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参数资料
| 型号： | LTC3452EUF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC LED DRIVER PHOTO FLASH 20-QFN |
| 标准包装： | 2,500 |
| 拓扑： | PWM，降压（降压），升压（升压） |
| 输出数： | 7 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光，闪灯/白光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 900kHz ~ 1.1MHz |
| 电源电压： | 2.7 V ~ 5.5 V |
| 输出电压： | 4.5V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-WFQFN 裸露焊盘 |
| 供应商设备封装： | 20-QFN 裸露焊盘（4x4） |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 85°C |
LTC3452
OPERATIO
LED Current Setting Amps
The maximum forward current per LED for all LEDs in a
given bank is programmed by a single external resistor to
ground at the corresponding I SETL,H pin according to the
implemented results in “smoother” brightness and dim-
ming control as perceived by the human eye, which is
logarithmic in nature.
Table 1. Low Power Bank Brightness Control
? , I MAXH = 768 ?
I MAXL = 256 ?
? R ISETH ?
? R ISETL ?
following formulas:
? 0 . 8 ? ? 0 . 8 ?
?
For operation at currents below I MAXL in the low power
bank, refer to the Exponential Brightness Control section
and also to external circuit options given in the Applica-
tions Section. For operation at currents below I MAXH in the
high power bank, refer only to the external circuit options
given in the Applications Section.
EN L DUTY CYCLE (% LOGIC HIGH)
0% (Logic Low)
0% < Duty Cycle < 12.5%
12.5% < Duty Cycle < 25%
25% < Duty Cycle < 37.5%
37.5% < Duty Cycle < 50%
50% < Duty Cycle < 62.5%
62.5% < Duty Cycle < 75%
75% < Duty Cycle < 87.5%
87.5% < Duty Cycle ≤ 100%
LED Lx CURRENT
0 (Shutdown)
1/128 ? I MAXL
1/64 ? I MAXL
1/32 ? I MAXL
1/16 ? I MAXL
1/8 ? I MAXL
1/4 ? I MAXL
1/2 ? I MAXL
I MAXL
Shutdown Circuit
The shutdown circuit monitors the voltages at the EN L,H
pins. Logic high on either/both inputs enables the part and
logic low on both puts the part in shutdown. Since the EN L
pin doubles as a PWM input for LED brightness control, an
output filter in the shutdown circuit is employed to prevent
the part from toggling in and out of shutdown for normal
PWMing of the EN L input when EN H is low. If EN H is low,
the LTC3452 is enabled immediately after a rising edge at
the EN L pin, but waits 200 μ s (typical) after a falling edge
to enter shutdown. Consequently, a minimum PWM fre-
quency is required for smooth brightness control at cur-
rents below I MAXL . The recommended PWM frequency is
LED Current Sources
Each LED pin is driven by a current source specifically
designed for low dropout. The LTC3452 employs a propri-
etary architecture that determines which of the seven
LEDs requires the largest forward voltage drop at its
programmed current, and then generates a feedback
voltage based on this one for closing the buck-boost
regulation loop. This results in the lowest output voltage
required for regulating all of the LEDs and thus the highest
LED power efficiency. The voltage present at the LED pin
of the “controlling LED” will be typically 130mV at 20mA
(low power bank) or 250mA at 100mA (high power bank)
of current.
10kHz to 50kHz.
LED Detect Circuit
Exponential Brightness Control
(Low Power LED Bank Only)
The LTC3452 implements an exponential brightness con-
trol function for the low power LED bank only in which the
LED Lx current is a function of the PWM duty cycle at the
EN L pin. The LED current will be equal to a fraction of
I MAXL as given in Table 1. As the duty cycle (that the PWM
waveform is logic high) increases linearly, the LED cur-
rent will increase exponentially from 1/128th I MAXL to
If fewer than five LED outputs in the low power bank and/
or fewer than two LED outputs in the high power bank are
required, unused outputs should be connected to V OUT .
Each LED pin has an internal LED detect circuit that
disables the output current source to save power if an
output is not needed. A small current is employed to detect
the presence of an LED at startup. This current is typically
10 μ A for the low power bank and 30 μ A for the high power
bank.
128/128ths I MAXL in seven binary steps. The function
3452f
10
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相关代理商/技术参数 |
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| LTC3453 | 制造商:LINER 制造商全称:Linear Technology 功能描述:700mA Low Noise High Current LED Charge Pump |
| LTC3453EUF | 制造商:Linear Technology 功能描述:LED DRVR 4Segment 3.3V/5V 16-Pin QFN EP |
| LTC3453EUF#PBF | 功能描述:IC LED DRIVER PHOTO FLASH 16-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LTC3453EUF#TRPBF | 功能描述:IC LED DRIVER PHOTO FLASH 16-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LTC3454 | 制造商:LINER 制造商全称:Linear Technology 功能描述:1A Synchronous Buck-Boost High Current LED Driver |
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