TPS7A11 Low Dropout Voltage Regulator

Many of the portable equipment we use today, are battery-powered. Voltage regulators play a crucial role in such devices. With the increase in the demand of voltage regulators for very sensitive applications which requires very low voltages for their operation, lead to an increase in the demand of LDO IC’s. Low Dropout voltage regulators can regulate small voltages which are in mV. They usually operate around the input voltage of 200mV to 500mV. An efficient small size solution for power supply in portable electronics is needed. They should also have low input and low output requirements. One of the LDO’s with such characteristics is TPS7A11.

What is TPS7A11 IC?

TPS7A11 is a low dropout voltage regulator. It is available as ultra-small, low quiescent current IC. This IC can be connected to the power supply as low as 140 mV above the output voltage.

With the use of V_BIAS  rail, which powers the internal circuitry of the device, TPS7A11 can support very low input voltages. These characteristics make TPS7A11 an ideal choice for battery-powered applications.

Block Diagram

Excellent Transient Response

Due to devices high input impedance and low output impedance, TPS7A11 responds quickly to a transient on input supply and output current.

This feature also gives the device the capability of a high power supply rejection ratio and low internal noise floor. TPS7A11 has excellent load and line transients.

Global Undervoltage Lockout

This IC has two Undervoltage lockout circuits. One on BIAS pin and the other on the IN pin. This circuit prevents TPS7A11 from turning ON before either BIAS or IN voltages rise above their lockout voltages.

These two UVLO signals are internally connected through an AND gate. Thus if either of these signals is below the lockout voltage the device gets Turned OFF.

Active Discharge

In order to actively discharge the output voltage, the active discharge option has an internal pulldown MOSFET. This MOSFET connects a 120Ω resistor to the ground when the device is disabled. This circuit is activated when the enable pin is low or when the device is in thermal shutdown mode.

Internal Foldback Current Limit

This circuit is used to protect TPS7A11 from high-load current faults or voltage shorting events.

Thermal Shutdown

When the thermal junction temperature of the device rises to the thermal shutdown temperature, this circuit disables the device. When the temperature falls below the shutdown temperature, thermal shutdown hysteresis ensures that the LDO resets again.

TPS7A11 operates in three functional modes – Normal operation, Dropout operation, and disabled mode. In Dropout mode, the device is not in regulation and the output voltage is the value equal to the input voltage minus voltage drop across the pass element of the device. In Disabled mode, the device is turned OFF.

Circuit Diagram

Based on the application requirement, external components are required along with TPS7A11 IC.

Capacitor Types

TPS7A11 requires capacitors at input, output and bias pins for stability. Mostly ceramic capacitors are recommended. Multilayer ceramic capacitors should be used with care.

Input-Output Capacitor Requirements

The minimum input capacitor required for TPS7A11 is 2.2 µF. The minimum value for the output capacitor is 2.2µF and maximum value is 22µF. Value of bias capacitor should be 0.1µF.

Pin Configuration of TPS7A11

TPS7A11 is available as a 2.00 mm X 2.00 mm WSON, 6-pin DRV package and an ultra-small 0.74mm X 1.09mm, 5-pin DSBGA( YKA) package.

DRV Package

For this package, it is recommended to connect the thermal pad to ground.

• Pin- 1 is the regulated output pin OUT. For stability, a capacitor is required to be connected from OUT to ground. For good transient values, the ceramic capacitors are used, which are placed close to the output pin of the device.
• Pin-2 is the NC pin which is not connected internally. This pin can be left as floating or can be connected to ground for good thermal dissipation.
• Pin-3 is the enable pin EN. To enable the device this pin is raised high and by making the pin low the device can be disabled. If enable functionality is required, this pin can be connected to IN or BIAS pin, but under the condition that the voltages at the IN pin is greater than 0.9V.
• Pin-4 is the bias pin BIAS. Low-input voltage and low-output voltage conditions enable using this pin. For best performance, a capacitor should be connected from this pin to ground.
• Pin-5 is the ground pin GND.
• Pin-6 is the input pin IN. From stability, a capacitor should be connected from this input pin to the ground. This capacitor should be placed close to the IN pin.

5-Pin DSBGA –YKA Package

For this package, the functioning of the Pin is the same as the above DRV package.

• A1 is the input pin IN.
• A3 is the output pin OUT.
• B2 is the ground pin GND.
• C1 is the bias pin BIAS.
• C3 is the enable pin EN.

Specifications of TPS7A11

Specifications of TPS7A11 are as follows-

• TPS7A11 has an ultra-low voltage range from 0.75V to 3.3V.
• This IC is available as DRV and YKA packages.
• For DRV package at 500-mA, the ultra-low dropout for minimum power loss is 140mV.
• For YKA package the ultra-low dropout is 110mV.
• Low quiescent current for V_IN is 1.6 µA.
• For V_BIAS IQ is 6 µA.
• Load, line and temperature have 1.5% accuracy.
• This IC has a high PSRR of 64dB at 1 kHz.
• TPS7A11 has an active output discharge.
• This Voltage regulator is available for fixed voltage ranging from 0.5V to 3V.
• The range for V_BIAS is from 1.7V to 5.5V.
• Recommended operating junction temperature of TPS7A11 is from -400C to 1250C.
• Output voltage drawn from this IC at the operating junction temperature conditions is from a minimum of 0.5V to a maximum of 3V.
• A bias capacitor of 0.1 µF is used along with the IC.
• Maximum ESR must be lower than 250mΩ when operating at junction temperature conditions.

Applications

Applications of TPS7A11 voltage regulator are as follows-

• These are used to supply power to the lower core voltages of modern microcontrollers and sensors.
• These are used in smartwatches and fitness trackers.
  Wireless headphones and Earbuds also make use of this voltage regulator.
• This voltage regulator can be found in camera modules.
  Portable medical devices, Smartphones, tablets, solid-state devices make use of TPS7A11 voltage regulator.

Alternative IC

The IC that can be used as an alternative to TPS7A11 is TPS7A26.

Because of its low input voltage and low output voltage requirements, TPS7A11 has become an ideal choice for battery-powered noise-sensitive portable electronics. Although traditional LDO’s have lower input and low output characteristics, their efficiency is low.

TPS7A11 uses bias rail to operate at lower input voltage, thereby reducing the power dissipation across the die. Further specification of this voltage regulator can be found in the datasheet of Texas Instrumentation. For which of your application was TPS7A11 useful? What are the capacitor values you used in the circuit?

Image Resource: Texas Instruments