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MC33486ADH bảng dữ liệu(PDF) 11 Page - Freescale Semiconductor, Inc |
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MC33486ADH bảng dữ liệu(HTML) 11 Page - Freescale Semiconductor, Inc |
11 / 30 page Analog Integrated Circuit Device Data Freescale Semiconductor 11 33486A FUNCTIONAL DESCRIPTION FUNCTIONAL INTERNAL BLOCK DESCRIPTION damage (low-side MOSFETs ON). The overtemperature protection circuitry incorporates hysteresis. Overtemperature fault condition is reported on the status output. High-Side Overcurrent Protection The 33486A incorporates a current shutdown threshold of 35 A typical. When this limit is reached due to an overload condition or a short to ground, the faulty output is tri-stated. To clear the fault, the input (INn) line needs to return low, then on the next high transition the output will be enabled. This information is reported on the status output. Low-Side Block The low-side block has control circuitry for two external N-channel power MOSFETs. The low-side control circuitry is PWM capable and protects the low-side MOSFETs in case of overcurrent (short to VBAT). This information is reported on the status output. The low-side gate controls are clamped at 14 V maximum to protect the gates of the low-side MOSFETs. Figures 13, page 15, and 14, page 15, depict the characteristics of the low-side block when a current is sourced from the GLS pin or sinked from the GLS pin, respectively. During normal operation, the outputs OUT1 and OUT2 are driven by the high side. The low-side gate driver will only turn on when the voltage (same connection as OUT1 or OUT2) of the internal high sides is less than 2.0 V, which prevents any cross-conduction in the bridge. Low-Side Overcurrent Protection Unlike the high-side overcurrent circuitry, this overcurrent protection does not measure the current; rather, it measures the effect of current on the low-side power MOSFETs through a condition: VGS > 4.3 V and VDS > 1.0 V. When this set of conditions occurs for 3.0 µs typical (blanking time), both outputs OUT1 and OUT2 are tri-stated. The full bridge is tri- stated to prevent the motor running in case of short to VBAT. Once the fault is removed, the input INn of the OUTn that experienced the fault must be reset in order to recover normal mode operation. The 33486A can be used without the external low-side MOSFETs only if the overcurrent protection condition is not reached. If the external low-side power MOSFETs are not used, a 470 pF capacitor in parallel with a 100 k Ω resistor can be connected at the GLSn pin to prevent the activation of the low-side MOSFET overcurrent protection. As VGS and VDS are measured in respect to the 33486A ground terminal, it is essential that the low-side source is connected to this same ground in order to prevent false overcurrent detection due to ground shifts. Thermal Management The high-side block is assembled into a power surface mount package. This package offers high thermal performances and high current capabilities. It offers 10 terminals on each package side and one additional connection, which is the package heat sink (called terminal 21). The heatsink acts as the device power VBAT connection. The junction-to-case thermal resistance is 2.0 °C/W maximum. The junction-to-ambient thermal resistance is dependant on the mounting technology and if an additional heat sink is used. One of the most commonly used mounting technique consists of using the printed circuit board and the copper lines as heatsink. Figure 7 is an example of printed circuit board layout. It has a total of 10 cm2 additional copper on two sides (2.5 cm2 on the top side and 7.5 cm2 on the down side). Figure 7. Printed Board Layout Example (not to scale) With the above layout, thermal resistance junction-to- ambient of 25 °C/W can be achieved. This value is split into: •Junction to case (RθJC) = 2.0°C/W •Case to ambient (RθCA) = 23°C/W Lower value can be reached with the help of larger and thicker copper metal, higher number of thermal via from top to bottom side PCB, and the use of additional thermal via from the circuit board to the module case. Bottom-side PCB Top-side PCB 2.0 cm2 8.0 cm2 33486A External PCB (4 x 4 cm) Thermal via from top to down- side PCB |
Số phần tương tự - MC33486ADH |
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Mô tả tương tự - MC33486ADH |
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