参数资料
型号: LTC3214EDD#TRPBF
厂商: Linear Technology
文件页数: 10/12页
文件大小: 0K
描述: IC LED DRIVR WHITE BCKLGT 10-DFN
标准包装: 2,500
拓扑: 升压(升压),切换式电容器(充电泵)
输出数: 1
内部驱动器:
类型 - 主要: 闪灯/白光
类型 - 次要: 白色 LED
频率: 600kHz ~ 1.2MHz
电源电压: 2.9 V ~ 4.5 V
安装类型: 表面贴装
封装/外壳: 10-WFDFN 裸露焊盘
供应商设备封装: 10-DFN(3x3)
包装: 带卷 (TR)
工作温度: -40°C ~ 85°C
LTC3214
APPLICATIONS INFORMATION
η≡
η IDEAL ≡
= ≈
= ≈ LED
η IDEAL ≡
Power Ef?ciency
To calculate the power ef?ciency ( η ) of a white LED
driver chip, the LED power should be compared to the
input power. The difference between these two numbers
represents lost power whether it is in the charge pump
or the current sources. Stated mathematically, the power
ef?ciency is given by:
P LED
P IN
The ef?ciency of the LTC3214 depends upon the mode in
which it is operating. Recall that the LTC3214 operates
as a pass switch, connecting V IN to CPO, until dropout
is detected at the I LED pin. This feature provides the op-
timum ef?ciency available for a given input voltage and
LED forward voltage. When it is operating as a switch, the
ef?ciency is approximated by:
In 1.5x boost mode, the ef?ciency is similar to that of a
linear regulator with an effective input voltage of 1.5 times
the actual input voltage. This is because the input current
for a 1.5x charge pump is approximately 1.5 times the
load current. In an ideal 1.5x charge pump, the power
ef?ciency would be given by:
P LED V LED ? I LED V LED
P IN V IN ? 1 . 5 I LED 1 . 5 V IN
Similarly, in 2x boost mode, the ef?ciency is similar to
that of a linear regulator with an effective input voltage
of 2 times the actual input voltage. In an ideal 2x charge
pump, the power ef?ciency would be given by:
P LED V LED ? I LED V
P IN V IN ? 2 ? I LED 2 V IN
Thermal Management
= ≈ LED
η≡
P LED
P IN
V LED ? I LED V
V IN ? I IN V IN
For higher input voltages and maximum output current,
there can be substantial power dissipation in the LTC3214.
since the input current will be very close to the LED
current.
At moderate to high output power, the quiescent current
of the LTC3214 is negligible and the expression above is
valid.
Once dropout is detected at the I LED pin, the LTC3214
enables the charge pump in 1.5x mode.
If the junction temperature increases above approximately
165°C, the thermal shutdown circuitry will automatically
deactivate the output. To reduce maximum junction tem-
perature, a good thermal connection to the PC board is
recommended. Connecting the Exposed Pad to a ground
plane and maintaining a solid ground plane under the
device can reduce the thermal resistance of the package
and PC board considerably.
3214fb
10
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