參數(shù)資料
型號(hào)： LTC3835IGN-1
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： 3 A SWITCHING CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PDSO16
封裝： 0.150 INCH, PLASTIC, SSOP-16
文件頁(yè)數(shù)： 13/28頁(yè)
文件大?。?/td> 303K
代理商： LTC3835IGN-1
LTC3835-1
20
38351fc
APPLICATIONS INFORMATION
Checking Transient Response
The regulator loop response can be checked by looking at
the load current transient response. Switching regulators
take several cycles to respond to a step in DC (resistive) load
current. When a load step occurs, VOUT shifts by an amount
equal to
ΔILOAD (ESR), where ESR is the effective series re-
sistance of COUT. ΔILOAD also begins to charge or discharge
COUT generating the feedback error signal that forces the
regulator to adapt to the current change and return VOUT to
its steady-state value. During this recovery time VOUT can be
monitored for excessive overshoot or ringing, which would
indicateastabilityproblem.OPTI-LOOPcompensationallows
the transient response to be optimized over a wide range of
output capacitance and ESR values. The availability of the
ITH pin not only allows optimization of control loop behavior
but also provides a DC coupled and AC ltered closed-loop
response test point. The DC step, rise time and settling at
this test point truly reects the closed-loop response. As-
suming a predominantly second order system, phase margin
and/or damping factor can be estimated using the percent-
age of overshoot seen at this pin. The bandwidth can also
be estimated by examining the rise time at the pin. The ITH
external components shown in Figure 10 circuit will provide
an adequate starting point for most applications.
The ITH series RC-CC lter sets the dominant pole-zero
loop compensation. The values can be modied slightly
(from 0.5 to 2 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 capacitors need to be selected
because the various types and values determine the loop
gain and phase. An output current pulse of 20% to 80%
of full-load current having a rise time of 1μs to 10μs will
produce output voltage and ITH pin waveforms that will
give a sense of the overall loop stability without break-
ing the feedback loop. Placing a power MOSFET directly
across the output capacitor and driving the gate with an
appropriate signal generator is a practical way to produce
a realistic load step condition. The initial output voltage
step resulting from the step change in output current may
not be within the bandwidth of the feedback loop, so this
signal cannot be used to determine phase margin. This
is why it is better to look at the ITH pin signal which is in
the feedback loop and is the ltered and compensated
control loop response. The gain of the loop will be in-
creased by increasing RC and the bandwidth of the loop
will be increased by decreasing CC. If RC is increased by
the same factor that CC is decreased, the zero frequency
will be kept the same, thereby keeping the phase shift the
same in the most critical frequency range of the feedback
loop. The output voltage settling behavior is related to the
stability of the closed-loop system and will demonstrate
the actual overall supply performance.
A second, more severe transient is caused by switching in
loads with large (>1μF) supply bypass capacitors. The dis-
charged bypass capacitors are effectively put in parallel with
COUT, causing a rapid drop in VOUT. No regulator can alter
its delivery of current quickly enough to prevent this sudden
step change in output voltage if the load switch resistance
is low and it is driven quickly. If the ratio of CLOAD to COUT is
greater than 1:50, the switch rise time should be controlled
so that the load rise time is limited to approximately 25
CLOAD. Thus a 10μF capacitor would require a 250μs rise
time, limiting the charging current to about 200mA.
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LTC3835IGN-1#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC3835IUFD#PBF 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁(yè)面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR
LTC3835IUFD#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
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