KMI25/2 & KMI25/4: 高性能旋转速度传感器数据手册
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更新于2024-07-15
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收藏 293KB PDF 举报 "KMI25_2_4.pdf 是一份关于KMI25/2和KMI25/4产品的数据手册，主要关注汽车电子领域的速度传感器技术，特别是涉及了AK传输协议的详细说明。"
这篇数据手册详细介绍了基于Anisotropic Magneto Resistive (AMR)效应的KMI25系列旋转速度传感器。KMI25/2适用于有源目标轮（多极编码器），而KMI25/4适用于无源目标轮（铁磁齿轮）。这两种设计都能在广泛的速度、空气间隙和温度范围内提供可靠的速度信息，并通过供电引脚上的电流协议进行传输。
手册中的亮点特性包括：
1. 系统级封装：将整个传感器集成在一个封装内，提高了系统的紧凑性和可靠性。
2. 两线电流接口：采用两线制通信，简化了电路设计，降低了对外部电路的需求。
3. 旋转方向检测：能够识别目标轮的旋转方向，增加了应用的灵活性。
4. 数字输出协议：采用了ArbeitsKreis协议（AK协议），这是一种专用于传感器数据传输的数字协议。
5. 宽范围的空气间隙：传感器能在较大的空气间隙下正常工作，适应不同的安装条件。
6. 宽泛的操作终端电压：允许在广泛的电压范围内运行，增强了电源兼容性。
7. 宽温范围：可在极端温度环境下稳定工作，满足汽车环境的严苛要求。
8. 高静电放电(ESD)保护：确保传感器在静电环境中不易损坏，提高了耐用性。
9. 极低的抖动：确保数据传输的精确度和稳定性。
10. 符合AEC-Q100 Rev-G (Grade 0)标准：证明该产品已经过汽车行业认证，满足高性能和高可靠性的要求。
手册中特别强调了不要将多个产品相互挤压或让它们碰撞，以防止磁力相互作用或损坏。
KMI25系列传感器是高性能旋转速度检测的解决方案，尤其适用于汽车电子系统。同时，对于那些需要理解AK协议的读者，5.3小节提供了深入的学习资料，帮助理解和实施这种传感器通信协议。
KMI25_2_4 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2016. All rights reserved.
Product data sheet Rev. 1 — 29 April 2016 5 of 26
NXP Semiconductors
KMI25/2; KMI25/4
High performance rotational speed sensor
The LDIC chip is fabricated using a robust high-voltage process. This measure shields the
other two dies from the harsh electrical environment on the supply line V
CC
. The constant
current source I
L
provides the LOW-level output signal of typically 7 mA and delivers the
supply current for the whole sensor system. Thus from I
L
the supply voltages for the PDIC,
the AMR bridge and the current source blocks I
M
and I
H
are derived. The switchable
current source I
M
also delivers typically 7 mA. Hence, if I
M
is active, the total supply
current is at its MID level of typically 14 mA. This current refers to a logic HIGH level at the
AK protocol. The switchable current source I
H
delivers typically 21 mA. Thus, I
H
being
active results in a total current of typically 28 mA, which is the level of a speed pulse. With
this current interface, safe sensor signal transport to the Electronic Control Unit (ECU)
using only a two-wire cable is provided. In addition, the digital input pin DI converts an
external resistance into a one-bit signal. This signal is passed on to the PDIC via a level
shifter.
Within the PDIC, the differential output voltage of the AMR sensor bridge leads as speed
signal into an analog signal chain. It comprises an amplifier with adjustable gain, followed
by an offset cancelation stage and finally, a smart comparator having adjustable
hysteresis levels. The latter converts the sinusoidal sensor signal into a rectangular output
signal. Via a one-shot, the rectangular signal controls the switchable current source I
H
on
the LDIC. The sensor system outputs HIGH-level speed pulses at each zero-crossing of
the magnetic input signal. As a result, the speed pulses occur at a repetition rate of twice
the magnetic field strength frequency. This repetition rate allows measuring the rotational
speed of the encoder wheel.
A peak detector within the digital control unit on the PDIC measures the amplitude and the
offset of the sensor signal. The peak detector has a resolution of 8 bit. This feature allows
the digital control unit on one hand, to eliminate the signal offset. This function is realized
with a dedicated Digital-to-Analog Converter (DAC). The DAC has a resolution of 12 bits.
On the other hand, it allows the digital control unit to optimize amplifier gain and
comparator hysteresis settings according to the actual signal amplitude. Due to these
measures, the sensor system can handle a wide amplitude range. This amplitude range in
turn allows the KMI25/2 and KMI25/4 to handle a wide range of air gaps between sensor
and encoder. The hysteresis of the smart comparator prevents erroneous multiple
switching due to mechanical vibrations of the encoder wheel. A further important feature
of the smart comparator is, that it switches its output level always at the zero-crossing of
its input signal. Thus, the phase of its rectangular output signal is independent of its
hysteresis setting and independent of the gain setting at the amplifier. For this reason,
adjustments of gain and hysteresis in the signal chain avoid the introduction of jitter into
the sensor output signal. The whole signal chain works even under DC conditions,
therefore having true zero Hertz capability.
The block labeled direction channel in Figure 1
within the PDIC builds the sum of the two
AMR half-bridge output signals, which is referred to as direction signal. As already
described above, the difference of the two half-bridge signals is processed as speed
signal. Due to the displacement of the two half bridges in direction of the y axis, there is a
phase shift between their output signals. The sign of this phase difference switches with
direction of rotation. As a mathematical fact, the difference and sum signals are phase
shifted to each other by either +90 or 90. The sign of this phase shift also depends on
the direction of rotation. Using these relations, the digital control unit detects the direction
information by measuring the phase relation between the difference signal and the sum
signal. For this purpose, also the offset at the sum signal is eliminated in the respective
offset cancelation block.
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