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參數(shù)資料
| 型號： | SC605 |
| 廠商： | Semtech Corporation |
| 英文描述： | Charge Pump Flash LED Driver |
| 中文描述： | 電荷泵閃光LED驅(qū)動器 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 356K |
| 代理商： | SC605 |
6
2005 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
Applications Information (Cont.)
Output Over-Voltage Protection
Output over-voltage protection is included to prevent the
SC605 from generating an output voltage that could dam
-
age other devices connected to it such as load LEDs and
bypass capacitors. When the output voltage exceeds 5.5V,
the OVP circuit disables the charge pump until the voltage
decreases to a level within the acceptable range. This cir-
cuit allows the device to drive LEDs with high forward volt
ages at a reduced level without exceeding the output volt-
age limits specified for the device. This is a consequence
of over-voltage protection, not the function of OVP.
SC605
Over-Temperature Protection
The OT circuit helps prevent the device from overheating
and experiencing a catastrophic failure. When the junction
temperature exceeds 150°C the device is disabled. It
remains disabled until the junction temperature drops
below this threshold. As with the OVP circuit, hysteresis is
included to prevent toggling between states.
Over-Current Protection
When the SC605 is in 2X charge pump mode, the input
current will be approximately double the required output.
When the steady-state load requires the maximum current
available in 2X mode, the OCP circuit prevents the device
from overheating due to excessive power dissipation.
Short-Circuit Current Protection
SCCP is provided to limit the current that can be sourced
when the output is shorted to ground. When the output
voltage drops below 2V, the SCCP detects the condition as
a short to ground and limits the output current.
ResistorSelection
The ISET resistor selection is critical to generating the cor
-
rect current. The value can be chosen to set the Spotlight
mode current or the Flash mode current, but it must be
noted that the two current settings are dependent on the
same resistor. It is recommended that the resistor be se
-
lected to match the LEDs desired current for Flash mode.
This will allow the designer to set the maximum current
out of the SC605. The typical application circuit shown on
page uses a 0.5
W
resistor to set a Flash mode current
of 500mA and Spotlight mode options of 100mA, 150mA,
and 200mA. A precision resistor should be used to ensure
the specified accuracy for LED current.
To avoid malfunction of the charge pump, it is recom
-
mended that the resistance seen at the ISET pin remain
constant while the device is active (Flash or Spotlight
mode). Changing the resistance value or the load current
while the device is active could cause instability or voltage
transients that would result in non-compliant behavior.
The load current return path is from the ISET sense point
through the resistor and back to the ground pin. Resistance
in this path adds to the total resistance and has the effect
of reducing the LED current by about 4% per 10mV of DC
drop across the return copper trace in Flash mode. For this
reason, it is crucial to have a low resistance return path.
Place and ground the resistor as close as possible to the
ground pin of the SC605. The trace from ISET has virtually
no current. The ISET trace should make contact at the pad
of the power sense resistor to minimize the effect of voltage
drop between the LED cathode and the resistor.
CapacitorSelection
The SC605 is designed to use low-ESR ceramic capaci
-
tors for the input and output bypass capacitors as well as
the charge pump bucket capacitors. Ideal performance
is achieved when C1 is exactly equal to C2. It is recom
-
mended that X5R or X7R ceramic capacitors be used for
best performance.
ThermalResistance
The SC605 package is thermally efficient when the circuit
board layout connects the thermal pad through multiple
vias to the ground plane. The thermal resistance is rated
at 0°C/W, but this rating is dependent on the connection
between the thermal pad and the ground plane. A layout
that is done correctly should keep the junction tempera
-
ture below the OT limit while operating the SC605 within
the specifed electrical conditions for I
and V
. A poor
layout may allow the junction temperature to reach the
OT limit while in Flash or Spotlight mode.
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相關代理商/技術參數(shù) |
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|---|---|
| SC605EVB | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Charge Pump Flash LED Driver |
| SC605MLTRT | 制造商:Semtech Corporation 功能描述:LED DRVR 1Segment 3.3V/5V 12-Pin MLPD T/R |
| SC605-R | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Speech And Music Processor |
| SC605-RL1 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Speech And Music Processor |
| SC606 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Low Noise Smart LED Driver with Serial Interface |
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