LT1616 Просмотр технического описания (PDF) - Linear Technology

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LT1616

600mA, 1.4MHz Step-Down Switching Regulator in SOT-23

Linear Technology 

APPLICATIO S I FOR ATIO

COUT = 4.7µF CERAMIC, CASE SIZE 0805

COUT = 10µF CERAMIC, CASE SIZE 1206

COUT = 47µF, ESR ≅ 0.080Ω (SANYO POSCAP 6TPA47M)

C CASE

COUT = 100µF, ESR ≅ 0.150Ω (TANTALUM AVX

TPSC107M006R0150) C CASE

VOUT

20mV/DIV

ILOAD

100mA/DIV

0

COUT = 100µF TANTALUM AND 2.2µF CERAMIC

Figure 3. Transient Load Response of the LT1616

LT1616

VIN

10V

5

VIN

1

BOOST

LT1616

4

SHDN

6

SW

GND

FB

2

3

10µH

COUT

VOUT

3.3V

22Ω

33Ω

1616 F04

Figure 4. Circuit Used for Transient Load Test Shown in Figure 3

Regardless of which capacitor or combination of capaci-

tors you choose, you should do transient load tests to

evaluate the circuit’s stability. Avoid capacitors or combi-

nations that result in a ringing response. Problems may

occur if the output capacitance is very low or if a high value

inductor is used in combination with a large value, low

ESR capacitor.

The high performance (low ESR), small size and robust-

ness of ceramic capacitors make them the preferred type

for LT1616 applications. However, all ceramic capacitors

are not the same. Many of the higher value capacitors use

poor dielectrics with high temperature and voltage

coefficients. In particular, Y5V types should be regarded

with suspicion. Stick with X7R and X5R types. Don’t be

afraid to run them at their rated voltage. Table 2 lists

several capacitor manufacturers.

Catch Diode

A 0.5A Schottky diode is recommended for the catch diode

D1. The ON Semiconductor MBR0530 is a good choice; it

is rated for 0.5A forward current and a maximum reverse

voltage of 30V. For circuits with VIN less than 20V, the

MBR0520L can be used. Other suitable diodes are the

Zetex ZHCS500TR and ZHCS750TR, and various versions

of the 1N5818.

9

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