IQ - What it is, what it isn’t, and how to use it

Oct 3, 2026

Quiescent current (IQ) is an essential but frequently misapplied parameter for low-power, energy-efficient designs. The article defines IQ for Texas Instruments power devices, explains how it is measured under no-load, nonswitching, yet enabled conditions, and clarifies what IQ does not represent. It also connects IQ to VIN/VOUT sources, discusses why IQ is an IC-only measurement versus system behavior, and highlights design and measurement considerations to avoid common errors, applicable to multiple TI TPS61xxx/TPS62xxx/TPS63xxx/TPS650xx families.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages7

Reading Time18 min

AccessFree to download

Introduction

What IQ is

What IQ isn’t

Power Management Texas Instruments Incorporated IQ: What it is, what it isn’t, and how to use it By Chris Glaser Applications Engineer Introduction A device’s quiescent current, or IQ , is an important yet often misused parameter for low-power, energy-efficient designs. In many battery-powered applications, such as metering, wearables, building security and the Internet of Things (IoT), the current drawn from the battery in a standby condition with light or no load defines the total run time of the system. In integrated switch converters, the IQ is only one portion of this battery current. This article defines IQ and how it is measured, explains what IQ is not and how it should not be used, and gives design considerations on how to use IQ while avoiding common measurement errors. This article applies to any of the Texas Instruments (TI) TPS61xxx, TPS62xxx, TPS63xxx, or TPS650xx devices. What IQ is Unless otherwise noted in the datasheet for a part, IQ is defined as the current drawn by the IC in a no-load and nonswitching but enabled condition.“No load” means that no current leaves the IC to the output. Typically, this would be current leaving via the SW pin on buck converters or via the VOUT pin on boost converters. All of the IQ simply travels inside the IC to ground.“Nonswitching” means that no power switch in the IC is on (closed) . This includes the main or control switch as well as the synchronous rectifier if both are integrated into the IC. In other words, the IC isin a high-impedance condition with a power stage that is completely disconnected from the output (except for integrated MOSFET body diodes on some devices that cannot be turned off) .“Enabled” means that the IC is turned on via its EN pin and is not in a UVLO or other shutdown condition. IQ measures operating current, not shutdown current, so the device must be on. Lastly, IQ is meaningful only in power-save mode, so if this mode is an option for the particular device, it must be enabled. If the device runs in pulse-width-modulation (PWM) mode, then the input current to the power stage and switching losses more than dwarfs the miniscule amount of current, the IQ , required to run the device. IQ fundamentally comes from two inputs: VIN and VOUT. The datasheet lists whether the IQ comes from either or both pins. Figure 1 shows the IQ specification from the datasheet for the TI TPS61220/21/22,1 which are boost converters that draw their IQ from both VIN and VOUT. Typically, a buck converter draws IQ only from its input, while a boost converter or buck-boost converter draws IQ from both the input and the output. IQ measures the current required to operate the device’s basic functionality, which includes powering things like the internal precision reference voltage, an oscillator, a thermal shutdown or UVLO circuit, the device’s state machine or other logic gates, etc. IQ does not include any input current to the power stage or gate drivers, as it is measured in anonswitching condition where these currents are zero. The reason for measuring IQ in this condition is that it is solely dependent on the IC, whereas the power-stage input current and gate-drive current are dependent on the selected external components, which in most cases dictate how often the IC switches in its power-save mode. Thus, IQ isan IC measurement, whereas including the other two currents is a system measurement. TI does not control and cannot guarantee such a system measurement but does control and can specify an IC measurement. In fact, TI guarantees the IQ specification and, for devices whose datasheets specify a maximum value for the IQ , tests it on each and every device that is produced. This is done by enabling the device, setting it to the test conditions specified in its datasheet, and then artificially raising (with externally applied voltages) the output voltage, FB pin, and any other pin voltages high enough to cause the IC not to switch. With no load and power-

FAQs

What does IQ mean in low-power device design?

IQ is the current drawn by the IC in a no-load, nonswitching but enabled condition, and it is important for estimating battery standby runtime.

How is IQ measured according to the article’s definition?

The device must be enabled, in power-save mode, with no load and no switching; under these conditions, the input current to the IC becomes the IQ used for specification.

Why is IQ not the same as no-load input current?

No-load input current can include switching activity needed to regulate the output, whereas IQ is defined specifically for a nonswitching condition where current to the power stage and gate drivers are effectively zero.

Oct 3, 2026

Upload by Taylor Morgan