LTC3370 datasheet(22/28 Pages) AD

22 / 28 page

LTC3376

Rev 0

For more information www.analog.com

APPLICATIONS INFORMATION

independently to PGNDA-H with a 1µF capacitor as close

to the pins as possible and at least a 10µF capacitor.

Connect each ground of each capacitor to a wide PCB

trace on the top layer of the PCB that connects directly to

the PGND pin and then to the GND plane.

Note that larger input capacitance is required when a lower

switching frequency is used. If the input power source has

high impedance, or if there is significant inductance due to

long wires or cables, additional bulk capacitance may be

necessary. This can be provided with a low performance

electrolytic capacitor.

A ceramic input capacitor combined with trace or cable

inductance forms a high quality (underdamped) tank cir-

cuit. If the LTC3376 circuit is plugged in to a live supply,

the input voltage can ring to twice its nominal value, pos-

sibly exceeding the LTC3376’s voltage rating. This situa-

tion is easily avoided (see Linear Technology Application

Note 88).

Table 3. Ceramic Capacitor Manufacturers

VENDOR

URL

AVX

www.avxcorp.com

Murata

www.murata.com

TDK

www.tdk.com

Taiyo Yuden

www.t-yuden.com

Output Capacitor, Output Ripple, and Loop Response

The output capacitor has two essential functions. Along

with the inductor, it filters the square wave generated at

the LTC3376 SW pins to produce the DC output. In this

role it determines the output ripple. Thus, low imped-

ance at the switching frequency is important. The second

function is to store energy in order to satisfy transient

loads and to stabilize the LTC3376’s control loop. Ceramic

capacitors have very low equivalent series resistance

(ESR) and provide the best ripple performance. For good

starting values, see the Typical Applications. Use X5R or

X7R ceramic capacitors. This choice will provide low out-

put ripple and good transient response.

The LTC3376 is internally compensated and has been

designed to operate at a high bandwidth for fast transient

response capability. The selection of COUT will affect the

bandwidth of the system and the optimal value is given

by the following equation:

COUT = 100 •

(# of power stages)

fSW • VOUT

(11)

where fSW is the switching frequency.

This calculated COUT value is the capacitance required

after voltage and temperature derating. A lower value of

output capacitor can be used to save space and cost but

transient performance will suffer and may cause loop

instability. See the Typical Applications in this data sheet

for suggested capacitor values.

When choosing a capacitor, special attention should be

given to the data sheet to calculate the effective capaci-

tance under the relevant operating conditions of voltage

Table 2. Recommended Inductors

PART NUMBER

(µH)

MAX DCR

(mΩ)

CURRENT RATING

(A)

DIMENSIONS

(L × W × H)

VENDOR

XEL4030-102MEB

XFL4020-152MEB

XEL4030-222MEB

XFL4020-472MEB

1.5

2.2

4.7

9.78

15.8

22.1

57.4

10.7

9.1

7.8

4mm × 4mm × 3.1mm

4.3mm × 4.3mm × 2.1mm

4mm × 4mm × 3.1mm

4.3mm × 4.3mm × 2.1mm

Coilcraft

www.coilcraft.com

744383360068

74438357010

74404042015

74439344022

0.68

1.5

2.2

13.5

10.5

4.5

7.4

2.95

3mm × 3mm × 2mm

4.1mm × 4.1mm × 3.1mm

4mm × 4mm × 1.8mm

6.65mm × 6.65mm × 3.3mm

Wurth Electronics Inc.

www.we-online.com

PCMB042T-1R0MS

PCMB053T-1R5MS

1.5

4.5

4.15mm × 4mm × 1.8mm

4.7mm × 4.85mm × 2.8mm

Susumu

www.susumu-usa.com

FDSD0420-H-R68M=P3

FDSD0420D-1R0M=P3

FDSD0420D-2R2M=P3

0.68

2.2

6.5

5.1

3.6

4.2mm × 4.2mm × 2mm

Murata

LTC3370 Datasheet(PDF) 22 Page - Analog Devices

LTC3370 Datasheet(HTML) 22 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datasheet Download

Link URL