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| 型号： | LT3437HFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.5A 16TSSOP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.25 V ~ 54 V |
| 输入电压： | 3.3 V ~ 60 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 200kHz |
| 电流 - 输出： | 500mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°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： | 带卷 (TR) |
| 供应商设备封装： | 16-TSSOP-EP |
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LT3437
APPLICATIO S I FOR ATIO
FEEDBACK PIN FUNCTIONS
Table 1
The feedback (FB) pin on the LT3437 is used to set output
voltage and provide several overload protection features.
The first part of this section deals with selecting resistors
to set output voltage, and the remaining part talks about
frequency foldback and soft-start features. Please read
both parts before committing to a final design.
Referring to Figure 2, the output voltage is determined by
a voltage divider from V OUT to ground which generates
1.25V at the FB pin. Since the output divider is a load on the
output, care must be taken when choosing the resistor
divider values. For light load applications the resistor
OUTPUT
VOLTAGE
(V)
2.5
3
3.3
5
6
8
10
12
R2
(k ? , 1%)
100
100
100
100
100
100
100
100
R1
NEAREST (1%)
(k ? )
100
140
165
300
383
536
698
866
OUTPUT
ERROR
(%)
0
0
0.38
0
0.63
– 0.63
– 0.25
0.63
values should be as large as possible to achieve peak
efficiency in Burst Mode operation. Extremely large values
for resistor R1 will cause an output voltage error due to the
50nA FB pin input current. The suggested value for the
output divider resistor (see Figure 2) from FB to ground
(R2) is 100k or less. A formula for R1 is shown below. A
table of standard 1% values is shown in Table 1 for
common output voltages.
More Than Just Voltage Feedback
The FB pin is used for more than just output voltage
sensing. It also reduces switching frequency and con-
trols the soft-start voltage ramp rate when output voltage
is below the regulated level (see the Frequency Foldback
and Soft-Start Current graphs in Typical Performance
Characteristics).
R 1 = R 2 ?
LT3437
V OUT – 1 . 25
1 . 25 + R 2 ? 50 nA
V OUT
Frequency foldback 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. As
a result, the average current through the diode and induc-
SOFT-START
SW 1
C SS
5
C1
tor is equal to the short-circuit current limit of the switch
(typically 500mA for the LT3437). Minimum switch on
time limitations would prevent the switcher from attaining
200kHz
OSCILLATOR
FOLDBACK
DETECT
R1
a sufficiently low duty cycle if switching frequency were
maintained at 200kHz, so frequency is reduced by about
10:1 when the FB pin voltage drops below 0.4V (see
–
ERROR
AMP
+
FB
1.25V
8
R2
Frequency Foldback graph). As the feedback voltage rises,
the switching frequency increases to 200kHz with 0.95V
on the FB pin. During frequency foldback, external syn-
chronization is disabled to prevent interference with fold-
V C
Figure 2. Feedback Network
7
3437 F02
back operation. Frequency foldback does not affect opera-
tion during normal load conditions.
In addition to lowering switching frequency, the soft-start
ramp rate is also affected by the feedback voltage. Large
capacitive loads or high input voltages can cause a
3437fc
11
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3437IDD | 制造商:Linear Technology 功能描述:SP-SWREG/Monolithic, 60V, 500mA, 200kHz Step-down Converter w/ BurstMode |
| LT3437IDD#PBF | 功能描述:IC REG BUCK ADJ 0.5A 10DFN 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 |
| LT3437IDD#PBF | 制造商:Linear Technology 功能描述:DC-DC CONVERTER BUCK 200KHZ 制造商:Linear Technology 功能描述:DC-DC CONVERTER, BUCK, 200KHZ, DFN-10 |
| LT3437IDD#TRPBF | 功能描述:IC REG BUCK ADJ 0.5A 10DFN 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 |
| LT3437IDDPBF | 制造商:Linear Technology 功能描述:500mA, Hi Volt Buck Sw Reg, LT3437IDD |
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