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參數(shù)資料
| 型號(hào)： | LTC3215 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | 700mA Low Noise High Current LED Charge Pump |
| 中文描述： | 700mA的低噪音，高電流LED電荷泵 |
| 文件頁(yè)數(shù)： | 10/12頁(yè) |
| 文件大?。?/td> | 162K |
| 代理商： | LTC3215 |
LTC3215
10
3215f
Power Efficiency
To calculate the power efficiency (
η
) of a white LED driver
chip, the LED power should be compared to the input
power. The difference between these two numbers repre-
sents lost power whether it is in the charge pump or the
current sources. Stated mathematically, the power effi-
ciency is given by:
η≡
P
P
LED
IN
(4)
The efficiency of the LTC3215 depends upon the mode in
which it is operating. Recall that the LTC3215 operates as
a pass switch, connecting V
IN
to CPO, until dropout is
detected at the I
LED
pin. This feature provides the optimum
efficiency available for a given input voltage and LED
forward voltage. When it is operating as a switch, the
efficiency is approximated by:
η≡
=
≈
P
P
V
I
I
V
V
V
LED
IN
LED
IN
LED
IN
LED
IN
(5)
since the input current will be very close to the LED
current.
At moderate to high output power, the quiescent current
of the LTC3215 is negligible and the expression above is
valid.
Once dropout is detected at the I
LED
pin, the LTC3215
enables the charge pump in 1.5x mode.
In 1.5x boost mode, the efficiency 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 efficiency
would be given by:
η
IDEAL
LED
P
P
IN
LED
V
V
LED
I
I
IN
LED
LED
V
.
1 5
IN
V
≡
=
≈
1 5
(6)
Similarly, in 2x boost mode, the efficiency 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 efficiency would be given by:
η
IDEAL
LED
IN
P
LED
IN
V
LED
LED
I
LED
V
2
IN
P
V
I
V
≡
=
≈
2
(7)
Thermal Management
For higher input voltages and maximum output current,
there can be substantial power dissipation in the LTC3215.
If the junction temperature increases above approximately
150
°
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.
APPLICATIOU
W
U
U
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| LTC3215EDD#TR | 功能描述:IC LED DRIVR WHITE BCKLGT 10-DFN RoHS:否 類別:集成電路 (IC) >> PMIC - LED 驅(qū)動(dòng)器 系列:- 標(biāo)準(zhǔn)包裝:6,000 系列:- 恒定電流:- 恒定電壓:- 拓?fù)?開路漏極，PWM 輸出數(shù):4 內(nèi)部驅(qū)動(dòng)器:是 類型 - 主要:LED 閃爍器 類型 - 次要:- 頻率:400kHz 電源電壓:2.3 V ~ 5.5 V 輸出電壓:- 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:8-HVSON 包裝:帶卷 (TR) 工作溫度:-40°C ~ 85°C 其它名稱:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LTC3215EDD#TRPBF | 功能描述:IC LED DRIVR WHITE BCKLGT 10-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - LED 驅(qū)動(dòng)器 系列:- 標(biāo)準(zhǔn)包裝:6,000 系列:- 恒定電流:- 恒定電壓:- 拓?fù)?開路漏極，PWM 輸出數(shù):4 內(nèi)部驅(qū)動(dòng)器:是 類型 - 主要:LED 閃爍器 類型 - 次要:- 頻率:400kHz 電源電壓:2.3 V ~ 5.5 V 輸出電壓:- 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:8-HVSON 包裝:帶卷 (TR) 工作溫度:-40°C ~ 85°C 其它名稱:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LTC3216 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:700mA Low Noise High Current LED Charge Pump |
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