STEVAL-ISA022V1 STMicroelectronics, STEVAL-ISA022V1 Datasheet - Page 9

• Manufacturer Part Number: STEVAL-ISA022V1
• Description: EVAL BOARD 6W POWER SUPPLY
• Manufacturer: STMicroelectronics
• Series: VIPER™r

Specifications of STEVAL-ISA022V1

• Design Resources: STEVAL-ISA022V1 Schematics STEVAL-ISA022V1 Bill of Material
• Main Purpose: AC/DC, Primary Side
• Outputs And Type: 2, Isolated
• Power - Output: 5.5W
• Voltage - Output: 5V, 15V
• Current - Output: 500mA, 200mA
• Voltage - Input: 90 ~ 264VAC
• Regulator Topology: Flyback
• Frequency - Switching: 60kHz
• Board Type: Fully Populated
• Utilized Ic / Part: VIPer12A
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-5520

VIPER12A-E
6
Feedback pin principle of operation
A feedback pin controls the operation of the device. Unlike conventional PWM control
circuits which use a voltage input (the inverted input of an operational amplifier), the FB pin
is sensitive to current.
Figure 5.
The power MOSFET delivers a sense current I
R2 receives this current and the current coming from the FB pin. The voltage across R2 is
then compared to a fixed reference voltage of about 0.23 V. The MOSFET is switched off
when the following equation is reached:
By extracting I
Using the current sense ratio of the MOSFET G
Internal current control structure
S
:
Figure 5.
I
Doc ID 11977 Rev 2
D
presents the internal current mode structure.
=
R
G
2
ID
⋅
(
I
I
⋅
S
S
I
S
+
=
I
=
FB
0.23V
--------------- - I
R
G
)
2
ID
s
=
ID
which is proportional to the main current Id.
⋅
0.23V
–
⎛
⎝
:
0.23V
--------------- - I
FB
R
Feedback pin principle of operation
2
–
FB
⎞
⎠
9/21