STEVAL-ISA050V1 STMicroelectronics, STEVAL-ISA050V1 Datasheet - Page 39

• Manufacturer Part Number: STEVAL-ISA050V1
• Description: KIT EVAL PM6641 CHIPSET/DDR2/3
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of STEVAL-ISA050V1

• Main Purpose: Special Purpose DC/DC, DDR Memory Supply
• Outputs And Type: 4, Non-Isolated
• Power - Output: 14.7W
• Voltage - Output: 1.05V, 1.5V, 1.8V, 0.9V
• Current - Output: 4A, 2.8A, 2.5A, 2A
• Voltage - Input: 2.7 ~ 5.5V
• Regulator Topology: Buck
• Frequency - Switching: 750kHz
• Board Type: Fully Populated
• Utilized Ic / Part: PM6641
• Input Voltage: 2.7 V to 5.5 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: PM6641
• Kit Application Type: Power Management - Voltage Regulator
• Application Sub Type: Monolithic Voltage Regulator
• Kit Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: PM6641
• Other names: 497-8425

PM6641
From the definition of cross-over frequency, the value of the compensation resistor is
derived:
Equation 25
A good choice for the cross-over frequency is to assign f
The fixed parameters g
feedback divider factor (α) is application dependant (see
loop on page 24
After computing R
compensation zero near the power stage pole:
Equation 26
The roll-off capacitance, as said previously, must compensate for the power stage high
frequency zero, when necessary:
Equation 27
As final step, it’s important to verify that the compensation zero is quite far from the cross-
over frequency. An empirical rule is satisfied if the following holds:
Equation 28
All these considerations are true if the cross-over frequency is quite lower than the switching
frequency, and the compensation zero and the power stage pole are far enough from f
section for details).
C
, the compensation capacitor can be designed in order to place the
G
m
LOOP
= 300 μs and K
(
2 j
Doc ID 13510 Rev 3
π
f
CO
f
C
)
ZC
C
=
C
=
1
=
RO
L
⇒
2
C
= 4.4 s are design parameters, whereas the
π
O
R
=
C
(
1
C
C
R
C
R
R
O
O
=
R
C
C
R
+
C
2
ES
≤
π
R
f
ES
CO
f
CO
5
g
C
)
m
CO
Chapter 7.3: SW regulators control
O
K
R (
L
equal to
α
ES
R
O
+
R
O
Components selection
)
f
SW
10
.
CO
39/47
.