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| 型号： | LT3507EUHF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/28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) |
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LT3507
15
3507fa
to oat, then the LT3507s internal circuitry will pull its
quiescent current through its SW pin. This is acceptable if
the system can tolerate a few mA of load in this state. With
all three RUN pins grounded, the LT3507 enters shutdown
mode and the SW pin current drops to <50糀. However, if
the V
IN
pin is grounded while the output is held high, then
parasitic diodes inside the LT3507 can pull large currents
from the output through the SW pin and the V
IN
pin. A
Schottky diode in series with the input to the LT3507, as
shown in Figure 5, will protect the LT3507 and the system
from a shorted or reversed input.
and is largest when V
IN
= 2V
OUT
(50% duty cycle). As
the second, lower power channel draws input current,
the input capacitors RMS current actually decreases as
the out-of-phase current cancels the current drawn by the
higher power channel. Considering that the maximum load
current from a single phase (if SW2 and SW3 are both at
maximum current) is ~3A, RMS ripple current will always
be less than 1.5A.
The high frequency of the LT3507 reduces the energy
storage requirements of the input capacitor, so that the
capacitance required is often less than 10糉. The combi-
nation of small size and low impedance (low equivalent
series resistance or ESR) of ceramic capacitors makes
them the preferred choice. The low ESR results in very
low voltage ripple. Ceramic capacitors can handle larger
magnitudes of ripple current than other capacitor types
of the same value. Use X5R and X7R types.
An alternative to a high value ceramic capacitor is a lower
value along with a larger electrolytic capacitor, for example
a 1糉 ceramic capacitor in parallel with a low ESR tantalum
capacitor. For the electrolytic capacitor, a value larger than
10糉 will be required to meet the ESR and ripple current
requirements. Because the input capacitor is likely to see
high surge currents when the input source is applied, tan-
talum capacitors should be surge rated. The manufacturer
may also recommend operation below the rated voltage
of the capacitor. Be sure to place the 1糉 ceramic as close
as possible to the V
IN
and GND pins on the IC for optimal
noise immunity.
A nal caution is in order regarding the use of ceramic
capacitors at the input. A ceramic input capacitor can
combine with stray inductance to form a resonant tank
circuit. If power is applied quickly (for example by plugging
the circuit into a live power source), this tank can ring,
doubling the input voltage and damaging the LT3507. The
solution is to either clamp the input voltage or dampen the
tank circuit by adding a lossy capacitor in parallel with the
ceramic capacitor. For details, see Application Note 88.
APPLICATIONS INFORMATION
Figure 5. Diode D4 Prevents a Shorted Input from
Discharging a Backup Battery Tied to the Output
V
IN
V
IN
V
OUT
SW
LT3507
D4
PARASITIC DIODE
3507 F05
Input Capacitor Selection
Bypass the input of the LT3507 circuit with a 10糉 or
higher ceramic capacitor of X7R or X5R type. A lower
value or a less expensive Y5V type will work if there is
additional bypassing provided by bulk electrolytic capaci-
tors, or if the input source impedance is low. The following
paragraphs describe the input capacitor considerations
in more detail.
Step-down regulators draw current from the input supply
in pulses with very fast rise and fall times. The input ca-
pacitor is required to reduce the resulting voltage ripple at
the LT3507 input and to force this switching current into a
tight local loop, minimizing EMI. The input capacitor must
have low impedance at the switching frequency to do this
effectively and it must have an adequate ripple current rat-
ing. With three switchers operating at the same frequency
but with different phases and duty cycles, calculating the
input capacitor RMS current is not simple; however, a
conservative value is the RMS input current for the phase
delivering the most power (V
OUT
" I
OUT
):
I
IN(RMS)
=I
OUT
"
V
OUT
V
IN
V
OUT
(
)
V
IN
<
I
OUT
2
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|---|---|
| LT3507HUHF#PBF | 功能描述:IC REG QD BUCK/LINEAR 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
| LT3507HUHF#TRPBF | 功能描述:IC REG QD BUCK/LINEAR 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
| LT3507HUHF-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Triple Monolithic Step-Down Regulator with LDO |
| LT3507HUHF-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Triple Monolithic Step-Down Regulator with LDO |
| LT3507IUHF#PBF | 功能描述:IC REG QD BUCK/LINEAR 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
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