双极开关霍尔效应IC

提供数字输出的霍尔效应IC器件有四大类：单极性开关、双极性开关、全极性开关和锁存器。双极开关在本应用说明中进行了描述。类似应用说明unipolar switches那omnipolar switches，和latches在快板上提供™ 网站。

双极传感器集成电路设计为敏感开关。（请注意，术语“双极性”指的是磁极性，与双极性半导体芯片结构无关。）双极性开关具有一致的磁滞，但单个单元具有出现在相对更正或更负范围内的开关点。这些装置适用于使用密集的、交替的北极和南极，从而产生所需的最小磁信号振幅ΔB，因为磁场极性的交替确保了开关，而一致的磁滞确保了周期性。

Applications for detecting the position of a rotating shaft, such as in a brushless dc motor (BLDC) are shown in figure 1. The multiple magnets are incorporated into a simple structure referred to as a "ring magnet," which incorporates alternating zones of opposing magnetic polarity. The IC package adjacent to each ring magnet is the Hall bipolar switch device. When the shaft rotates, the magnetic zones are moved past the Hall device. The device is subjected to the nearest magnetic field and is turned-on when a south field is opposite, and turned-off when a north field is opposite. Note that the branded face of the device is toward the ring magnet.

图1。Two bipolar device applications using ring magnets. The ring magnets have alternating N (north) and S (south) polarity zones, which are rotated past the Hall devices, causing them to turn on and off.

磁性开关点术语

以下是用于定义过渡点的术语，或switchpoints.那of Hall switch operation:

图2.

图2.。The Hall effect refers to the measurable voltage present when an applied current is influenced by a perpendicular magnetic field.

B.−磁通密度的符号，用于确定霍尔器件开关点的磁场特性。用高斯（G）或特斯拉（T）测量。换算为1克=0.1公吨。

B.can have a north or south polarity, so it is useful to keep in mind the algebraic convention, by which B is indicated as a negative value for north-polarity magnetic fields, and as a positive value for south-polarity magnetic fields. This convention allows arithmetic comparison of north and south polarity values, where the relative strength of the field is indicated by the absolute value of B, and the sign indicates the polarity of the field. For example, a − 100 G (north) field and a 100 G (south) field have equivalent strength, but opposite polarity. In the same way, a − 100 G field is stronger than a − 50 G field.
B._操作− Magnetic operate point; the level of a strengthening magnetic field at which a Hall device switches on. The resulting state of the device output depends on the individual device electronic design.
B._rp.- 磁释放点;霍尔器件关闭的弱化磁场的水平（或用于某些类型的霍尔设备，给出阳性b的强化负面的水平_操作). 设备输出的结果状态取决于单个设备的电子设计。
B._HYS− Magnetic switchpoint hysteresis. The transfer function of a Hall device is designed with this offset between the switchpoints to filter out small fluctuations in the magnetic field that can result from mechanical vibration or electromagnetic noise in the application. B_HYS= |B._操作−B级_rp.|.

典型的操作

双极开关通常有一个正B_操作和阴性B_rp.那but these switchpoints occur at field strength levels that are not precisely symmetrical with respect to the neutral level, B = 0 G. This characteristic is allowed so bipolar switches can provide greater sensitivity and narrower B_HYSthan latching switches (bipolar switches were originally conceived as a lower-cost alternative to early latches). A small percentage (≈10%) of bipolar switches have switchpoint ranges entirely in the positive (south) polarity range or entirely in the negative (north) polarity range. All of these characteristic ranges can be reliably operated using alternating positive (south) and negative (north) polarity fields. Turn-off will usually occur when the magnetic field is removed, but to ensure release, a field reversal is required.

双极开关的示例将是具有最大操作点的设备，B_操作（最多），45克，最小释放点，b_rp.(min), of –40 G, and a minimum hysteresis, B_HYS(min), of 15 G. However, the minimum operate point, B_操作(min), could be as low as –25 G, and the maximum release point, B_rp.（最大值）可能高达30克。图3显示了带有这些开关点的假设装置单元的这些特性。在图3的顶部，轨迹“最小ΔB”显示了振幅有多小可以导致可靠的切换。

图3.

图3.。Demonstration of possible switchpoint ranges for a bipolar switch, for use with low magnetic flux amplitude, narrow pitch alternating pole targets

图3说明了双极交换机的三种一般操作模式之间的差异：

“锁存模式”描述了具有正B的任何双极开关单元_操作和阴性B_rp.那behaving like a Hall latching switch by requiring both magnetic fields to be present for complete operation (but without actual latching of the device state)
"unipolar mode" describes any bipolar switch unit with both B_操作和B_rp.在正面（南）范围内
"negative unipolar mode" (sometimes referred to as "negative switch" mode) describes any bipolar switch unit with both B_操作和B_rp.在负面（北）范围内

The release point flux density becomes less important because, if the Hall switch has not switched when the pole has passed and the flux density approaches the neutral level, B = 0 G, the switch will certainly turn off when the following pole increases the flux density in the opposite polarity. Bipolar Hall switches take advantage of this extra margin in release-point flux values to achieve lower operate-point flux densities, a definite advantage in ring magnet applications.

