SP6686ER-L/TR 查看數據表（PDF） - Signal Processing Technologies

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SP6686ER-L/TR

400mA Buck/Boost Charge Pump LED Driver

Signal Processing Technologies 

regulation point for more than 32 cycles of

the internal clock, the SP6686 automati-

cally switches to the 2X mode. The SP6686

remains in the 2X mode until one of four

things happens: 1) the enable pin EN has

been toggled, 2) the Flash pin has changed

from high to low, 3) VIN is cycled or 4) a

thermal fault occurs. The 2X mode is the

charge pump mode where the output can be

pumped as high as two times the input

voltage, provided the output does not ex-

ceed the maximum voltage for the SP6686,

which is internally limited to about 5.5V. In

the 2X mode, as in the 1X mode, the output

current is regulated by the voltage at the FB

pin.

In the Torch mode, (Flash = GND) the Flash

pin is set to logic low and the SP6686 FB pin

regulates to 50mV output:

V = 50mV (Torch Mode)

FB

When in Flash mode, (Flash = VIN), the FB

regulation voltage is set by the resistor RSET

connected between the RSET pin and SGND

and the equation:

VFB = (1.26V/ RSET)*11.2KΩ (Flash Mode)

Where 1.26V is the internal bandgap refer-

ence voltage and 11.2KΩ is an internal

resistance used to scale the RSET current.

Typical values of RSET are 40KΩ to 180KΩ

for a range of VFB = 300mV to 75mV in Flash

mode.

The output current is then set in either Flash

or Torch mode by the equation:

IOUT = VFB / RSENSE

THEORY OF OPERATION

_______________OVERTEMPERATURE

PROTECTION

When the temperature of the SP6686 rises

above 145 degrees Celsius, the over tem-

perature protection circuitry turns off the

output switches to prevent damage to the

device. If the temperature drops back down

below 135 degrees Celsius, the part auto-

matically recovers and executes a soft start

cycle.

____________________OVERVOLTAGE

PROTECTION

The SP6686 has over voltage protection. If

the output voltage rises above the 5.5V

threshold, the over voltage protection shuts

off all of the output switches to prevent the

output voltage from rising further. When the

output decreases below 5.5V, the device

resumes normal operation

____________________OVERCURRENT

PROTECTION

The over current protection circuitry moni-

tors the average current out of the VOUT =

50mV (Torch Mode) pin. If the average

output current exceeds approximately

1Amp, then the over current protection cir-

cuitry shuts off the output switches to pro-

tect the chip.

Date: 03/10/06

SP6686 400mA, Buck/Boost Charge Pump LED Driver

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© Copyright 2006 Sipex Corporation

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