NCP5080

http://onsemi.com

6

supply a regulated 300 V across the external reservoir

capacitor.

Note that although an OVP circuit is built-in the

NCP5080 chip, it is strongly recommended to avoid

operation without an external reservoir capacitor, a 1

mF /

315 V being the minimum value.

When the NMOS is ON, the current increases into the

been reached, or the time out is finished: at this point, the

NMOS is switched OFF and the energy stored into the

primary is dumped to the secondary, providing the current

to recharge the reservoir capacitor. The OFF period is

monitored by sensing the primary voltage and the system

is finished. The external resistor divider, connected across

feedback loop at FBD pin. The output voltage is based on the

((R1 + R2) / R2).

The output voltage is regulated when the EN = H, but

drops to zero when EN = L. In this case, the discharge time

of the external reservoir depends solely upon the value of the

passive component and the leakage currents that might exist

at system level.

The DC/DC converter is switched OFF when either EN =

Low, or TRGFL = High, or when the output voltage has

reached the programmed value (see Figure 3).

Inductor Peak Current

In order to provide more flexibility to the NCP5080

driver, an extra pin, IPKREF, is provided to set up the peak

current flowing into the primary inductor of the transformer.

value of the external resistor:

I

RIPK

(eq. 1)

The primary peak current is given by Equation 1:

I

(eq. 2)

maximum, assuming the transformer is sized to sustain such

amount of electromagnetic energy. The efficiency of the

DC/DC converter, and the recharge cycle time as well,

depends upon the ESR and leakage inductance of the power

transformer: a poor transformer will generate large

oscillations during the operation which will be difficult to

filter out at PCB level.

Table 1. PREFERRED POWER TRANSFORMER

MANUFACTURERS

Manufacturer

Model

Comments

TDK

LDT565620ST-20 3

Coilcraft

CJ5143-AL

Max

Table 2. PREFERRED HIGH VOLTAGE TRIGGER FUNCTION

Component

Manufacturer

Model

Comments

High Voltage Trigger

PCA

EPC3215G-X

High Voltage Ceramic Capacitor

TDK

C3225X7R2J473M

Reference design+

22

mF/330 V to 120 mF/330 V

RUBYCON

FW series

Preferred

Table 3. PREFERRED XENON LAMP

Component

Manufacturer

Model

Comments

Flash Lamp-Reflector Assembly

Perkin-Elmer

RF-ASYRF160709 PKI08 (H)

Flash Lamp-Reflector Assembly

Perkin-Elmer

RF-ASY RF160709 PKI07 (H)

Flash Lamp-Reflector Assembly

Nam Kwong Co.

LTD.

FET-O-D03150220E-02

9.8 Joule,

Flash Lamp-Reflector Assembly

Nam Kwong Co.

LTD.

FET-O-D02230202A-07

8.0 Joule,

Perkin Elmer

coordinates: kimguan.lim@perkinelmer.com

Flash Strobe

The flash is activated by the digital status present at the

TRGFL Pin and the logic condition of the EN and

PHSEN Pins as defined in Table 4.