LT3800 데이터 시트보기 (PDF) - Linear Technology

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LT3800

High-Voltage Synchronous Current Mode Step-Down Controller

Linear Technology 

TYPICAL PERFOR A CE CHARACTERISTICS

VCC UVLO Threshold (Rising)

vs Temperature

6.30

ICC vs VCC (SHDN = 0V)

25

TA = 25°C

20

6.25

15

6.20

6.15

–50 –25

0 25 50 75

TEMPERATURE (°C)

100 125

3800 G07

I(SENSE+

+

–

SENSE )

vs

VSENSE(CM)

800

TA = 25°C

600

400

200

0

–200

–400

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

VSENSE(CM) (V)

3800 G09

10

5

0

0 2 4 6 8 10 12 14 16 18 20

VCC (V)

3800 G12

Operating Frequency

vs Temperature

220

210

200

190

180

–50 –25

0 25 50 75

TEMPERATURE (°C)

100 125

3800 G10

LT3800

Error Amp Transconductance

vs Temperature

380

360

340

320

–50 –25

0 25 50 75

TEMPERATURE (°C)

Error Amp Reference

vs Temperature

1.232

100 125

3800 G08

1.231

1.230

1.229

1.228

1.227

–50 –25

0 25 50 75

TEMPERATURE (°C)

100 125

3800 G11

PI FU CTIO S

VIN (Pin 1): Converter Input Supply.

NC (Pin 2): No Connection.

SHDN (Pin 3): Precision Shutdown Pin. Enable threshold

is 1.35V (rising) with 120mV of input hysteresis. When in

shutdown mode, all internal IC functions are disabled. The

precision threshold allows use of the SHDN pin to incor-

porate UVLO functions. If the SHDN pin is pulled below

0.7V, the IC enters a low current shutdown mode with

IVIN < 10µA. In low-current shutdown, the IC will sink 20µA

from the VCC pin until that local supply has collapsed.

Typical pin input bias current is <10nA and the pin is

internally clamped to 6V.

CSS (Pin 4): Soft-Start AC Coupling Capacitor Input.

Connect capacitor (CSS) in series with a 200k resistor from

pin to converter output (VOUT). Controls converter start-

up output voltage slew rate (∆VOUT/∆t). Slew rate corre-

sponds to 2µA average current through the soft-start

coupling capacitor. The capacitor value for a desired

output startup slew rate follows the relation:

CSS = 2µA/(∆VOUT/∆t)

Shorting this pin to SGND disables the soft-start function

BURST_EN (Pin 5): Burst Mode Operation Enable Pin.

This pin also controls reverse-inhibit mode of operation.

When the pin voltage is below 0.5V, Burst Mode operation

3800fb

5

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