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| 型号： | LTC3822EMSE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 10-MSOP |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 850kHz |
| 占空比： | 99% |
| 电源电压： | 2.75 V ~ 4.5 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： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
LTC3822
APPLICATIONS INFORMATION
105
3) I 2 R losses are calculated from the DC resistances of the
100
95
90
85
80
75
V REF
MAXIMUM
SENSE VOLTAGE
2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0
MOSFETs, inductor and/or sense resistor. In continuous
mode, the average output current ?ows through L but
is “chopped” between the top MOSFET and the bottom
MOSFET. Each MOSFET’s R DS(ON) can be multiplied by its
respective duty cycle and summed together with the DCR
of the inductor to obtain I 2 R losses.
4) Transition losses apply to the external MOSFET and
increase with higher operating frequencies and input
voltages. Transition losses can be estimated from:
INPUT VOLTAGE (V)
3822 F04
Transition Loss = 2 ? V IN2 ? I O(MAX) ? C RSS ? f
Figure 4. Line Regulation of V REF and Maximum Sense Voltage
Ef?ciency Considerations
The ef?ciency of a switching regulator is equal to the
output power divided by the input power. It is often useful
to analyze individual losses to determine what is limiting
ef?ciency and which change would produce the most
improvement. Ef?ciency can be expressed as:
Ef?ciency = 100% – (L1 + L2 + L3 + …)
where L1, L2, etc. are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, four main sources usually account for most of
the losses in LTC3822 circuits: 1) LTC3822 DC bias cur-
rent, 2) MOSFET gate charge current, 3) I 2 R losses and
4) transition losses.
1) The V IN (pin) current is the DC supply current, given
in the Electrical Characteristics, which excludes MOSFET
driver currents. V IN current results in a small loss that
increases with V IN .
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 BOOST to ground. The
resulting dQ/dt is a current out of BOOST, which is typically
much larger than the V IN supply current. In continuous
mode, I GATECHG = f ? Q P .
Other losses, including C IN and C OUT ESR dissipative losses
and inductor core losses, generally account for less than
2% total additional loss.
Checking Transient Response
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, V OUT immediately shifts by an amount
equal to ( Δ I LOAD ) ? (ESR), where ESR is the effective se-
ries resistance of C OUT . Δ I LOAD also begins to charge or
discharge C OUT generating a feedback error signal used
by the regulator to return V OUT to its steady-state value.
During this recovery time, V OUT can be monitored for
overshoot or ringing that would indicate a stability problem.
OPTI-LOOP compensation allows the transient response
to be optimized over a wide range of output capacitance
and ESR values.
The I TH series R C -C C ?lter (see the Functional Diagram)
sets the dominant pole-zero loop compensation.
The I TH external components showed in the ?gure on the
?rst page of this data sheet will provide adequate compen-
sation for most applications. The values can be modi?ed
slightly (from 0.2 to 5 times their suggested values) to
optimize transient response once the ?nal PC layout is done
and the particular output capacitor type and value have
been determined. The output capacitor needs to be decided
upon because the various types and values determine the
loop feedback factor gain and phase. An output current
pulse of 20% to 100% of full load current having a rise
time of 1μs to 10μs will produce output voltage and I TH
3822fa
14
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| LTC3823EGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP 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) |
| LTC3823EGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP 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) |
| LTC3823EUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN 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:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 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:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
| LTC3823EUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN 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) |
| LTC3823IGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP 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:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 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:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
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