TI’s Newest LDO Linear Voltage Regulator Boasts Sub-25 nA IQ for Power-Sensitive ApplicationsSeptember 23, 2019 by Gary Elinoff
Texas Instruments’ TPS7A02 low-dropout linear regulator combines ultra-low IQ with fast transient response.
TI’s TPS7A02 quiescent current of less than 25 nA is said by the company to be the lowest in the industry and only one-tenth that of competing ultra-small devices. Its fast transient response, claimed to be best-in-class, provides for faster wake-up times, improving application response times and dynamic performance.
Texas Instruments is presenting the TPS7A02 as suitable for "power-sensitive" devices. Image modified from Texas Instruments
The TPS7A02 works with an input voltage range of 1.5 to 6.0 V and has an output range of 0.8 V to 5.0 V available in 50-mV steps. The dropout voltage is 0.205 volts, maximum. The device can source up to 200 mA, and can settle in under 5 us for 1-to-50-mA load transients, which TI claims to be half the time of competing devices. The TPS7A02 also sports a shutdown current of 3 nA.
The device is available in a 1.0-mm × 1.0-mm X2SON package. The tiny footprint enables engineers to design smaller, lighter, more efficient products by effectively reducing the necessary power-supply size.
The Difference Between Quiescent Current and Shutdown Current
This can be a point of confusion. As TI’s Wilson Fwu explains in his blog, "Quiescent is defined as 'a state or period of inactivity or dormancy.' Thus, quiescent current, or IQ, is the current drawn by a system in standby mode with light or no load."
According to Fwu, if you've mistaken quiescent current with shutdown current, you are not alone. These two concepts are often conflated. Shutdown current, in comparison to quiescent current, is the current drawn when a system is turned completely off but is still connected to a battery. Though different, both specifications are important when designing low-power applications with battery systems.
Block diagram for the TPS7A02: Image from Texas Instruments
The TPS7A02’s exceptionally low IQ provides for longer battery life for applications employing lithium-ion batteries, while the ultra low shutdown current can greatly extend battery shelf life in portable medical and wearable applications.
No Additional Circuitry Required
The TPS7A02 automatically transitions from its power-saving, low-load state to its full-output state without the need for any additional circuitry or components. Thus, designers can use the device to shrink the solution size by as much as 70%, freeing up board space, saving on the parts count, simplifying the manufacturing process and increasing overall system reliability.
Applications that May Require the "Rapid Wake-Up" Feature
The device’s fast 5 µs settling time enables it to quickly respond to rapidly changing loads while providing minimal variation in output voltage. This is important in applications that spend much of their time in “sleep” mode, but must nonetheless be able to quickly “wake up.”
- Portable medical equipment
- Thermostats, smoke detectors, and heat detectors
- Smart meters
- Wireless IoT
- Building security and surveillance systems
Eval Kit for Faster Time to Market
To help engineers to more quickly finish their designers, TI offers the MULTIPKGLDOEVM-823 evaluation module.
The MULTIPKGLDOEVM-823 evaluation module. Image from TI.
Options for LDO Linear Voltage Regulators
Many manufacturers offer LDO linear voltage regulators, and many manufacturers offer a wide range of products.
The LDBL20 from STMicroelectronics is a 200 mA LDO in a 0.47 mm x 0.47 mm package. The input voltage can range from 1.5 to 5.5 V, with output voltages available on request from 0.8 V up to 5.0 V in 50 mV steps.
The NCP716B from On Semiconductors is aimed at portable devices with requirements for low standby current. It can work with input voltages of up to 24 volts, and can provide a fixed output ranging from 1.5 volts to 5.0 volts.
Do you develop devices that require rapid "wake up" capabilities? Share your thoughts about designing around this specification in the comments below.