MAX8834Y 데이터 시트보기 (PDF) - Maxim Integrated

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MAX8834Y

Adaptive Step-Up Converters with 1.5A Flash Driver

Maxim Integrated 

MAX8834Y/MAX8834Z

Adaptive Step-Up Converters

with 1.5A Flash Driver

GSMB (ACTIVE-HIGH)

GSMB EVENT

INPUT CURRENT

FLED2 OUTPUT

CURRENT

PREDEFINED INPUT CURRENT

LIMIT DURING GSMB

FLED1/FLED2 DECREASED ONE

LSB SINCE IIN > ILIM[3:0]

FLED1/FLED2 INCREASED

ONE LSB SINCE IIN < ILIM[3:0]

FLED1 OUTPUT

CURRENT

FLASH1_CUR

SETTING

1µs AFTER GSMB

ACTIVATED, FLED_ GOES

TO THE MINIMUM SETTING

Figure 10. Input Current Limit During GSMB Event

HC_TMR[1:0]

TIME

1µs AFTER GSMB

DEACTIVATED, FLED_ GOES

TO THE PREVIOUS SETTING

GSM Blank Function (GSMB)

The GSMB input is provided to allow the flash current to

be momentarily reduced during a GSM transmit to

reduce the peak current drawn from the battery. The

input current limit ensures that the maximum possible

output current is always provided, regardless of the

input voltage and the LED forward voltages.

When a GSMB event is triggered, the FLED1 and

FLED2 current regulators go to the lowest setting to

ensure the current drawn from the battery is quickly

reduced to a safe level. The MAX8834Y/MAX8834Z

then start increasing the FLED1 and FLED2 current by

one LSB steps, at a time interval set by HC_TMR[1:0]

(see Table 11). The increasing continues until either the

predefined FLED1/FLED2 current setting is reached or

the input current exceeds the maximum predefined

input current limit during a GSMB event. When the input

current exceeds the predefined input current limit, the

FLED1/FLED2 current is reduced by one LSB. The

MAX8834Y/MAX8834Z continue to adjust the FLED1

and FLED2 up and down depending on the input cur-

rent limit as long as the GSMB event is present. See

Figure 10 for more detailed information.

16

Maxim Integrated

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