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參數(shù)資料
| 型號： | LTC3405AES6 |
| 英文描述： | Analog IC |
| 中文描述： | 模擬IC |
| 文件頁數(shù)： | 11/16頁 |
| 文件大小： | 239K |
| 代理商： | LTC3405AES6 |
11
LTC3405A
3405af
equal to (
I
LOAD
ESR), where ESR is the effective series
resistance of C
OUT
.
I
LOAD
also begins to charge or
discharge C
OUT
, which generates a feedback error signal.
The regulator loop then acts to return V
OUT
to its steady-
state value. During this recovery time V
OUT
can be moni-
tored for overshoot or ringing that would indicate a stability
problem. For a detailed explanation of switching control
loop theory, see Application Note 76.
A second, more severe transient is caused by switching in
loads with large (>1
μ
F) supply bypass capacitors. The
discharged bypass capacitors are effectively put in parallel
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
).
Thus, a 10
μ
F capacitor charging to 3.3V would require a
250
μ
s rise time, limiting the charging current to about
130mA.
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC3405A. These items are also illustrated graphically in
Figures 5 and 6. Check the following in your layout:
APPLICATIOU
The junction temperature, T
J
, is given by:
T
J
= T
A
+ T
R
where T
A
is the ambient temperature.
As an example, consider the LTC3405A in dropout at an
input voltage of 2.7V, a load current of 300mA and an
ambient temperature of 70
°
C. From the typical perfor-
mance graph of switch resistance, the R
DS(ON)
of the
P-channel switch at 70
°
C is approximately 0.94
. There-
fore, power dissipated by the part is:
P
D
= I
LOAD2
R
DS(ON)
= 84.6mW
For the SOT-23 package, the
θ
JA
is 250
°
C/W. Thus, the
junction temperature of the regulator is:
T
J
= 70
°
C + (0.0846)(250) = 91.15
°
C
which is well below the maximum junction temperature of
125
°
C.
Note that at higher supply voltages, the junction tempera-
ture is lower due to reduced switch resistance (R
DS(ON)
).
W
U
U
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
Figure 5. LTC3405A Layout Diagram
RUN
LTC3405A
GND
SW
6
L1
R2
R1
C
FWD
BOLD LINES INDICATE HIGH CURRENT PATHS
V
IN
V
OUT
3405A F05
4
5
1
3
+
–
2
MODE
V
FB
V
IN
C
IN
C
OUT
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3405AES6#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 1.5 MHz 6-SOT-23 制造商:Linear Technology 功能描述:BUCK 0.3A 1.8V 1.5MHZ 6TSOT23 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 1.5 MHz, 6-SOT-23 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 1.5 MHz, 6-SOT-23; Primary Input Voltage:5.5V; No. of Outputs:1; Output Voltage:800mV; Output Current:300mA; No. of Pins:6; Operating Temperature Min:-40C; Operating Temperature Max:85C; MSL:MSL 1 - Unlimited ;RoHS Compliant: Yes |
| LTC3405AES6#TR | 功能描述:IC REG BUCK SYNC ADJ .3A SOT23-6 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC3405AES6#TRM | 功能描述:IC REG BUCK SYNC ADJ .3A SOT23-6 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC3405AES6#TRMPBF | 功能描述:IC REG BUCK SYNC ADJ .3A SOT23-6 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 產(chǎn)品培訓(xùn)模塊:High Efficiency Current Mode Switching Regulators CMOS LDO Regulators 特色產(chǎn)品:BD91x Series Step-Down Regulators 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:兩者兼有 輸出數(shù):2 輸出電壓:3.3V，0.8 V ~ 2.5 V 輸入電壓:4.5 V ~ 5.5 V PWM 型:電流模式 頻率 - 開關(guān):1MHz 電流 - 輸出:1.5A 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:20-VFQFN 裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:VQFN020V4040 產(chǎn)品目錄頁面:1373 (CN2011-ZH PDF) 其它名稱:BD9152MUV-E2TR |
| LTC3405AES6#TRPBF | 功能描述:IC REG BUCK SYNC ADJ .3A SOT23-6 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
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