TS30111

Final Datasheet

Rev 1.0

June 2, 2015

www.semtech.com

7 of 21

Semtech

Functional Description

The TS30111 current-mode synchronous step-down power

supply product is ideal for use in the commercial, industrial,

and automotive market segments. It includes flexibility to be

used for a wide range of output voltages and is optimized for

high efficiency power conversion with low RDSON integrated

synchronous switches. A 1MHz internal switching frequency

facilitates low cost LC filter combinations. Additionally, the

fixed output versions enable a minimum external component

count to provide a complete regulation solution with only 4

external components: an input bypass capacitor, an inductor,

an output capacitor, and the bootstrap capacitor. The regulator

automatically transitions between PFM and PWM mode to

maximize efficiency for the load demand.

The TS30111 was designed to provide these system benefits:

•

Reduced board real estate

•

Lower system cost

Œ

Lower cost inductor

Œ

Low external parts count

•

Ease of design

Œ

Bill of Materials and suggested board layout provided

Œ

Power Good output

Œ

Integrated compensation network

Œ

Wide input voltage range

•

Robust solution

Œ

Over current, over voltage and over temperature pro-

tection

Detailed Pin Description

Unregulated input, VCC

This terminal is the unregulated input voltage source for the

IC. It is recommended that a 10uF bypass capacitor be placed

close to the device for best performance. Since this is the main

supply for the IC, good layout practices need to be followed for

this connection.

Bootstrap control, BST

This terminal will provide the bootstrap voltage required for

the upper internal NMOS switch of the buck regulator. An

external ceramic capacitor placed between the BST input

terminal and the VSW pin will provide the necessary voltage

for the upper switch. In normal operation the capacitor is

re-charged on every low side synchronous switching action.

In the case of where the switch mode approaches 100% duty

cycle for the high side FET, the device will automatically reduce

the duty cycle switch to a minimum off time on every 8th cycle

to allow this capacitor to re-charge.

Sense feedback, FB

This is the input terminal for the output voltage feedback.

For the fixed mode versions, this should be hooked directly

to V

as possible, and should be made as close as possible to the

capacitor. The trace should not be shared with any other

connection. (Figure 23)

For adjustable mode versions, this should be connected to

the external resistor divider. To choose the resistors, use the

following equation:

V

The input to the FB pin is high impedance, and input current

should be less than 100nA. As a result, good layout practices

are required for the feedback resistors and feedback traces.

When using the adjustable version, the feedback trace should

be kept as short as possible and minimum width to reduce

stray capacitance and to reduce the injection of noise.

For the adjustable version, the ratio of VCC/V

16.

Switching output, VSW

This is the switching node of the regulator. It should be

connected directly to the 3.3uH inductor with a wide, short

trace and to one end of the Bootstrap capacitor. It is switching

between VCC and PGND at the switching frequency.

Ground, GND

This ground is used for the majority of the device including the

analog reference, control loop, and other circuits.

Power Ground, PGND

This is a separate ground connection used for the low side

synchronous switch to isolate switching noise from the rest of

the device. (Figure 23)

Enable, EN

This is the input terminal to activate the regulator. The input

threshold is TTL/CMOS compatible. It also has an internal pull-

up to ensure a stable state if the pin is disconnected.