1 Features

1 Input voltage range: 1.8 V to 5.5 V

Fixed and Adjustable Output Voltage Options

1.2V to 5.5V

Efficiency up to 96%

1200 mA output current at 3.3 V in buck mode (VIN = 3.6 V to 5.5 V)

Up to 800 mA output current at 3.3 V in boost mode (VIN > 2.4 V)

Automatic transition between buck and boost modes

Equipment quiescent current is less than 50μA

Energy saving mode for increased efficiency at low output power

Forced fixed frequency operation and synchronization possible

Disconnect load during shutdown

Overheating protection

Available in 3-mm × 3-mm 10-pin VSON package (QFN)

2 apps

All two- and three-chamber alkaline, NiCd or

Ni-MH or single-cell lithium battery powered products

Portable Audio Player

smart phone

illustrate

The TPS6300x devices provide power solutions for products powered by dual- or triple-cell alkaline, NiCd or NiMH, single-cell Li-Ion, or Li-polymer batteries. When using a single-cell Li-Ion or Li-Polymer battery, the output current can be as high as 1200 mA and it can be discharged to 2.5 volts or less. Buck-boost converters are based on fixed-frequency, pulse-width modulation (PWM) controllers that employ synchronous rectification for maximum efficiency. At low load currents, the converter enters a power-saving mode to maintain high efficiency over a wide load current range. The power saving mode can be disabled, forcing the converter to operate at a fixed switching frequency. The maximum average current in the switch is limited to 1800 mA typical. The output voltage can be programmed using an external resistor divider, or fixed inside the chip. The converter can be disabled to minimize battery drain. During shutdown, the load is disconnected from the battery.

The TPS6300x devices operate over a free air temperature range of -40°C to 85°C. The device is packaged in a 10-pin VSON package (QFN) measuring 3 mm by 3 mm (DRC).

Overview

The control circuit of the device is based on an average current mode topology. The average inductor current is regulated by a fast current regulation loop controlled by a voltage control loop. The controller also uses input and output voltage feedforward. Changes in the input and output voltages are monitored, and the duty cycle in the modulator can be changed immediately to achieve a fast response to these errors. The voltage error amplifier gets its feedback input from the FB pin. With adjustable output voltages, a resistor divider must be connected to this pin. At a fixed output voltage, FB must be connected to the output voltage to sense the voltage directly. Fixed output voltage versions use trimmed internal resistor dividers. The feedback voltage is compared to an internal reference voltage to generate a stable and accurate output voltage.

The controller circuit also senses the average input current and peak input current. In this way, the maximum input power and maximum peak current can be controlled for safe and stable operation under all possible conditions. To ultimately prevent the device from overheating, an internal temperature sensor is designed.

The device uses 4 internal N-channel mosfets to maintain synchronous power conversion under all possible operating conditions. This enables the device to maintain high efficiency over a wide range of input voltage and output power.

To avoid ground offset issues due to high current in the switch, two separate ground pins are grounded and

Use PGND. The reference for all control functions is the GND pin. The power switch is connected to PGND. Both grounds must be connected to the PCB at only one point, preferably close to the ground pins. Due to the four-switch topology, the load is always disconnected from the input during drive shutdown.

Functional block diagram

device enabled

When EN is set high, the device is put into operation. When EN is set to GND, it will enter shutdown mode. In shutdown mode, the regulator stops switching, all internal control circuits are turned off, and the load is disconnected from the input. This also means that during shutdown, the output voltage may be lower than the input voltage. During startup of the converter, the duty cycle and peak current are limited to avoid high peak currents flowing from the input.

undervoltage lockout

The undervoltage lockout feature prevents the device from starting up if the supply voltage to VINA falls below its threshold (see ). During operation, if the voltage at VINA falls below the undervoltage lockout threshold, the device will automatically enter shutdown mode. If the input voltage returns to the minimum operating input voltage, the device will automatically restart. Electrical Characteristics

Over temperature protection

This unit has a built-in temperature sensor that monitors the temperature of the internal IC. If the temperature exceeds a programmed threshold (see ), the device will stop working. Once the IC temperature drops below the programming threshold, it starts working again. There is a built-in hysteresis to avoid unstable operation at IC temperature over temperature threshold. Electrical Characteristics

Device functional mode

Soft-Start and Short-Circuit Protection

Once enabled, the device starts functioning. The average current limit increases gradually from the initial 400 mA as the output voltage increases. When the output voltage is about 1.2v, the current limit is its nominal value. If the output voltage does not increase, the current limit does not increase. No timer is implemented. Therefore, the output voltage overshoot and inrush current at startup are kept to a minimum. Even with a very large capacitor connected to the output, the device boosts the output voltage in a controllable manner. When the output voltage does not exceed 1.2v, the device short-circuits at the output and maintains a low current limit to protect itself and the application. When the output is shorted during operation, the current limit will also be reduced accordingly. For example, at an output voltage of 0 V, the output current will not exceed about 400 mA.

