ST1S06

Typical application

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Typical application

Application notes

The ST1S06 is an adjustable current mode PWM step-down DC/DC converter with internal 1.5A power

switch, packaged in a 6-lead DFN 3x3.

It’s a complete 1.5A switching regulator with its internal compensation eliminating additional component.

The constant frequency, current mode, PWM architecture and stable operation with ceramic capacitors

results in low, predictable output ripple. However, in order to maximize the power conversion efficiency

with light load, the regulator reduces automatically the switching frequency when the output load

becomes less than 250mA typically.

To clamp the error amplifier reference voltage a Soft Start control block generating a voltage ramp, has

been implemented. Besides an On-Chip Power on Reset of 50=100µs ensure the proper operation when

switching on the power supply. Other circuits fitted to the device protection are the Thermal Shut down

block which turn off the regulator when the junction temperature exceeds 150°C typically and the Cycle-

by-cycle Current Limiting that provides protection against shorted outputs.

Being the ST1S06 an adjustable regulator, the output voltage is determined by an external resistor

divider. The desired value is given by the following equation:

To make the device working, only few component are required: an inductor and two capacitors and the

resistor divider. The chosen inductor must be able to not saturate at the peak current level. Besides, its

value can be selected keeping in account that a large inductor value increases the efficiency at low output

current and reduces output voltage ripple, while a smaller inductor can be chosen when it is important to

reduce the package size and the total cost of the application. Finally, the ST1S06 has been designed to

work properly with X5R or X7R SMD ceramic capacitors both at the input and at the output. this kind of

capacitors, thanks to their very low series resistance (ESR), minimize the output voltage ripple. Other low

ESR capacitors can be used according to the need of the application without invalidate the right

functioning of the device.

Figure 24. Application circuit