BD622X Series H Bridge Motor Driver

The BD622X series of circuits is the latest in Rohm Microelectronics' Intelligent PWM DC brush motor driver ICs, offering high-efficiency PWM H-bridge drive capabilities. This series includes six models: BD6220, BD6221, BD6222, BD6225, BD6226, and BD6227. Among them, BD6226/1/2 are single-channel drivers, while BD6225/6/7 are dual-channel drivers. The BD622X series is known for its excellent dynamic performance and comprehensive protection features, making it ideal for a wide range of applications such as DVD recorders, digital cameras, and video cameras. In this article, we'll take the BD6222 as an example to explore its characteristics and working principles. ### 1. Internal Structure and Features The BD6222 offers several key performance features: - **Speed Setting Voltage to PWM Conversion**: It automatically converts speed setting voltage into PWM signals. - **Adjustable PWM Frequency**: Ranges from 20kHz to 100kHz. - **Low Standby Power Consumption**: Zero current when the motor is stopped. - **Built-in Current Protection Circuit**: Prevents misoperation during standby. - **Low On-State Resistance (RON)**: Typically 1.5Ω. - **PWM Input via Control Terminal**: Flexible control options. - **Wide Operating Voltage Range**: 6V to 15V, with a maximum limit of 18V. - **VREF Input Range**: 3V to 15V. - **High Drive Current Capability**: Up to 2.0A. - **Integrated Protection Circuits**: Includes overcurrent, overvoltage, overtemperature, and under-voltage lockout. - **Extended Operating Temperature Range**: -40°C to +85°C. The BD6222 comes in a 25-pin HSOP package, as shown in the diagram. The chip integrates various components such as a PWM controller, logic control circuit, temperature protection, current/voltage protection, under-voltage lockout, MOSFET driver, and power MOSFETs. The internal block diagram and typical application circuit are illustrated below. Each pin has a specific function: - **Pin 1 & 2 (OUT1)**: Motor drive terminal 1. - **Pin 6 (GND)**: Control ground. - **Pins 7 & 8 (GND)**: Power ground. - **Pins 12 & 13 (OUT2)**: Motor drive terminal 2. - **Pin 17 (VREF)**: Speed setting voltage input. - **Pin 19 (RIN)**: Reverse signal input. - **Pin 20 (FIN)**: Forward rotation signal input. - **Pin 21 (VCC)**: Control power supply input. - **Pins 22 & 23**: Power supply input for the driver section. - **Pin 24 (FIN)**: Heat sink pin, should be grounded and connected to a large copper area on the PCB for better heat dissipation. ### 2. Application Circuit and Working Principle The figure above shows the BD6222 pinout and typical application circuit. The BD6222 supports four operating modes: forward rotation, reverse rotation, brake, and standby. These modes are controlled using the VREF, FIN, and RIN pins. #### 2.1 Motor Control Modes - **Standby Mode**: Activated by setting the VREF pin to a low level, with both FIN and RIN at low. In this mode, the internal circuitry, including the output MOSFETs, is turned off. The system automatically enters idle mode when switching from active to standby. - **Forward Mode**: When OUT1 is high and OUT2 is low, the motor rotates forward. This requires the FIN pin to be high, RIN low, and VREF set to VCC. - **Reverse Mode**: When OUT1 is low and OUT2 is high, the motor rotates in reverse. This requires the FIN pin to be low, RIN high, and VREF set to VCC. - **Brake Mode**: Used for quick motor stop, but not recommended for regular use due to high power consumption. Instead, the standby mode is preferred for energy efficiency. Additionally, the FIN and RIN signals can be used independently to control the motor state, with frequencies ranging from 20kHz to 100kHz. #### 2.2 Motor Speed Control The BD6222 automatically adjusts the PWM duty cycle based on the VREF voltage, which acts as the speed-setting input. The duty cycle is calculated as: **Duty Cycle = (VREF / VCC) × 100%** For example, if VCC = 12V and VREF = 9V, the duty cycle is approximately 75%. The PWM frequency typically ranges from 20kHz to 35kHz (with a typical value of 25kHz). As shown in the graph, there's a linear relationship between the VREF voltage and the PWM duty cycle. When VREF equals VCC, the motor runs at full speed. This makes the BD6222 a versatile and efficient solution for controlling DC brush motors in various applications.

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