Datasheet > MIC4685WR

MIC4685WR

更新时间： 2024-01-03 08:36:20

品牌	Logo	应用领域
麦瑞 - MICREL		稳压器开关
页数	文件大小	规格书
17页	332K
描述
3A SPAK SuperSwitcher Buck Regulator

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MIC4685WR 技术参数

是否Rohs认证：	符合	生命周期：	Active
包装说明：	,	Reach Compliance Code：	compliant
ECCN代码：	EAR99	HTS代码：	8542.39.00.01
风险等级：	5.17	模拟集成电路 - 其他类型：	SWITCHING REGULATOR
控制模式：	VOLTAGE-MODE	控制技术：	PULSE WIDTH MODULATION
最大输入电压：	30 V	最小输入电压：	4 V
标称输入电压：	12 V	JESD-30 代码：	R-PSSO-G7
JESD-609代码：	e3	长度：	9.395 mm
湿度敏感等级：	3	功能数量：	1
端子数量：	7	最高工作温度：	125 °C
最低工作温度：	-40 °C	封装主体材料：	PLASTIC/EPOXY
封装形状：	RECTANGULAR	封装形式：	SMALL OUTLINE
峰值回流温度（摄氏度）：	260	认证状态：	Not Qualified
座面最大高度：	2.16 mm	表面贴装：	YES
切换器配置：	BUCK	最大切换频率：	225 kHz
温度等级：	AUTOMOTIVE	端子面层：	Matte Tin (Sn)
端子形式：	GULL WING	端子节距：	1.27 mm
端子位置：	SINGLE	处于峰值回流温度下的最长时间：	40
宽度：	8 mm	Base Number Matches：	1

MIC4685WR 数据手册

Micrel, Inc.

MIC4685

Bootstrap (BS, Pin 1)

Detailed Pin Description

The bootstrap pin, in conjunction with the external

bootstrap capacitor, provides a bias voltage higher than

the input voltage to the MIC4685’s main NPN pass

element. The bootstrap capacitor sees the dv/dt of the

switching action at the SW pin as an AC voltage. The

bootstrap capacitor then couples the AC voltage back to

the BS pin, plus the dc offset of V_INwhere it is rectiﬁed and

used to provide additional drive to the main switch; in this

case, a NPN transistor.

Switch (SW, Pin 6)

The switch pin is tied to the emitter of the main internal

NPN transistor. This pin is biased up to the input voltage,

minus the V_SAT, of the main NPN pass element. The

emitter is also driven negative when the output inductor’s

magnetic ﬁeld collapses at turn-off. During the OFF time,

the SW pin is clamped by the output Schottky diode

typically to a –0.5V.

This additional drive reduces the NPN’s saturation voltage

and increases efﬁciency, from a V_SATof 1.8V, and 75%

Ground (GND, Pin 4, Tab)

There are two main areas of concern when it comes to the

ground pin, EMI and ground current. In a buck regulator or

any other non-isolated switching regulator, the output

capacitor(s) and diode(s) ground is referenced back to the

switching regulator’s or controller’s ground pin. Any

resistance between these reference points causes an

offset voltage/IR drop proportional to load current and poor

load regulation. This is why it’s important to keep the

output grounds placed as close as possible to the

switching regulator’s ground pin. To keep radiated EMI to

a minimum, it is necessary to place the input capacitor

ground lead as close as possible to the switching

regulator’s ground pin.

efﬁciency to

respectively.

a V_SATof 0.5V and 88% efﬁciency

Feedback (FB, Pin 3)

The feedback pin is tied to the inverting side of an error

ampliﬁer. The noninverting side is tied to a 1.235V

bandgap reference. An external resistor voltage divider is

required from the output-to-ground, with the center tied to

the feedback pin. See Tables 1 and 2 for recommended

resistor values.

Enable (EN, Pin 5)

The enable (EN) input is used to turn on the regulator and

is TTL compatible. Note: connect the enable pin to the

input if unused. A logic-high enables the regulator. A logic-

low shuts down the regulator and reduces the stand-by

quiescent input current to typically 150µA. The enable pin

has an up-per threshold of 2.0V minimum and lower

threshold of 0.8V maximum. The hysterisis provided by the

upper and lower thresholds acts as an UVLO and prevents

unwanted turn on of the regulator due to noise.

Input Voltage (V_IN, Pin 2)

The V_INpin is the collector of the main NPN pass element.

This pin is also connected to the internal regulator. The

output diode or clamping diode should have its cathode as

close as possible to this point to avoid voltage spikes

adding to the voltage across the collector.

M9999-012610

January 2010

1 234 5 6 7...17

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