参数资料
| 型号： | MIC2169AYMM |
| 厂商： | Micrel Inc |
| 文件页数： | 8/15页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR DIVIDER PWM 10-MSOP |
| 标准包装： | 100 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 550kHz |
| 占空比： | 92% |
| 电源电压： | 3 V ~ 14.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 是 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1092 (CN2011-ZH PDF) |
| 其它名称： | 576-1709-5 MIC2169AYMM-ND |
D ? duty cycle ? O ?
t T ?
V OUT ? (V IN ? max ? ? V OUT )
MIC2169A
low-side switches. For applications where V IN < 5V, the internal
V DD regulator operates in dropout mode, and it is necessary
that the power MOSFETs used are sub-logic level and are in
full conduction mode for V GS of 2.5V. For applications when
V IN > 5V; logic-level MOSFETs, whose operation is specified
at V GS = 4.5V must be used.
It is important to note the on-resistance of a MOSFET
increases with increasing temperature. A 75°C rise in junc -
tion temperature will increase the channel resistance of the
MOSFET by 50% to 75% of the resistance specified at 25°C.
This change in resistance must be accounted for when cal -
culating MOSFET power dissipation and in calculating the
value of current-sense (CS) resistor. Total gate charge is the
charge required to turn the MOSFET on and off under speci -
fied operating conditions (V DS and V GS ). The gate charge
is supplied by the MIC2169A gate-drive circuit. At 500kHz
switching frequency and above, the gate charge can be a
significant source of power dissipation in the MIC2169A. At
low output load, this power dissipation is noticeable as a
reduction in efficiency. The average current required to drive
the high-side MOSFET is:
I G[high-side](avg) ? Q G ? f S
where:
I G[high-side](avg) = average high-side MOSFET gate
current.
Q G = total gate charge for the high-side MOSFET taken from
manufacturer ’s data sheet for V GS = 5V.
The low-side MOSFET is turned on and off at V DS = 0 because
the freewheeling diode is conducting during this time. The
switching loss for the low-side MOSFET is usually negligible.
Also, the gate-drive current for the low-side MOSFET is
more accurately calculated using CISS at V DS = 0 instead
of gate charge.
For the low-side MOSFET:
I G[low-side](avg) ? C ISS ? V GS ? f S
Since the current from the gate drive comes from the input volt -
age, the power dissipated in the MIC2169A due to gate drive is:
P GATEDRIVE ? V IN ? I G[high-side](avg) ? I G[low-side](avg) ?
A convenient figure of merit for switching MOSFETs is the on
resistance times the total gate charge R DS(ON) × Q G . Lower
numbers translate into higher efficiency. Low gate-charge
logic-level MOSFETs are a good choice for use with the
MIC2169A.
Parameters that are important to MOSFET switch selection
are:
? Voltage rating
? On-resistance
? Total gate charge
The voltage ratings for the top and bottom MOSFET are
essentially equal to the input voltage. A safety factor of 20%
should be added to the V DS (max) of the MOSFETs to account
for voltage spikes due to circuit parasitics.
The power dissipated in the switching transistor is the sum
Micrel
of the conduction losses during the on-time (P CONDUCTION )
and the switching losses that occur during the period of time
when the MOSFETs turn on and off (P AC ).
P SW ? P CONDUCTION ? P AC
where:
P CONDUCTION ? I SW(rms) 2 ? R SW
P AC ? P AC(off) ? P AC(on)
R SW = on-resistance of the MOSFET switch
? V ?
? V IN ?
Making the assumption the turn-on and turn-off transition times
are equal; the transition times can be approximated by:
C ISS ? V GS ? C OSS ? V IN
I G
where:
C ISS and C OSS are measured at V DS = 0
I G = gate-drive current (1A for the MIC2169A)
The total high-side MOSFET switching loss is:
P AC ? (V IN ? V D ) ? I PK ? t T ? f S
where:
t T = switching transition time (typically 20ns to 50ns)
V D = freewheeling diode drop, typically 0.5V
f S it the switching frequency, nominally 500kHz
The low-side MOSFET switching losses are negligible and
can be ignored for these calculations.
Inductor Selection
Values for inductance, peak, and RMS currents are required
to select the output inductor. The input and output voltages
and the inductance value determine the peak-to-peak induc -
tor ripple current. Generally, higher inductance values are
used with higher input voltages. Larger peak-to-peak ripple
currents will increase the power dissipation in the inductor
and MOSFETs. Larger output ripple currents will also require
more output capacitance to smooth out the larger ripple cur -
rent. Smaller peak-to-peak ripple currents require a larger
inductance value and therefore a larger and more expensive
inductor. A good compromise between size, loss and cost is
to set the inductor ripple current to be equal to 20% of the
maximum output current. The inductance value is calculated
by the equation below.
L ?
V IN ? max ? ? f S ? 0.2 ? I OUT ? max ?
where:
f S = switching frequency, 500kHz
0.2 = ratio of AC ripple current to DC output current
V IN (max) = maximum input voltage
The peak-to-peak inductor current (AC ripple current) is:
M9999-040609
8
April 2009
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PDF描述 |
|---|---|
| MIC2169BMM TR | IC REG CTRLR BUCK PWM VM 10-MSOP |
| MIC2169BYMME | IC REG CTRLR BUCK PWM VM 10-MSOP |
| MIC2171BU TR | IC REG MULTI CONFIG 2.5A TO263-5 |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2169A-YMM | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:500kHz PWM Synchronous Buck Control IC |
| MIC2169AYMM TR | 功能描述:DC/DC 开关控制器 500KHz Synchronous Buck Controller (Lead Free) RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MIC2169B | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:500kHz PWM Synchronous Buck Control IC |
| MIC2169B_10 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:500kHz PWM Synchronous Buck Control IC |
| MIC2169BMM | 功能描述:IC REG CTRLR BUCK PWM VM 10-MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
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