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参数资料
| 型号： | LTC3407AEDD |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1.25 A DUAL SWITCHING CONTROLLER, 1800 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封装： | 3 X 3 MM, PLASTIC, MO-229WEED-2, DFN-10 |
| 文件页数： | 16/16页 |
| 文件大小： | 263K |
| 代理商： | LTC3407AEDD |
LTC3407A
9
3407af
trace inductance can lead to significant ringing. Other
capacitor types include the Panasonic Special Polymer
(SP) capacitors.
In most cases, 0.1
F to 1F of ceramic capacitors should
also be placed close to the LTC3407A in parallel with the
main capacitors for high frequency decoupling.
Ceramic Input and Output Capacitors
Higher value, lower cost ceramic capacitors are now
becoming available in smaller case sizes. These are tempt-
ing for switching regulator use because of their very low
ESR. Unfortunately, the ESR is so low that it can cause
loop stability problems. Solid tantalum capacitor ESR
generates a loop “zero” at 5kHz to 50kHz that is instrumen-
tal in giving acceptable loop phase margin. Ceramic ca-
pacitors remain capacitive to beyond 300kHz and usually
resonate with their ESL before ESR becomes effective.
Also, ceramic caps are prone to temperature effects which
requires the designer to check loop stability over the
operating temperature range. To minimize their large
temperature and voltage coefficients, only X5R or X7R
ceramic capacitors should be used. A good selection of
ceramic capacitors is available from Taiyo Yuden, TDK,
and Murata.
Great care must be taken when using only ceramic input
and output capacitors. When a ceramic capacitor is used
at the input and the power is being supplied through long
wires, such as from a wall adapter, a load step at the output
can induce ringing at the VIN pin. At best, this ringing can
couple to the output and be mistaken as loop instability.
APPLICATIO S I FOR ATIO
WU
U
Figure 1. LTC3407A General Schematic
VOUT2
RUN/SS2
VIN
VIN = 2.5V TO 5.5V
VOUT1
RUN/SS1
POR
SW1
VFB1
GND
VFB2
SW2
MODE/SYNC
LTC3407A
CIN
R7
POWER-ON
RESET
C1
C2
L1
L2
R4
R2
R1
R3
COUT2
C4
C3
COUT1
3407A F02
PULSESKIP*
BURST*
*MODE/SYNC = 0V: PULSE SKIP
MODE/SYNC = VIN: Burst Mode
R6
R5
Output Capacitor (COUT) Selection
The selection of COUT is driven by the required ESR to
minimize voltage ripple and load step transients. Typically,
once the ESR requirement is satisfied, the capacitance is
adequate for filtering. The output ripple (
VOUT) is deter-
mined by:
≈
+
V
I
ESR
fC
OUT
L
O
OUT
1
8
where fO = operating frequency, COUT = output capacitance
and
IL = ripple current in the inductor. The output ripple
is highest at maximum input voltage since
IL increases
with input voltage. With
IL = 0.3 ILIM the output ripple
will be less than 100mV at maximum VIN and fO = 1.5MHz
with:
ESRCOUT < 150m
Once the ESR requirements for COUT have been met, the
RMS current rating generally far exceeds the IRIPPLE(P-P)
requirement, except for an all ceramic solution.
In surface mount applications, multiple capacitors may
have to be paralleled to meet the capacitance, ESR or RMS
current handling requirement of the application. Alumi-
num electrolytic, special polymer, ceramic and dry tantulum
capacitors are all available in surface mount packages. The
OS-CON semiconductor dielectric capacitor available from
Sanyo has the lowest ESR(size) product of any aluminum
electrolytic at a somewhat higher price. Special polymer
capacitors, such as Sanyo POSCAP, offer very low ESR,
but have a lower capacitance density than other types.
Tantalum capacitors have the highest capacitance density.
However, they also have a larger ESR and it is critical that
they are surge tested for use in switching power supplies.
An excellent choice is the AVX TPS series of surface mount
tantalums, available in case heights ranging from 2mm to
4mm. Aluminum electrolytic capacitors have a signifi-
cantly larger ESR, and are often used in extremely cost-
sensitive applications provided that consideration is given
to ripple current ratings and long term reliability. Ceramic
capacitors have the lowest ESR and cost, but also have the
lowest capacitance density, a high voltage and tempera-
ture coefficient, and exhibit audible piezoelectric effects.
In addition, the high Q of ceramic capacitors along with
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| LTC3407AEDD#PBF | 功能描述:IC REG BUCK SYNC ADJ 1A DL 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LTC3407AEDD#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 1A DL 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC3407AEDD-2 | 制造商:Linear Technology 功能描述:Conv DC-DC Dual Step Down 2.5V to 5.5V 10-Pin DFN EP |
| LTC3407AEDD-2#PBF | 功能描述:IC REG BUCK SYNC ADJ 1A DL 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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