Rainbow-electronics MAX17127 Manual de usuario descargar pdf (Pagina 14)

14 _____________________________________________________________________________________

MAX17127

Six-String WLED Driver with Integrated

Step-Up Converter

Shutdown

The MAX17127 can be placed into shutdown by pulling

the EN pin low. When a critical failure is detected, the

IC also enters shutdown mode. In shutdown mode, all

functions of the IC are turned off, including the 5V lin-

ear regulator. Only a crude linear regulator remains on,

providing a 3.3V (typ) output voltage to V

DDIO

with 1FA

current-sourcing capability.

Frequency Selection

The boost converter switching frequency can be adjust-

ed by the external resistor on the FSLCT pin. The

switching frequency adjustable range is 250kHz to

1MHz. High-frequency (1MHz) operation optimizes the

regulator for the smallest component size at the expense

of efficiency due to increased switching losses. Low-

frequency (250kHz) operation offers the best overall effi-

ciency, but requires larger components and PCB area.

Figure 3. Startup Sequence

MIN FB_ CONTROL

(1ms)

DDIO

OUT

CHECK LED

LED

STEP-UP REGULATOR

SOFT-START

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 20 21 22

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Rainbow-electronics MAX17127 Manual de usuario Pagina 14