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參數(shù)資料
| 型號(hào)： | LTC3809EMS-1#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 600 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | PLASTIC, MSOP-10 |
| 文件頁數(shù)： | 13/24頁 |
| 文件大?。?/td> | 318K |
| 代理商： | LTC3809EMS-1#PBF |
LTC3809-1
38091f
20
current pulse of 20% to 100% of full load current having
a rise time of 1
s to 10s will produce output voltage and
ITH pin waveforms that will give a sense of the overall loop
stability. The gain of the loop will be increased by increas-
ing RC and the bandwidth of the loop will be increased by
decreasing CC. 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 com-
ponents, including a review of control loop theory, refer to
Application Note 76.
A second, more severe transient is caused by switching in
loads with large (>1
F) supply bypass capacitors. The
discharged bypass capacitors are effectively put in parallel
with COUT, causing a rapid drop in VOUT. 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)
(CLOAD). Thus a 10F capacitor would be require a 250s
rise time, limiting the charging current to about 200mA.
Design Example
As a design example, assume VIN 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. Efficiency 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 floating, so the maximum current sense
threshold
VSENSE(MAX) is approximately 125mV.
Maximum Duty Cycle
V
OUT
IN MIN
=
()
.%
= 65 5
From Figure 1, SF = 82%.
RSF
V
I
DS ON MAX
SENSE MAX
OUT MAX
T
()
.
.
=
=
5
6
09
0032
ρ
A 0.032
P-channel MOSFET in Si7540DP is close to
this value.
The N-channel MOSFET in Si7540DP has 0.017
RDS(ON).
The short circuit current is:
I
mV
A
SC =
=
90
0 017
53
.
So the inductor current rating should be higher than 5.3A.
The LTC3809-1 operates at a frequency of 550kHz. For
continuous Burst Mode operation with 600mA IRIPPLE, the
required minimum inductor value is:
L
V
kHz
mA
V
H
MIN =
=
18
550
600
1
18
275
188
.
.
A 6A 2.2
H inductor works well for this application.
CIN will require an RMS current rating of at least 1A at
temperature. A COUT with 0.1 ESR will cause approxi-
mately 60mV output ripple.
PC Board Layout Checklist
When laying out the printed circuit board, use the
following checklist to ensure proper operation of the
LTC3809-1.
The power loop (input capacitor, MOSFET, inductor,
output capacitor) should be as small as possible and
isolated as much as possible from LTC3809-1.
Put the feedback resistors close to the VFB pins. The ITH
compensation components should also be very close to
the LTC3809-1.
The current sense traces should be Kelvin connections
right at the P-channel MOSFET source and drain.
Keeping the switch node (SW) and the gate driver nodes
(TG, BG) away from the small-signal components, espe-
cially the feedback resistors, and ITH compensation
components.
APPLICATIO S I FOR ATIO
WU
UU
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| LTC3809EMSE | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:否 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:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3809EMSE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3809EMSE#TR | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:否 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:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3809EMSE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3809EMSE-1 | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:否 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:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
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