可以在v中看到_OUTtraces at the bottom of figure 3, for each of these modes, switching at each pole alternation is reliable, with the duty cycle of the output differing somewhat according to the operating mode. A bipolar device operating in latch mode has nearly symmetrical switchpoints. This tends to set the duty cycle to near perfection when working with equally-spaced ring magnet poles. Having said that, even if the switchpoints were skewed, the duty cycle will still be close to 50% on and 50% off. For motor commutation this is ideal, resulting in high efficiency. Units having unipolar mode turn on and off with the south pole and do nothing as the north pole passes. Units in this mode will have a duty cycle of perhaps 40% on and 60% off. Units in negative unipolar mode turn off and on with the north pole and do nothing as the south pole passes. Units in this mode will have a duty cycle of perhaps 60% on and 40% off.

The three panels of figure 4 show the transfer characteristics of the operating modes of bipolar sensor ICs.

Figure 4a

图4A.闩锁模式特性。注意开关点滞后区，B_HYS，包括中性通量密度水平，B=0 G。

出于图4A的说明的目的，假设器件在左侧的磁通密度上的电源，其中磁通（B，水平轴上）比B更负_rp.or B_操作。Here the device is off, and the output voltage (V_OUT那on the vertical axis) is high.
Following the arrows toward the right, the magnetic field becomes increasingly positive. When the field is more positive than B_操作那the device turns on. This causes the output voltage to change to the opposite state, low.
虽然磁场比b更积极_rp.，设备保持打开，输出状态保持不变。即使B变得比B略弱，这也是正确的_操作那within the built-in zone of switching hysteresis, B_HYS。
Following the arrows back toward the left, the magnetic field becomes less positive and then more negative. When the magnetic field again drops below B_rp.那the device turns off. This causes the output to change back to the original state, high.

Figure 4b

为了解释图4B，假设设备在最左边的磁通密度下通电，其中磁通量（B，在水平轴上）小于B_rp.or B_操作。Here the device is off, and the output voltage (V_OUT那on the vertical axis) is high.
Following the arrows toward the right, the magnetic field becomes increasingly positive. When the field is more positive than B_操作那the device turns on. This causes the output voltage to change to the opposite state, low.
虽然磁场比b更积极_rp.，设备保持打开，输出状态保持不变。即使B变得比B略弱，这也是正确的_操作那within the built-in zone of switching hysteresis, B_HYS。
Following the arrows back toward the left, the magnetic field becomes less positive. When the magnetic field again drops below B_rp.那the device turns off. This causes the output to change back to the original state, high.

Figure 4c

Figure 4C. Negative unipolar (negative switch) mode characteristic. Note that the switchpoint hysteresis zone, B_HYS那is entirely more magnetically north than the neutral flux density level, B = 0 G. A south magnetic field has no effect on the device, although it can aid switching by dissipating any flux remaining after a north field has passed.

For purposes of explanation of figure 4C, assume the device powers-on with the magnetic flux density at the far left, where the magnetic flux (B, on the horizontal axis) is more negative than B_rp.or B_操作。Here the device is off, and the output voltage (V_OUT那on the vertical axis) is high.
Following the arrows toward the right, the magnetic field becomes less negative. When the field is less negative than B_操作那the device turns on. This causes the output voltage to change to the opposite state, low.
While the magnetic field remains less negative than B_操作，设备保持打开，输出状态保持不变。即使B变得比B略弱，这也是正确的_操作那within the built-in zone of switching hysteresis, B_HYS。
Following the arrows back toward the left, the magnetic field becomes less positive. When the magnetic field again drops below B_rp.那the device turns off. This causes the output to change back to the original state, high.

Magnets

各个磁铁可用于提供两个相反的磁极极度，然而，使用环或带磁体材料通常更具成本效益。环形和条带磁铁用具有指定间距的交流杆磁化。环磁体是环形或盘形组件（参见图1），其具有交替的径向或轴向磁化的磁极。条带磁铁是具有交替磁极的平坦条带。环形磁铁配有各种材料，包括陶瓷，稀土和柔性材料。条带磁铁几乎始终利用柔性材料，例如含有定向钡铁氧体的丁腈橡胶粘合剂，或更高的能量稀土材料。

环形磁铁通常被指定为具有多个磁极，而带材磁铁通常以每英寸杆指定。四极环形磁铁含有两个北部和两个以南方为导向的交替极点（N-S-N-S），而11杆每英寸条带磁铁配有0.0909英寸间隔开的交替极电极。中心。磁铁制造商提供各种极间距。

