- 您现在的位置：买卖IC网 > PDF目录20862 > LT3956EUHE#TRPBF (Linear Technology)IC LED DVR BUCK BOOST 36-VQFN PDF资料下载
参数资料
| 型号： | LT3956EUHE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 12/20页 |
| 文件大小： | 0K |
| 描述： | IC LED DVR BUCK BOOST 36-VQFN |
| 标准包装： | 2,500 |
| 恒定电流： | 是 |
| 恒定电压： | 是 |
| 拓扑： | 回扫，低端，PWM，SEPIC，降压（降压），升压（升压） |
| 输出数： | 1 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 车载，通用 |
| 类型 - 次要： | 白色 LED |
| 频率： | 100kHz ~ 1MHz |
| 电源电压： | 4.5 V ~ 80 V |
| 输出电压： | 80V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 36-WFQFN 裸露焊盘 |
| 供应商设备封装： | 36-QFN-EP（6x5） |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 125°C |
LT3956
APPLICATIONS INFORMATION
Dimming Control
There are two methods to control the current source for
dimming using the LT3956. One method uses the CTRL
pin to adjust the current regulated in the LEDs. A second
method uses the PWM pin to modulate the current source
between zero and full current to achieve a precisely pro-
grammed average current. To make this method of current
control more accurate, the switch demand current is stored
on the V C node during the quiescent phase when PWM is
low. This feature minimizes recovery time when the PWM
signal goes high. To further improve the recovery time, a
disconnect switch may be used in the LED current path to
prevent the ISP node from discharging during the PWM
signal low phase. The minimum PWM on or off time will
depend on the choice of operating frequency through the
R T input. For best overall performance, the minimum PWM
low or high time should be at least six switching cycles
(6μs for f SW = 1MHz).
Programming the Switching Frequency
Duty Cycle Considerations
Switching duty cycle is a key variable defining converter
operation, therefore, its limits must be considered when
programming the switching frequency for a particular
application. The fixed minimum on-time and minimum
off-time (see Figure 4) and the switching frequency define
the minimum and maximum duty cycle of the switch,
respectively. The following equations express the mini-
mum/maximum duty cycle:
Min Duty Cycle = (minimum on-time) ? switching
frequency
Max Duty Cycle = 1 – (minimum off-time) ? switching
frequency
When calculating the operating limits, the typical values
for on/off-time in the data sheet should be increased by at
least 60ns to allow margin for PWM control latitude and
SW node rise/fall times.
The R T frequency adjust pin allows the user to program
the switching frequency from 100kHz to 1MHz to optimize
efficiency/performance or external component size. Higher
frequency operation yields smaller component size but
increases switching losses and gate driving current, and
may not allow sufficiently high or low duty cycle operation.
Lower frequency operation gives better performance at the
cost of larger external component size. For an appropriate
R T resistor value see Table 1. An external resistor from the
RT pin to GND is required—do not leave this pin open.
300
250
200
150
100
50
0
–50
–25
MINIMUM ON-TIME
MINIMUM OFF-TIME
0 25 50
75
100
125
Table 1. Switching Frequency vs R T Value
TEMPERATURE (°C)
3956 F04
f OSC (kHz)
1000
900
800
700
600
500
400
300
200
100
R T (k)
10
11.8
13
15.4
17.8
21
26.7
35.7
53.6
100
Figure 4. Typical Switch Minimum On
and Off Pulse Width vs Temperature
Thermal Considerations
The LT3956 is rated to a maximum input voltage of 80V.
Careful attention must be paid to the internal power dis-
sipation of the IC at higher input voltages to ensure that a
junction temperature of 125°C is not exceeded. This junction
limit is especially important when operating at high ambient
temperatures. If the LT3956’s junction temperature reaches
165°C (typ), the power switch will be turned off and the
soft-start (SS) pin will be discharged to GND. Switching
3956f
相关PDF资料 |
PDF描述 |
|---|---|
| XLN3640-GL | POWER SUPPLY PROGRAM DC 36V/40A |
| REC8-243.3SRW/H2/A/M | CONV DC/DC 8W 24VIN 3.3VOUT |
| EBC13DRTH | CONN EDGECARD 26POS DIP .100 SLD |
| P51-500-A-R-M12-4.5OVP-000-000 | SENSOR 500PSI M12-1.0 6G .5-4.5V |
| ECC05DRAN | CONN EDGECARD 10POS R/A .100 SLD |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3956IUHE#PBF | 功能描述:IC LED DVR BUCK BOOST 36-VQFN 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 |
| LT3956IUHE#TRPBF | 功能描述:IC LED DVR BUCK BOOST 36-VQFN 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 |
| LT3956IUHE-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:80VIN, 80VOUT Constant-Current, Constant-Voltage Converter |
| LT3956IUHE-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:80VIN, 80VOUT Constant-Current, Constant-Voltage Converter |
| LT3957 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Wide Input Voltage Range |
发布紧急采购，3分钟左右您将得到回复。