- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄384734 > MIC2185 (Micrel Semiconductor,Inc.) Low Voltage Synchronous Boost PWM Control IC PDF資料下載
參數(shù)資料
| 型號： | MIC2185 |
| 廠商： | Micrel Semiconductor,Inc. |
| 英文描述： | Low Voltage Synchronous Boost PWM Control IC |
| 中文描述： | 低電壓同步升壓PWM控制IC |
| 文件頁數(shù)： | 9/15頁 |
| 文件大?。?/td> | 141K |
| 代理商： | MIC2185 |
May 2002
9
MIC2185
MIC2185
Micrel
zero output current. This reduces parasitic ringing that
occurs during the discontinuous mode of operation found in
lightly loaded, non-synchronous boost converters. Pulling
the SKIP pin (pin 2) low will force the controller to operate in
PWM mode for all load conditions. Pulling the SKIP pin high
will force the controller to operate in SKIP mode.
Skip Mode Operation
This control method is used to improve efficiency at low
output loads. A block diagram of the MIC2185 skip mode is
shown in Figure 2. The power drawn by the MIC2185 control
IC is (I
VINA
·
V
VINA
) + (I
VINP
·
V
VINP
). The power dissipated by
the IC can be a significant portion of the total output power
during periods of low output current, which lowers the effi-
ciency of the power supply. In skip mode the MIC2185 lowers
the IC supply current by disabling the high side drive and
running at lower than the PWM switching frequency. It also
turns off portions of the control and drive circuitry when the IC
is not switching. The disadvantage of this method is greater
output ripple and variable switching frequency. The Soft Start
and Sync pins have no effect when operating in skip mode.
In skip mode, switching starts when the feedback voltage
drops below the lower threshold level of the hysteresis
comparator. The OutN pin goes high, turning on the N-channel
MOSFET, Q1. Current ramps up in the inductor until either
the SKIP mode current limit comparator or the hysteretic
voltage comparator turns off Q1
’
s gate drive. If the feedback
voltage exceeds the upper hysteretic threshold, Q1
’
s gate
drive is terminated. Or, if the voltage at the CSH pin exceeds
the skip mode current limit threshold, it terminates the gate
drive for that switching cycle. The gate drive remains off for
a constant period at the end of each switching cycle. This off
time period is typically 1us when the F/2 pin is low and 2us
when the F/2 pin is high. Figure 3 shows some typical
switching waveforms in SKIP mode.
SKIP Mode Waveform
TIME (50
μ
s/div)
Switch Node Voltage
(Low Side FET Drain)
5V/div
Low Side FET
Gate Drive
5V/div
V
OUT
Ripple Voltage
200mV/div
Inductor Current
5A/div
V
IN
= 3.3V
V
OUT
= 9VI
OUT
= 0.55A
Figure 3. SKIP mode waveforms
The skip mode current threshold limits the peak inductor
current per cycle. Depending on the input, output and circuit
parameters, many switching cycles can occur before the
feedback voltage exceeds the upper hysteretic threshold.
Once the voltage on the feedback pin exceeds the upper
hysteretic threshold the gate drive is disabled. The output
load discharges the output capacitance causing Vout to
decrease until the feedback voltage drops below the lower
threshold voltage limit. The switching converter then turns the
gate drive back on. While the gate drive is disabled, the
MIC2185 draws less IC supply current then while it is switch-
ing, thereby improving efficiency at low output loads.
Figure 4 shows the improvement in efficiency that SKIP mode
makes when at lower output currents.
0
20
40
60
80
100
0
OUTPUT CURRENT (A)
Figure 4.
0
0
0
E
MIC2185 PWM vs.
Skip Mode Efficiency
PWM
400kHz
SKIP
V
IN
=3.3V
V
OUT
=5V
The maximum peak inductor current depends on the skip
current limit threshold and the value of the current sense
resistor, R
SENSE
. For a typical 50mV current limit threshold
in skip mode, the peak inductor current is:
I
50mV
R
SENSE
INDUCTOR_pk
=
The maximum output current in skip mode depends on the
input conditions, output conditions and circuit component
values. Assuming a discontinuous mode where the inductor
current starts from zero at each cycle, the maximum output
current is calculated below:
I
2.5 10
L
fs
η
2 R
V
V
O(max)
3
SENSE
2
O
IN
=
×
×
(
×
×
)
(
)
where: I
O(max)
is the maximum output current
V
O
is the output voltage
V
IN
is the input voltage
L is the value of the boost inductor
f
S
is the switching frequency
η
is the efficiency of the boost converter
R
SENSE
is the value of the current sense resistor
2.5
·
10
-3
is a constant based on the skip mode
current threshold (50mV)
2
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MIC2185BM | Low Voltage Synchronous Boost PWM Control IC |
| MIC2185BQS | Low Voltage Synchronous Boost PWM Control IC |
| MIC2193 | 400KHZ SO 8 SYNCHRONOUS BUCK CONTROL IC |
| MIC2193BM | 400KHZ SO 8 SYNCHRONOUS BUCK CONTROL IC |
| MIC2193YM | 400KHZ SO 8 SYNCHRONOUS BUCK CONTROL IC |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MIC2185_05 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Low Voltage Synchronous Boost PWM Control IC |
| MIC2185BM | 功能描述:IC REG CTRLR BST PWM CM 16-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| MIC2185BM TR | 功能描述:IC REG CTRLR BST PWM CM 16-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| MIC2185BQS | 功能描述:IC REG CTRLR BST PWM CM 16-QSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| MIC2185BQS TR | 功能描述:IC REG CTRLR BST PWM CM 16-QSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。