TPS732XX -Specifications and Circuit Diagram

Voltage regulators are used for generating a constant output current value. Op-amps can also provide the same functionality but they are not useful for high output current values. Linear voltage regulators such as TPS732XX are also known as LDO. These provide high power dissipation and good tolerance to higher voltage values at the input.

Usually, for the designing of linear voltage regulators, a negative feedback circuit with a fixed current source is used. These regulators are available as fixed output regulators and adjustable output voltage regulators. Besides positive voltage regulators, negative voltage regulators which are useful for providing negative reference voltages are also available. TPS73 series is a low drop out regulator series with reverse current protection.

What is TPS732XX?

TPS732XX is a series of low drop out voltage regulators introduced by Texas Instruments. This series of regulators use NMOS pass element to achieve the low drop out values. Besides this, the NMOS also provides protection from reverse current. These regulators don’t require any external capacitors when circuits are formed.

This series contains various choices for both adjustable voltage versions and fixed voltage versions. This series is also provided with thermal and overcurrent protection. Foldback current limit is also given. To get high precision while generating low drop out voltage and low ground pin current advanced BICMOS process is used in TPS732 series.

How to Use?

To maintain regulation and function properly TPS732 family requires an input voltage of 1.7 V. The device should not be operated at the DC voltages greater than 5.5V. Any transient spike that rises above 6V absolute maximum voltage rating should be suppressed when working at 5.5V.

Below are the diagrams for connection in a fixed voltage model and the adjustable voltage model.

Block Diagram of TPS732

Output Noise

The internal reference voltage is generated using a precision band-gap reference. This internal reference is the cause for output noise in TPS732 and its value is approximately 32μV_RMS at the output NR. A low pass filter for voltage reference is formed using an internal resistor of 27kΩ in series to the NR pin.

From NR to the ground an external noise reduction capacitor C_NR is connected. The total noise is reduced by a factor of 3.2 when the value of C_NR is 10nF. As the adjustable version doesn’t have an NR pin a feedback capacitor is connected from ground to Feedback pin FB to reduce the noise.

Dropout Voltage

In TPS73XX NMOS pass transistor helps in receiving the low dropout values. The NMOS pass transistor is in the linear region of operation when the difference between input and output voltage is less than the dropout voltage.
To avoid degraded transient response larger voltage drop from V_IN to V_OUT is required. Increase in recovery time is seen when operated in a transient dropout region.

Reverse Current

NMOS pass element provides protection against the reverse current. When the gate of the pass device is pulled low, the current cannot pass from the output of the regulator to input. Before the input voltage is removed, EN pin must be driven low, to ensure that all the charge is removed from the gate of the pass element.

Pin Configuration of TPS732

TPS73XX series is available in three types of packages.

5-pin SOT-23 DBV Package

• Pin -1 input power supply.
• The Pin -2 is the ground pin.
• Pin -3 is EN if EN=1 regulator is turned on when EN =0 regulator goes into shutdown mode.
• The Pin -4 as NR in fixed voltage versions. When an external capacitor is connected to this pin, the noise produced by the internal band gap is bypassed and output noise is also reduced.
• Pin – 4 as FB in adjustable voltage versions. Control loop error amplifier’s input pin and output voltage of the devices is set using this pin.
• The pin-5 output of the regulator.

6-Pin SOT-223 DCQ Package

• Here Pin -1 and Pin-4 are similar to 5 Pin SOT package.
• Pin-2 is the output pin.
• Pin-5 is the EN pin.
• Pin-3 and 6 are the ground pins.
• DRB 8 Pin SON with Exposed Thermal Pad.
• Pin-1 is the output pin of the regulator.
• Pin-8 is the input supply pin.
• Pin-4 and Pad are the ground.
• Pin -5 is the EN.
• Pin- 3 is used as NR pin in fixed voltage version and as FB pin in adjustable voltage version.

Applications of TPS732

Application of TPS732XX are as follows-

• These are used in portable equipment which is battery powered.
• TPS732XX are applied as post-regulation for switching supplies.
• These are the best choice for Noise-sensitive circuitry such as in VCO’s.
• TPS732XX are used for point-of-load regulation for applications seen in DSP’s, FPGA’s, ASICs and microprocessors.

Specifications of TPS732

Specifications of TPS732XX are as follows-

• These circuits are stable even without any output capacitor.
• The input voltage range is from 1.7V to 5.5V.
• The low dropout voltage of 40mV.
• Output current value is 250mA.
• With or without any output capacitor these are capable of excellent load transient response.
• For pass element in voltage follower configuration, these IC’s use NMOS pass element.
• Low reverse leakage current is provided by NMOS topology.
• These give low noise of 30μV_RMS which is about 10 – 100 kHz.
• These have an initial accuracy of 0.5%.
• Line, load and temperature accuracy .i.e. the overall accuracy is 1%.
• In shutdown mode, these have a maximum IQ of less than 1-μA.
• These have specified minimum and maximum current limit protection.
• Thermal shutdown is also provided.
• These are available as fixed output versions for the voltages 1.2V to 5V.
• Adjustable voltages from 1.2V to 5.5V are also available.
• Besides the above configurations, these are also available for custom output values.
• Available as a 5-pin SOT-23, 6-pin SOT-223 and 8-pin SON packages.
• Junction temperature range is from -550C to 1500C.
• Storage temperature range is from -650C to 1500C.

Alternative IC of TPS732

Linear voltage regulators and low drop linear voltage regulators are two different kinds. Linear voltage regulators usually have high dropout values whereas low-dropout voltage regulators have dropout values of mV. There are various types of IC’s available in the market for different values of output voltages and dropout values.

IC’s similar to TPS732XX series are LP2957, TPS795, TPS718XX, TPS719XX, UA78MXX, LP7805, REG102 series etc… Electrical characteristics of TPS732XX series can be found at the official datasheet provided by Texas Instrumentations. Which of the voltage model of TPS732 series have you worked with?

Image Resources: Texas Instruments