- 您现在的位置：买卖IC网 > PDF目录14835 > LT3505EDD#PBF (Linear Technology)IC REG BUCK ADJ 1.2A 8DFN PDF资料下载
参数资料
| 型号： | LT3505EDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1.2A 8DFN |
| 标准包装： | 121 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.78 V ~ 33.8 V |
| 输入电压： | 3.6 V ~ 36 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 200kHz ~ 3.01MHz |
| 电流 - 输出： | 1.2A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-WFDFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 8-DFN-EP（3x3） |
| 产品目录页面： | 1331 (CN2011-ZH PDF) |
LT3505
APPLICATIONS INFORMATION
Finite transistor bandwidth limits the speed at which the
power switch can be turned on and off, effectively setting
the minimum on-time of the LT3505. For a given output volt-
age, the minimum on-time determines the maximum input
voltage to remain in continuous mode operation, V IN(PS) .
See the “Input Voltage Range” section of the datasheet for
more information on determining V IN(PS) . For switching
frequencies below 750kHz, operation above V IN(PS) (up
to 40V) is safe provided that the system will tolerate the
pulse-skipping behavior outlined in the “Minimum On
Time” section of the datasheet. At switching frequencies
exceeding 750kHz, edge loss limits operation to input
voltages below V IN(PS) .
Finite transition time results in a small amount of power
dissipation each time the power switch turns on and off
(edge loss). Edge loss increases with frequency, switch
current, and input voltage.
Input Voltage Frequency Foldback
In constant frequency operation (below V IN(PS) ) edge
loss only reduces the application ef?ciency. However, at
high switching frequencies exceeding 750kHz and input
voltages exceeding V IN(PS) , the part operates in pulse-skip-
ping mode and the switch current can increase above the
current limit of the part, 1.75A. This further increases the
power dissipated during switch transitions and increases
die temperature. To remedy the situation a single resis-
tor (R5) and a zener diode (D3) can be added to a typical
LT3505 circuit as shown in Figure 4.
When the input voltage is below 16V, the zener diode
path conducts no current and the current ?owing out
of the R T pin (and through R4) is nominally 0.5V/20k =
25μA, which programs a 2.2MHz switching frequency.
As the input voltage is increased above 16V, the zener
diode begins to conduct and gradually reduces the cur-
rent ?owing out of the R T pin. This mechanism reduces
the switching frequency as the input voltage is increased
above 16V (up to 36V) to ensure that the part constantly
operates in continuous mode without skipping pulses,
thereby preventing the excessive die temperature rise
encountered in pulse-skipping mode.
Although the circuit can be operated inde?nitely above
V ZENER , this frequency foldback method is intended to
protect circuits during temporary periods of high input
voltage. For example, in many automotive systems, the
normal operating input range might be 9V to 16V, and
the LT3505 can be programmed to operate above the
AM band (>1.8MHz). At the same time, the circuit must
be able to withstand higher input voltages due to load
dump or double-battery jump starts. During these brief
periods, it is usually acceptable to switch at a frequency
within the AM band.
If the output is shorted while the input voltage is greater than
V ZENER , the switching frequency will be reduced to 30kHz
and the part will not be able to recover from the short until
the input voltage is reduced below V ZENER (see the following
discussion).
R1
6.8 μ H
V IN
6.7V TO 36V
ON OFF
D3
BZT52C16T
16V
R5
806k
C2
1 μ F
V IN
SHDN
LT3505
R T GND
R4
20.0k
BOOST
SW
FB
V C
R3
100k
C4
22pF
D2
1N4148
C3
0.1 μ F
L1
61.9k
D1 R2
MBRM140 11.5k
C5
22pF
V OUT
5V
C1
10 μ F
2.50
2.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
0
5
10
Switching
Frequency
Maximum
Load Current
15 20
25
30
35
40
3505 F04
Input Voltage [V]
LTC3505 ? F04b
Figure 4. 2.2MHz, 5V Application with Input Voltage Frequency Foldback Circuit
3505fc
11
相关PDF资料 |
PDF描述 |
|---|---|
| MAX6464UK44+T | IC VOLT DETECTOR LP SOT23-5 |
| VI-BTY-EY-F1 | CONVERTER MOD DC/DC 3.3V 33W |
| RCM25DREF | CONN EDGECARD 50POS .156 EYELET |
| EBM40DRSN | CONN EDGECARD 80POS DIP .156 SLD |
| RBA36DTMN | CONN EDGECARD 72POS R/A .125 SLD |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3505EDD-TR | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.2A, Step-Down Switching Regulator in 3mm × 3mm DFN |
| LT3505EDDTRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.2A, Step-Down Switching Regulator in 3mm x 3mm DFN |
| LT3505EDD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.2A, Step-Down Switching Regulator in 3mm × 3mm DFN |
| LT3505EMS8E | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.2A, Step-Down Switching Regulator in 3mm × 3mm DFN |
| LT3505EMS8E#PBF | 功能描述:IC REG BUCK ADJ 1.2A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
发布紧急采购，3分钟左右您将得到回复。