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| 型号： | LTC3809EDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 20/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 10-DFN |
| 标准包装： | 121 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 825kHz |
| 占空比： | 100% |
| 电源电压： | 2.75 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： | 10-WFDFN 裸露焊盘 |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
LTC3809
APPLICATIONS INFORMATION
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 Functional Diagram) sets
Design Example
As a design example, assume V IN will be operating from a
maximum of 4.2V down to a minimum of 2.75V (powered
by a single lithium-ion battery). Load current requirement
is a maximum of 2A, but most of the time it will be in a
standby mode requiring only 2mA. Ef ?ciency at both low
and high load currents is important. Burst Mode operation
at light loads is desired. Output voltage is 1.8V. The IPRG
pin will be left ?oating, so the maximum current sense
threshold Δ V SENSE(MAX) is approximately 125mV.
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-
MaximumDuty Cycle =
V OUT
V IN ( MIN )
= 65 . 5 %
sation for most applications. The values can be modi?ed
From Figure 1, SF = 82%.
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
R DS ( ON ) MAX =
5
6
? 0 . 9 ? SF ?
Δ V SENSE(MAX )
I OUT ( MAX ) ? ρ T
= 0 . 032 Ω
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
A 0.032Ω P-channel MOSFET in Si7540DP is close to
this value.
The N-channel MOSFET in Si7540DP has 0.017Ω R DS(ON) .
The short circuit current is:
pin waveforms that will give a sense of the overall loop
stability. The gain of the loop will be increased by increas-
ing R C and the bandwidth of the loop will be increased
I SC =
90 mV
0 . 017 Ω
= 5 . 3 A
by decreasing C C . The output voltage settling behavior is
related to the stability of the closed-loop system and will
demonstrate the actual overall supply performance. For
a detailed explanation of optimizing the compensation
components, including a review of control loop theory,
refer to Application Note 76.
So the inductor current rating should be higher than
5.3A.
The PLLLPF pin will be left ?oating, so the LTC3809 will
operate at its default frequency of 550kHz. For continuous
Burst Mode operation with 600mA I RIPPLE , the required
minimum inductor value is:
? ? 1 ?
? = 1 . 88 μ H
A second, more severe transient is caused by switching
in loads with large (>1μF) supply bypass capacitors. The
discharged bypass capacitors are effectively put in parallel
L MIN =
1 . 8 V ?
550 kHz ? 600 mA ?
1 . 8 V ?
2 . 75 V ?
with C OUT , causing a rapid drop in V OUT . No regulator can
deliver enough current to prevent this problem if the load
switch resistance is low and it is driven quickly. The only
solution is to limit the rise time of the switch drive so that
the load rise time is limited to approximately (25) ? (C LOAD ).
A 6A 2.2μH inductor works well for this application.
C IN will require an RMS current rating of at least 1A at
temperature. A C OUT with 0.1Ω ESR will cause approxi-
mately 60mV output ripple.
Thus a 10μF capacitor would be require a 250μs rise time,
limiting the charging current to about 200mA.
3809fc
20
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相关代理商/技术参数 |
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| LTC3809EMSE | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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) |
| LTC3809EMSE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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) |
| LTC3809EMSE#TR | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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) |
| LTC3809EMSE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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) |
| LTC3809EMSE-1 | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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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