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| 型号： | LT1507CS8-3.3#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/20页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 3.3V 1.5A 8SOIC |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 3.3V |
| 输入电压： | 4 V ~ 15 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 500kHz |
| 电流 - 输出： | 1.5A |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-SOIC |
LT1507
APPLICATIO N S I N FOR M ATIO N
committing to a final design. The fixed 3.3V LT1507-3.3
has internal divider resistors and the FB pin is renamed
SENSE, connected directly to the output.
The suggested value for the output divider resistor from FB
to ground (R2) is 5k or less and the formula for R1 is
shown below. The output voltage error caused by ignoring
the input bias current on the FB pin is less than 0.25% with
R2 = 5k. Please read below if R2 is increased above the
suggested value.
pin voltage drops below 1V (see Frequency Foldback
graph). This does not affect operation with normal load
conditions; one simply sees a gear shift in switching
frequency during start-up as the output voltage rises.
In addition to lower switching frequency, the LT1507 also
operates at lower switch current limit when the feedback
pin voltage drops below 1.5V. This foldback current limit
greatly reduces power dissipation in the IC, diode and
inductor during short-circuit conditions. Again, it is nearly
R1 =
R2(V OUT – 2.42)
2.42
transparent to the user under normal load conditions. The
only loads which may be affected are current source loads
which maintain full-load current with output voltage less
More Than Just Voltage Feedback
The feedback pin is used for more than just output voltage
sensing. It also reduces switching frequency and current
limit when output voltage is very low (see graph in Typical
Performance Characteristics). This is done to control
power dissipation in both the IC and in the external diode
and inductor during short-circuit conditions. A shorted
output requires the switching regulator to operate at very
low duty cycles and the average current through the diode
and inductor is equal to the short-circuit current limit of the
switch (typically 2A of the LT1507, folding back to less
than 1A). Minimum switch ON time limitations would
prevent the switcher from attaining a sufficiently low duty
cycle if switching frequency were maintained at 500kHz,
so frequency is reduced by about 5:1 when the feedback
than 50% of final value. In these rare situations, the
feedback pin can be clamped above 1.5V with an external
diode to defeat foldback current limit. Caution: clamping
the feedback pin means that frequency shifting will also be
defeated, so a combination of high input voltage and dead
shorted output may cause the LT1507 to lose control of
current limit.
The internal circuitry which forces reduced switching
frequency also causes current to flow out of the feedback
pin when output voltage is low. If the FB pin falls below 1V,
current begins to flow out of the pin and reduces frequency
at the rate of approximately 5kHz/ μ A. To ensure adequate
frequency foldback (under worst-case short-circuit con-
ditions) the external divider Thevinin resistance must be
low enough to pull 150 μ A out of the FB pin with 0.6V on the
D2
1N914
C2
0.1 μ F
V IN
C3*
33 μ F
20V
+
DEFAULT
(OPEN)
V IN
SHDN
BOOST
LT1507
V SW
FB
L1***
5 μ H
R1
5.36k
OUTPUT
5V
TANTALUM
= ON
GND
V C
C C
3.3nF
D1
1N5818
R2
4.99k
+
C1**
100 μ F
10V
TANTALUM
8
* AVX TPSD337M020R0200 OR SPRAGUE 593 EQUIVALENT.
RIPPLE CURRENT RATING ≥ 0.6A
** AVX TPSD108M010R0100 OR SPRAGUE 593 EQUIVALENT
*** COILTRONICS CTX5-1. SUBSTITUTION UNITS SHOULD BE RATED
AT ≥ 1.25A, USING LOW LOSS CORE MATERIAL. LOAD CURRENTS
ABOVE 0.85A MAY NEED A 10 μ H OR 20 μ H INDUCTOR
Figure 2. Typical Schematic for LT1507 Adjustable Application
LT1507 ? F01
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1507CS8PBF | 制造商:Linear Technology 功能描述:LT1507CS8PBF |
| LT1507G | 制造商:DIODES 制造商全称:Diodes Incorporated 功能描述:1.5A GLASS PASSIVATED RECTIFIER |
| LT1507I | 制造商:LINER 制造商全称:Linear Technology 功能描述:500kHz Monolithic Buck Mode Switching Regulator |
| LT1507IN8 | 功能描述:IC REG BUCK ADJ 1.5A 8DIP RoHS:否 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 |
| LT1507IN8#PBF | 功能描述:IC REG BUCK ADJ 1.5A 8DIP 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 |
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