One of the key challenges faced by mobile robot platforms is their power supply. Except for a few specialized systems, batteries—whether dry or rechargeable—are the predominant electrical power sources for robots. In the case of zBot, its power supply system comprises two components: the primary accumulator and the auxiliary battery. The main power source is created using a NiCd or NiMH battery pack, customized to fit the Tamya chassis battery holder (consisting of six 1.2V/1400 mAh C cells). This primary power source is utilized for driving DC motors and operating the servos.
Voltage Default Setting and Regulation
In the absence of a connection to pin 4, the output voltage defaults to its lowest value. Focusing on the two positive-output regulators, the -W variant requires VMIN and Rp values of 2.5 V and 6.49 kΩ respectively. For the -H model, these values should be 11.824 V and 6.65 kΩ. It’s important to note that for the regulator to maintain proper regulation, the input voltage must exceed the output voltage by a specific minimum differential voltage.
Pulse Width Modulation Range and Input Voltage Range
Another crucial factor to consider is the pulse width modulation (PWM) range of the regulator’s internal control circuit. To ensure stable operation, the duty cycle should not fall below a certain minimum percentage. This constraint defines the maximum advisable ratio between the input and output voltage magnitudes of the regulator. For optimal performance, the PTN78060x’s operating input voltage range must meet the following criteria:
- For PTN78060W devices delivering output voltages lower than 10 V, the minimum input voltage is either (V0+2 V) or 7 V, whichever is higher.
Texas Instruments PTN78060 Integrated Switching Regulator
The Texas Instruments PTN78060 Integrated Switching Regulator (ISR) offers efficient step-down voltage conversion capabilities, accommodating loads of up to 3A. The PTN78060W variant allows adjustment to any voltage within the output range of 2.5V to 12.6V. While the PTN78060H version can be set within the output range of 11.85V to 22V.