SM8132A 데이터 시트보기 (PDF) - Nippon Precision Circuits

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SM8132A

White LED Driver IC

Nippon Precision Circuits  

SM8132A

Switching to power-save mode

The internal circuit operating mode switches from ×1.0/×1.5 mode to power-save mode when EN goes LOW

and do not switch HIGH for an interval of 1.63ms (max). This function turns the LEDs OFF and automatically

transfers internal circuit control to power-save mode, suppressing current consumption.

EN

Internal

enable (CE)

Power

save

1.0 or 1.5

CE hold time 1.63ms (max)

Power

save

EN input signal and internal enable signal “CE”

I If the EN input signal is held for an interval greater than the “CE” hold time 1.63ms (max), the SM8132A

switches to power-save mode. The internal circuits are reset on the “CE” falling edge, and the current setting

must be re-established before restart.

Switching from ×1.0 mode to ×1.5 mode

If the LEDs can be driven solely by the current determined by RSET and EN pulse input without boosting the

VIN input voltage, the VOUT output operates in ×1.0 mode. In other words, if sufficient current flows even with

the LED forward-direction voltage drop “VF”, then VOUT is less than 4.2V. Operation in the more efficient

×1.0 mode reduces the total power dissipation and extends the battery drive time. And if low “VF” LEDs are

used or the LED drive current setting is LOW, the operating time in ×1.0 mode is also extended.

1.0 mode

(high efficiency)

High VF LED

1.5 mode

(low efficiency)

1.0 mode

(high efficiency)

Low VF LED

High

VIN input

1.5 mode

(low efficiency)

Low

VOUT mode switching time comparison due to drive LED “VF” variation

If the VIN voltage falls or RSET increases such that the LED drive current is too low in ×1.0 mode, then the

LED drive circuit low-current detector operates, the VOUT output is automatically switched to ×1.5 mode, and

the charge pump boosts the output voltage. This occurs even if only one LED low-current condition is detected

among the 4-channel LED drive circuits, thus it is recommended that LEDs have small “VF” variation to opti-

mize the total efficiency.

NIPPON PRECISION CIRCUITS INC.—11

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