st1s12 STMicroelectronics, st1s12 Datasheet - Page 10

• Manufacturer Part Number: st1s12
• Description: Synchronous Rectification With Enable, 0.7 A, 1.7 Mhz Fixed Or Adjustable Step-down Switching Regulator In Tsot23-5l
• Manufacturer: STMicroelectronics

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Application notes
The ST1S12Gxx is an adjustable current mode PWM step-down DC-DC converter with
internal 0.7 A power switch, packaged in TSOT23-5L. This device is a complete 0.7 A
switching regulator, with its internal compensation eliminating the need for additional
components.
Because the ST1S12Gxx an adjustable regulator, the output voltage is determined by an
external resistor divider. The desired value is derived by the following equation:
V
For the device to function only a few component are required: an inductor, two capacitors
and the resistor divider. The inductor selected must be capable of non saturation at peak
current level. Moreover, its value can be selected taking into account that a large inductor
value increases efficiency at low output current and reduces output voltage ripple, while a
smaller inductor can be used when it is important to reduce package size and the total cost
of the application. Finally, the ST1S12Gxx has been designed to work properly with X5R or
X7R SMD ceramic capacitors both at the input and at the output. These types of capacitors,
due 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 compromising
the correct functioning of the device.
O
= V
FB
[1+R
1
/R
2
]