TPS65160, TPS65160A

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SLVS566C – MARCH 2005 – REVISED MARCH 2013

DETAILED DESCRIPTION

Boost Converter

The main boost converter operates in pulse-width modulation (PWM) and at a fixed switching frequency of

500 kHz or 750 kHz set by the FREQ pin. The converter uses an unique fast response, voltage-mode controller

scheme with input voltage feedforward. This achieves excellent line and load regulation (0.03%-A load regulation

typical) and allows the use of small external components. To add higher flexibility to the selection of external

component values, the device uses external loop compensation. Although the boost converter looks like a

nonsynchronous boost converter topology operating in discontinuous conduction mode at light load, the

TPS65160 maintains continuous conduction even at light-load currents. This is achieved with a novel architecture

using an external Schottky diode with an integrated MOSFET in parallel connected between SW and OS. See

the Functional Block Diagram. The intention of this MOSFET is to allow the current to go negative that occurs at

light-load conditions. For this purpose, a small integrated P-Channel MOSFET with typically 10-

Ω rDS(on) is

sufficient. When the inductor current is positive, the external Schottky diode with the lower forward voltage

conducts the current. This causes the converter to operate with a fixed frequency in continuous conduction mode

over the entire load current range. This avoids the ringing on the switch pin as seen with standard

nonsynchronous boost converter and allows a simpler compensation for the boost converter.

Soft Start (Boost Converter)

The main boost converter has an adjustable soft start to prevent high inrush current during start-up. The soft-start

time is set by the external capacitor connected to the SS pin. The capacitor connected to the SS pin is charged

with a constant current that increases the voltage on the SS pin. The internal current limit is proportional to the

voltage on the soft-start pin. When the threshold voltage of the internal soft-start comparator is reached, the full

current limit is released. The larger the soft-start capacitor value, the longer the soft-start time.

Overvoltage Protection of the Boost Converter

The main boost converter has an overvoltage protection to protect the main switch Q2 at pin (SW) in case the

feedback (FB) pin is floating or shorted to GND. In such an event, the output voltage rises and is monitored with

the overvoltage protection comparator over the OS pin. See the functional block diagram. As soon as the

comparator trips at typically 23 V, TPS65160, (19 V, TPS65160A), the boost converter turns the N-Channel

MOSFET switch off. The output voltage falls below the overvoltage threshold and the converter continues to

operate.

Frequency Select Pin (FREQ)

The frequency select pin (FREQ) allows setting the switching frequency of the entire device to 500 kHz (FREQ =

low) or 750 kHz (FREQ = high). A lower switching frequency gives a higher efficiency with a slightly reduced load

transient regulation.

Thermal Shutdown

A thermal shutdown is implemented to prevent damage caused by excessive heat and power dissipation.

Typically, the thermal shutdown threshold is 155°C.

Step-Down Converter

The nonsynchronous step-down converter operates at a fixed switching frequency using a fast response voltage

mode topology with input voltage feedforward. This topology allows simple internal compensation, and it is

designed to operate with ceramic output capacitors. The converter drives an internal 2.6-A N-channel MOSFET

switch. The MOSFET driver is referenced to the switch pin SWB. The N-channel MOSFET requires a gate drive

voltage higher than the switch pin to turn the N-Channel MOSFET on. This is accomplished by a bootstrap gate

drive circuit running of the step-down converter switch pin. When the switch pin SWB is at ground, the bootstrap

capacitor is charged to 8 V. This way, the N-channel gate drive voltage is typically around 8 V.

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Product Folder Links: TPS65160 TPS65160A