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| 型号： | LT3689IUD-5#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1.95 A SWITCHING REGULATOR, 2160 kHz SWITCHING FREQ-MAX, PQCC16 |
| 封装： | 3 X 3 MM, LEAD FREE, PLASTIC, MO-220WEED-2, QFN-16 |
| 文件页数： | 5/32页 |
| 文件大小： | 2188K |
| 代理商： | LT3689IUD-5#PBF |
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LT3689/LT3689-5
13
3689fd
The output voltage is programmed with a resistor divider
between the output and the FB pin. Choose 1% resistors
according to:
R1= R2
VOUT
0.8V
1
For reference designators, refer to the Block Diagram.
Setting the Switching Frequency
The LT3689 uses a constant-frequency PWM architecture
that can be programmed to switch from 350kHz to 2.2MHz
by using a resistor tied from the RT pin to ground. Table
1 shows the RT values for various switching frequencies.
Table 1. Switching Frequency vs RT
SWITCHING FREQUENCY (MHz)
RT (kΩ)
0.35
48.7
0.5
31.6
0.6
24.9
0.7
20.5
0.8
16.9
0.9
14.7
1
12.7
1.2
9.53
1.4
7.5
1.6
6.04
1.8
4.87
2
4.02
2.2
3.16
APPLICATIONS INFORMATION
Operating Frequency Trade-Offs
Selection of the operating frequency is a trade-off be-
tween efficiency, component size and maximum input
voltage. The advantage of high frequency operation is
that smaller inductor and capacitor values may be used.
The disadvantages are lower efficiency, and narrower
input voltage range at constant-frequency. The highest
constant-switching frequency (fSW(MAX)) for a given ap-
plication can be calculated as follows:
fSW(MAX) =
VOUT + VD
tON(MIN) VIN – VSW + VD
(
)
where VIN is the typical input voltage, VOUT is the output
voltage, VD is the catch diode drop (~0.5V) and VSW is
the internal switch drop (~0.5V at maximum load). If the
LT3689 is programmed to operate at a frequency higher
than fSW(MAX) for a given VIN input voltage, the LT3689
enters pulse-skipping mode, where it skips switching
cycles to maintain regulation. At frequencies higher than
fSW(MAX), the LT3689 no longer operates with constant-
frequency. The LT3689 enters pulse-skipping mode at
frequencies higher than fSW(MAX) because of the limita-
tion on the LT3689’s minimum on-time of 130ns. As the
switching frequency is increased above fSW(MAX), the part
isrequiredtoswitchforshorterperiodsoftimetomaintain
the same duty cycle. Delays associated with turning off
the power switch dictate the minimum on-time of the part.
When the required on-time decreases below the minimum
on-time of 130ns, the switch pulse width remains fixed at
130ns (instead of becoming narrower to accommodate
the duty cycle requirement). The inductor current ramps
up to a value exceeding the load current and the output
ripple increases. The part then remains off until the output
voltage dips below the programmed value before it begins
switching again.
相关PDF资料 |
PDF描述 |
|---|---|
| LT3689EMSE-5#TRPBF | 1.95 A SWITCHING REGULATOR, 2160 kHz SWITCHING FREQ-MAX, PDSO16 |
| LT3689EUD-5#TRPBF | 1.95 A SWITCHING REGULATOR, 2160 kHz SWITCHING FREQ-MAX, PQCC16 |
| LT3689EMSE-5#PBF | 1.95 A SWITCHING REGULATOR, 2160 kHz SWITCHING FREQ-MAX, PDSO16 |
| LT3689IUD-5#TRPBF | 1.95 A SWITCHING REGULATOR, 2160 kHz SWITCHING FREQ-MAX, PQCC16 |
| LT3689IMSE-5#TRPBF | 1.95 A SWITCHING REGULATOR, 2160 kHz SWITCHING FREQ-MAX, PDSO16 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3689IUD-5-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:700mA Step-Down Regulator with Power-On Reset and Watchdog Timer |
| LT3689IUD-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:700mA Step-Down Regulator with Power-On Reset and Watchdog Timer |
| LT3689IUD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:700mA Step-Down Regulator with Power-On Reset and Watchdog Timer |
| LT3690 | 制造商:LINER 制造商全称:Linear Technology 功能描述:36V, 4A, 1.5MHz Synchronous Step-Down Switching Regulator |
| LT3690EUFE#PBF | 功能描述:IC REG BUCK SYNC ADJ 4A 26QFN 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 |
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