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| 型号： | MC34845EPR2 |
| 厂商： | Freescale Semiconductor |
| 文件页数： | 13/24页 |
| 文件大小： | 0K |
| 描述： | IC DVR LED BACKLIGHT 6CH 24-QFN |
| 标准包装： | 2,500 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 6 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 频率： | 600kHz |
| 电源电压： | 5 V ~ 21 V |
| 输出电压： | 8 V ~ 60 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 24-UFQFN 裸露焊盘 |
| 供应商设备封装： | 24-QFN 裸露焊盘（4x4） |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 85°C |
FUNCTIONAL DEVICE OPERATION
INTRODUCTION
voltage and ground with its output connected to the OVP pin.
The OVP can be set up to 60V by varying the resistor divider
to match the OVP internal reference of 6.9V (typical).
EN
LED DRIVER
PWM
The 6 channel LED driver provides current matching for 6
LED strings to within ± 2% maximum. The current in the
VIN
5V
2 ms
Boost
strings is set using a resistor tied to GND from the ISET pin.
The LED current level is given by the equation: RSET = 153/
ILED. The accuracy of the RSET resistor should be 0.1% for
best performance.
Soft Start
VOUT
UVLO Rising
LED ERROR DETECT
VIN ramp
Figure 5. Power up sequence case 2, VIN applied after
the ENABLE and PWM signals. VIN ramp up time
between 0V and 5V should be not higher than 2ms
BOOST CONVERTER
The boost converter uses a Dynamic Headroom Control
(DHC) loop to automatically set the output voltage needed to
drive the LED strings. The DHC is designed to operate under
specific pulse width conditions in the LED drivers. It operates
for pulse widths higher than 400 ns. If the pulse widths are
shorter than specified, the DHC circuit will not operate and
the voltage across the LED drivers will increase to a value
given by the OVP, minus the total LED voltage in the LED
string. It is therefore imperative to select the proper OVP level
to avoid exceeding the max off state voltage of the LED
drivers (45V).
The boost operates in current mode and is compensated
externally through a type 2 network on the COMP pin. A
modification of the compensation network is suggested to
minimize the amplitude of the ripple at V OUT . The details of
the suggested compensation network are shown in Figures
10 and 11 .
An integrated 2.0A minimum FET supplies the required
output current. An Over-current Protection circuit limits the
output current cycle-by-cycle to I OCP . If the condition exists
longer than 10 ms, then the device will shut down. The
frequency of the boost converter is internally set to 300 kHz,
600 kHz or 1.2 MHz, depending on the device’s version.
The boost also includes a soft start circuit. Each time the
IC comes out of shutdown mode, the soft start period lasts for
t SS .
Over-voltage Protection is also included. The device has
an internally fixed OVP value of 60V (typical) which serves as
a secondary fault protection mechanism, in the event the
externally programmed OVP fails (i.e. resistor divider opens
up). While the internal 60V OVP detector can be used
exclusively without the external OVP network, this is only
recommended for applications where the LED string voltage
approaches 55 V or more. The OVP level can be set by using
an external resistor divider connected between the output
If an LED is open, the output voltage ramps to the OVP
level. If there is still no current in the LED string, the LED
channel is turned off and the output voltage ramps back down
to normal operating level.
If LEDs are shorted and the voltage in any of the channels
is greater than the SFDV threshold (7.0 V typical), then the
device will turn off that channel. However if the on-time of the
channels is less than 10 μ s, the SFDV circuit will not disable
any of the channels, regardless of the voltage across them.
All the LED errors can be cleared by recycling the EN pin
or applying a complete power-on-reset (POR).
WAKE OPERATION
The WAKE pin provides the means to set the device for
low power consumption (shutdown mode) without the need of
an extra logic signal for enable. This is achieved by
connecting the WAKE and PWM pins together, and tying the
EN pin to ground. In this configuration, the PWM signal is
used to control the LED channels, while allowing low power
consumption by setting the device into its shutdown mode
every time the PWM signal is kept low for longer time than the
WAKE time out of 27 ms.
OVER-TEMPERATURE SHUTDOWN AND
TEMPERATURE CONTROL CIRCUITS
The 34845 includes over-temperature protection. If the
internal temperature exceeds the over-temp threshold
OTT SHUTDOWN , then the device shuts down all functions.
Once the temperature falls below the low level threshold, the
device is re-enabled.
FAIL PIN
The FAIL pin is at its low-impedance state when no error
is detected. However, if an error such as an LED channel
open or boost over-current is detected, the FAIL pin goes into
high-impedance. Once a failure is detected, the FAIL pin can
be cleared by recycling the EN pin or applying a complete
power-on-reset (POR). If the detected failure is an Over-
current time-out, the EN pin or a POR must be cycled/
executed to restart the part.
34845
Analog Integrated Circuit Device Data
Freescale Semiconductor
13
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MC34846EP | 功能描述:LED照明驱动器 6-Ch LED Backlt Drvr RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| MC34846EPR2 | 功能描述:LED照明驱动器 6-Ch LED Backlt Drvr RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| MC34847 | 制造商:SPC Multicomp 功能描述:RECEPTACLE FREE 18WAY |
| MC34848EP | 功能描述:LED照明驱动器 8 CHANNEL LED DRIVER RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| MC34848EPR2 | 功能描述:LED照明驱动器 8 CHANNEL LED DRIVER RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
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