参数资料
| 型号： | MIC2821-4GJLYML TR |
| 厂商： | Micrel Inc |
| 文件页数： | 13/17页 |
| 文件大小： | 0K |
| 描述： | IC PWR MGMT DGTL TRPL LDO 16-MLF |
| 标准包装： | 1 |
| 应用： | 手持/移动设备 |
| 电源电压： | 2.7 V ~ 5.5 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-VFQFN 裸露焊盘，16-MLF? |
| 供应商设备封装： | 16-MLF?（4x4） |
| 包装： | 标准包装 |
| 产品目录页面： | 1086 (CN2011-ZH PDF) |
| 其它名称： | 576-3083-6 |
Efficiency _ Loss = ? 1 ? ? ? ? × 100
Micrel, Inc.
considerations and it reduces consumption of current for
battery powered applications. Reduced current draw
from a battery increases the devices operating time and
is critical in hand held devices.
There are two types of losses in switching converters;
DC losses and switching losses. DC losses are simply
the power dissipation of I 2 R. Power is dissipated in the
high side switch during the on cycle. Power loss is equal
to the high side MOSFET R DSON multiplied by the Switch
Current 2 . During the off cycle, the low side N-channel
MOSFET conducts, also dissipating power. Device
operating current also reduces efficiency. The product of
the quiescent (operating) current and the supply voltage
is another DC loss.
Over 100mA, efficiency loss is dominated by MOSFET
R DSON and inductor losses. Higher input supply voltages
will increase the Gate to Source threshold on the internal
MOSFETs, reducing the internal R DSON . This improves
efficiency by reducing DC losses in the device. All but
the inductor losses are inherent to the device. In which
case, inductor selection becomes increasingly critical in
efficiency calculations. As the inductors are reduced in
size, the DC resistance (DCR) can become quite
significant. The DCR losses can be calculated as
follows:
L _ Pd = Iout 2 × DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as follows;
? ? Vout × Iout ? ?
? ? Vout × Iout + L _ Pd ? ?
Efficiency loss due to DCR is minimal at light loads and
gains significance as the load is increased. Inductor
selection becomes a trade-off between efficiency and
size in this case.
PGND
Power ground (PGND) is the ground path for the high
current PWM mode. The current loop area for the power
ground should be as small as possible.
SGND
Signal ground (SGND) is the ground path for the biasing
and control circuitry. The current loop for the signal
ground should be as small as possible.
BYP (MIC2811 only)
For enhanced noise and PSRR performance on LDO1 &
LDO2, the internal reference of the MIC2811 can be
bypassed with a capacitor to ground. A quick-start
feature allows for quick turn-on of the output voltage.
The recommended nominal bypass capacitor is 0.1 μ F,
but it can be increased, which will also result in an
increase to the start-up time.
MIC2811/2821
MIC2811 Layout Recommendations
A poor layout of the MIC2811 may cause unwanted
voltage and current spikes. This can lead to noise on DC
voltages and EMI radiating to nearby devices. The
following are recommendations for the MIC2811/21
layout. The evaluation board layout is included as an
example.
1. Place the MIC2811/21 with the pad size designated
in the “Recommended Land Patterns” page of the Micrel
website.
2. When laying out the components, keep the MIC2811,
inductor, and filter capacitors physically close to keep
traces as short as possible. The traces between these
components carry relatively high switching currents and
can affect adjacent signals.
3. The input capacitor between DVIN and PGND should
be placed right next to the MIC2811/21. This will
eliminate trace inductance effects and reduce internal
noise for the MIC2811/21 control circuitry. The trace
from the DVIN filter capacitor to the MIC2811/21 device
should not be routed through any vias. This lessens the
chance of noise coupling by the effective antenna of the
via.
4. Monitoring the path of the switching currents will help
minimize the radiated noise. In the first half of the
switching cycle, current flows from the input filter
capacitor through the high side switch within the
MIC2811, then through the inductor to the output filter
capacitor and lastly through ground. In the second half of
the switching cycle, current is pulled up from ground
through the low side synchronous switch within the
MIC2807 by the inductor, to the output filter capacitor
and then back through ground, forming a second current
loop. Route these loops to ensure the current curls in the
same direction, preventing magnetic field reversal
between the switching cycles.
5. Connect the Bypass capacitor (MIC2811 Only) to the
BYP pin and the AGND pin. AGND and PGND should be
connected close to the chip at a single point in order to
minimize undesirable behavior due to ground bounce.
Input and output filter capacitors should be connected to
PGND.
6. Connections between power components and the
MIC2811 should have wide traces. It is good practice to
use a minimum of 30mils (0.762mm) per Ampere for 1oz
copper weight.
7. Route noise sensitive traces such as Feedback (FB),
BIAS, and BYP away from the switching traces and the
inductor. Noise coupled into these pins can affect the
accuracy of the output. The Feedback pin should be
connected at point of load for an accurate load
regulation.
April 2008
13
M9999-042208-A
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2821-4GMSYML | 制造商:Rochester Electronics LLC 功能描述: 制造商:RF Micro Devices Inc 功能描述: 制造商:Micrel Inc 功能描述: |
| MIC2821-4GMSYML TR | 功能描述:直流/直流开关转换器 Single DC/DC + 3 LDOs w/ Indep Enables RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MIC2821-4GMSYML-TR | 功能描述:Handheld/Mobile Devices PMIC 16-MLF? (4x4) 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:停产 应用:手持/移动设备 电流 - 电源:- 电压 - 电源:2.7 V ~ 5.5 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:16-VFQFN 裸露焊盘，16-MLF? 供应商器件封装:16-MLF?（4x4） 标准包装:1 |
| MIC2826-A0YMT TR | 功能描述:直流/直流开关调节器 Single 500mA Step-Down and Triple 150mA LDOs with I2C Voltage Control & Sequencing RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MIC2826-A0YMT-TR | 功能描述:Processor PMIC 14-TMLF? (2.5x2.5) 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:停产 应用:处理器 电流 - 电源:- 电压 - 电源:2.7 V ~ 5.5 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:14-UFQFN 裸露焊盘，14-TMLF? 供应商器件封装:14-TMLF?（2.5x2.5） 标准包装:1 |
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