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| 型号： | LTC3560ES6 |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 2.1 A SWITCHING REGULATOR, 2700 kHz SWITCHING FREQ-MAX, PDSO6 |
| 封装： | 1 MM HEIGHT, PLASTIC, MO-193, TSOT-23 |
| 文件页数： | 3/16页 |
| 文件大小： | 323K |
| 代理商： | LTC3560ES6 |
11
LTC3560
3560f
APPLICATIO S I FOR ATIO
WU
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both power switches will be turned off and the SW node
will become high impedance.
To avoid the LTC3560 from exceeding the maximum
junction temperature, the user will need to do some
thermal analysis. The goal of the thermal analysis is to
determine whether the power dissipated exceeds the
maximum junction temperature of the part. The tempera-
ture rise is given by:
TR = (PD)(θJA)
where PD is the power dissipated by the regulator and θJA
is the thermal resistance from the junction of the die to the
ambient temperature.
The junction temperature, TJ, is given by:
TJ = TA + TR
where TA is the ambient temperature.
As an example, consider the LTC3560 in dropout at an
input voltage of 2.7V, a load current of 800mA and an
ambient temperature of 70
°C. From the typical perfor-
mance graph of switch resistance, the RDS(ON) of the
P-channel switch at 70
°C is approximately 0.31. There-
fore, power dissipated by the part is:
PD = ILOAD2 RDS(ON) = 198mW
For the SOT-23 package, the
θJA is 250°C/W. Thus, the
junction temperature of the regulator is:
TJ = 70°C + (0.198)(250) = 120°C
which is 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 (RDS(ON)).
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, VOUT immediately shifts by an amount
equal to (
ILOAD ESR), where ESR is the effective series
resistance of COUT. ILOAD also begins to charge or dis-
charge COUT, which generates a feedback error signal. The
regulator loop then acts to return VOUT to its steady-state
value. During this recovery time VOUTcan be monitored for
overshoot or ringing that would indicate a stability prob-
lem. 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
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 10
F capacitor charging to 3.3V would require a
250
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
LTC3560. These items are also illustrated graphically in
Figures 4 and 5. Check the following in your layout:
1. The power traces, consisting of the GND trace, the SW
trace and the VIN trace should be kept short, direct and
wide.
2. Does the VFB pin connect directly to the feedback
resistors? The resistive divider R1/R2 must be con-
nected between the (+) plate of COUT and ground.
3. Does the (+) plate of CIN connect to VIN as closely as
possible? This capacitor provides the AC current to the
internal power MOSFETs.
4. Keep the (–) plates of CIN and COUT as close as possible.
5. Keep the switching node, SW, away from the sensitive
VFB node.
Design Example
As a design example, assume the LTC3560 is used in a
single lithium-ion battery-powered cellular phone
application. The VIN will be operating from a maximum of
4.2V down to about 2.7V. The load current requirement
is a maximum of 0.8A but most of the time it will be in
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3560ES6#PBF | 制造商:Linear Technology 功能描述:2.1 A SWITCHING REGULATOR, 2700 kHz SWITCHING FREQ-MAX, PDSO6 |
| LTC3560ES6#TRMPBF | 功能描述:IC REG BUCK SYNC ADJ TSOT23-6 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 |
| LTC3560ES6#TRPBF | 功能描述:IC REG BUCK SYNC ADJ TSOT23-6 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:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LTC3560ES6LTCFY | 制造商:LINER 制造商全称:Linear Technology 功能描述:2.25MHz, 800mA Synchronous Step-Down Regulator in ThinSOT |
| LTC3560ES6PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:2.25MHz, 800mA Synchronous Step-Down Regulator in ThinSOT |
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