STEVAL-ISA023V2 STMicroelectronics, STEVAL-ISA023V2 Datasheet - Page 25

• Manufacturer Part Number: STEVAL-ISA023V2
• Description: EVAL BOARD 24W NEG OUT VIPER53E
• Manufacturer: STMicroelectronics
• Series: VIPER™r
• Type: AC/DC Switching Convertersr

Specifications of STEVAL-ISA023V2

• Mfg Application Notes: VIPer53EDIP - AppNote
• Design Resources: STEVAL-ISA023V2 Gerber Files STEVAL-ISA023V2 Schematic STEVAL-ISA023V2 Bill of Materials
• Main Purpose: AC/DC, Primary Side
• Outputs And Type: 2, Isolated
• Power - Output: 24W
• Voltage - Output: -5V, -12V
• Current - Output: 3A, 800mA
• Voltage - Input: 90 ~ 265VAC
• Regulator Topology: Flyback
• Frequency - Switching: 60kHz
• Board Type: Fully Populated
• Utilized Ic / Part: VIPer53
• Input Voltage: 90 V to 265 V
• Output Voltage: - 5 V, - 12 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: VIPer53-E
• Kit Application Type: Power Management
• Application Sub Type: SMPS
• Kit Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: VIPer53-E
• Other names: 497-5866

VIPer53 - E
11
Transconductance error amplifier
The VIPer53-E includes a transconductance error amplifier. Transconductance Gm is the
change in output current I
Equation 8
The output impedance Z
Equation 9
This last equation shows that the open loop gain A
Equation 10
where Gm value for VIPer53 is typically 1.4mA/V.
Gm is well defined by specification, but Z
tolerances. An impedance Z must be connected between the COMP pin and ground in order
to accurately define the transfer function F of the error amplifier, the following equation, very
similar to the one above:
Equation 11
The error amplifier frequency response is shown in .0 for different values of a simple
resistance connected on the COMP pin. The unloaded transconductance error amplifier
shows an internal Z
the COMP pin to achieve different compensation methods. A capacitor provides an
integrator function, thus eliminating the DC static error, and a resistance in series leads to a
flat gain at higher frequency, introducing a zero level and ensuring a correct phase margin.
This configuration illustrated in
the error amplifier transfer function for a typical set of values of C
Note that a 10nF capacitor (8nF, minimum value) should always be connected to the COMP
pin to ensure a correct stability of the internal error amplifier.
The complete converter open loop transfer function can be built from both power cell and
error amplifier transfer functions. A theoretical example can be seen in
discontinuous mode flyback loaded by a simple resistor, regulated from primary side (no
COMP
COMP
COMP
of about 140K . More complex impedances can be connected on
Z
COMP
at the output of this amplifier (COMP pin) can be defined as:
Figure
versus change in input voltage V
A
=
VOL
F s
22, for the schematic and
--------------------- -
Gm
V
I
COMP
COMP,
COMP
=
=
=
Gm
Gm
------------------- -
=
I
COMP
and therefore A
V
--------- -
Gm
DD
Z
1
Z s
VOL
COMP
--------------------- -
can be related to Gm and Z
Transconductance error amplifier
V
V
COMP
DD
VOL,
Figure 23 on page 28
DD
COMP
. Thus:
are subject to large
and R
Figure 24
COMP
for a
.
COMP
for
25/36
: