A Brief on TPS7B81-Q1 Voltage Regulator

To get regulated voltages for sensitive electronic devices, linear voltage regulators are used. Low dropout regulators are also known as LDO. There are various types and categories of LDO available based on their operating input voltage ranges, quiescent current values and output current values. These are also available in different sizes. Voltage regulators are available as fixed voltages versions and Adjustable voltage versions where the output voltages can be adjusted for a voltage range using external feedback voltage divider resistors. Applications such as automotive battery-powered systems and Always-on systems require low and ultralow quiescent currents. For such applications, LDO such as TPS7B81-Q1 is used.

What is TPS7B81-Q1?

TPS7B81-Q1 is an ultralow quiescent current, low dropout voltage regulator. It can work with an input voltage of 40V. TPS7B81-Q1 has integrated fault protection circuits. This LDO is available in the various sizes and thermal conductivity. TPS7B81-Q1 is considered as an optimal solution for powering microcontrollers, control area network and local interconnect network due to its low quiescent current feature.

Block Diagram

Block diagram of TPS7B81-Q1
Block diagram of TPS7B81-Q1

Undervoltage Shutdown
To shut down the output when input voltages fall below an internal UVLO threshold, this device has an internal Undervoltage lockout circuit. During low input voltage conditions, this circuit prevents the device from locking into an unknown state.

Current Limit
A current limit circuit is provided to the device, to keep the device in a safe operating area when an overload or output shorting occurs. Current limit protection circuit also protects this IC from excessive power dissipation.

Thermal Shutdown
To protect LDO from overheating, a thermal shutdown circuit is provided. When the junction temperature exceeds the thermal shutdown trip point, this circuit shutdown’s the device. When the device cools down to a temperature below the thermal shutdown point this circuit turns on the output again.

Circuit Diagram of TPS7B81-Q1

Circuit Diagram of TPS7B81-Q1
Circuit Diagram of TPS7B81-Q1

Depending on the application requirements, external components such as capacitors with different values are used along with this LDO.Before beginning the design process input voltage range output voltage range and output current values has to be determined.


Input Capacitor

Usually, a 10-µF to a 22-µF capacitor is attached from IN pin to the ground. Input capacitor can improve transient response, input ripple rejection and PSRR of the device.

Output Capacitor
This LDO requires an output capacitor for stability. A capacitor in the range of 1µF to 200µF is preferred. The ESR range of the capacitor should be between 0.001Ω and 5Ω. To improve the load transient response, a ceramic capacitor with low ESR is selected.

Pin Configuration of TPS7B81-Q1

KVU Package of TPS7B81-Q1
KVU Package of TPS7B81-Q1

TPS7B81-Q1 is available in 8-pin HVSSOP DGN package, 6-pin WSON DRV package and 5-pin TO-252 KVU package.

DGN Package

  • Pin-1 is the input power supply pin IN. To minimize the input impedance and to get the best transient response an input capacitor is recommended. This capacitor is connected from IN pin to the ground and should be placed as close as possible to the output of the device.
  • Pin-2 is the Enable input pin EN. The device is turned on by driving this pin greater than the logic input high level of the device. TPS7B81-Q1 go into shutdown mode when the value at this pin is less than the logic-input low level.
  • Pin-3 and Pin-7 are not internally connected. Pin-4, 5, 6 are the ground reference pins GND. Pin-8 is the regulated output pin OUT. For stability, an output capacitor should be placed between OUT and ground. This capacitor should be placed as close as possible to the output of the device.

DRV Package

  • Pin-1 is the input pin IN.
  • Pin-2 is the enable pin EN.
  • Pin-3 and pin-4 are the ground reference GND.
  • Pin-5 is the DNC pin. It should not be connected to any bias voltage. This pin is either tied to ground or left floating.
  • Pin-6 is the output pin OUT. The functioning of the pin is similar to the pins of DGN package but their configuration changes.

KVU package

  • Pin-1 is the input pin IN. Pin-2 is the enable input pin EN.
  • Pin -3 and TAB are the ground reference GND. Pin-4 is the DNC pin. Pin-5 is the output pin OUT.
  • For improved thermal performance, the thermal pad of all the packages is connected to the ground GND.


TPS7B81-Q1 has following specifications-

  • TPS7B81-Q1 is an off –battery, ultra low IQ, low dropout regulator.
  • It has temperature grade 1 ranging from -400C to 1250C.
  • TPS7B81-Q1 has a wide input voltage range from 3-V to 40-V.
  • The maximum output current of this device is 150mA.
  • TPS7B81-Q1 has a low quiescent current of 300nA when the device is in shutdown mode.
  • For light loads typical quiescent current value is 2.7µA.
  • A maximum quiescent current of 4.5µA is obtained for light loads.
  • TPS7B81-Q1 has 1.5% of output-voltage accuracy over the line, load and temperature.
  • For a fixed 5V output version, TPS7B81-Q1 has a maximum dropout voltage of 525mV at 150-mA.
  • For stability ceramic output capacitor of value in the range of 1µF to 200µF with low ESR is used.
  • This IC is available in fixed voltage versions for 5V and 3.3V output voltages.
  • This LDO has fault protection circuits.
  • Thermal shutdown circuit, short-circuit and overcurrent protection circuit are also provided to TPS7B81-Q1.
  • TPS7B81-Q1 is available in the 3 types of packages- 8-pin DGN, 6-pin DRV, 5-Pin KVU packages.


Some of the areas where TPS7B81-Q1 is applied are as follows-

  • The cluster power supply uses TPS7B81-Q1.
  • A TPS7B81-Q1 voltage regulator is also present in body control modules.
  • TPS7B81-Q1 is an ideal choice for always-on battery-powered applications such as gateway applications, remote keyless entry systems.
  • TPS7B81-Q1 is used in powering MCU and CAN/LIN transceivers.

Alternative IC

IC’s that can be used as an alternative to TPS7B81-Q1 are TPS7A66, TPS7A69, TPS7B69 etc…

Low quiescent current is required to conserve energy and extend the battery lifetime of automotive battery-connected applications. To enable sustained operations when the vehicle ignition is off, ultralow quiescent current over an extended temperature range is required for Always-on systems.

As TPS7B81-Q1 meet all these requirements, it is considered an ideal choice for these applications. Further electrical characteristics can be found in the datasheet of Texas Instruments. Which of the features of TPS7B81-Q1 were useful for your application?

Image Resource: Texas Instrument