参数资料
| 型号： | MC33470DW |
| 厂商： | ON Semiconductor |
| 文件页数： | 9/15页 |
| 文件大小： | 0K |
| 描述： | IC CONV DC/DC SYNC RECT 20-SOIC |
| 产品变化通告： | Product Obsolescence 11/Feb/2009 |
| 标准包装： | 38 |
| 应用： | 控制器，Intel Pentium? II |
| 输入电压： | 4.5 V ~ 5.5 V |
| 输出数： | 1 |
| 输出电压： | 1.8 V ~ 3.5 V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-SOIC（0.295"，7.50mm 宽） |
| 供应商设备封装： | 20-SOIC |
| 包装： | 管件 |
MC33470
External loop compensation is required for converter
stability. Compensation components may be connected from
the compensation pin to ground. The error amplifier input is
tied to the sense pin which also has an internal 20 m A current
Because the I max pin draws 190 m A of input current, the
overcurrent threshold is programmed by an external resistor.
Referring to Figure 14, the current limit resistor value can be
determined from the following equation:
L(max)
DS(on)
source to ground. The current source is intended to provide a
24 mV offset when an external 1.2 k resistor is placed
between the output voltage and the sense pin. The 24 mV
offset voltage is intended to allow a greater dynamic load
where:
R1 +
[( I )( R )]
(Imax)
) I
regulation range within a given specified tolerance for the
output voltage. The offset may be increased by increasing the
resistor value. The offset can be eliminated by connecting the
I
L(max)
+
I
O
ripple
2
sense pin directly to the regulated output voltage.
The voltage reference consists of an internal, low
temperature coefficient, reference circuit with an added offset
voltage. The offset voltage level is the output of the
digital?to?analog converter. Control bits VID0 through VID4
control the amount of offset voltage which sets the value of
the voltage reference, as shown in Table 1. The VID0?4 input
bits each have internal 10 k pullup resistances. Therefore, the
reference voltage, and the output voltage, may be
programmed by connecting the VID pins to ground for logic
“0” or by an open for a logic “1”. Typically, a logic “1” will
be recognized by a voltage > 0.67 x V CC . A logic “0” is a
voltage < V CC /3.
MOSFET Switch Outputs
The output MOSFETs are designed to switch a maximum
of 18 V, with a peak drain current of 2.0 A. Both G1 and G2
output drives are designed to switch N?channel MOSFETs.
Output drive controls to G1 and G2 are phased to prevent
cross conduction of the internal IC output stages. Output dead
time is typically 100 nanoseconds between G1 and G2 in
order to minimize cross conduction of the external switching
MOSFETs.
Current Limit and Soft?Start Controls
The soft?start circuit is used both for initial power
application and during current limit operation. A single
external capacitor and an internal 10 m A current source
control the rate of voltage increase at the error amplifier
output, establishing the circuit turn on time. The G1 output
I O = Maximum load current
I ripple = Inductor peak to peak ripple current
OUTEN Input and OT Output Pins
On and off control of the MC33470 may be implemented
with the OUTEN pin. A logic “1” applied the OUTEN pin,
where a logic “1” is above 2.0 V, will allow normal operation
of the MC33470. The OUTEN pin also has multiple
thresholds to provide over temperature protection. An
negative temperature coefficient thermistor can be connected
to the OUTEN pin, as shown in Figure 16. Together with R S ,
a voltage divider is formed. The divider voltage will decrease
as the thermistor temperature increases. Therefore, the
thermistor should be mounted to the hottest part on the circuit
board. When the OUTEN voltage drops below 2.0 V
typically, the MC33470 OT pin open collector output will
switch from a logic “1” to a logic “0”, providing a warning to
the system. If the OUTEN voltage drops below 1.7 V, both G1
and G2 output driver pins are latched to a logic “0” state.
V CC
10 k
OT
V CC
will increase from zero duty cycle as the voltage across the
soft?start capacitor increases beyond about 0.5 V. When the
soft?start capacitor voltage has reached about 1.5 V, normal
duty cycle operation of G1 will be allowed.
An overcurrent condition is detected by the current limit
amplifier. The current limit amplifier is activated whenever the
G1 output is high. The current limit amplifier compares the
voltage drop across the external MOSFET driven by G1, as
R S
NTC
Thermistor
OUTEN
MC33470
measured at the I FB pin, with the voltage at the I max pin.
Figure 16. OUTEN/OT Overtemperature Function
http://onsemi.com
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MC33470DWG | 功能描述:直流/直流开关调节器 5-Bit Synchronous Rectification Buck 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 |
| MC33470DWR2 | 功能描述:直流/直流开关调节器 5-Bit Synchronous 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 |
| MC33470DWR2G | 功能描述:直流/直流开关调节器 5-Bit Synchronous Rectification Buck 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 |
| MC33486ADH | 功能描述:电源开关 IC - 配电 DUALHIGH-SIDE BRIDGE RoHS:否 制造商:Exar 输出端数量:1 开启电阻（最大值）:85 mOhms 开启时间（最大值）:400 us 关闭时间（最大值）:20 us 工作电源电压:3.2 V to 6.5 V 电源电流（最大值）: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOT-23-5 |
| MC33486ADHR2 | 功能描述:电源开关 IC - 配电 DUALHIGH-SIDE BRIDGE RoHS:否 制造商:Exar 输出端数量:1 开启电阻（最大值）:85 mOhms 开启时间（最大值）:400 us 关闭时间（最大值）:20 us 工作电源电压:3.2 V to 6.5 V 电源电流（最大值）: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOT-23-5 |
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