STEVAL-ISA043V2 STMicroelectronics, STEVAL-ISA043V2 Datasheet - Page 5

• Manufacturer Part Number: STEVAL-ISA043V2
• Description: BOARD EVAL BASED ON ST1S06
• Manufacturer: STMicroelectronics

Specifications of STEVAL-ISA043V2

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 3.3V
• Current - Output: 1.5A
• Voltage - Input: 2.7 ~ 6V
• Regulator Topology: Buck
• Frequency - Switching: 1.5MHz
• Board Type: Fully Populated
• Utilized Ic / Part: ST1S06
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: ST1S06PUR
• Kit Application Type: Power Management - Voltage Regulator
• Application Sub Type: Synchronous Buck Converter
• Kit Contents: Board
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-6420; STEVAL-ISA043V2

AN2371
1.2
1.3
The maximum and minimum duty cycles are:
Equation 3
Equation 4
Where V
the internal PDMOS. Considering the range DMIN to DMAX, it is possible to determine the
max IRMS following through the input capacitor.
Different types of capacitors can be considered:
●
●
●
Output capacitor
The output capacitor is very important to satisfy the output voltage ripple requirement. Using
a small inductor value is useful to reduce the size of the choke but increases the current
ripple. So, to reduce the output voltage ripple a low ESR capacitor is required.
Inductor
The inductor value is very important because it sets the ripple current flowing through output
capacitor. The ripple current is usually set to 20-40% of I
1.5 A. The approximate inductor value is obtained by the following formula:
Equation 5
Where t
For example, with V
µH. The peak current thought the inductor is given by:
Equation 6
Electrolytic Capacitors. These are the most used because they are the least expensive
and are available with a wide range of RMS current ratings. The only drawback is that,
considering a requested ripple current rating, they are physically larger than other
capacitors.
Ceramic Capacitors. If available for the requested value and voltage rating, these
capacitors have usually a higher RMS current rating for a given physical dimension
(due to the very low ESR). The drawback is the quite high cost.
Tantalum Capacitor. Very good tantalum capacitors are coming available, with very low
ESR and small size. The only problem is that they occasionally can burn if subjected to
very high current during the charge. So, it is better to avoid using this type of capacitor
for the input filter of the device. In fact, they can be subject to high surge currents when
connected to the power supply.
ON
F
is the voltage drop across the internal NMOS and VSW the voltage drop across
is the ON time of the internal switch, given by D • T.
OUT
= 3.3 V, V
IN
D
D
L
= 5 V and ∆I
MAX
MIN
=
I
V
----------------------------- -
PK
=
=
IN
------------------------------------- -
V
=
------------------------------------ -
V
–
I ∆
INMAX
V
V
INMIN
V
Selecting components for your application
I
OUT
O
OUT
OUT
+
O
I ∆
---- -
2
+
+
–
–
•
= 0.45 A, the inductor value is about 2.8
V
V
V
V
t
ON
SW
F
SW
F
Omax
, that is 0.3-0.6 A with I
Omax
5/12
=