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| 型号： | MIC23155-GYMT TR |
| 厂商： | Micrel Inc |
| 文件页数： | 13/19页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC 1.8V 2A 10TMLF |
| 标准包装： | 1 |
| 系列： | HyperLight Load® |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 1.8V |
| 输入电压： | 2.7 V ~ 5.5 V |
| PWM 型： | 混合物 |
| 频率 - 开关： | 3MHz |
| 电流 - 输出： | 2A |
| 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-UFDFN 裸露焊盘，10-TMLF? |
| 包装： | 标准包装 |
| 供应商设备封装： | 10-TMLF?（2.5x2.5） |
| 其它名称： | 576-3970-6 |
Micrel Inc.
Once in CCM mode, the T OFF time will not vary.
Therefore, it is important to note that if L is large enough,
the HLL transition level will not be triggered.
That inductor is illustrated in Figure 3:
MIC23155
Figure 4 illustrates an efficiency curve. From no load to
100mA, efficiency losses are dominated by quiescent
current losses, gate drive and transition losses. By using
the HyperLight Load mode, the MIC23155 is able to
maintain high efficiency at low output currents.
L MAX =
V OUT ? 135ns
2 ? 50mA
Eq. 3
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, thereby reducing the internal R DSON . This
improves efficiency by reducing DC losses in the device.
Duty Cycle
The typical maximum duty cycle of the MIC23155 is
80%.
Efficiency Considerations
Efficiency is defined as the amount of useful output
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 in
:
P DCR = I OUT x DCR
power, divided by the amount of power supplied (see
Figure 4):
2
Eq. 5
Efficiency % = ? ? OUT
?? × 100
? V × I OUT
? V IN × I IN
?
?
Eq. 4
From that, the loss in efficiency due to inductor
resistance can be calculated as in Equation 6:
the power dissipation of I R. Power is dissipated in the
V OUT × I OUT
Efficiency Loss = ? 1 ? ??
? ?
? ? × 100
There are two types of losses in switching converters;
DC losses and switching losses. DC losses are simply
2
high side switch during the on cycle. Power loss is equal
? ?
?
? ? V OUT × I OUT + P DCR
?
? ? ?
Eq. 6
to the high side MOSFET R DSON multiplied by the switch
current squared. 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 represents another DC loss. The current
required driving the gates on and off at a constant 3MHz
frequency and the switching transitions make up the
switching losses.
Efficiency (V OUT = 1.8V)
100
90
80
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.
HyperLight Load Mode
The MIC23155 uses a minimum on and off time
proprietary control loop (patented by Micrel). When the
output voltage falls below the regulation threshold, the
error comparator begins a switching cycle that turns the
PMOS on and keeps it on for the duration of the
minimum-on-time. This increases the output voltage. If
the output voltage is over the regulation threshold, then
the error comparator turns the PMOS off for a minimum-
off-time until the output drops below the threshold. The
70
60
50
V IN =2.7V
V IN = 4.2V
V IN = 3.6V
V IN = 5V
NMOS acts as an ideal rectifier that conducts when the
PMOS is off. Using a NMOS switch instead of a diode
allows for lower voltage drop across the switching device
40
30
20
10
0
1
C OUT = 4.7μF
10 100 1000
OUTPUT CURRENT (mA)
10000
when it is on. The asynchronous switching combination
between the PMOS and the NMOS allows the control
loop to work in discontinuous mode for light load
operations. In discontinuous mode, the MIC23155 works
in HyperLight Load to regulate the output. As the output
current increases, the off time decreases, thus provides
more energy to the output. This switching scheme
improves the efficiency of MIC23155 during light load
Figure 4. Efficiency under Load
currents by only switching when it is needed.
November 2012
13
M9999-110812-A
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| MIC23155YMT TR | 功能描述:直流/直流开关调节器 3MHz PWM 2A Buck Switcher with HyperLight Load and Power Good in a 2.5mm x 2.5mm Thin MLF 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 |
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| MIC23156-0YCS-EV | 功能描述:MIC23156 HyperLight Load? DC/DC, Step Down 1, Non-Isolated Outputs Evaluation Board 制造商:microchip technology 系列:HyperLight Load? 零件状态:有效 主要用途:DC/DC，步降 输出和类型:1，非隔离 功率 - 输出:- 电压 - 输出:0.8V 或 1V 电流 - 输出:1.5A 电压 - 输入:2.7 V ~ 5.5 V 稳压器拓扑:降压 频率 - 开关:3MHz 板类型:完全填充 所含物品:板 使用的 IC/零件:MIC23156 标准包装:1 |
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