Buck-Boost Operation

To properly regulate the output voltage under all possible input voltage conditions, the device automatically switches from buck to boost operation and back as required by the configuration. It always uses one active switch, one rectifying switch, one switch permanently on and one switch permanently off. So, when the input voltage is higher than the output voltage, it works as a buck converter (buck); when the input voltage is lower than the output voltage, it works as a boost converter. There is no operating mode where all 4 switches are permanently toggled. When the input voltage is close to the output voltage, controlling the switch in this way allows the converter to maintain high efficiency at the most important operating point. The rms current through the switch and inductor is kept to a minimum to minimize switching and conduction losses. Using only one active switch and one passive switch also keeps switching losses low. For the remaining 2 switches, one remains permanently on and the other is permanently off, so there is no switching loss.

Power Saver and Sync

The PS/SYNC pin can be used to select different modes of operation. To enable power saving mode, PS/SYNC must be set low. To improve efficiency at light loads, a power saving mode is employed. If power saving mode is enabled, the converter stops operating if the average inductor current falls below about 300mA and the output voltage is at or above its nominal value. If the output voltage drops below its nominal value, the device starts operation with a programmed average inductor current higher than required by the current load conditions, increasing the output voltage again. Operation can last for one or more pulses. Once the conditions for stopping operation are met again, the inverter stops running again.

Power saving mode can be disabled by setting high on PS/SYNC. Connecting a clock signal at PS/SYNC forces the device to synchronize to the connected clock frequency. Synchronization is done by a phase locked loop (PLL), so there is no problem synchronizing to lower and higher frequencies compared to the internal clock. The PLL can also tolerate missing clock pulses without converter failure. The PS/SYNC input supports standard logic thresholds.

Application Information

The TPS6300x DC-DC converters are suitable for systems powered by single-cell Li-Ion or Li-polymer batteries with typical voltages between 2.3 V and 4.5 V. They can also be used in systems powered by two- or three-cell alkaline, NiCd, or NiMH batteries with typical terminal voltages between 1.8 V and 5.5 V. Also, any other voltage source when the typical output voltage is between 1.8 V and 5.5 V can use the TPS6300x's can power system.

typical application

Typical Application Circuit for Adjustable Output Voltage Selection

Design requirements

The TPS63000 series of buck-boost converters have an inner loop compensation function. Therefore, the external LC filter must be selected based on the internal compensation.

Design guidelines provide component selection for operating the device in. Recommended Operating Conditions

For the fixed output voltage option, the feedback pin needs to be connected to VOUT.

Capacitor selection

input capacitor

An input capacitor of at least 4.7µF is recommended to improve the transient characteristics of the regulator and the EMI characteristics of the entire power supply circuit. It is recommended to place ceramic capacitors as close as possible to the VIN and PGND pins of the IC.

output capacitor

For the output capacitors, it is recommended to use small ceramic capacitors as close as possible to the VOUT and PGND pins of the IC. The recommended nominal output capacitor value is 15µF.

There is also no upper limit to the output capacitor value. During load transients, larger capacitors result in lower output voltage ripple and lower output voltage drop.

Layout Guidelines

As with all switching power supplies, layout is an important step in the design, especially at high peak currents and high switching frequencies. If the layout is not careful, the regulator can have stability problems and electromagnetic interference problems. Therefore, wide and short traces should be used for the main current paths and power ground traces. The input capacitance, output capacitance, and inductance are placed as close as possible to the integrated circuit. The power supply grounding adopts the same grounding node, and the control grounding adopts different grounding nodes to reduce the influence of ground noise. Connect these ground nodes anywhere close to one of the IC's ground pins.

The feedback splitter should be placed as close as possible to the control ground pin of the IC. To lay out the control ground, TI recommends also using a short trace, separate from the power ground trace. This avoids ground offset problems due to the superposition of power supply ground currents and control ground currents.

layout example

Thermal factor

Implementing integrated circuits in low-profile and fine-pitch surface mount packages often requires special attention to power dissipation. Many system-related issues, such as thermal coupling, airflow, added heat sinks and convective surfaces, and the presence of other heat-generating components, can affect the power consumption limit of a given component.

Three basic ways to improve thermal performance are as follows:

Improve the power dissipation capability of PCB design

Improve component-to-PCB thermal coupling by soldering exposed thermal pads

Introduce airflow into the system

The maximum recommended junction temperature (TJ) for TPS6300x devices is 125°C. If the exposed thermal pad is soldered, the thermal resistance of the 10-pin QFn 3mm × 3mm package (DRC) is Rθ=48.7°C/W. The specified regulator operation ensures a maximum ambient temperature TA of 85°C. Therefore, as calculated in Equation 5, the maximum power dissipation is approximately 820 mW. If the maximum ambient temperature of the application is lower, more power can be dissipated.