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参数资料
| 型号： | LTC3404EMS8#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 0.6A 8MSOP |
| 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： | 0.8 V ~ 6 V |
| 输入电压： | 2.65 V ~ 6 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1.4MHz |
| 电流 - 输出： | 600mA |
| 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： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-MSOP |
LTC3404
OPERATIO
When the converter is in Burst Mode operation, the peak
current of the inductor is set to approximately 250mA,
even though the voltage at the I TH pin indicates a lower
value. The voltage at the I TH pin drops when the inductor’s
average current is greater than the load requirement. As
the I TH voltage drops below approximately 0.55V, the
BURST comparator trips, causing the internal sleep line to
go high and forces off both power MOSFETs. The I TH pin
is then disconnected from the output of the EA amplifier
and held a diode voltage (0.7V) above ground.
In sleep mode, both power MOSFETs are held off and a
majority of the internal circuitry is partially turned off,
reducing the quiescent current to 10 μ A. The load current
is now being supplied solely from the output capacitor.
When the output voltage drops, the I TH pin reconnects to
the output of the EA amplifier and the top MOSFET is again
turned on and this process repeats.
Short-Circuit Protection
When the output is shorted to ground, the frequency of the
oscillator is reduced to about 200kHz, 1/7 the nominal
frequency. This frequency foldback ensures that the
inductor current has ample time to decay, thereby prevent-
ing runaway. The oscillator’s frequency will progressively
increase to 1.4MHz (or the synchronized frequency) when
V FB rises above 0.3V.
Frequency Synchronization
A phase-locked loop (PLL) is available on the LTC3404 to
allow the internal oscillator to be synchronized to an
low audio noise and reduced RF interference while provid-
ing reasonable low current efficiency.
Frequency synchronization is inhibited when the feedback
voltage V FB is below 0.6V. This prevents the external clock
from interfering with the frequency foldback for short-
circuit protection.
Dropout Operation
When the input supply voltage decreases toward the
output voltage, the duty cycle increases toward the maxi-
mum on-time. Further reduction of the supply voltage
forces the main switch to remain on for more than one
cycle until it reaches 100% duty cycle. The output voltage
will then be determined by the input voltage minus the
voltage drop across the internal P-channel MOSFET and
the inductor.
Low Supply Operation
The LTC3404 is designed to operate down to an input
supply voltage of 2.65V although the maximum allowable
output current is reduced at this low voltage. Figure 1
shows the reduction in the maximum output current as a
function of input voltage for various output voltages.
Another important detail to remember is that at low input
supply voltages, the R DS(ON) of the P-channel switch
increases. Therefore, the user should calculate the power
dissipation when the LTC3404 is used at 100% duty cycle
with a low input voltage (see Thermal Considerations in
the Applications Information section).
external source connected to the SYNC/MODE pin. The
output of the phase detector at the PLL LPF pin operates
over a 0V to 2.4V range corresponding to 1MHz to 1.7MHz.
When locked, the PLL aligns the turn-on of the top MOS-
1200
1000
800
L = 4.7 μ H
V OUT = 3.3V
FET to the rising edge of the synchronizing signal.
600
When the LTC3404 is clocked by an external source, Burst
V OUT = 2.5V
Mode operation is disabled; the LTC3404 then operates in
PWM pulse skipping mode. In this mode, when the output
load is very low, current comparator I COMP may remain
400
200
V OUT = 1.5V
tripped for several cycles and force the main switch to stay
off for the same number of cycles. Increasing the output
0
2.5
3.5
4.5 5.5 6.5
SUPPLY VOLTAGE (V)
7.5
load slightly allows constant frequency PWM operation to
resume. This mode exhibits low output ripple as well as
3404 ? F01
Figure 1. Maximum Output Current vs Input Voltage
3404fb
8
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| LTC3404IMS8#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 0.6A 8MSOP 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 |
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