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参数资料
| 型号： | SC668ULTRT |
| 厂商： | Semtech |
| 文件页数： | 13/46页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR LMU 8CH MLPQUT20 |
| 特色产品： | Semtech sc667 and sc668 |
| 标准包装： | 1 |
| 拓扑： | 线性（LDO），PWM |
| 输出数： | 12 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光，LED 闪烁器，照明管理装置（LMU） |
| 频率： | 400kHz |
| 电源电压： | 2.9 V ~ 5.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-UFQFN 裸露焊盘 |
| 供应商设备封装： | 20-MLPQ（3x3） |
| 包装： | 标准包装 |
| 工作温度： | -40°C ~ 85°C |
| 其它名称： | SC668ULDKR |
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SC668
Applications Information
General Description
The SC668 is optimized for handheld applications sup-
plied from a single cell Li-Ion and includes the following
key features:
forward voltage of the LEDs is available. The resulting
efficiency in this scenario would be optimal. To achieve
best accuracy, the current sink amplifier requires the
LED sink pin (BLn) to be within the operational range of
?
Eight matched current sinks — BL1, BL2, BL3,
BL4, BL5, BL6, BL7, and BL8 regulate LED back-
V DO ≤ V BLn ≤ 4.2V. When the sink is off, V BLn may float as
high as 5.5V.
?
?
?
?
lighting current, with 0mA to 25mA per LED.
Four adjustable LDOs — LDO1, LDO3, and LDO4
are adjustable with 15 settings from 1.5V to 3.3V.
LDO2 is adjustable with 7 settings from 1.2V to
1.8V.
ALS with a sigma-delta ADC that can also be used
for general purpose ADC functions.
PWM with an internal digital low-pass filter
I 2 C Bus fast mode and standard mode
C IN
V IN
IN
SC668
GND
BL1
BL2
BL3
BL4
BL5
BL6
BL7
BL8
V BL 1
V BL 2
V BL3
V BL4
V BL5
V BL6
V BL7
V BL8
V A
LED Backlight Current Settings
The backlight current is set via the I 2 C interface. The current
is regulated to one of 32 values between 0mA and 25mA.
The step size varies depending upon the current setting.
The first three steps are 50μA, 100μA, and 200μA. Between
0.5mA and 5mA, the step size is 0.5mA. The step size
increases to 1mA for settings between 5mA and 21mA.
Steps are 2mA between 21mA and 25mA. The variation in
step size allows finer adjustment for dimming functions in
the low current range and coarse adjustment at higher
current settings where larger changes are not visible. The
settings are psuedo-logarithmic. A zero setting also disables
the current sink, providing an alternative to the enable bit.
LED Backlight Current Sinks
Backlight current is independent of forward voltage mis-
match (?V F ) between LEDs. When two or more backlight
sinks are set to the same target current, their currents will
match, even if the LED voltages are different. The backlight
current sinks are designed with a low dropout voltage (typi-
cally 59mV for a bank of 6 LEDs at 20mA) to optimize run-time
when the LED anode voltage is provided by a battery.
LED Anode Supply
In the typical application circuit, the battery voltage sup-
plies the LEDs. An alternative to this configuration is to
connect the LED anodes to a second DC supply as shown
in Figure 1. Such a connection is especially useful when
an alternate voltage that is slightly higher than the
Figure 1 — Anode Supply
Unused Backlight Current Sinks
The backlight LEDs default to the off state upon power-
up. For backlight applications using fewer than 8 LEDs,
any unused output must be left open or grounded and
the unused LED must remain disabled. When writing to
the backlight enable register, a zero (0) must be written
to the corresponding enable bit of any unused output.
Backlight Quiescent Current
The quiescent current required to operate the backlights
is reduced when backlight current is less than 8.0mA. This
feature results in higher efficiency under light-load con-
ditions. Further quiescent current reduction will result
from using fewer LEDs.
Backlight Configuration into Banks
The eight LED backlight drivers can be assigned to a single
bank or divided among up to four independent banks —
refer to the Register Map section for more details. The
independent banks can each be configured with different
settings for backlight current and fade operation.
Bank Configuration into Groups
The four backlight banks can be assigned to two groups
(group #1 and group #2). Each group provides indepen-
dent settings for the fade and breathe effect rate options.
Each group also provides independent settings for target
time and start time, which are used to customize the
13
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