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参数资料
| 型号： | LTC1772ES6#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 9/12页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM SOT23-6 |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 650kHz |
| 占空比： | 100% |
| 电源电压： | 2.5 V ~ 9.8 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | SOT-23-6 细型，TSOT-23-6 |
| 包装： | 带卷 (TR) |
LTC1772
APPLICATIO N S I N FOR M ATIO N
Low Supply Operation
Although the LTC1772 can function down to approxi-
mately 2V, the maximum allowable output current is
reduced when V IN decreases below 3V. Figure 3 shows the
amount of change as the supply is reduced down to 2V.
Also shown in Figure 3 is the effect of V IN on V REF as V IN
goes below 2.3V.
105
Efficiency Considerations
The efficiency of a switching regulator is equal to the
output power divided by the input power times 100%. It is
often useful to analyze individual losses to determine what
is limiting the efficiency and which change would produce
the most improvement. Efficiency can be expressed as:
Efficiency = 100% – ( η 1 + η 2 + η 3 + ...)
where η 1, η 2, etc. are the individual losses as a percent-
100
95
90
85
80
V REF
V ITH
age of input power.
Although all dissipative elements in the circuit produce
losses, four main sources usually account for most of the
losses in LTC1772 circuits: 1) LTC1772 DC bias current,
2) MOSFET gate charge current, 3) I 2 R losses and 4)
voltage drop of the output diode.
1. The V IN current is the DC supply current, given in the
75
2.0
2.2
2.4 2.6 2.8
INPUT VOLTAGE (V)
3.0
1772 F03
electrical characteristics, that excludes MOSFET driver
and control currents. V IN current results in a small loss
which increases with V IN .
Figure 3. Line Regulation of V REF and V ITH
Setting Output Voltage
The LTC1772 develops a 0.8V reference voltage between
the feedback (Pin 3) terminal and ground (see Figure 4). By
selecting resistor R1, a constant current is caused to flow
through R1 and R2 to set the overall output voltage. The
regulated output voltage is determined by:
2. MOSFET gate charge current results from switching
the gate capacitance of the power MOSFET. Each time
a MOSFET gate is switched from low to high to low
again, a packet of charge dQ moves from V IN to ground.
The resulting dQ/dt is a current out of V IN which is
typically much larger than the DC supply current. In
continuous mode, I GATECHG = f(Qp).
3. I 2 R losses are predicted from the DC resistances of the
V OUT = 0 . 8 ? 1 +
?
?
?
R 2 ?
R 1 ?
MOSFET, inductor and current shunt. In continuous
mode the average output current flows through L but
is “chopped” between the P-channel MOSFET (in se-
For most applications, an 80k resistor is suggested for R1.
To prevent stray pickup, locate resistors R1 and R2 close
to LTC1772.
ries with R SENSE) and the output diode. The MOSFET
R DS(ON) plus R SENSE multiplied by duty cycle can be
summed with the resistances of L and R SENSE to obtain
I 2 R losses.
LTC1772
V FB
3
R2
V OUT
4. The output diode is a major source of power loss at
high currents and gets worse at high input voltages.
R1
1772 F04
Figure 4. Setting Output Voltage
The diode loss is calculated by multiplying the forward
voltage times the diode duty cycle multiplied by the
load current. For example, assuming a duty cycle of
50% with a Schottky diode forward voltage drop of
1772fb
9
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1772HS6#TRMPBF | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC1772HS6#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC1772IS6 | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.5V to 9.8V Input 6-Pin TSOT-23 |
| LTC1772IS6#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.5V to 9.8V Input 6-Pin TSOT-23 |
| LTC1772IS6#TR | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
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