SC600 데이터 시트보기 (PDF) - Semtech Corporation

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SC600

mAhXLife™ LED Driver with 5.0V, 4.5V, or 4.0V Output

Semtech Corporation 

SC600

POWER MANAGEMENT

Applications Information (Cont.)

Table 2 -Ripple Performance (Cont.)

Part No.

Freq. [kHz] IOUT [mA] Output Ripple [mVp-p] Ouput Ripple [mVp-p] COUT [μF] CBUCKET [μF]

1.5x mode

2x mode

SC600B(1) 4.5V

8

10

215

50

1

1

32

40

300

90

1

1

262

120

40

25

1

1

650

120

15

25

1

1

650

120

30

45

0.33

1

SC600D 4.0V

8

10

105

50

1

1

32

40

240

45

1

1

262

120

30

20

1

1

650

120

11

20

1

1

650

120

25

Note: (1) SC600C is very similar to SC600B.

40

0.33

1

Mode Transition Impedance

The mode transition impedance Ro refers to the output

resistance of the charge pump before a transition to a

stronger mode occurs. Ro is dependent upon the frac-

tional charge pump, switching frequency, bucket capaci-

tor value, bucket capacitor ESR, and the internal switch

resistances.

1

Ro is proportional to,

f˜C

Ro can be measured to verify a low transition imped-

ance. Before measuring Ro, select the capacitors, set

the operating frequency and a constant load current. Find

the input voltage just before a weak to strong mode tran-

sition (i.e., 1.5x to 2x mode). Measure VIN, VOUT, and IOUT

before the transition.

A lower value of Ro will improve efficiency, so low ESR

ceramic capacitors are required. An X7R or X5R dielec-

tric is recommended. Y5V dielectric can require 2 to 3

times the rated value of an X7R dielectric for the same

performance over the operating temperature range.

Efficiency

Efficiency for the SC600 is defined as,

V O˜I O

  η = V IN˜ mode˜I O  I Q

Ro will be,

mode˜V IN  V OUT

Ro=

I OUT

© 2006 Semtech Corp.

11

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