- 您现在的位置：买卖IC网 > PDF目录20621 > LT3507IUHF#TRPBF (Linear Technology)IC REG QD BUCK/LINEAR 38-QFN PDF资料下载
参数资料
| 型号： | LT3507IUHF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/28页 |
| 文件大小： | 302K |
| 描述： | IC REG QD BUCK/LINEAR 38-QFN |
| 产品培训模块： | More Information on LDOs |
| 标准包装： | 2,500 |
| 拓扑： | 降压（降压）（1），线性（LDO）（1） |
| 功能： | 任何功能 |
| 输出数： | 4 |
| 频率 - 开关： | 900kHz ~ 1.1MHz |
| 电压/电流 - 输出 1： | 0.8 V ~ 32.4 V，2.4A |
| 电压/电流 - 输出 2： | 0.8 V ~ 32.4 V，1.5A |
| 电压/电流 - 输出 3： | 0.8 V ~ 32.4 V，1.5A |
| 带 LED 驱动器： | 无 |
| 带监控器： | 无 |
| 带序列发生器： | 是 |
| 电源电压： | 4 V ~ 36 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 38-WFQFN 裸露焊盘 |
| 供应商设备封装： | 38-QFN（5x7） |
| 包装： | 带卷 (TR) |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页当前第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页
LT3507
11
3507fa
f
MAX2
is the frequency at which the maximum duty cycle
is exceeded. If there is suf cient charge on the BOOST
capacitor, the regulator will skip OFF periods to increase
the overall duty cycle at frequencies about f
MAX2
. It will
continue to regulate but with increased inductor current
and greatly increased output ripple.
Note that the restriction on the operating input voltage
refers to steady-state limits to keep the output in regula-
tion; the circuit will tolerate input voltage transients up to
the absolute maximum rating.
Switching Frequency
Once the upper and lower bounds for the switching
frequency are found from the duty cycle requirements,
the frequency may be set within those bounds. Lower
frequencies result in lower switching losses, but require
larger inductors and capacitors. The user must decide
the best trade-off.
The switching frequency is set by a resistor connected
from the R
T
/SYNC pin to ground, or by forcing a clock
signal into R
T
/SYNC. The LT3507 applies a voltage of
~1.25V across this resistor and uses the current to set
the oscillator speed. The switching frequency is given by
the following formula:
f
SW
=
55
R
T
+12
where f
SW
is in MHz and R
T
is in k?
The frequency sync signal will support V
H
logic levels from
1.8V to 5V CMOS or TTL. The duty cycle is not important,
but it needs a minimum on time of 100ns and a minimum
off time of 100ns. If the sync circuit is to be powered from
one of the LT3507 outputs there may be start-up problems
if the driving gate is high impedance without a supply or
pulls high or low at some intermediate supply voltage.
The circuit shown in Figure 2 prevents these problems by
isolating the clock sync circuit until the clock is operating.
The Schottky diode should be a low leakage type such as
the BAS70 from On Semi or CMOD6263 from Central Semi.
R
T
should be set to provide a frequency within ?5% of
the nal sync frequency.
Inductor Selection and Maximum Output Current
The current in the inductor is a triangle wave with an average
value equal to the load current. The peak switch current
is equal to the output current plus half the peak-to-peak
inductor ripple current. The LT3507 limits its switch current
in order to protect itself and the system from overload
faults. Therefore, the maximum output current that the
LT3507 will deliver depends on the switch current limit,
the inductor value and the input and output voltages.
When the switch is off, the potential across the inductor
is the output voltage plus the catch diode drop. This gives
the peak-to-peak ripple current in the inductor:
擨
L
= 1DC
(
)
V
OUT
+V
F
L"f
where f is the switching frequency of the LT3507 and L
is the value of the inductor. The peak inductor and switch
current is:
I
SWPK
=I
LPK
=I
OUT
+
擨
L
2
To maintain output regulation, this peak current must
be less than the LT3507s switch current limit, I
LIM
. For
SW1, I
LIM
is at least 3A at low duty cycles and decreases
linearly to 2.4A at DC = 0.8. For SW2 and SW3, I
LIM
is at
least 2A for at low duty cycles and decreases linearly to
1.6A at DC = 0.8.
The minimum inductance can now be calculated as:
L
MIN
=
1DC
MIN
2"f
"
V
OUT
+V
F
I
LIM
I
OUT
However, its generally better to use an inductor larger
than the minimum value. The minimum inductor has large
ripple currents which increase core losses and require
large output capacitors to keep output voltage ripple low.
APPLICATIONS INFORMATION
Figure 2. Clock Powered from LT3507 Output
R
T
/SYNC
V
OUT1
3507 F02
LT3507
SW1
CLK
CLOCK
SYNC
V
CC
R
T
BAS70
1k
470pF
相关PDF资料 |
PDF描述 |
|---|---|
| TH3D107M010D0600 | CAP TANT 100UF 10V 20% 2917 |
| R1D-1515/HP | CONV DC/DC 1W 15VIN +/-15VOUT |
| FIN0.75RD | FIREFLEX FIBERGLASS 3/4" RED 50' |
| ISL6613ACRZ-T | IC MOSFET DRVR SYNC BUCK 10-DFN |
| 76000724 | CABLE BARE WIRE 4' DB-9F |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3508 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Monolithic 1.4A Step-Down Switching Regulator |
| LT3508EFE#PBF | 功能描述:IC REG BUCK ADJ 1.4A DL 16TSSOP 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 |
| LT3508EFE#TRPBF | 功能描述:IC REG BUCK ADJ 1.4A DL 16TSSOP 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:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3508EFEPBF | 制造商:Linear Technology 功能描述:Dual 1.4A Step-Down Regulator LT3508 |
| LT3508EFE-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Monolithic 1.4A Step-Down Switching Regulator |
发布紧急采购，3分钟左右您将得到回复。