Datasheet > UC2845BDR2

UC2845BDR2

更新时间： 2024-02-16 20:58:40

品牌	Logo	应用领域
安森美 - ONSEMI		开关光电二极管控制器
页数	文件大小	规格书
20页	320K
描述
HIGH PERFORMANCE CURRENT MODE CONTROLLERS

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技术参数
数据手册

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UC2845BDR2 技术参数

是否无铅：	不含铅	是否Rohs认证：	符合
生命周期：	Active	零件包装代码：	SOIC
包装说明：	SOP, SOP14,.25	针数：	14
Reach Compliance Code：	compliant	ECCN代码：	EAR99
HTS代码：	8542.39.00.01	风险等级：	0.53
模拟集成电路 - 其他类型：	SWITCHING CONTROLLER	控制模式：	CURRENT-MODE
控制技术：	PULSE WIDTH MODULATION	最大输入电压：	25 V
最小输入电压：	12 V	标称输入电压：	15 V
JESD-30 代码：	R-PDSO-G14	JESD-609代码：	e3
长度：	8.65 mm	湿度敏感等级：	1
功能数量：	1	端子数量：	14
最高工作温度：	85 °C	最低工作温度：	-25 °C
最大输出电流：	1 A	封装主体材料：	PLASTIC/EPOXY
封装代码：	SOP	封装等效代码：	SOP14,.25
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：	1.75 mm	子类别：	Switching Regulator or Controllers
表面贴装：	YES	切换器配置：	SINGLE
最大切换频率：	275 kHz	技术：	BIPOLAR
温度等级：	OTHER	端子面层：	Tin (Sn)
端子形式：	GULL WING	端子节距：	1.27 mm
端子位置：	DUAL	处于峰值回流温度下的最长时间：	40
宽度：	3.9 mm	Base Number Matches：	1

UC2845BDR2 数据手册

UC3844B, UC3845B, UC2844B, UC2845B

Undervoltage Lockout

designer added flexibility in tailoring the drive voltage

Two undervoltage lockout comparators have been

incorporated to guarantee that the IC is fully functional

before the output stage is enabled. The positive power

supply terminal (V ) and the reference output (V ) are

each monitored by separate comparators. Each has built−in

hysteresis to prevent erratic output behavior as their

independent of V . A Zener clamp is typically connected

to this input when driving power MOSFETs in systems

where V is greater than 20 V. Figure 23 shows proper

power and control ground connections in a current−sensing

power MOSFET application.

ref

Reference

respective thresholds are crossed. The V

comparator

The 5.0 V bandgap reference is trimmed to ±1.0%

upper and lower thresholds are 16 V/10 V for the UCX844B,

tolerance at T = 25°C on the UC284XB, and ±2.0% on the

and 8.4 V/7.6 V for the UCX845B. The V comparator

ref

UC384XB. Its primary purpose is to supply charging current

to the oscillator timing capacitor. The reference has

short−circuit protection and is capable of providing in

excess of 20 mA for powering additional control system

circuitry.

upper and lower thresholds are 3.6 V/3.4 V. The large

hysteresis and low startup current of the UCX844B makes

it ideally suited in off−line converter applications where

efficient bootstrap startup techniques are required

(Figure 30). The UCX845B is intended for lower voltage

dc−dc converter applications. A 36 V Zener is connected as

Design Considerations

a shunt regulator from V to ground. Its purpose is to

Do not attempt to construct the converter on

wire−wrap or plug−in prototype boards. High frequency

circuit layout techniques are imperative to prevent

pulse−width jitter. This is usually caused by excessive noise

pick−up imposed on the Current Sense or Voltage Feedback

inputs. Noise immunity can be improved by lowering circuit

impedances at these points. The printed circuit layout should

contain a ground plane with low−current signal and

high−current switch and output grounds returning on

separate paths back to the input filter capacitor. Ceramic

protect the IC from excessive voltage that can occur during

system startup. The minimum operating voltage for the

UCX844B is 11 V and 8.2 V for the UCX845B.

Output

These devices contain a single totem pole output stage that

was specifically designed for direct drive of power

MOSFETs. It is capable of up to ±1.0 A peak drive current

and has a typical rise and fall time of 50 ns with a 1.0 nF load.

Additional internal circuitry has been added to keep the

Output in a sinking mode whenever an undervoltage lockout

is active. This characteristic eliminates the need for an

external pulldown resistor.

bypass capacitors (0.1 mF) connected directly to V , V ,

and V may be required depending upon circuit layout.

ref

This provides a low impedance path for filtering the high

frequency noise. All high current loops should be kept as

short as possible using heavy copper runs to minimize

radiated EMI. The Error Amp compensation circuitry and

the converter output voltage divider should be located close

to the IC and as far as possible from the power switch and

other noise−generating components.

The SOIC−14 surface mount package provides separate

pins for V (output supply) and Power Ground. Proper

implementation will significantly reduce the level of

switching transient noise imposed on the control circuitry.

This becomes particularly useful when reducing the I

pk(max)

clamp level. The separate V supply input allows the

ref

8(14)

Bias

5.0k

Osc

4(7)

0.01

External

Sync

Input

2(3)

1(1)

2(3)

1(1)

5.0k

MC1455

5(9)

To Additional

UCX84XBs

The diode clamp is required if the Sync amplitude is large enough to cause

the bottom side of C to go more than 300 mV below ground.

1.44

(R ꢁ )ꢁ 2R )C

fꢁ +ꢁ

(max)

ꢁ +ꢁ

R ꢁ )ꢁ 2R

A B

Figure 18. External Clock Synchronization

Figure 19. External Duty Cycle Clamp and

Multi−Unit Synchronization

http://onsemi.com

1...7 8 91011 12 13...20

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UC2845BL	ONSEMI	HIGH PERFORMANCE CURRENT MODE CONTROLLERS	获取价格
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UC2845BN	MOTOROLA	Switching Controller, Current-mode, 1A, 500kHz Switching Freq-Max, BIPolar, PDIP8, PLASTIC	获取价格
UC2845BNG	ONSEMI	High Performance Current Mode Controllers	获取价格

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