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DRV8412 Datasheet(PDF) 10 Page - Texas Instruments |
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DRV8412 Datasheet(HTML) 10 Page - Texas Instruments |
10 / 31 page DRV8412 DRV8432 SLES242D – DECEMBER 2009 – REVISED JULY 2011 www.ti.com THEORY OF OPERATION Special attention should be paid to the power-stage POWER SUPPLIES power supply; this includes component selection, PCB placement, and routing. As indicated, each To facilitate system design, the DRV8412/32 need half-bridge has independent power-stage supply pin only a 12-V supply in addition to H-Bridge power (PVDD_X). For optimal electrical performance, EMI supply (PVDD). An internal voltage regulator provides compliance, and system reliability, it is important that suitable voltage levels for the digital and low-voltage each PVDD_X pin is decoupled with a ceramic analog circuitry. Additionally, the high-side gate drive capacitor (X5R or better) placed as close as possible requiring a floating voltage supply, which is to each supply pin. It is recommended to follow the accommodated by built-in bootstrap circuitry requiring PCB layout of the DRV8412/32 EVM board. external bootstrap capacitor. The 12-V supply should be from a low-noise, To provide symmetrical electrical characteristics, the low-output-impedance voltage regulator. Likewise, the PWM signal path, including gate drive and output 50-V power-stage supply is assumed to have low stage, is designed as identical, independent output impedance and low noise. The power-supply half-bridges. For this reason, each half-bridge has a sequence is not critical as facilitated by the internal separate gate drive supply (GVDD_X), a bootstrap power-on-reset circuit. Moreover, the DRV8412/32 pin (BST_X), and a power-stage supply pin are fully protected against erroneous power-stage (PVDD_X). Furthermore, an additional pin (VDD) is turn-on due to parasitic gate charging. Thus, provided as supply for all common circuits. Special voltage-supply ramp rates (dv/dt) are non-critical attention should be paid to place all decoupling within the specified voltage range (see the capacitors as close to their associated pins as Recommended Operating Conditions section of this possible. In general, inductance between the power data sheet). supply pins and decoupling capacitors must be avoided. Furthermore, decoupling capacitors need a short ground path back to the device. SYSTEM POWER-UP/POWER-DOWN SEQUENCE For a properly functioning bootstrap circuit, a small ceramic capacitor (an X5R or better) must be Powering Up connected from each bootstrap pin (BST_X) to the power-stage output pin (OUT_X). When the The DRV8412/32 do not require a power-up power-stage output is low, the bootstrap capacitor is sequence. The outputs of the H-bridges remain in a charged through an internal diode connected high impedance state until the gate-drive supply between the gate-drive power-supply pin (GVDD_X) voltage GVDD_X and VDD voltage are above the and the bootstrap pin. When the power-stage output undervoltage protection (UVP) voltage threshold (see is high, the bootstrap capacitor potential is shifted the Electrical Characteristics section of this data above the output potential and thus provides a sheet). Although not specifically required, holding suitable voltage supply for the high-side gate driver. RESET_AB and RESET_CD in a low state while In an application with PWM switching frequencies in powering up the device is recommended. This allows the range from 10 kHz to 500 kHz, the use of 100-nF an internal circuit to charge the external bootstrap ceramic capacitors (X5R or better), size 0603 or capacitors by enabling a weak pulldown of the 0805, is recommended for the bootstrap supply. half-bridge output. These 100-nF capacitors ensure sufficient energy storage, even during minimal PWM duty cycles, to Powering Down keep the high-side power stage FET fully turned on The DRV8412/32 do not require a power-down during the remaining part of the PWM cycle. In an sequence. The device remains fully operational as application running at a switching frequency lower long as the gate-drive supply (GVDD_X) voltage and than 10 kHz, the bootstrap capacitor might need to be VDD voltage are above the UVP voltage threshold increased in value. (see the Electrical Characteristics section of this data sheet). Although not specifically required, it is a good practice to hold RESET_AB and RESET_CD low during power down to prevent any unknown state during this transition. 10 Copyright © 2009–2011, Texas Instruments Incorporated |
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Similar Description - DRV8412_11 |
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