参数资料
| 型号： | MIC2182-3.3YSM |
| 厂商： | Micrel Inc |
| 文件页数： | 13/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SSOP |
| 标准包装： | 77 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 330kHz |
| 占空比： | 86% |
| 电源电压： | 4.5 V ~ 32 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： | 16-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1092 (CN2011-ZH PDF) |
| 其它名称： | 576-2157 MIC2182-3.3YSM-ND |
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MIC2182
Switching from PWM to Skip Mode
The current sense amplifier in Figure 3 monitors the average
voltage across the current-sense resistor. The controller will
switch from PWM to skip mode when the average voltage
across the current-sense resistor drops below approximately
Micrel
rent-limit threshold is 100mV+35mV – 25mV. The current-
sense resistor must be sized using the minimum current-limit
threshold. The external components must be designed to
withstand the maximum current limit. The current-sense
resistor value is calculated by the equation below:
12mV. This is shown in Figure 7b. The average output current
at this transition level for is calculated below.
R CS =
75mV
I OUT(max)
I OUT(skipmode) =
I OUT(max) =
0.012
R CS
where:
0.012 = threshold voltage of the internal comparator
R CS = current-sense resistor value
Switching from Skip to PWM Mode
The frequency of occurrence of the skip-mode current pulses
increase as the output current increases until the hysteretic
duty cycle reaches 100% (continuous pulses). Increasing the
current past this point will cause the output voltage will drop.
The low limit comparator senses the output voltage when it
drops below 2% of the set output and automatically switches
the converter to PWM mode.
The inductor current in skip mode is a triangular wave shape
a minimum value of 0 and a maximum value of 35mV/R CS
(see Figure 7b). The maximum average output current in skip
mode is the average value of the inductor waveform:
The maximum output current is:
135mV
R CS
The current-sense pins CSH (pin 8) and V OUT (pin 9) are
noise sensitive due to the low signal level and high input
impedance. The PCB traces should be short and routed close
to each other. A small (1nF to 0.1 μ F) capacitor across the pins
will attenuate high frequency switching noise.
When the peak inductor current exceeds the current-limit
threshold, the current-limit comparator, in Figure 2, turns off
the high-side MOSFET for the remainder of the cycle. The
output voltage drops as additional load current is pulled from
the converter. When the output voltage reaches approxi-
mately 0.95V, the circuit enters frequency-foldback mode
and the oscillator frequency will drop to 60kHz while maintain-
ing the peak inductor current equal to the nominal 100mV
across the external current-sense resistor. This limits the
I OUT(max skipmode) = 0.5 ×
35mV
R CS
maximum output power delivered to the load under a short
circuit condition.
Reference, Enable, and UVLO Circuits
The capacitor on the PWM pin (pin 2) is discharged when the
IC transitions from skip to PWM mode. This forces the IC to
remain in PWM mode for a fixed period of time. The added
delay prevents unwanted switching between PWM and skip
mode. The capacitor is charged with a 10uA current source
on pin 2. The threshold on pin 2 is 2.5V. The delay for a typical
1nF capacitor is:
The output drivers are enabled when the following conditions
are satisfied:
? The V DD voltage (pin 11) is greater than its
undervoltage threshold (typically 4.2V).
? The voltage on the enable pin is greater than the
enable UVLO threshold (typically 2.5V)
t delay =
C PWM × V threshold
I source
=
1nF × 2.5V
10 μ A
= 250 μ s
The internal bias circuit generates a 1.245V bandgap refer-
ence voltage for the voltage error amplifier and a 5V V DD
voltage for the gate drive circuit. The reference voltage in the
where:
C PWM = capacitor connected to pin 2
Current Limit
The current-limit circuit operates during PWM mode. The
output current is detected by the voltage drop across the
fixed-output-voltage versions of the MIC2182 is buffered and
brought to pin 7. The V REF pin should be bypassed to GND
(pin 4) with a 0.1 μ F capacitor. The adjustable version of the
MIC2182 uses pin 7 for output voltage sensing. A decoupling
capacitor on pin 7 is not used in the adjustable output voltage
version.
external current-sense resistor (R CS in Figure 2.). The cur-
35mV THRESHOLD
Inductor
Current
Inductor
Current
I LIM(skip)
0A
I MIN(PWM)
0A
Figure 7a. Maximum Skip-Mode-Load Inductor Current
ACROSS R CS .
12mV THRESHOLD
OF AVERAGE VOLTAGE
ACROSS R CS .
Figure 7b. Minimum PWM-Mode-Load Inductor Current for PWM Operation
April 22, 2004
13
M9999-042204
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2182-5.0BM | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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) |
| MIC2182-5.0BM TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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) |
| MIC2182-5.0BSM | 功能描述:DC/DC 开关控制器 High EfficiencySynchronous Buck Controller SSOP Pkg 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 |
| MIC2182-5.0BSM TR | 功能描述:DC/DC 开关控制器 High EfficiencySynchronous Buck Controller SSOP Pkg 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 |
| MIC2182-5.0YM | 功能描述:DC/DC 开关控制器 High EfficiencySynchronous Buck Controller SO Pkg (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 |
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