulator.

Set external components, especially the output capacitor,

as close as possible to the circuit, and make leads as short as

possible.

Thermal

As power across the NCP785B increases, it might become

necessary to provide some thermal relief. The maximum

power dissipation supported by the device is dependent

upon board design layout and used package. Mounting pad

configuration on the PCB, the board material, and also the

ambient temperature affect the rate of temperature rise for

the part. This is stating that when the NCP785B has good

thermal conductivity through the PCB, the junction

temperature will be relatively low with high power

dissipation applications.

ENABLE Operation

The enable pin EN of the NCP785B will turn on or off the

regulator’s output. The threshold limits are covered in the

electrical specification section of this data sheet. If the

enable function is not used then the EN pin should be left

disconnected. An internal current source pulls this pin high

to a voltage given by the internal resistor divider. The limit

of this voltage is mentioned in the electrical specification

section of this data sheet. Maximum applicable external

voltage at this pin from external source is limited to 5.0 V.

+

−

1.25 V

VIN

Thermal

Shutdown

EN

EN

NCP785B

EN

EN

5.3 V

500 kW

600 kW

5 mA

ORDERING INFORMATION:

Part Number

Output

Voltage

Case

Package

Marking

Shiping

Released PN

Marking

NCP785BST33T3G

3.3 V

TBD

SOT223−4

HVH

TBD

PCP785BST33T3G

XAH

NCP785BST50T3G

5 V

TBD

SOT223−4

HVJ

TBD

PCP785BST50T3G

XAJ

NCP785BST120T3G

12 V

TBD

SOT223−4

HVK

TBD

PCP785BST120T3G

XAK

NCP785BST150T3G

15 V

TBD

SOT223−4

HVL

TBD

PCP785BST150T3G

XAL