参数资料
型号: LT3754IUH#TRPBF
厂商: Linear Technology
文件页数: 14/30页
文件大小: 0K
描述: IC LED DVR 16CH 50MA 32QFN
标准包装: 2,500
恒定电流:
拓扑: PWM,升压(升压)
输出数: 16
内部驱动器:
类型 - 主要: 车载,背光
类型 - 次要: 白色 LED
频率: 100kHz ~ 1MHz
电源电压: 6 V ~ 40 V
安装类型: 表面贴装
封装/外壳: 32-WFQFN 裸露焊盘
供应商设备封装: 32-QFN
包装: 带卷 (TR)
工作温度: -40°C ~ 125°C
LT3754
APPLICATIONS INFORMATION
I D(OVERCURRENT ) =
The power rating of RS should be selected to exceed
the I 2 R losses in the resistor. The peak inductor current
should be recalculated for the chosen RS value to ensure
the chosen inductor will not saturate.
Power MOSFET: Overcurrent and Hiccup Mode
For severe external faults which may cause the external
MOSFET to reach currents greater than the peak current
defined by RS and the 52mV sense pin threshold described
above, the LT3754 has an overcurrent comparator which
triggers soft start and turns off the MOSFET driver for
currents exceeding,
100mV
RS
In this fault mode the LT3754 only allows MOSFET turn
on for approximately 100ns every 2ms. This hiccup mode
significantly reduces the power rating required for the
MOSFET.
GATE
V C
V C MIN
CLAMP
SS
(INTERNAL)
Soft-Start
To limit inductor inrush current and output voltage during
start-up or recovery from a fault condition, the LT3754 pro-
vides a soft-start function. The LT3754 when entering these
faults will discharge an internal soft-start node and prevent
switching at the GATE pin for any of the following faults: V IN ,
SHDN /UVLO or INTV CC voltages too low or MOSFET current
too high (see the timing diagram in Figure 2). When exiting
these faults the LT3754 ramps up an internal soft-start
node at approximately 0.5V/ms to control V C pin voltage
rise and hence control MOSFET switch current rise. In ad-
dition the soft start period gradually ramps up switching
frequency from approximately 33% to 100% of full scale.
The conditions required to exit all faults and allow a soft-
start ramp of the V C pin are listed in Figure 2. An added
feature of the LT3754 is that it waits for the first PWM pin
active high (minimum 200ns pulse width) before it allows
the soft-start of V C pin to begin. This feature ensures that
0.5V/ms
0.4V + V BE (V C SWITCHING
THRESHOLD)
0.1V + V BE
0.5V/ms
0.4V
0.1V
ANY OF THE FOLLOWING FAULTS
TRIGGERS SOFT START LATCH
WITH GATE TURNED OFF
IMMEDIATELY:
V IN < 3.7V, SHDN < 1.476V,
INTVCC < 3.4V
I DSS (EXTERNAL MOSFET) > 100mV/RS
SOFT-START
LATCH SET:
SOFT-START LATCH RESET REQUIRES
ALL CONDITIONS SATISFIED:
SS (INTERNAL) < 0.2V, V IN ≥ 4.2V,
SHDN > 1.476V, INTV CC > 3.8V,
I DSS (EXTERNAL MOSFET) < 100mV/RS,
PWM > 1.4V (FOR AT LEAST 200ns)
3754 F02
Figure 2. LT3754 Fault Detection and Soft Start Timing for V C Pin and Internal SS Node
3754fc
14
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