ST2S08B STMicroelectronics, ST2S08B Datasheet - Page 11

• Manufacturer Part Number: ST2S08B
• Description: Dual synchronous rectification, 1.5 A, 1.5 MHz adjustable step-down switching regulator
• Manufacturer: STMicroelectronics

Specifications of ST2S08B

• Typical Efficiency: > 80 % at VOUT= 1.2 V
• Non-switching Quiescent Current: max 1 mA over temperature range

ST2S08B
8
8.1
8.2
8.3
Application information
Introduction
The following technical information is used for estimating typical external component
characteristics using standard equations. Nevertheless, it is strongly recommended to
validate the suitability of external components to the application requirements by thoroughly
testing any solution at bench level on a real evaluation circuit.
Programming the output voltage
The output voltage for both channels can be adjusted from 0.8 V up to 85 % of the input
voltage value by connecting a resistor divider between V
divider must be connected to the feedback (FB) pin, as shown in
The resistor divider must be chosen according to the following equations:
Equation 1
Equation 2
Using a resistor with a value in the range of 1 kΩ to 50 kΩ is recommended. Lower values
are also suitable, but increase current consumption.
Inductor selection
The inductor is the key passive component for switching converters.
The critical inductance values can then be obtained according to the following formulas:
Equation 3
F
ΔI
can be set at 20 % - 40 % of the output current.
The peak current of the inductor can be calculated as:
L
V
V
SW
MIN
L
O
O
= the peak-to-peak inductor ripple current. As a rule of thumb, the peak-to-peak ripple
1
2
= switching frequency
=
=
=
V
V
V
V
O
FB
IN
FB
×
_
1
2
V (
MAX
×
×
IN
⎛
⎜ ⎜
⎝
⎛
⎜ ⎜
⎝
_
1
1
×
MAX
+
+
F
SW
R
R
R
R
1
2
3
4
−
×
⎞
⎟ ⎟
⎠
⎞
⎟ ⎟
⎠
V
Δ
O
I
L
)
Doc ID 18290 Rev 1
O
and GND, the middle point of the
Figure
Application information
3.
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