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| 型号： | LTC3835IFE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 18/30页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 20TSSOP |
| 标准包装： | 74 |
| PWM 型： | 电流模式，混合 |
| 输出数： | 1 |
| 频率 - 最大： | 580kHz |
| 占空比： | 99.4% |
| 电源电压： | 4 V ~ 36 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： | 20-TSSOP（0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
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LTC3835
APPLICATIONS INFORMATION
V IN
BAT85
BAT85
VN2222LL
V OUT
EXTV CC
SW
4. EXTV CC ConnectedtoanOutput-DerivedBoostNetwork.
For 3.3V and other low voltage regulators, efficiency
gains can still be realized by connecting EXTV CC to an
output-derived voltage that has been boosted to greater
than 4.7V. This can be done with the capacitive charge
pump shown in Figure 6.
1μF
+
C IN
0.22μF
V IN
LTC3835
BAT85
TG1
R SENSE
N-CH
L1
Fault Conditions: Current Limit and Current Foldback
The LTC3835 includes current foldback to help limit load
current when the output is shorted to ground. If the output
falls below 70% of its nominal output level, then the
maximum sense voltage is progressively lowered from
100mV to 30mV. Under short-circuit conditions with very
low duty cycles, the LTC3835 will begin cycle skipping in
order to limit the short-circuit current. In this situation the
bottom MOSFET will be dissipating most of the power but
less than in normal operation. The short-circuit ripple cur-
rent is determined by the minimum on-time t ON(MIN) of the
LTC3835 (≈180ns), the input voltage and inductor value:
?I L(SC) = t ON(MIN) (V IN /L)
The resulting short-circuit current is:
– ? I L(SC)
BG1
N-CH
+
C OUT
I SC =
10mV
R SENSE
1
2
PGND
3835 F06
Fault Conditions: Overvoltage Protection (Crowbar)
Figure 6. Capacitive Charge Pump for EXTV CC
Topside MOSFET Driver Supply (C B , D B )
External bootstrap capacitors C B connected to the BOOST
pins supply the gate drive voltages for the topside MOSFET.
Capacitor C B in the Functional Diagram is charged
though external diode D B from INTV CC when the SW pin
is low. When the topside MOSFET is to be turned on,
the driver places the C B voltage across the gate-source
of the desired MOSFET. This enhances the MOSFET and
turns on the topside switch. The switch node voltage, SW,
rises to V IN and the BOOST pin follows. With the topside
MOSFET on, the boost voltage is above the input supply:
V BOOST = V IN + V INTVCC . The value of the boost capacitor
C B needs to be 100 times that of the total input capacitance
of the topside MOSFET. The reverse breakdown of the
external Schottky diode must be greater than V IN(MAX) .
When adjusting the gate drive level, the final arbiter is the
total input current for the regulator. If a change is made
and the input current decreases, then the efficiency has
improved. If there is no change in input current, then there
is no change in efficiency.
The overvoltage crowbar is designed to blow a system
input fuse when the output voltage of the regulator rises
much higher than nominal levels. The crowbar causes huge
currents to flow, that blow the fuse to protect against a
shorted top MOSFET if the short occurs while the controller
is operating.
A comparator monitors the output for overvoltage
conditions. The comparator (OV) detects overvoltage faults
greater than 10% above the nominal output voltage. When
this condition is sensed, the top MOSFET is turned off and
the bottom MOSFET is turned on until the overvoltage
condition is cleared. The bottom MOSFET remains on
continuously for as long as the overvoltage condition
persists; if V OUT returns to a safe level, normal operation
automatically resumes. A shorted top MOSFET will result in
a high current condition which will open the system fuse.
The switching regulator will regulate properly with a leaky
top MOSFET by altering the duty cycle to accommodate
the leakage.
3835fd
18
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| LTC3835IUFD#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 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:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
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