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MAX14870 Datasheet(PDF) 11 Page - Maxim Integrated Products |
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MAX14870 Datasheet(HTML) 11 Page - Maxim Integrated Products |
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11 / 15 page  Detailed Description The MAX14870/MAX14872 DC brushed motor drivers provide a low-power and flexible solution for driving and controlling brushed motors with voltages between 4.5V and 36V. Peak motor currents of up to 2.5A ensure large motor torque that is controllable by an external PWM signal and/or by autonomous internal current regulation. The MAX14870 has PWM and direction-control inputs, while the MAX14872 has forward and reverse inputs for direction control. See the MAX14870 Function Table and MAX14872 Function Table. Charge-pump-less design requires minimal external components and low supply current. Integrated current regulation allows limiting peak start- up motor currents. Shoot-through protection with a 140ns (typ) dead time ensures low operating current. Internal free-wheeling diodes absorb inductive motor cur- rents. The FAULT output signals thermal overload and overcurrents. Overcurrent Protection The MAX14870/MAX14872 are protected against shorts on M1/M2 to any voltage between VDD and GND, includ- ing shorts to GND, VDD, and between M1 and M2 via overcurrent limiting. When a current above 6A (typ) flows through M1 or M2 for longer than 1µs, an overcur- rent condition is detected and the H-bridge drivers are automatically disabled and the FAULT output asserts. If the overcurrent condition continues for longer than the overcurrent autoretry timeout (2ms (typ)) the MAX14870/ MAX14872 enters autoretry mode. In autoretry mode, the M1 and M2 outputs are re-enabled for 1µs (typ) and FAULT goes high-impedance. The drivers are disabled again and FAULT is re-asserted if the overcurrent condi- tion persists. PWM Control (MAX14870 Only) The PWM input is used for motor speed/torque control. Increasing or decreasing the duty cycle at PWM sets the effective (average) voltage across the motor terminals and allows first-order speed control. When PWM is logic-high, the motor is driven in the direc- tion defined by DIR. When PWM is logic-low, the bridge is in brake mode. In brake mode, the motor current continues flowing and recirculates through the low-side transistors of the H-bridge driver, due to its inductive impedance and back EMF. FWD/REV Control (MAX14872 only) The FWD input is used to drive the motor forward/turn a relay on. The REV input reverses the M1 and M2 polarity, to drive the motor in reverse/turn a relay off. FWD/REV control can be optionally used to implement either bipolar motor control (with both M1 and M2 switch- ing) or unipolar control, where only M1 or M2 switches. Slope Control The MAX14871 drivers turn-on and turn-off with active slope-control during the M1/M2 transition times. The integrated slew rate-limiting reduces EMC (like conducted and radiated EMI) associated with high di/dt rates. Thermal Shutdown The MAX14870/MAX14872 include integrated protection against thermal overload. When the junction temperature exceeds 160°C (typ), the H-bridge is three-stated, M1 and M2 are disabled, and FAULT is asserted. If the motor was spinning before thermal shutdown occurred, the motor’s inductance will push current through the internal M1 and M2 diodes, forcing the motor into fast decay, with a voltage across its terminals of VDD. M1 and M2 are automatically reenabled when the junction temperature falls to 150°C (typ). Current Sensing Connect a sense resistor (RSENSE) between COM and GND to monitor the motor current during operation. Select RSENSE such that the voltage at COM created by motor current flowing through the sense resistor is limited to within 250mV relative to GND (-250mV ≤ VCOM ≤ +250mV). Minimize series trace resistance from RSENSE to GND to minimize voltage sense errors due to parasitic trace interconnect resistance. Use a star ground connection between the MAX14870/MAX14872 GND pins and the GND-side of RSENSE. Connect the voltage sense close to the RSENSE resistor and/or use differential voltage sensing. See Figure 4. MAX14870/MAX14872 Compact 4.5V to 36V Full-Bridge DC Motor Drivers www.maximintegrated.com Maxim Integrated │ 11 |
Similar Part No. - MAX14870_15 |
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Similar Description - MAX14870_15 |
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