LT1913IDD 查看數據表（PDF） - Linear Technology

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LT1913IDD

25V, 3.5A, 2.4MHz Step-Down Switching Regulator

Linear Technology 

APPLICATIONS INFORMATION

Table 2. Capacitor Vendors

VENDOR

Panasonic

PHONE

(714) 373-7366

URL

www.panasonic.com

Kemet

Sanyo

(864) 963-6300

(408) 749-9714

www.kemet.com

www.sanyovideo.com

Murata

AVX

Taiyo Yuden

(408) 436-1300

(864) 963-6300

www.murata.com

www.avxcorp.com

www.taiyo-yuden.com

PART SERIES

Ceramic,

Polymer,

Tantalum

Ceramic,

Tantalum

Ceramic,

Polymer,

Tantalum

Ceramic

Ceramic,

Tantalum

Ceramic

LT1913

COMMANDS

EEF Series

T494, T495

POSCAP

TPS Series

rating, may be required. High performance tantalum or

electrolytic capacitors can be used for the output capacitor.

Low ESR is important, so choose one that is intended for

use in switching regulators. The ESR should be speci-

fied by the supplier, and should be 0.05 or less. Such a

capacitor will be larger than a ceramic capacitor and will

have a larger capacitance, because the capacitor must be

large to achieve low ESR. Table 2 lists several capacitor

vendors.

Catch Diode

The catch diode conducts current only during switch off

time. Average forward current in normal operation can

be calculated from:

ID(AVG) = IOUT (VIN – VOUT)/VIN

where IOUT is the output load current. The only reason to

consider a diode with a larger current rating than necessary

for nominal operation is for the worst-case condition of

shorted output. The diode current will then increase to the

typical peak switch current. Peak reverse voltage is equal

to the regulator input voltage. Use a schottky diode with a

reverse voltage rating greater than the input voltage. Table

3 lists several Schottky diodes and their manufacturers.

Table 3. Diode Vendors

VR

PART NUMBER

(V)

On Semiconductor

MBRA340

40

Diodes Inc.

B330

30

B320

20

IAVE

VF AT 3A

(A)

(mV)

3

500

3

500

3

450

Frequency Compensation

The LT1913 uses current mode control to regulate the

output. This simplifies loop compensation. In particular, the

LT1913 does not require the ESR of the output capacitor

for stability, so you are free to use ceramic capacitors to

achieve low output ripple and small circuit size. Frequency

compensation is provided by the components tied to the

1913f

13

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