LT3485 데이터 시트보기 (PDF) - Linear Technology

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LT3485

Photoflash Capacitor Chargers with Output Voltage Monitor and Integrated IGBT Drive

Linear Technology 

LT3485-0/LT3485-1/

LT3485-2/LT3485-3

APPLICATIO S I FOR ATIO

Note that the absolute maximum rating of the SW pin is

not exceeded. Make sure to check the SW voltage wave-

form with VOUT near the target output voltage, as this is the

worst case condition for SW voltage. Figure 4 shows the

various limits on the SW voltage during switch turn off.

It is important not to minimize the leakage inductance to

a very low level. Although this would result in a very low

leakage spike on the SW pin, the parasitic capacitance of

the transformer would become large. This will adversely

affect the charge time of the photoflash circuit.

Linear Technology has worked with several leading mag-

netic component manufacturers to produce pre-designed

flyback transformers for use with the LT3485-0/LT3485-

1/LT3485-2/LT3485-3. Table 2 shows the details of sev-

eral of these transformers.

Capacitor Selection

For the input bypass capacitors, high quality X5R or X7R

types should be used. Make sure the voltage capability of

the part is adequate.

Output Diode Selection

The rectifying diode(s) should be low capacitance type

with sufficient reverse voltage and forward current rat-

ings. The peak reverse voltage that the diode(s) will see is

approximately:

VPK−R = VOUT + (N • VIN)

IPRI

1A/DIV 2

VSW

10A/DIV

VIN = 5V

VOUT = 320V

100ns/DIV

3485 F03

Figure 3. LT3485 SW Voltage Waveform

“B”

“A”

VSW

MUST BE

LESS THAN 50V

MUST BE

LESS THAN 40V

0V

3485 F04

Figure 4. New Transformer Design Check (Not to Scale)

Table 2. Pre-Designed Transformers – Typical Specifications Unless Otherwise Noted

FOR USE WITH

TRANSFORMER

SIZE

LPRI LPRI-LEAKAGE

RPRI

RSEC

NAME

(W × L × H) mm (µH)

(nH)

N (mΩ) (Ω)

LT3485-0/LT3485-2

LT3485-1

SBL-5.6-1

SBL-5.6S-1

5.6 × 8.5 × 4.0 10 200 Max 10.2 103

26

5.6 × 8.5 × 3.0 24 400 Max 10.2 305

55

LT3485-0

LT3485-1

LT3485-2

LT3485-3

LT3485-0/LT3485-1

LT3485-1

LT3485-3

LDT565630T-001

LDT565630T-002

LDT565630T-003

LDT565630T-041

T-15-089

T-15-083

T-17-109A

5.8 × 5.8 × 3.0 6 200 Max 10.4 100 Max 10 Max

5.8 × 5.8 × 3.0 14.5 500 Max 10.2 240 Max 16.5 Max

5.8 × 5.8 × 3.0 10.5 550 Max 10.2 210 Max 14 Max

5.8 × 5.8 × 3.0 4.7 150 Max 10.4 90 Max 6.4 Max

6.4 × 7.7 × 4.0 12 400 Max 10.2 211 Max 27 Max

8.0 × 8.9 × 2.0 20 500 Max 10.2 675 Max 35 Max

6.5 × 7.9 × 4.0 5.9 300 Max 10.2 78 Max 18.61 Max

VENDOR

Kijima Musen

Hong Kong Office

852-2489-8266 (ph)

kijimahk@netvigator.com (email)

TDK

Chicago Sales Office

(847) 803-6100 (ph)

www.components.tdk.com

Tokyo Coil Engineering

Japan Office

0426-56-6262 (ph)

www.tokyo-coil.co.jp

34850123fb

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