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AMT49413 датащи(PDF) 10 Page - Allegro MicroSystems |
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AMT49413 датащи(HTML) 10 Page - Allegro MicroSystems |
10 / 21 page 3-Phase BLDC Controller and MOSFET Driver AMT49413 10 Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com for internal PWM: tBLANK (µs) = 1260× CT (µF), and for external PWM: tBLANK (µs) = 2000× CT (µF) . A nominal CT value of 680 pF yields a tBLANKof 1.3 µs for exter- nal PWM, and 860 ns for internal PWM. The user must ensure that CT is large enough to cover the current spike duration when using the internal sense amplifier. Diagnostics Several diagnostic features integrated into the AMT49413 provide speed and direction feedback and indications of fault conditions. TACHO and DIRO. These outputs provide speed and direction informationbasedontheHEinputsfromthemotor.Asshownin Figure1,ateachcommutationpoint,theTACHOoutputchanges state independent of motor direction. The DIRO output is updated at each commutation point to show the motor direction. When the motor is rotating in the “forward” or positive direction, DIRO will be high. When rotation is in the “reverse” or negative direc- tion, DIRO will be low. The actual direction of rotation is deter- minedfromthesequenceofthethreeHallinputs,Hx. Forward is when the sequence follows Table 2 top-to-bottom and reverse when the sequence follows Table 2 bottom-to-top. Note that there are some circumstances in which the direction reported on the DIRO output pin and the direction demanded on the DIR input pin may not be the same. This may happen if the motor and load have reasonably high inertia. In this case, changing the state of the DIR pin will cause the torque to reverse, braking the motor. During this braking, the direction indicated on the DIRO output will not change. ESF. The state of the enable stop on fault (ESF) pin will deter- mine the action taken when a short is detected. For other fault conditions, the action is defined by the type of fault. The action taken follows the states shown in Table 1. When ESF = 1, any short fault condition will disable all the gate drive outputs and coast the motor. This disabled state will be latched until the next phase commutation or until COAST or RESET go low. When ESF = 0, under most conditions, although the fault flags, FF1 and FF2, are still activated, the AMT49413 will not disrupt normal operation and will therefore not protect the motor or the drive circuit from damage. It is imperative that the master control circuit or an external circuit take any necessary action when a fault occurs, to prevent damage to components. If desired, the active low COAST input can be used as a crude disable circuit by connecting the fault flags FF1 and FF2 to the COAST input and a pull-up resistor to V5. FF1, FF2, and VDSTH. Fault conditions are indicated by the state of two open drain output fault flags, FF1 and FF2, as shown in Table 1. In addition to internal temperature, voltage, and logic monitoring, the AMT49413 monitors the state of the external MOSFETs and the motor current to determine if short-circuit faults occur or a low load condition exists. In the event that two or more faults are detected simultaneously, the state of the fault flags will be determined by a logical AND of the fault states of each flag. • Undervoltage. VREG supplies the low-side gate driver and the bootstrap charge current. It is critical to ensure that the volt- ages are sufficiently high before enabling any of the outputs. The undervoltage circuit is active during power-up, and will pull both fault flags low and coast the motor (all gate drives low) until VREG is greater than approximately 8 V. Note that this is sufficient to turn on the external power FETs at a battery voltage as low as 5.5 V, but will not normally provide the rated on-resistance of the FET. This could lead to excessive power dissipation in the external FET. In addition to a monitor on VREG, the AMT49413 also moni- tors both the bootstrap charge voltage, to ensure sufficient high- side drive, and the 5 V reference voltage at V5, to ensure correct logical operation. If either of these fall below the lockout volt- age level, the fault flags are set. • Overtemperature. This event pulls both fault flags low but does not disable any circuitry. It is left to the user to turn off the device to prevent overtemperature damage to the chip and unpredictable device operation. • Logic Fault: Hall Invalid.WhenallHx have the same value, the AMT49413 evaluates this as an illegal code, and pulls both Commutation Points TACHO DIRO "Forward" Motor Rotation "Reverse" Motor Rotation Figure 1: Direction Indication Outputs |
Аналогичный номер детали - AMT49413 |
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Аналогичное описание - AMT49413 |
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