SM8131B00B Просмотр технического описания (PDF) - Nippon Precision Circuits

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SM8131B00B

White LED Driver IC

Nippon Precision Circuits  

SM8131B

VOUT Output Circuit Mode Switching

The SM8131B switches between 3 output states: power-save mode (standby state), ×1.0 mode (VIN through

mode), and ×1.5 mode (×1.5 charge pump boost). This automatically adjusts the VOUT output to match the

drive LED characteristics and reduces the total power dissipation. Switching to and from ×1.0 and ×1.5 mode

occurs automatically in an internal circuit, and cannot be controlled using an external input.

Power-ON internal reset time

The SM8131B switches from standby condition (power-save mode) to normal operating condition (×1.0/×1.5

mode) on the first rising edge of either EN1 or EN2. Note that if the VIN supply voltage is applied when EN1

or EN2 is HIGH, startup occurs after the internal power-ON reset time (approximately 50µs) expires. At star-

tup, operation commences in ×1.5 mode for a fixed interval during the soft-start time in order to determine

whether a LED is connected to each DIN pin.

VIN

power source

(1)

VIN

Power on

POR time

reset output

typ: 50µs

(2)

Internal

enable (CE)

Power save

mode

Soft start time

(3)

1.5 mode

Power-ON reset operation

(1) VIN voltage rises when power is applied.

(2) Power-ON reset (POR) circuit resets internal circuits approximately 50µs after the power is applied.

(3) If EN1 or EN2 is HIGH when power is applied, the internal circuits start operating when the internal “CE”

signal rising edge occurs after the power-ON reset time. If EN1 and EN2 are LOW when power is applied,

the “CE” rising edge occurs simultaneously with the first rising edge.

EN1

input signal

LED current

EN1

Dimming pulses enable

Soft start time

typ: 1.3ms

(1)

LED ON (2)

Soft start time and LED current

(1) If the EN signals are input after POR time is expired, the soft start time begin from the first EN input rising

edge. The current setting can be adjusted during the soft-start time.

(2) LED current starts flow immediately before the soft start time expires.

NIPPON PRECISION CIRCUITS INC.—9

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