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| 型号： | LT3958EUHE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/28页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG ADJ 36VQFN |
| 特色产品： | LT?3957/LT?3958 Converters |
| 标准包装： | 61 |
| 类型： | 升压（升压），反相，回扫，Sepic |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.6 V ~ 80 V |
| 输入电压： | 5 V ~ 80 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 100kHz ~ 1MHz |
| 电流 - 输出： | 3.3A |
| 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： | 36-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 36-QFN-EP（6x5） |
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LT3958
APPLICATIONS INFORMATION
Operating Frequency and Synchronization
The choice of operating frequency may be determined by
on-chip power dissipation (a low switching frequency may
be required to ensure IC junction temperature does not
exceed 125°C), otherwise it is a trade-off between ef?ciency
and component size. Low frequency operation improves
ef?ciency by reducing gate drive current and MOSFET
and diode switching losses. However, lower frequency
operation requires a physically larger inductor. Switching
frequency also has implications for loop compensation.
The LT3958 uses a constant-frequency architecture that
can be programmed over a 100kHz to 1000kHz range
with a single external resistor from the RT pin to ground,
as shown in Figure 1. The RT pin must have an external
resistor to SGND for proper operation of the LT3958.
A table for selecting the value of R T for a given operating
frequency is shown in Table 1.
Table 1. Timing Resistor (R T ) Value
Duty Cycle Consideration
Switching duty cycle is a key variable de?ning converter
operation. As such, its limits must be considered. Minimum
on-time is the smallest time duration that the LT3958 is
capable of turning on the power MOSFET. This time is
generally about 250ns (typical) (see Minimum On-Time
in the Electrical Characteristics table). In each switching
cycle, the LT3958 keeps the power switch off for at least
200ns (typical) (see Minimum Off-Time in the Electrical
Characteristics table).
The minimum on-time, minimum off-time and the switching
frequency de?ne the minimum and maximum switching
duty cycles a converter is able to generate:
Minimum duty cycle = minimum on-time ? frequency
Maximum duty cycle = 1 – (minimum off-time ? frequency)
Programming the Output Voltage
V OUT,POSITIVE = 1.6V ? ? 1 +
? R2 ?
R1 ?
?
V OUT,NEGATIVE = –0.8V ? ? 1 +
? R2 ?
R1 ?
?
SWITCHING FREQUENCY (kHz)
100
200
300
400
500
600
700
800
900
1000
R T (kΩ)
140
63.4
41.2
30.9
24.3
19.6
16.5
14
12.1
10.5
The output voltage V OUT is set by a resistor divider, as
shown in Figure 1. The positive and negative V OUT are set
by the following equations:
?
?
The resistors R1 and R2 are typically chosen so that
the error caused by the current ?owing into the FBX pin
during normal operation is less than 1% (this translates
to a maximum value of R1 at about 158k).
The operating frequency of the LT3958 can be synchro-
nized to an external clock source. By providing a digital
clock signal into the SYNC pin, the LT3958 will operate
at the SYNC clock frequency. The LT3958 detects the ris-
ing edge of each Sync clock cycle. If this feature is used,
an R T resistor should be chosen to program a switching
frequency 20% slower than SYNC pulse frequency. Tie
the SYNC pin to SGND if this feature is not used. It is
recommended that the Sync input clock has a minimum
pulse width of 200ns.
3958f
11
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3958EUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
| LT3958IUHE#PBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN 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 |
| LT3958IUHE#TRPBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN 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 |
| LT3958IUHEPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
| LT3958IUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
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