LTC1530CS8-1.9(RevA) View Datasheet(PDF) - Linear Technology

Part Name

Description

MFG CO.

LTC1530CS8-1.9
(Rev.:RevA)

High Power Synchronous Switching Regulator Controller

Linear Technology 

LTC1530

APPLICATIO S I FOR ATIO

Table 1. Recommended MOSFETs for LTC1530 Applications

MANUFACTURER

PART NO.

PACKAGE

RDS(ON)

AT 25°C

(Ω)

RATED CURRENT

(A)

TYPICAL INPUT

CAPACITANCE

Ciss (pF)

θJC

(°C/W)

TJMAX

(°C)

Siliconix

SUD50N03-10

TO-252

0.019

15A at 25°C

3200

10A at 100°C

1.8

175

Siliconix

Si4410DY

SO-8

0.020

10A at 25°C

2700

8A at 75°C

—

150

ON Semiconductor

MTD20N03HDL

DPAK

0.035

20A at 25°C

880

16A at 100°C

1.67

150

Fairchild

FDS6680

SO-8

0.01

11.5A at 25°C

2070

ON Semiconductor MTB75N03HDL*

D2PAK

0.0075

75A at 25°C

4025

59A at 100°C

IR

IRL3103S

D2PAK

0.014

56A at 25°C

1600

40A at 100°C

25

150

1.0

150

1.8

175

IR

IRLZ44

TO-220

0.028

50A at 25°C

3300

1.0

175

36A at 100°C

Fuji

2SK1388

TO-220

0.037

35A at 25°C

1750

2.08

150

Note: Please refer to the manufacturer’s data sheet for testing conditions and detailed information.

*Users must consider the power dissipation and thermal effects in the LTC1530 if driving external MOSFETs with high values of input capacitance.

Refer to the PVCC Supply Current vs GATE Capacitance in the Typical Performance Characteristics section.

where L is the inductor value in µH. With proper frequency

compensation, the combination of the inductor and output

capacitor values determine the transient recovery time. In

general, a smaller value inductor improves transient

response at the expense of ripple and inductor core

saturation rating. A 2µH inductor has a 0.9A/µs rise time

in this application, resulting in a 5.5µs delay in responding

to a 5A load current step. During this 5.5µs, the difference

between the inductor current and the output current is

made up by the output capacitor. This action causes a

temporary voltage droop at the output. To minimize this

effect, the inductor value should usually be in the 1µH to

5µH range for most 5V input LTC1530 circuits. Different

combinations of input and output voltages and expected

loads may require different values.

Once the required inductor value is selected, choose the

inductor core type based on peak current and efficiency

requirements. Peak current in the inductor is equal to the

maximum output load current plus half of the peak-to-

peak inductor ripple current. Inductor ripple current is set

by the inductor’s value, the input voltage, the output

voltage and the operating frequency. If the efficiency is

high, ripple current is approximately equal to:

( ( )( ))(( ) ) IRIPPLE =

VIN − VOUT

fOSC LO

VOUT

VIN

where

fOSC = LTC1530 oscillator frequency

LO = Inductor value

Solving this equation for a typical 5V to 2.8V application

with a 2µH inductor, ripple current is:

(2.2V)(0.56)

( )( ) 300kHz 2µH = 2AP-P

Peak inductor current at 11.2A load:

11.2A + 2A = 12.2A

2

The ripple current should generally fall between 10% and

40% of the output current. The inductor must be able to

withstand this peak current without saturating, and the

copper resistance in the winding should be kept as low as

possible to minimize resistive power loss. Note that in

1530fa

13

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