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| 型号： | LT3508HFE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 17/26页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1.4A DL 16TSSOP |
| 标准包装： | 95 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 0.8 V ~ 35.3 V |
| 输入电压： | 3.7 V ~ 36 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 920kHz ~ 1.06MHz |
| 电流 - 输出： | 1.4A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 150°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 16-TSSOP-EP |
| 产品目录页面： | 1331 (CN2011-ZH PDF) |
LT3508
APPLICATIONS INFORMATION
Ratiometric tracking is achieved in Figure 8b by connecting
both the TRACK/SS pins together. In this con?guration the
TRACK/SS pin source current is doubled (2.4μA) which
must be taken into account when calculating the output
rise time.
Do not tie TRACK/SS1 and TRACK/SS2 together if using
multiple inputs. If V IN2 is below 3V, TRACK/SS2 pulls low
and would hold TRACK/SS1 low as well if the two pins
are tied together, which would prevent channel 1 from
operating.
By connecting a feedback network from V OUT1 to the
TRACK/SS2 pin with the same ratio that set the V OUT2
voltage, absolute tracking shown in Figure 8c is imple-
mented. A small V OUT2 voltage offset will be present due
to the TRACK/SS2 1.2μA source current. This offset can
be corrected for by slightly reducing the value of R2. Use
a resistor divider such that when V OUT1 is in regulation,
TRACK/SS2 is pulled up to 1V or greater. If TRACK/SS is
below 1V, the output may regulate FB to a voltage lower
than the 800mV reference voltage.
Figure 8d illustrates output sequencing. When V OUT1 is
within 10% of its regulated voltage, PG1 releases the
TRACK/SS2 soft-start pin allowing V OUT2 to soft-start.
In this case PG1 will be pulled up to 1.3V by the TRACK/
SS pin.
If precise output ramp up and down is required, drive the
TRACK/SS pins as shown in Figure 8e.
Multiple Inputs
For applications requiring large inductors due to high V IN
to V OUT ratios, a 2-stage step down approach may reduce
inductor size by allowing an increase in frequency. A dual
step-down application (Figure 9) steps down the input
voltage (V IN1 ) to the highest output voltage, then uses that
voltage to power the second output (V IN2 ). V OUT1 must
be able to provide enough current for its output plus the
input current at V IN2 when V OUT2 is at its maximum load.
For applications with multiple input voltages, the LT3508
can accommodate input voltages as low as 3V on V IN2 .
This can be useful in applications regulating outputs from
a PCI Express bus, where the 12V input is power limited
and the 3.3V input has power available to drive other
outputs. In this case, tie the 12V input to V IN1 and the
3.3V input to V IN2 . See the Typical Application section for
an example circuit.
Shorted and Reverse Input Protection
If the inductor is chosen so that it won’t saturate exces-
sively, an LT3508 step-down regulator will tolerate a shorted
output. There is another situation to consider in systems
where the output will be held high when the input to the
V IN
5.7V TO 36V
C1
OUT1
D1
4.7μF
ON OFF
V IN1
SHDN
V IN2
D2
OUT1
L1 6.8μH
C2
0.1μF
BOOST1
BOOST2
C3
0.1μF
L2
3.3μH
OUT2
5V
SW1
SW2
1.8V
0.9A
R1
D3
LT3508
D4
R2
1A
56.2k
FB1
FB2
18.7k
R3
10.7k
R5
39k
V C1
TRACK/SS1
V C2
PG1
R6
47k
R4
15.0k
C5
47μF
TRACK/SS2
PG2
C4
10μF
C6
100pF
C8
1nF
GND
C9
3.3nF
RT/SYNC
R8
33.2k
C7
330pF
R7
100k
f SW = 1MHz
3508 F09
POWER
GOOD
Figure 9. 1MHz, Wide Input Range 5V and 1.8V Outputs
3508fd
17
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3508HFE-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Monolithic 1.4A Step-Down Switching Regulator |
| LT3508HUF#PBF | 功能描述:IC REG BUCK ADJ 1.4A DL 24QFN 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 |
| LT3508HUF#TRPBF | 功能描述:IC REG BUCK ADJ 1.4A DL 24QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 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:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3508HUF-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Monolithic 1.4A Step-Down Switching Regulator |
| LT3508HUF-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Monolithic 1.4A Step-Down Switching Regulator |
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