www.ti.com

Technical Article

How to Choose the Right LDO for Your Satellite
Application

Sree Alvarado
Radiation-hardened low-dropout regulators (LDOs) are vital power components of many space-grade
subsystems, including field-programmable gate arrays (FPGAs), data converters and analog circuitry. LDOs
help ensure a stable, low-noise and low-ripple supply of power for components whose performance depends ona clean input.
But with so many LDOs available on the market, how do you choose the right radiation-hardened device for yoursubsystem? Let’s look at some design specifications and device features to help you with this decision.
Dropout Voltage for Space-grade LDOs
An LDO’s dropout voltage is the voltage differential between the input and output voltage, at which point theLDO ceases to regulate the output voltage. The smaller the dropout voltage specification, the lower the operating
voltage differential one is able to operate with, which results in less power and thermal dissipation as well as
inherently higher maximum efficiency. These benefits become more significant at higher currents, as expressedby Equation 1:
LDO power dissipation = (VIN-VOUT)xIOUT(1)

In the radiation-hardened market, it can be difficult to find truly low dropout regulators that offer strong
performance over radiation, temperature and aging. TI’s radiation-hardened LDO, the TPS7H1101A-SP, is one
example, offering a typical dropout voltage (Vdo) of 210 mV at 3 A – currently, the lowest on the market. If you
have a standard 5-V, 3.3-V, 2.5-V or 1.8-V rail available, this LDO can regulate output voltages down to 0.8
V to supply any required voltage, as well as the current needed for one or more space-grade analog-to-digitalconverters (ADCs) or clocks.
Noise Performance for Space LDOs
With satellites in space for 10 or more years, getting the maximum performance out of the onboard integrated
circuits helps ensure design longevity. In order to provide a clean, low-noise rail for high-performance clocks,
data converters, digital signal processors or analog components, the internal noise generated by the LDO’s
circuitry needs to be minimal. Since it is not easy to filter internally generated 1/f noise, look for LDOs withinherent low-noise characteristics. Lower-frequency noise is often the largest and most difficult to filter out. The
TPS7H1101A-SP offers one of the lowest 1/f noise levels, with a peak around 1 µV/√Hz at 10 Hz. See Figure 1
below for RMS noise over frequency.

SSZT176 – APRIL 2021
Submit Document Feedback

How to Choose the Right LDO for Your Satellite Application
Copyright © 2023 Texas Instruments Incorporated1

www.ti.com

Figure 1. TPS7H1101A-sp Noise
PSRR for Space LDOs
The power-supply rejection ratio (PSRR) is a measure of how well an LDO can clean up, or reject, incoming
noise from other components upstream. For higher-end ADCs, the input supply noise requirements continue toget tighter to minimize bit errors. At higher frequencies, it is difficult to have high PSRR given the characteristicsof the control loop. Often, designers need to use external components to filter the noise to reach an acceptableeffective PSRR, which increases solution size – an obvious issue for space applications, where size and weighttie directly to satellite launch costs. The PSRR is most important at the switching frequency of the upstream
supply (since there is a voltage ripple at this frequency). Additionally, PSRR is important above this frequency
because of the switching harmonics. If you’re looking for good PSRR, the TPS7A4501-SP LDO offers a PSRR ofover 45 dB at 100 kHz.
Other Important LDO Features
Outside of dropout voltage, PSRR and noise, let’s look at several smart features that can be integral to theperformance of a radiation-hardened LDO.
••••

Enable. In space, there is only a set amount of power available from the solar panel, from which many
functions need to run. The enable feature allows you to specify whether the LDO should be on or off at any
given time, and proves critical for overall savings in a power budget. The enable pin is also important for
power-up sequencing, which is of increasing need in newer-generation FPGAs.
Soft start. A voltage that rises too quickly can cause current overshoot or an excessive peak inrush current,
damaging downstream components such as the FPGA or ADC. The soft-start feature regulates how quickly
the output voltage rises at startup. Soft start also prevents a level of voltage droop that could be unacceptableby preventing an overcurrent draw on the upstream supply.
Output voltage accuracy. Often, newer space-grade FPGAs such as the Xilinx KU060 have strict inputvoltage tolerance requirements on each rail to enable their best performance. To ensure that your design
meets strict accuracy requirements over radiation exposure and end-of-life conditions, look for devices likethe TPS7H1101A-SP, which is on the KU060 development board.
Size. Other than having a small, easy-to-layout package, other ways to reduce solution size include limiting
the number of external components to the LDO; having more integrated features, better PSRR and noisespecifications; and more reliable radiation performance under single-event effects. TI’s TPS7A4501-SP is oneof the industry’s smallest radiation-hardened LDOs, both in package size, layout and solution size.

Conclusion
With so many options available, it can be difficult to pick the right LDO. Consider which capabilities and features
are the most important. For example, if your application is powering a high-end FPGA or high-speed data2

How to Choose the Right LDO for Your Satellite Application
Copyright © 2023 Texas Instruments Incorporated

SSZT176 – APRIL 2021
Submit Document Feedback

www.ti.com

converter, features like output-voltage accuracy, reference accuracy, PSRR and noise might be the priorities. If,
however, you are designing a low-performance analog circuit or working with an older FPGA where tolerance
requirements are not so stringent, having the smallest-sized, lowest-cost solution while retaining good-enoughcapability might be the better option.
Additional Resources• Read the white paper, “Powering a New Era of High-Performance Space-Grade Xilinx FPGAs.”• Download the TI Space Products Guide.
• Download the Radiation Handbook for Electronics.

SSZT176 – APRIL 2021
Submit Document Feedback

How to Choose the Right LDO for Your Satellite Application
Copyright © 2023 Texas Instruments Incorporated3

IMPORTANT NOTICE AND DISCLAIMER
TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATA SHEETS), DESIGN RESOURCES (INCLUDING REFERENCEDESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”
AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANYIMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRDPARTY INTELLECTUAL PROPERTY RIGHTS.
These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate
TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicablestandards, and any other safety, security, regulatory or other requirements.
These resources are subject to change without notice. TI grants you permission to use these resources only for development of an
application that uses the TI products described in the resource. Other reproduction and display of these resources is prohibited. No license
is granted to any other TI intellectual property right or to any third party intellectual property right. TI disclaims responsibility for, and you
will fully indemnify TI and its representatives against, any claims, damages, costs, losses, and liabilities arising out of your use of theseresources.
TI’s products are provided subject to TI’s Terms of Sale or other applicable terms available either on ti.com or provided in conjunction withsuch TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicable warranties or warranty disclaimers for
TI products.
TI objects to and rejects any additional or different terms you may have proposed. IMPORTANT NOTICE
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2023, Texas Instruments Incorporated