Accurate current detection and fast short-circuit protection-TLV9062 helps the development of sweeping robots

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Accurate current detection and fast short-circuit protection-TLV9062 helps the development of sweeping robots [Copy link]

 With the accelerated pace of urban life and the continuous improvement of the quality of life, sweeping robots have become the new favorite of young urban white-collar workers. Sweeping robots are usually composed of a host, a dust box, a remote control, a charging station, etc. Sweeping robots can not only complete trivial sweeping tasks, but also automatically recharge. They are usually powered by a 20V adapter and 4 lithium batteries in series. Lithium battery charging management can be divided into integrated solutions and discrete solutions. The integrated solution usually uses BQ24610 or BQ24773 (SMBUS/I2C interface), with ±0.5% charging voltage and ±2% charging current accuracy, with power path management to stabilize the system voltage at the battery voltage, and support system instant startup operation when there is no battery or the battery is deeply discharged. The discrete solution is usually composed of MCU, MOS and op amp (as shown in Figure 1). The MCU samples the battery charging voltage and charging current in real time, and the charging cutoff current is usually 1/5~1/10 of the charging current. The ordinary op amp has a large input offset bias voltage (~3mV), which makes the charging current sampling accuracy low. For example, for a 10mR current detection resistor at 1A and 0.2A charging, the measurement error caused by the op amp is as high as 30% and 150%, while the error is only 3% and 15% when TLV9062 is used as the pre-stage op amp. TLV9062 is a dual-channel low-voltage 5V amplifier with a 300uV input offset, which is particularly suitable for high-precision current detection pre-stage amplification, and has rail-to-rail input and output swing capabilities. In addition, TLV9062 can also be used as a voltage feedback pre-stage buffer. A larger resistance divider resistor can be selected for the 0.5pA input leakage current to reduce the system standby power consumption.

Figure 1 TLV9062 for Lithium Battery Charging Management of Sweeping Robots

The quality of the roller determines the ability of the sweeping robot to climb and overcome obstacles. The stronger the roller power, the more efficient the shuttle ability of the sweeping robot. Considering that the roller may be overloaded or stalled in actual applications, the MCU needs to sample the roller motor current in real time and take corresponding protective actions. TLV9062 is also suitable for DC motor current preamplification, as shown in Figure 2. The 10M unit gain bandwidth allows designers to obtain smaller signal delay and distortion.

Figure 2 TLV9062 for DC motor current preamplification

At present, most of the side brush motor drivers of sweepers use a single MOS tube PWM drive method. When too much hair is wrapped around the side brush, the side brush motor will inevitably stall, and in severe cases, the motor may burn out. The circuit in Figure 3 uses TLV9062 as the motor current preamplifier, which is sent to the ADC for sampling and monitoring current. The post-stage uses TLV9062 as a comparator. When the motor stalls, the MOS tube is quickly turned off to protect the side brush system. This circuit is a comparator without hysteresis. TLV9062 can also be designed as a comparator with hysteresis. For details, please refer to the application manual SOBA219.

Figure 3 TLV9062 for DC motor stall protection

Take a closer look at the detailed introduction of TLV9062 Description TLV9061 (single channel), TLV9062 (dual channel) and TLV9064 (quad channel) are single, dual and quad low voltage (1.8V to 5.5V) operational amplifiers with rail-to-rail input and output swing capabilities. These devices are cost-effective solutions for applications that require low operating voltage, small package size and high capacitive load driving capability. Although the capacitive load driving capability of TLV906x is 100pF, the resistive open-loop output impedance makes it easier to achieve stability under higher capacitive loads. These op amps are designed for low voltage operation (1.8 V to 5.5 V) and have performance specifications similar to the OPAx316 and TLVx316 devices. The TLV900x devices have a shutdown mode that allows the amplifier to switch to a standby mode with a typical current consumption of less than 1 μA. The TLV906xS family helps simplify system design because it is unity-gain stable, has integrated RFI and EMI suppression filters, and does not exhibit phase reversal under overdrive conditions. Features Rail-to-rail input and output Low input offset voltage: ±0.3mV Unity-gain bandwidth: 10MHz Low broadband noise: 10nV/√Hz Low input bias current: 0.5pA Low quiescent current: 538μA Unity-gain stable Internal radio frequency interference (RFI) and electromagnetic interference (EMI) filters Operates with supply voltages as low as 1.8V Resistive open-loop output impedance makes it easier to achieve stability with higher capacitive loads Shutdown version: TLV906xS Extended temperature range: –40°C to +125°C Functional Block Diagram

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