One particularly difficult rail to optimize is the negative voltage rail. Even more challenging is when this power rail is used solely as a bias supply for operational amplifiers or other basic circuitry and consumes very little power. The already limited options for creating a negative voltage rail put pressure on the focus on small size, high efficiency, and good output voltage regulation in systems designed for small size, high efficiency, and good output voltage regulation. For example, a negative voltage charge pump might be less efficient than the battery-powered sensor required under very light loads. However, dedicated inverting buck-boost converters add another IC to the bill of materials (BOM), along with its inductors and other passive components required for operation. This results in a disproportionate increase in the BOM compared to the output power on the negative rail.
Fortunately, many Texas Instruments (TI) wide-input-voltage buck converters are available for inverting buck-boost configurations. Since the same IC can be used as both a buck and an inverting buck-boost converter, and uses the same passive components, the BOM is significantly simplified. The TPS621xx wide-input-voltage, low-power buck converters are specifically optimized for high efficiency under light load currents. For example, the TPS62120's 11 µA Iq and the TPS62175's 4.8 µA Iq achieve over 70% efficiency in inverting topologies even with load currents below 1 mA. Furthermore, the DCS-Control architecture used in the latest TPS621xx devices provides excellent output voltage regulation compared to other topologies. These devices measure 2mm x 2mm and 2mm x 3mm respectively, which will not take up too much board space, and their high integration and support for application specifications, such as “using TPS62120 in inverting buck-boost topology” and “using TPS62175 in inverting topology” (SLVA478 and SLVA542), will certainly simplify system integration.
The TPS6212x is a high-efficiency synchronous buck DC-DC converter optimized for low-power applications. It supports up to 75 mA of output current and allows the use of small external inductors and capacitors. A wide operating input voltage range of 2V to 15V supports energy harvesting, battery power, and 9-V or 12-V line-powered applications. The inverter employs an advanced hysteresis control scheme, providing energy-saving mode operation. Under optical loads, the converter operates in Pulse Frequency Modulation (PFM) mode and automatically switches to Pulse Width Modulation (PWM) mode under higher load currents. The power-saving mode maintains high efficiency across the entire load current range. In PFM mode, low output ripple voltage is optimized to minimize output noise. In PFM mode, the device consumes only VIN10µA of quiescent current. In shutdown mode, the device is turned off.
The TPS62120 has good open-drain power output, meaning that once the output voltage is regulated...
The TPS62120 has an additional SGND pin, which is connected to GND in shutdown mode. This output can be used to discharge the output capacitor.
The TPS6212x can operate in a free temperature range from -40°C to 85°C. The TPS62120 comes in a small 8-pin SOT-23 package, while the TPS62122 comes in a 2mm x 2mm 6-pin DFN package.
The TPS62175/7 is a high-efficiency synchronous buck DC-DC converter based on a distributed control system (DCS) controlled buck converter topology.
With a wide operating input voltage of 4.75V to 28V, this device is ideal for systems powered by multiple lithium-ion batteries and 12V and higher impedance power rails, providing up to 500mA of output current.
The TPS62175/7 automatically enters power-saving mode under light loads to maintain high efficiency across the entire load range. Additionally, it features a sleep mode for applications with advanced power-saving modes, such as ultra-low-power microcontrollers. The power normal output can be used for power sequencing and/or power-on reset.
This device has a typical quiescent current of 22uA in normal mode and 4.8uA in sleep mode. In sleep mode, efficiency at very low load currents can be increased by as much as 20%. In shutdown mode, the shutdown current is less than 2uA and the output is actively discharged.
The TPS62175/7, available in adjustable and fixed output voltage versions, is housed in a small 2mm x 3mm 10-pin WSON package.
• Distributed Control System (DCS) - Buck Converter Topology Technology for Control
• Input voltage range 4.75V to 28V
• Typical quiescent current 4.8µA (sleep mode)
• 100% duty cycle mode
• Active output discharge
• Power supply is outputting normally
• 500mA output current
• Output voltage range is 1V to 6V
• Typical switching frequency of 1MHz
Seamless power-saving mode switching
• Undervoltage lockout
Short circuit protection
• Overheat protection
• Utilizes a 2mm x 3mm 10-lead wafer-level small outline no-lead (WSON) package.
