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参数资料
| 型号： | APEK4985SLP-01-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 7/22页 |
| 文件大小： | 0K |
| 描述： | Board Eval Motor Control A4985 |
| 标准包装： | 1 |
| 主要目的： | 电源管理，电机控制，步进控制器 |
| 嵌入式： | 否 |
| 已用 IC / 零件： | A4985 |
| 已供物品： | 板 |
| 相关产品： | 620-1344-2-ND - IC STEPPER MOTOR DRIVER 24TSSOP |
| 其它名称： | 620-1374 |
A4985
DMOS Microstepping Driver with Translator
And Overcurrent Protection
Functional Description
Device Operation. The A4985 is a complete microstepping
motor driver with a built-in translator for easy operation with
minimal control lines. It is designed to operate bipolar stepper
motors in full-, half-, quarter-, and eighth-step resolution modes.
The currents in each of the two output full-bridges and all of the
N-channel DMOS FETs are regulated with fixed off-time PWM
(pulse width modulated) control circuitry. At each step, the current
for each full-bridge is set by the value of its external current-sense
resistor (R S1 and R S2 ), a reference voltage (V REF ), and the output
voltage of its DAC (which in turn is controlled by the output of
the translator).
At power-on or reset, the translator sets the DACs and the phase
current polarity to the initial Home state (shown in figures 8
through 11), and the current regulator to Mixed Decay Mode for
both phases. When a step command signal occurs on the STEP
input, the translator automatically sequences the DACs to the
next level and current polarity. (See table 2 for the current-level
sequence.) The microstep resolution is set by the combined effect
of the MS1 and MS2 inputs , as shown in table 1.
When stepping, if the new output levels of the DACs are lower
than their previous output levels, then the decay mode for the
active full-bridge is set to Mixed. If the new output levels of the
DACs are higher than or equal to their previous levels, then the
decay mode for the active full-bridge is set to Slow. This auto-
matic current decay selection improves microstepping perfor-
mance by reducing the distortion of the current waveform that
results from the back EMF of the motor.
Microstep Select (MS1 and MS2). The microstep resolu-
tion is set by the voltage on logic inputs MS1 and MS2, as shown
in table 1. MS1 has a 100 k Ω pull-down resistance, and MS2 has
a 50 k Ω pull-down resistance. When changing the step mode the
change does not take effect until the next STEP rising edge.
If the step mode is changed without a translator reset, and abso-
lute position must be maintained, it is important to change the
step mode at a step position that is common to both step modes in
order to avoid missing steps. When the device is powered down,
or reset due to TSD or an over current event the translator is set to
the home position which is by default common to all step modes.
Mixed Decay Operation. The bridge operates in Mixed
decay mode, at power-on and reset, and during normal running
according to the ROSC configuration and the step sequence, as
decay mode for the remainder of t OFF . A timing diagram for this
feature appears in figure 7.
Typically, mixed decay is only necessary when the current in the
winding is going from a higher value to a lower value as determined
by the translator setting. For most loads automatically-selected mixed
decay is convenient because it minimizes ripple when the current is
rising and prevents missed steps when the current is falling. For some
applications where microstepping at very low speeds is necessary,
the lack of back EMF in the winding causes the current to increase in
the load quickly, resulting in missed steps. This is shown in figure 2.
By pulling the ROSC pin to ground, mixed decay is set to be active
100% of the time, for both rising and falling currents, and prevents
missed steps as shown in figure 3. If this is not an issue, it is recom-
mended that automatically-selected mixed decay be used, because
it will produce reduced ripple currents. Refer to the Fixed Off-Time
section for details.
Low Current Microstepping. Intended for applications
where the minimum on-time prevents the output current from
regulating to the programmed current level at low current steps.
To prevent this, the device can be set to operate in Mixed decay
mode on both rising and falling portions of the current waveform.
This feature is implemented by shorting the ROSC pin to ground.
In this state, the off-time is internally set to 30 μ s.
Reset Input (ˉRˉ ˉEˉ ˉSˉ ˉEˉ ˉTˉ ). The ˉRˉ ˉEˉ ˉS ˉEˉ ˉTˉ input sets the translator
to a predefined Home state (shown in figures 8 through 11), and
turns off all of the FET outputs. All STEP inputs are ignored until
the ˉRˉ ˉEˉ ˉS ˉEˉ ˉTˉ input is set to high.
Step Input (STEP) . A low-to-high transition on the STEP
input sequences the translator and advances the motor one incre-
ment. The translator controls the input to the DACs and the direc-
tion of current flow in each winding. The size of the increment is
determined by the combined state of the MS1and MS2 inputs.
Direction Input (DIR). This determines the direction of rota-
tion of the motor. Changes to this input do not take effect until the
next STEP rising edge.
Internal PWM Current Control. Each full-bridge is con-
trolled by a fixed off-time PWM current control circuit that limits
the load current to a desired value, I TRIP . Initially, a diagonal pair
of source and sink FET outputs are enabled and current flows
shown in figures 8 through 11. During Mixed decay, when the trip through the motor winding and the current sense resistor, R S x .
point is reached, the A4982 initially goes into a fast decay mode When the voltage across R S x equals the DAC output voltage, the
for 31.25% of the off-time, t OFF . After that, it switches to Slow current sense comparator resets the PWM latch. The latch then
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
7
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| APEK4985SLP-01-T-DK | 功能描述:A4985 - Power Management, Motor Control, Stepper Evaluation Board 制造商:allegro microsystems, llc 系列:- 零件状态:有效 主要用途:电源管理，电机控制，步进控制器 嵌入式:否 使用的 IC/零件:A4985 主要属性:- 辅助属性:- 所含物品:板 标准包装:1 |
| APEK4986SLP-01-T | 功能描述:Board Eval Motor Control A4986 RoHS:是 类别:编程器，开发系统 >> 评估演示板和套件 系列:- 标准包装:1 系列:PSoC® 主要目的:电源管理，热管理 嵌入式:- 已用 IC / 零件:- 主要属性:- 次要属性:- 已供物品:板，CD，电源 |
| APEK4986SLP-01-T-DK | 功能描述:A4986 - Power Management, Motor Control, Stepper Evaluation Board 制造商:allegro microsystems, llc 系列:- 零件状态:有效 主要用途:电源管理，电机控制，步进控制器 嵌入式:否 使用的 IC/零件:A4986 主要属性:- 辅助属性:- 所含物品:板 标准包装:1 |
| APEK4987SLP-01-T | 功能描述:BOARD EVAL MOTOR CONTROL A4987 RoHS:是 类别:编程器，开发系统 >> 评估演示板和套件 系列:- 标准包装:1 系列:PSoC® 主要目的:电源管理，热管理 嵌入式:- 已用 IC / 零件:- 主要属性:- 次要属性:- 已供物品:板，CD，电源 |
| APEK4987SLP-01-T-DK | 功能描述:A4987 - Power Management, Motor Control, Stepper Evaluation Board 制造商:allegro microsystems, llc 系列:- 零件状态:有效 主要用途:电源管理，电机控制，步进控制器 嵌入式:否 使用的 IC/零件:A4987 主要属性:- 辅助属性:- 所含物品:板 标准包装:1 |
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