收藏本站
Circuit Description
Overview
The FAN5346 is an inductive current-mode boost serial
LED driver that achieves LED current regulation by
maintaining 0.250V across the R SET resistor. The current
through the LED string (I LED ) is given by:
I LED =
0 . 250
R SET
(1)
The voltage V OUT is determined by the sum of the forward
voltages across each LED, plus the voltage across R SET ,
which is always 250mV.
Driving Eight LEDs in Series
FAN5346S30X can drive 8 LEDs in series, but the minimum
input voltage (V IN ) must be greater than or equal to 2.9V,
while the forward voltage of the white LED should be less
than or equal to 3.2V, and the maximum LED current
cannot exceed 20mA to maintain stable operation.
UVLO and Soft-Start
If EN has been LOW for more than 1ms, the IC may
initiate a “cold start” soft-start cycle when EN rises,
provided V IN is above the UVLO threshold.
PWM Dimming
The FAN5346 uses a PWM signal to directly modulate
output current in the LED string to vary the perceived LED
brightness. When the EN pin is held HIGH, the FB voltage
is 250mV. This voltage is reduced when a PWM signal is
applied to the EN pin, thereby enabling the LEDs to be
dimmed. The FB voltage is given by the equation:
V FB = DutyCycle × 250 mV (2)
where DutyCycle = the duty cycle of the PWM signal
and 250mV is the internal reference voltage.
Figure 28 illustrates how the FAN5346 divides the internal
250mV reference voltage at the duty cycle of the PWM
signal. A low-pass filter filters the PWM signal, which then
is input into the error amplifier as the reference voltage for
the FB pin.
? 2011 Fairchild Semiconductor Corporation
FAN5346 ? Rev. 1.0.1
Figure 28. Block Diagram of FB and EN Circuit for
PWM Dimming
Over-Current and Short-Circuit Detection
The boost regulator employs a cycle-by-cycle peak inductor
current limit of 300mA (typical) and 750mA (typical) for
FAN5346S20X and FAN5346S30X, respectively.
Over-Voltage / Open-Circuit Protection
If the LED string is an open circuit, FB remains at 0V and the
output voltage continues to increase in the absence of an over-
voltage protection (OVP) circuit. The FAN5346S20X OVP
circuit disables the boost regulator when V OUT exceeds 20V
and continues to keep the regulator off until V OUT drops below
19V. For FAN5346S30X, the OVP is 30V and it turns back on
when V OUT is below 29V
Thermal Shutdown
When the die temperature exceeds 150°C, a reset occurs and
remains in effect until the die cools to 115°C; at which time, the
circuit is allowed to begin the soft-start sequence.
www.fairchildsemi.com
10
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
FAN53540UCX IC REG SYNC BUCK 5A 20WLCSP
FAN5626LX IC LED DVR 6CH INTERFACE 10-UMLP
FAN5640S7X IC LED DRIVER DUAL CC SC70-6
FAN5646S700X IC LED DRIVER BLINKER SC70-5
FAN5701UMP30X IC LED DVR MULTI 30MA 16-UMLP
FAN5702UC30X IC LED DVR 6LED 30MA I2C 16WLCSP
FAN7080MX_GF085 IC GATE DRIVER HALF BRIDGE 8SOIC
FAN7081MX_GF085 IC GATE DRIVER HI SIDE 8-SOIC
相关代理商/技术参数
FAN5350 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:3MHz, 600mA Step-Down DC-DC Converter in Chip-Scale and MLP Packaging
FAN5350_08 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:3MHz, 600mA Step-Down DC-DC Converter in Chip-Scale and MLP Packaging
FAN53501UCX 功能描述:直流/直流开关转换器 ANG FG 3MHz 600mA DC-DC Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
FAN5350M_BAB3086B WAF 制造商:Fairchild Semiconductor Corporation 功能描述:
FAN5350MPX 功能描述:直流/直流开关转换器 3MHz 600mA DC/DC Buck Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
FAN5350UCX 功能描述:直流/直流开关转换器 3MHz 600mA DC/DC Buck Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
FAN5353 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:3MHz, 3A Synchronous Buck Regulator
FAN5353MPX 功能描述:直流/直流开关调节器 3MHz, 3a TinyBuck Sync Buck Regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5