拉动电阻

上拉电阻必须连接在正电源和输出引脚之间（参见图4）。上拉电阻的通用值是1至10kΩ。最小上拉电阻是传感器IC最大输出电流（吸收电流）和实际电源电压的函数。20 mA是典型的最大输出电流，在这种情况下，最小上拉将是v_CC./0.020 A。在需要考虑电流消耗的情况下，上拉电阻可能高达50到100 kΩ。注意：当上拉值较大时，可能会导致外部泄漏电流接地，即使在设备磁关闭的情况下，也足以降低输出电压。这不是设备问题，而是上拉电阻器和传感器IC输出引脚之间的导体中发生的泄漏。极端情况下，这会降低传感器IC输出电压，足以抑制正常的外部逻辑功能。

图5.

图5。典型的程序图。

Use of Bypass Capacitors

Refer to figure 5 for a layout of bypass capacitors. In general:

对于没有斩波稳定的设计 - 建议将0.01μF电容放置在输出和接地销之间以及供电和接地引脚之间。
对于具有斩波稳定的设计 - 电源和接地引脚之间必须放置0.1μF电容，并且在输出和接地引脚之间建议使用0.01μF电容。

开机状态

只有当磁场强度超过B时，双极器件才能在有效状态下通电_操作或小于B_rp.应用电源时。如果磁场强度在滞后带中，则在B之间_操作和B_rp.那the device can assume either an on or off state initially, and then attains the correct state at the first excursion beyond a switchpoint. Devices can be designed with power-on logic that sets the device off until a switchpoint is reached.

开机状态s
传感器IC类型	上电状态（0 G字段）
Unipolar Switch	Off
闩锁	Either state^1那2
负极开关	在²
¹Unless power-on logic is incorporated in the design. ²Unless power-on of the device occurs while the magnetic field is inside the specified magnetic hysteresis of the device.

上电时间

Power-on time depends to some extent on the device design. Digital output sensor ICs, such as the bipolar device, reach stability on initial power-on in the following times.

Device type	Power-on time
Non-chopped designs	<4 µs
斩波稳定	<25微秒

基本上，这意味着在提供电源之后的这段时间之前，设备输出可能不处于正确的状态，但是在这段时间之后，设备输出保证处于正确的状态。

功耗

Total power dissipation is the sum of two factors:

Power consumed by the sensor IC, excluding power dissipated in the output. This value is V_CC.电源电流的时间。V._CC.是否在数据表上指定了设备电源电压和电源电流。例如，给定V_CC.= 12 V and Supply current = 9 mA. Power dissipation = 12 × 0.009 or 108 mW.
输出晶体管中消耗的功率。这个值是v_{（开）（周六）}倍啊utput current (set by the pull-up resistor). If V_{（开）（周六）}是0.4 V（最坏情况），输出电流为20 mA（通常最坏情况），功耗耗散为0.4×0.02 = 8兆瓦。正如您所看到的，因为饱和电压非常低，输出中的功率不受巨大的关注。

本例的总功耗为108+8=116MW。将此数字记录到相关包装数据表中的降额表中，并检查是否必须降低最大允许工作温度。

经常问的问题

Q: How do I orient the magnets?

磁铁的两极是面向品牌ed face of the device. The branded face is where you will find the identification markings of the device, such as partial part number or date code.

问：我可以用磁铁向侧面接近设备吗？

A：是的，但是要记住：如果磁铁的磁极保持在同一方向上，那么穿过装置的磁场方向与正面进近保持不变（例如，如果南极在正面进近时更接近装置，然后，北极将更接近背面接近的装置）。北极将产生一个相对于霍尔元件的正磁场，而南极将产生一个负磁场。

Q：接近设备背面是否有权衡？

答：是的。从包装前侧接近时，可以使用“清洁剂”信号，因为霍尔元件位于靠近前侧（封装品牌面部）而不是背面。例如，对于“UA”封装，带有霍尔元件的芯片在包装的品牌面内为0.50毫米，距离后侧面积约为1.02毫米。（从品牌面对霍尔元素的距离被称为“有源区域深度”。）

问：哈哈效应装置是否会造成非常大的田间损坏？

A: No. A very large field will not damage an Allegro Hall-effect device nor will such a field add additional hysteresis (other than the designed hysteresis).

Q: Why would I want a chopper-stabilized device?

答：斩波稳定的传感器IC允许比非切碎的设计更加紧密控制的开关点更大的灵敏度。这也可能允许更高的操作温度。大多数新设备设计利用切碎的霍尔元素。

Suggested Devices

Allegro双极开关在公司网站的选择指南中列出，网址为霍尔效应闩锁和双极开关。

可能的应用雷竞技最新网址

无刷直流电机旋转
速度感应
脉冲计数器，编码器
Automotive

Application Notes on Related Device Types

Reference: AN27705